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 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * attrib.c - NTFS attribute operations.  Part of the Linux-NTFS project.
  *
  * Copyright (c) 2001-2012 Anton Altaparmakov and Tuxera Inc.
  * Copyright (c) 2002 Richard Russon
  */
 
 #include <linux/buffer_head.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/writeback.h>
 
 #include "attrib.h"
 #include "debug.h"
 #include "layout.h"
 #include "lcnalloc.h"
 #include "malloc.h"
 #include "mft.h"
 #include "ntfs.h"
 #include "types.h"
 
 /**
  * ntfs_map_runlist_nolock - map (a part of) a runlist of an ntfs inode
  * @ni:     ntfs inode for which to map (part of) a runlist
  * @vcn:    map runlist part containing this vcn
  * @ctx:    active attribute search context if present or NULL if not
  *
  * Map the part of a runlist containing the @vcn of the ntfs inode @ni.
  *
  * If @ctx is specified, it is an active search context of @ni and its base mft
  * record.  This is needed when ntfs_map_runlist_nolock() encounters unmapped
  * runlist fragments and allows their mapping.  If you do not have the mft
  * record mapped, you can specify @ctx as NULL and ntfs_map_runlist_nolock()
  * will perform the necessary mapping and unmapping.
  *
  * Note, ntfs_map_runlist_nolock() saves the state of @ctx on entry and
  * restores it before returning.  Thus, @ctx will be left pointing to the same
  * attribute on return as on entry.  However, the actual pointers in @ctx may
  * point to different memory locations on return, so you must remember to reset
  * any cached pointers from the @ctx, i.e. after the call to
  * ntfs_map_runlist_nolock(), you will probably want to do:
  *  m = ctx->mrec;
  *  a = ctx->attr;
  * Assuming you cache ctx->attr in a variable @a of type ATTR_RECORD * and that
  * you cache ctx->mrec in a variable @m of type MFT_RECORD *.
  *
  * Return 0 on success and -errno on error.  There is one special error code
  * which is not an error as such.  This is -ENOENT.  It means that @vcn is out
  * of bounds of the runlist.
  *
  * Note the runlist can be NULL after this function returns if @vcn is zero and
  * the attribute has zero allocated size, i.e. there simply is no runlist.
  *
  * WARNING: If @ctx is supplied, regardless of whether success or failure is
  *      returned, you need to check IS_ERR(@ctx->mrec) and if 'true' the @ctx
  *      is no longer valid, i.e. you need to either call
  *      ntfs_attr_reinit_search_ctx() or ntfs_attr_put_search_ctx() on it.
  *      In that case PTR_ERR(@ctx->mrec) will give you the error code for
  *      why the mapping of the old inode failed.
  *
  * Locking: - The runlist described by @ni must be locked for writing on entry
  *        and is locked on return.  Note the runlist will be modified.
  *      - If @ctx is NULL, the base mft record of @ni must not be mapped on
  *        entry and it will be left unmapped on return.
  *      - If @ctx is not NULL, the base mft record must be mapped on entry
  *        and it will be left mapped on return.
  */
 int ntfs_map_runlist_nolock(ntfs_inode *ni, VCN vcn, ntfs_attr_search_ctx *ctx)
 {
     VCN end_vcn;
     unsigned long flags;
     ntfs_inode *base_ni;
     MFT_RECORD *m;
     ATTR_RECORD *a;
     runlist_element *rl;
     struct page *put_this_page = NULL;
     int err = 0;
     bool ctx_is_temporary, ctx_needs_reset;
     ntfs_attr_search_ctx old_ctx = { NULL, };
 
     ntfs_debug("Mapping runlist part containing vcn 0x%llx.",
             (unsigned long long)vcn);
     if (!NInoAttr(ni))
         base_ni = ni;
     else
         base_ni = ni->ext.base_ntfs_ino;
     if (!ctx) {
         ctx_is_temporary = ctx_needs_reset = true;
         m = map_mft_record(base_ni);
         if (IS_ERR(m))
             return PTR_ERR(m);
         ctx = ntfs_attr_get_search_ctx(base_ni, m);
         if (unlikely(!ctx)) {
             err = -ENOMEM;
             goto err_out;
         }
     } else {
         VCN allocated_size_vcn;
 
         BUG_ON(IS_ERR(ctx->mrec));
         a = ctx->attr;
         BUG_ON(!a->non_resident);
         ctx_is_temporary = false;
         end_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
         read_lock_irqsave(&ni->size_lock, flags);
         allocated_size_vcn = ni->allocated_size >>
                 ni->vol->cluster_size_bits;
         read_unlock_irqrestore(&ni->size_lock, flags);
         if (!a->data.non_resident.lowest_vcn && end_vcn <= 0)
             end_vcn = allocated_size_vcn - 1;
         /*
          * If we already have the attribute extent containing @vcn in
          * @ctx, no need to look it up again.  We slightly cheat in
          * that if vcn exceeds the allocated size, we will refuse to
          * map the runlist below, so there is definitely no need to get
          * the right attribute extent.
          */
         if (vcn >= allocated_size_vcn || (a->type == ni->type &&
                 a->name_length == ni->name_len &&
                 !memcmp((u8*)a + le16_to_cpu(a->name_offset),
                 ni->name, ni->name_len) &&
                 sle64_to_cpu(a->data.non_resident.lowest_vcn)
                 <= vcn && end_vcn >= vcn))
             ctx_needs_reset = false;
         else {
             /* Save the old search context. */
             old_ctx = *ctx;
             /*
              * If the currently mapped (extent) inode is not the
              * base inode we will unmap it when we reinitialize the
              * search context which means we need to get a
              * reference to the page containing the mapped mft
              * record so we do not accidentally drop changes to the
              * mft record when it has not been marked dirty yet.
              */
             if (old_ctx.base_ntfs_ino && old_ctx.ntfs_ino !=
                     old_ctx.base_ntfs_ino) {
                 put_this_page = old_ctx.ntfs_ino->page;
                 get_page(put_this_page);
             }
             /*
              * Reinitialize the search context so we can lookup the
              * needed attribute extent.
              */
             ntfs_attr_reinit_search_ctx(ctx);
             ctx_needs_reset = true;
         }
     }
     if (ctx_needs_reset) {
         err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                 CASE_SENSITIVE, vcn, NULL, 0, ctx);
         if (unlikely(err)) {
             if (err == -ENOENT)
                 err = -EIO;
             goto err_out;
         }
         BUG_ON(!ctx->attr->non_resident);
     }
     a = ctx->attr;
     /*
      * Only decompress the mapping pairs if @vcn is inside it.  Otherwise
      * we get into problems when we try to map an out of bounds vcn because
      * we then try to map the already mapped runlist fragment and
      * ntfs_mapping_pairs_decompress() fails.
      */
     end_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn) + 1;
     if (unlikely(vcn && vcn >= end_vcn)) {
         err = -ENOENT;
         goto err_out;
     }
     rl = ntfs_mapping_pairs_decompress(ni->vol, a, ni->runlist.rl);
     if (IS_ERR(rl))
         err = PTR_ERR(rl);
     else
         ni->runlist.rl = rl;
 err_out:
     if (ctx_is_temporary) {
         if (likely(ctx))
             ntfs_attr_put_search_ctx(ctx);
         unmap_mft_record(base_ni);
     } else if (ctx_needs_reset) {
         /*
          * If there is no attribute list, restoring the search context
          * is accomplished simply by copying the saved context back over
          * the caller supplied context.  If there is an attribute list,
          * things are more complicated as we need to deal with mapping
          * of mft records and resulting potential changes in pointers.
          */
         if (NInoAttrList(base_ni)) {
             /*
              * If the currently mapped (extent) inode is not the
              * one we had before, we need to unmap it and map the
              * old one.
              */
             if (ctx->ntfs_ino != old_ctx.ntfs_ino) {
                 /*
                  * If the currently mapped inode is not the
                  * base inode, unmap it.
                  */
                 if (ctx->base_ntfs_ino && ctx->ntfs_ino !=
                         ctx->base_ntfs_ino) {
                     unmap_extent_mft_record(ctx->ntfs_ino);
                     ctx->mrec = ctx->base_mrec;
                     BUG_ON(!ctx->mrec);
                 }
                 /*
                  * If the old mapped inode is not the base
                  * inode, map it.
                  */
                 if (old_ctx.base_ntfs_ino &&
                         old_ctx.ntfs_ino !=
                         old_ctx.base_ntfs_ino) {
 retry_map:
                     ctx->mrec = map_mft_record(
                             old_ctx.ntfs_ino);
                     /*
                      * Something bad has happened.  If out
                      * of memory retry till it succeeds.
                      * Any other errors are fatal and we
                      * return the error code in ctx->mrec.
                      * Let the caller deal with it...  We
                      * just need to fudge things so the
                      * caller can reinit and/or put the
                      * search context safely.
                      */
                     if (IS_ERR(ctx->mrec)) {
                         if (PTR_ERR(ctx->mrec) ==
                                 -ENOMEM) {
                             schedule();
                             goto retry_map;
                         } else
                             old_ctx.ntfs_ino =
                                 old_ctx.
                                 base_ntfs_ino;
                     }
                 }
             }
             /* Update the changed pointers in the saved context. */
             if (ctx->mrec != old_ctx.mrec) {
                 if (!IS_ERR(ctx->mrec))
                     old_ctx.attr = (ATTR_RECORD*)(
                             (u8*)ctx->mrec +
                             ((u8*)old_ctx.attr -
                             (u8*)old_ctx.mrec));
                 old_ctx.mrec = ctx->mrec;
             }
         }
         /* Restore the search context to the saved one. */
         *ctx = old_ctx;
         /*
          * We drop the reference on the page we took earlier.  In the
          * case that IS_ERR(ctx->mrec) is true this means we might lose
          * some changes to the mft record that had been made between
          * the last time it was marked dirty/written out and now.  This
          * at this stage is not a problem as the mapping error is fatal
          * enough that the mft record cannot be written out anyway and
          * the caller is very likely to shutdown the whole inode
          * immediately and mark the volume dirty for chkdsk to pick up
          * the pieces anyway.
          */
         if (put_this_page)
             put_page(put_this_page);
     }
     return err;
 }
 
 /**
  * ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
  * @ni:     ntfs inode for which to map (part of) a runlist
  * @vcn:    map runlist part containing this vcn
  *
  * Map the part of a runlist containing the @vcn of the ntfs inode @ni.
  *
  * Return 0 on success and -errno on error.  There is one special error code
  * which is not an error as such.  This is -ENOENT.  It means that @vcn is out
  * of bounds of the runlist.
  *
  * Locking: - The runlist must be unlocked on entry and is unlocked on return.
  *      - This function takes the runlist lock for writing and may modify
  *        the runlist.
  */
 int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
 {
     int err = 0;
 
     down_write(&ni->runlist.lock);
     /* Make sure someone else didn't do the work while we were sleeping. */
     if (likely(ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn) <=
             LCN_RL_NOT_MAPPED))
         err = ntfs_map_runlist_nolock(ni, vcn, NULL);
     up_write(&ni->runlist.lock);
     return err;
 }
 
 /**
  * ntfs_attr_vcn_to_lcn_nolock - convert a vcn into a lcn given an ntfs inode
  * @ni:         ntfs inode of the attribute whose runlist to search
  * @vcn:        vcn to convert
  * @write_locked:   true if the runlist is locked for writing
  *
  * Find the virtual cluster number @vcn in the runlist of the ntfs attribute
  * described by the ntfs inode @ni and return the corresponding logical cluster
  * number (lcn).
  *
  * If the @vcn is not mapped yet, the attempt is made to map the attribute
  * extent containing the @vcn and the vcn to lcn conversion is retried.
  *
  * If @write_locked is true the caller has locked the runlist for writing and
  * if false for reading.
  *
  * Since lcns must be >= 0, we use negative return codes with special meaning:
  *
  * Return code  Meaning / Description
  * ==========================================
  *  LCN_HOLE    Hole / not allocated on disk.
  *  LCN_ENOENT  There is no such vcn in the runlist, i.e. @vcn is out of bounds.
  *  LCN_ENOMEM  Not enough memory to map runlist.
  *  LCN_EIO Critical error (runlist/file is corrupt, i/o error, etc).
  *
  * Locking: - The runlist must be locked on entry and is left locked on return.
  *      - If @write_locked is 'false', i.e. the runlist is locked for reading,
  *        the lock may be dropped inside the function so you cannot rely on
  *        the runlist still being the same when this function returns.
  */
 LCN ntfs_attr_vcn_to_lcn_nolock(ntfs_inode *ni, const VCN vcn,
         const bool write_locked)
 {
     LCN lcn;
     unsigned long flags;
     bool is_retry = false;
 
     BUG_ON(!ni);
     ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, %s_locked.",
             ni->mft_no, (unsigned long long)vcn,
             write_locked ? "write" : "read");
     BUG_ON(!NInoNonResident(ni));
     BUG_ON(vcn < 0);
     if (!ni->runlist.rl) {
         read_lock_irqsave(&ni->size_lock, flags);
         if (!ni->allocated_size) {
             read_unlock_irqrestore(&ni->size_lock, flags);
             return LCN_ENOENT;
         }
         read_unlock_irqrestore(&ni->size_lock, flags);
     }
 retry_remap:
     /* Convert vcn to lcn.  If that fails map the runlist and retry once. */
     lcn = ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn);
     if (likely(lcn >= LCN_HOLE)) {
         ntfs_debug("Done, lcn 0x%llx.", (long long)lcn);
         return lcn;
     }
     if (lcn != LCN_RL_NOT_MAPPED) {
         if (lcn != LCN_ENOENT)
             lcn = LCN_EIO;
     } else if (!is_retry) {
         int err;
 
         if (!write_locked) {
             up_read(&ni->runlist.lock);
             down_write(&ni->runlist.lock);
             if (unlikely(ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn) !=
                     LCN_RL_NOT_MAPPED)) {
                 up_write(&ni->runlist.lock);
                 down_read(&ni->runlist.lock);
                 goto retry_remap;
             }
         }
         err = ntfs_map_runlist_nolock(ni, vcn, NULL);
         if (!write_locked) {
             up_write(&ni->runlist.lock);
             down_read(&ni->runlist.lock);
         }
         if (likely(!err)) {
             is_retry = true;
             goto retry_remap;
         }
         if (err == -ENOENT)
             lcn = LCN_ENOENT;
         else if (err == -ENOMEM)
             lcn = LCN_ENOMEM;
         else
             lcn = LCN_EIO;
     }
     if (lcn != LCN_ENOENT)
         ntfs_error(ni->vol->sb, "Failed with error code %lli.",
                 (long long)lcn);
     return lcn;
 }
 
 /**
  * ntfs_attr_find_vcn_nolock - find a vcn in the runlist of an ntfs inode
  * @ni:     ntfs inode describing the runlist to search
  * @vcn:    vcn to find
  * @ctx:    active attribute search context if present or NULL if not
  *
  * Find the virtual cluster number @vcn in the runlist described by the ntfs
  * inode @ni and return the address of the runlist element containing the @vcn.
  *
  * If the @vcn is not mapped yet, the attempt is made to map the attribute
  * extent containing the @vcn and the vcn to lcn conversion is retried.
  *
  * If @ctx is specified, it is an active search context of @ni and its base mft
  * record.  This is needed when ntfs_attr_find_vcn_nolock() encounters unmapped
  * runlist fragments and allows their mapping.  If you do not have the mft
  * record mapped, you can specify @ctx as NULL and ntfs_attr_find_vcn_nolock()
  * will perform the necessary mapping and unmapping.
  *
  * Note, ntfs_attr_find_vcn_nolock() saves the state of @ctx on entry and
  * restores it before returning.  Thus, @ctx will be left pointing to the same
  * attribute on return as on entry.  However, the actual pointers in @ctx may
  * point to different memory locations on return, so you must remember to reset
  * any cached pointers from the @ctx, i.e. after the call to
  * ntfs_attr_find_vcn_nolock(), you will probably want to do:
  *  m = ctx->mrec;
  *  a = ctx->attr;
  * Assuming you cache ctx->attr in a variable @a of type ATTR_RECORD * and that
  * you cache ctx->mrec in a variable @m of type MFT_RECORD *.
  * Note you need to distinguish between the lcn of the returned runlist element
  * being >= 0 and LCN_HOLE.  In the later case you have to return zeroes on
  * read and allocate clusters on write.
  *
  * Return the runlist element containing the @vcn on success and
  * ERR_PTR(-errno) on error.  You need to test the return value with IS_ERR()
  * to decide if the return is success or failure and PTR_ERR() to get to the
  * error code if IS_ERR() is true.
  *
  * The possible error return codes are:
  *  -ENOENT - No such vcn in the runlist, i.e. @vcn is out of bounds.
  *  -ENOMEM - Not enough memory to map runlist.
  *  -EIO    - Critical error (runlist/file is corrupt, i/o error, etc).
  *
  * WARNING: If @ctx is supplied, regardless of whether success or failure is
  *      returned, you need to check IS_ERR(@ctx->mrec) and if 'true' the @ctx
  *      is no longer valid, i.e. you need to either call
  *      ntfs_attr_reinit_search_ctx() or ntfs_attr_put_search_ctx() on it.
  *      In that case PTR_ERR(@ctx->mrec) will give you the error code for
  *      why the mapping of the old inode failed.
  *
  * Locking: - The runlist described by @ni must be locked for writing on entry
  *        and is locked on return.  Note the runlist may be modified when
  *        needed runlist fragments need to be mapped.
  *      - If @ctx is NULL, the base mft record of @ni must not be mapped on
  *        entry and it will be left unmapped on return.
  *      - If @ctx is not NULL, the base mft record must be mapped on entry
  *        and it will be left mapped on return.
  */
 runlist_element *ntfs_attr_find_vcn_nolock(ntfs_inode *ni, const VCN vcn,
         ntfs_attr_search_ctx *ctx)
 {
     unsigned long flags;
     runlist_element *rl;
     int err = 0;
     bool is_retry = false;
 
     BUG_ON(!ni);
     ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, with%s ctx.",
             ni->mft_no, (unsigned long long)vcn, ctx ? "" : "out");
     BUG_ON(!NInoNonResident(ni));
     BUG_ON(vcn < 0);
     if (!ni->runlist.rl) {
         read_lock_irqsave(&ni->size_lock, flags);
         if (!ni->allocated_size) {
             read_unlock_irqrestore(&ni->size_lock, flags);
             return ERR_PTR(-ENOENT);
         }
         read_unlock_irqrestore(&ni->size_lock, flags);
     }
 retry_remap:
     rl = ni->runlist.rl;
     if (likely(rl && vcn >= rl[0].vcn)) {
         while (likely(rl->length)) {
             if (unlikely(vcn < rl[1].vcn)) {
                 if (likely(rl->lcn >= LCN_HOLE)) {
                     ntfs_debug("Done.");
                     return rl;
                 }
                 break;
             }
             rl++;
         }
         if (likely(rl->lcn != LCN_RL_NOT_MAPPED)) {
             if (likely(rl->lcn == LCN_ENOENT))
                 err = -ENOENT;
             else
                 err = -EIO;
         }
     }
     if (!err && !is_retry) {
         /*
          * If the search context is invalid we cannot map the unmapped
          * region.
          */
         if (IS_ERR(ctx->mrec))
             err = PTR_ERR(ctx->mrec);
         else {
             /*
              * The @vcn is in an unmapped region, map the runlist
              * and retry.
              */
             err = ntfs_map_runlist_nolock(ni, vcn, ctx);
             if (likely(!err)) {
                 is_retry = true;
                 goto retry_remap;
             }
         }
         if (err == -EINVAL)
             err = -EIO;
     } else if (!err)
         err = -EIO;
     if (err != -ENOENT)
         ntfs_error(ni->vol->sb, "Failed with error code %i.", err);
     return ERR_PTR(err);
 }
 
 /**
  * ntfs_attr_find - find (next) attribute in mft record
  * @type:   attribute type to find
  * @name:   attribute name to find (optional, i.e. NULL means don't care)
  * @name_len:   attribute name length (only needed if @name present)
  * @ic:     IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
  * @val:    attribute value to find (optional, resident attributes only)
  * @val_len:    attribute value length
  * @ctx:    search context with mft record and attribute to search from
  *
  * You should not need to call this function directly.  Use ntfs_attr_lookup()
  * instead.
  *
  * ntfs_attr_find() takes a search context @ctx as parameter and searches the
  * mft record specified by @ctx->mrec, beginning at @ctx->attr, for an
  * attribute of @type, optionally @name and @val.
  *
  * If the attribute is found, ntfs_attr_find() returns 0 and @ctx->attr will
  * point to the found attribute.
  *
  * If the attribute is not found, ntfs_attr_find() returns -ENOENT and
  * @ctx->attr will point to the attribute before which the attribute being
  * searched for would need to be inserted if such an action were to be desired.
  *
  * On actual error, ntfs_attr_find() returns -EIO.  In this case @ctx->attr is
  * undefined and in particular do not rely on it not changing.
  *
  * If @ctx->is_first is 'true', the search begins with @ctx->attr itself.  If it
  * is 'false', the search begins after @ctx->attr.
  *
  * If @ic is IGNORE_CASE, the @name comparisson is not case sensitive and
  * @ctx->ntfs_ino must be set to the ntfs inode to which the mft record
  * @ctx->mrec belongs.  This is so we can get at the ntfs volume and hence at
  * the upcase table.  If @ic is CASE_SENSITIVE, the comparison is case
  * sensitive.  When @name is present, @name_len is the @name length in Unicode
  * characters.
  *
  * If @name is not present (NULL), we assume that the unnamed attribute is
  * being searched for.
  *
  * Finally, the resident attribute value @val is looked for, if present.  If
  * @val is not present (NULL), @val_len is ignored.
  *
  * ntfs_attr_find() only searches the specified mft record and it ignores the
  * presence of an attribute list attribute (unless it is the one being searched
  * for, obviously).  If you need to take attribute lists into consideration,
  * use ntfs_attr_lookup() instead (see below).  This also means that you cannot
  * use ntfs_attr_find() to search for extent records of non-resident
  * attributes, as extents with lowest_vcn != 0 are usually described by the
  * attribute list attribute only. - Note that it is possible that the first
  * extent is only in the attribute list while the last extent is in the base
  * mft record, so do not rely on being able to find the first extent in the
  * base mft record.
  *
  * Warning: Never use @val when looking for attribute types which can be
  *      non-resident as this most likely will result in a crash!
  */
 static int ntfs_attr_find(const ATTR_TYPE type, const ntfschar *name,
         const u32 name_len, const IGNORE_CASE_BOOL ic,
         const u8 *val, const u32 val_len, ntfs_attr_search_ctx *ctx)
 {
     ATTR_RECORD *a;
     ntfs_volume *vol = ctx->ntfs_ino->vol;
     ntfschar *upcase = vol->upcase;
     u32 upcase_len = vol->upcase_len;
 
     /*
      * Iterate over attributes in mft record starting at @ctx->attr, or the
      * attribute following that, if @ctx->is_first is 'true'.
      */
     if (ctx->is_first) {
         a = ctx->attr;
         ctx->is_first = false;
     } else
         a = (ATTR_RECORD*)((u8*)ctx->attr +
                 le32_to_cpu(ctx->attr->length));
     for (;; a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))) {
         u8 *mrec_end = (u8 *)ctx->mrec +
                        le32_to_cpu(ctx->mrec->bytes_allocated);
         u8 *name_end = (u8 *)a + le16_to_cpu(a->name_offset) +
                    a->name_length * sizeof(ntfschar);
         if ((u8*)a < (u8*)ctx->mrec || (u8*)a > mrec_end ||
             name_end > mrec_end)
             break;
         ctx->attr = a;
         if (unlikely(le32_to_cpu(a->type) > le32_to_cpu(type) ||
                 a->type == AT_END))
             return -ENOENT;
         if (unlikely(!a->length))
             break;
         if (a->type != type)
             continue;
         /*
          * If @name is present, compare the two names.  If @name is
          * missing, assume we want an unnamed attribute.
          */
         if (!name) {
             /* The search failed if the found attribute is named. */
             if (a->name_length)
                 return -ENOENT;
         } else if (!ntfs_are_names_equal(name, name_len,
                 (ntfschar*)((u8*)a + le16_to_cpu(a->name_offset)),
                 a->name_length, ic, upcase, upcase_len)) {
             register int rc;
 
             rc = ntfs_collate_names(name, name_len,
                     (ntfschar*)((u8*)a +
                     le16_to_cpu(a->name_offset)),
                     a->name_length, 1, IGNORE_CASE,
                     upcase, upcase_len);
             /*
              * If @name collates before a->name, there is no
              * matching attribute.
              */
             if (rc == -1)
                 return -ENOENT;
             /* If the strings are not equal, continue search. */
             if (rc)
                 continue;
             rc = ntfs_collate_names(name, name_len,
                     (ntfschar*)((u8*)a +
                     le16_to_cpu(a->name_offset)),
                     a->name_length, 1, CASE_SENSITIVE,
                     upcase, upcase_len);
             if (rc == -1)
                 return -ENOENT;
             if (rc)
                 continue;
         }
         /*
          * The names match or @name not present and attribute is
          * unnamed.  If no @val specified, we have found the attribute
          * and are done.
          */
         if (!val)
             return 0;
         /* @val is present; compare values. */
         else {
             register int rc;
 
             rc = memcmp(val, (u8*)a + le16_to_cpu(
                     a->data.resident.value_offset),
                     min_t(u32, val_len, le32_to_cpu(
                     a->data.resident.value_length)));
             /*
              * If @val collates before the current attribute's
              * value, there is no matching attribute.
              */
             if (!rc) {
                 register u32 avl;
 
                 avl = le32_to_cpu(
                         a->data.resident.value_length);
                 if (val_len == avl)
                     return 0;
                 if (val_len < avl)
                     return -ENOENT;
             } else if (rc < 0)
                 return -ENOENT;
         }
     }
     ntfs_error(vol->sb, "Inode is corrupt.  Run chkdsk.");
     NVolSetErrors(vol);
     return -EIO;
 }
 
 /**
  * load_attribute_list - load an attribute list into memory
  * @vol:        ntfs volume from which to read
  * @runlist:        runlist of the attribute list
  * @al_start:       destination buffer
  * @size:       size of the destination buffer in bytes
  * @initialized_size:   initialized size of the attribute list
  *
  * Walk the runlist @runlist and load all clusters from it copying them into
  * the linear buffer @al. The maximum number of bytes copied to @al is @size
  * bytes. Note, @size does not need to be a multiple of the cluster size. If
  * @initialized_size is less than @size, the region in @al between
  * @initialized_size and @size will be zeroed and not read from disk.
  *
  * Return 0 on success or -errno on error.
  */
 int load_attribute_list(ntfs_volume *vol, runlist *runlist, u8 *al_start,
         const s64 size, const s64 initialized_size)
 {
     LCN lcn;
     u8 *al = al_start;
     u8 *al_end = al + initialized_size;
     runlist_element *rl;
     struct buffer_head *bh;
     struct super_block *sb;
     unsigned long block_size;
     unsigned long block, max_block;
     int err = 0;
     unsigned char block_size_bits;
 
     ntfs_debug("Entering.");
     if (!vol || !runlist || !al || size <= 0 || initialized_size < 0 ||
             initialized_size > size)
         return -EINVAL;
     if (!initialized_size) {
         memset(al, 0, size);
         return 0;
     }
     sb = vol->sb;
     block_size = sb->s_blocksize;
     block_size_bits = sb->s_blocksize_bits;
     down_read(&runlist->lock);
     rl = runlist->rl;
     if (!rl) {
         ntfs_error(sb, "Cannot read attribute list since runlist is "
                 "missing.");
         goto err_out;   
     }
     /* Read all clusters specified by the runlist one run at a time. */
     while (rl->length) {
         lcn = ntfs_rl_vcn_to_lcn(rl, rl->vcn);
         ntfs_debug("Reading vcn = 0x%llx, lcn = 0x%llx.",
                 (unsigned long long)rl->vcn,
                 (unsigned long long)lcn);
         /* The attribute list cannot be sparse. */
         if (lcn < 0) {
             ntfs_error(sb, "ntfs_rl_vcn_to_lcn() failed.  Cannot "
                     "read attribute list.");
             goto err_out;
         }
         block = lcn << vol->cluster_size_bits >> block_size_bits;
         /* Read the run from device in chunks of block_size bytes. */
         max_block = block + (rl->length << vol->cluster_size_bits >>
                 block_size_bits);
         ntfs_debug("max_block = 0x%lx.", max_block);
         do {
             ntfs_debug("Reading block = 0x%lx.", block);
             bh = sb_bread(sb, block);
             if (!bh) {
                 ntfs_error(sb, "sb_bread() failed. Cannot "
                         "read attribute list.");
                 goto err_out;
             }
             if (al + block_size >= al_end)
                 goto do_final;
             memcpy(al, bh->b_data, block_size);
             brelse(bh);
             al += block_size;
         } while (++block < max_block);
         rl++;
     }
     if (initialized_size < size) {
 initialize:
         memset(al_start + initialized_size, 0, size - initialized_size);
     }
 done:
     up_read(&runlist->lock);
     return err;
 do_final:
     if (al < al_end) {
         /*
          * Partial block.
          *
          * Note: The attribute list can be smaller than its allocation
          * by multiple clusters.  This has been encountered by at least
          * two people running Windows XP, thus we cannot do any
          * truncation sanity checking here. (AIA)
          */
         memcpy(al, bh->b_data, al_end - al);
         brelse(bh);
         if (initialized_size < size)
             goto initialize;
         goto done;
     }
     brelse(bh);
     /* Real overflow! */
     ntfs_error(sb, "Attribute list buffer overflow. Read attribute list "
             "is truncated.");
 err_out:
     err = -EIO;
     goto done;
 }
 
 /**
  * ntfs_external_attr_find - find an attribute in the attribute list of an inode
  * @type:   attribute type to find
  * @name:   attribute name to find (optional, i.e. NULL means don't care)
  * @name_len:   attribute name length (only needed if @name present)
  * @ic:     IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
  * @lowest_vcn: lowest vcn to find (optional, non-resident attributes only)
  * @val:    attribute value to find (optional, resident attributes only)
  * @val_len:    attribute value length
  * @ctx:    search context with mft record and attribute to search from
  *
  * You should not need to call this function directly.  Use ntfs_attr_lookup()
  * instead.
  *
  * Find an attribute by searching the attribute list for the corresponding
  * attribute list entry.  Having found the entry, map the mft record if the
  * attribute is in a different mft record/inode, ntfs_attr_find() the attribute
  * in there and return it.
  *
  * On first search @ctx->ntfs_ino must be the base mft record and @ctx must
  * have been obtained from a call to ntfs_attr_get_search_ctx().  On subsequent
  * calls @ctx->ntfs_ino can be any extent inode, too (@ctx->base_ntfs_ino is
  * then the base inode).
  *
  * After finishing with the attribute/mft record you need to call
  * ntfs_attr_put_search_ctx() to cleanup the search context (unmapping any
  * mapped inodes, etc).
  *
  * If the attribute is found, ntfs_external_attr_find() returns 0 and
  * @ctx->attr will point to the found attribute.  @ctx->mrec will point to the
  * mft record in which @ctx->attr is located and @ctx->al_entry will point to
  * the attribute list entry for the attribute.
  *
  * If the attribute is not found, ntfs_external_attr_find() returns -ENOENT and
  * @ctx->attr will point to the attribute in the base mft record before which
  * the attribute being searched for would need to be inserted if such an action
  * were to be desired.  @ctx->mrec will point to the mft record in which
  * @ctx->attr is located and @ctx->al_entry will point to the attribute list
  * entry of the attribute before which the attribute being searched for would
  * need to be inserted if such an action were to be desired.
  *
  * Thus to insert the not found attribute, one wants to add the attribute to
  * @ctx->mrec (the base mft record) and if there is not enough space, the
  * attribute should be placed in a newly allocated extent mft record.  The
  * attribute list entry for the inserted attribute should be inserted in the
  * attribute list attribute at @ctx->al_entry.
  *
  * On actual error, ntfs_external_attr_find() returns -EIO.  In this case
  * @ctx->attr is undefined and in particular do not rely on it not changing.
  */
 static int ntfs_external_attr_find(const ATTR_TYPE type,
         const ntfschar *name, const u32 name_len,
         const IGNORE_CASE_BOOL ic, const VCN lowest_vcn,
         const u8 *val, const u32 val_len, ntfs_attr_search_ctx *ctx)
 {
     ntfs_inode *base_ni, *ni;
     ntfs_volume *vol;
     ATTR_LIST_ENTRY *al_entry, *next_al_entry;
     u8 *al_start, *al_end;
     ATTR_RECORD *a;
     ntfschar *al_name;
     u32 al_name_len;
     int err = 0;
     static const char *es = " Unmount and run chkdsk.";
 
     ni = ctx->ntfs_ino;
     base_ni = ctx->base_ntfs_ino;
     ntfs_debug("Entering for inode 0x%lx, type 0x%x.", ni->mft_no, type);
     if (!base_ni) {
         /* First call happens with the base mft record. */
         base_ni = ctx->base_ntfs_ino = ctx->ntfs_ino;
         ctx->base_mrec = ctx->mrec;
     }
     if (ni == base_ni)
         ctx->base_attr = ctx->attr;
     if (type == AT_END)
         goto not_found;
     vol = base_ni->vol;
     al_start = base_ni->attr_list;
     al_end = al_start + base_ni->attr_list_size;
     if (!ctx->al_entry)
         ctx->al_entry = (ATTR_LIST_ENTRY*)al_start;
     /*
      * Iterate over entries in attribute list starting at @ctx->al_entry,
      * or the entry following that, if @ctx->is_first is 'true'.
      */
     if (ctx->is_first) {
         al_entry = ctx->al_entry;
         ctx->is_first = false;
     } else
         al_entry = (ATTR_LIST_ENTRY*)((u8*)ctx->al_entry +
                 le16_to_cpu(ctx->al_entry->length));
     for (;; al_entry = next_al_entry) {
         /* Out of bounds check. */
         if ((u8*)al_entry < base_ni->attr_list ||
                 (u8*)al_entry > al_end)
             break;  /* Inode is corrupt. */
         ctx->al_entry = al_entry;
         /* Catch the end of the attribute list. */
         if ((u8*)al_entry == al_end)
             goto not_found;
         if (!al_entry->length)
             break;
         if ((u8*)al_entry + 6 > al_end || (u8*)al_entry +
                 le16_to_cpu(al_entry->length) > al_end)
             break;
         next_al_entry = (ATTR_LIST_ENTRY*)((u8*)al_entry +
                 le16_to_cpu(al_entry->length));
         if (le32_to_cpu(al_entry->type) > le32_to_cpu(type))
             goto not_found;
         if (type != al_entry->type)
             continue;
         /*
          * If @name is present, compare the two names.  If @name is
          * missing, assume we want an unnamed attribute.
          */
         al_name_len = al_entry->name_length;
         al_name = (ntfschar*)((u8*)al_entry + al_entry->name_offset);
         if (!name) {
             if (al_name_len)
                 goto not_found;
         } else if (!ntfs_are_names_equal(al_name, al_name_len, name,
                 name_len, ic, vol->upcase, vol->upcase_len)) {
             register int rc;
 
             rc = ntfs_collate_names(name, name_len, al_name,
                     al_name_len, 1, IGNORE_CASE,
                     vol->upcase, vol->upcase_len);
             /*
              * If @name collates before al_name, there is no
              * matching attribute.
              */
             if (rc == -1)
                 goto not_found;
             /* If the strings are not equal, continue search. */
             if (rc)
                 continue;
             /*
              * FIXME: Reverse engineering showed 0, IGNORE_CASE but
              * that is inconsistent with ntfs_attr_find().  The
              * subsequent rc checks were also different.  Perhaps I
              * made a mistake in one of the two.  Need to recheck
              * which is correct or at least see what is going on...
              * (AIA)
              */
             rc = ntfs_collate_names(name, name_len, al_name,
                     al_name_len, 1, CASE_SENSITIVE,
                     vol->upcase, vol->upcase_len);
             if (rc == -1)
                 goto not_found;
             if (rc)
                 continue;
         }
         /*
          * The names match or @name not present and attribute is
          * unnamed.  Now check @lowest_vcn.  Continue search if the
          * next attribute list entry still fits @lowest_vcn.  Otherwise
          * we have reached the right one or the search has failed.
          */
         if (lowest_vcn && (u8*)next_al_entry >= al_start        &&
                 (u8*)next_al_entry + 6 < al_end         &&
                 (u8*)next_al_entry + le16_to_cpu(
                     next_al_entry->length) <= al_end    &&
                 sle64_to_cpu(next_al_entry->lowest_vcn) <=
                     lowest_vcn              &&
                 next_al_entry->type == al_entry->type       &&
                 next_al_entry->name_length == al_name_len   &&
                 ntfs_are_names_equal((ntfschar*)((u8*)
                     next_al_entry +
                     next_al_entry->name_offset),
                     next_al_entry->name_length,
                     al_name, al_name_len, CASE_SENSITIVE,
                     vol->upcase, vol->upcase_len))
             continue;
         if (MREF_LE(al_entry->mft_reference) == ni->mft_no) {
             if (MSEQNO_LE(al_entry->mft_reference) != ni->seq_no) {
                 ntfs_error(vol->sb, "Found stale mft "
                         "reference in attribute list "
                         "of base inode 0x%lx.%s",
                         base_ni->mft_no, es);
                 err = -EIO;
                 break;
             }
         } else { /* Mft references do not match. */
             /* If there is a mapped record unmap it first. */
             if (ni != base_ni)
                 unmap_extent_mft_record(ni);
             /* Do we want the base record back? */
             if (MREF_LE(al_entry->mft_reference) ==
                     base_ni->mft_no) {
                 ni = ctx->ntfs_ino = base_ni;
                 ctx->mrec = ctx->base_mrec;
             } else {
                 /* We want an extent record. */
                 ctx->mrec = map_extent_mft_record(base_ni,
                         le64_to_cpu(
                         al_entry->mft_reference), &ni);
                 if (IS_ERR(ctx->mrec)) {
                     ntfs_error(vol->sb, "Failed to map "
                             "extent mft record "
                             "0x%lx of base inode "
                             "0x%lx.%s",
                             MREF_LE(al_entry->
                             mft_reference),
                             base_ni->mft_no, es);
                     err = PTR_ERR(ctx->mrec);
                     if (err == -ENOENT)
                         err = -EIO;
                     /* Cause @ctx to be sanitized below. */
                     ni = NULL;
                     break;
                 }
                 ctx->ntfs_ino = ni;
             }
             ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
                     le16_to_cpu(ctx->mrec->attrs_offset));
         }
         /*
          * ctx->vfs_ino, ctx->mrec, and ctx->attr now point to the
          * mft record containing the attribute represented by the
          * current al_entry.
          */
         /*
          * We could call into ntfs_attr_find() to find the right
          * attribute in this mft record but this would be less
          * efficient and not quite accurate as ntfs_attr_find() ignores
          * the attribute instance numbers for example which become
          * important when one plays with attribute lists.  Also,
          * because a proper match has been found in the attribute list
          * entry above, the comparison can now be optimized.  So it is
          * worth re-implementing a simplified ntfs_attr_find() here.
          */
         a = ctx->attr;
         /*
          * Use a manual loop so we can still use break and continue
          * with the same meanings as above.
          */
 do_next_attr_loop:
         if ((u8*)a < (u8*)ctx->mrec || (u8*)a > (u8*)ctx->mrec +
                 le32_to_cpu(ctx->mrec->bytes_allocated))
             break;
         if (a->type == AT_END)
             break;
         if (!a->length)
             break;
         if (al_entry->instance != a->instance)
             goto do_next_attr;
         /*
          * If the type and/or the name are mismatched between the
          * attribute list entry and the attribute record, there is
          * corruption so we break and return error EIO.
          */
         if (al_entry->type != a->type)
             break;
         if (!ntfs_are_names_equal((ntfschar*)((u8*)a +
                 le16_to_cpu(a->name_offset)), a->name_length,
                 al_name, al_name_len, CASE_SENSITIVE,
                 vol->upcase, vol->upcase_len))
             break;
         ctx->attr = a;
         /*
          * If no @val specified or @val specified and it matches, we
          * have found it!
          */
         if (!val || (!a->non_resident && le32_to_cpu(
                 a->data.resident.value_length) == val_len &&
                 !memcmp((u8*)a +
                 le16_to_cpu(a->data.resident.value_offset),
                 val, val_len))) {
             ntfs_debug("Done, found.");
             return 0;
         }
 do_next_attr:
         /* Proceed to the next attribute in the current mft record. */
         a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length));
         goto do_next_attr_loop;
     }
     if (!err) {
         ntfs_error(vol->sb, "Base inode 0x%lx contains corrupt "
                 "attribute list attribute.%s", base_ni->mft_no,
                 es);
         err = -EIO;
     }
     if (ni != base_ni) {
         if (ni)
             unmap_extent_mft_record(ni);
         ctx->ntfs_ino = base_ni;
         ctx->mrec = ctx->base_mrec;
         ctx->attr = ctx->base_attr;
     }
     if (err != -ENOMEM)
         NVolSetErrors(vol);
     return err;
 not_found:
     /*
      * If we were looking for AT_END, we reset the search context @ctx and
      * use ntfs_attr_find() to seek to the end of the base mft record.
      */
     if (type == AT_END) {
         ntfs_attr_reinit_search_ctx(ctx);
         return ntfs_attr_find(AT_END, name, name_len, ic, val, val_len,
                 ctx);
     }
     /*
      * The attribute was not found.  Before we return, we want to ensure
      * @ctx->mrec and @ctx->attr indicate the position at which the
      * attribute should be inserted in the base mft record.  Since we also
      * want to preserve @ctx->al_entry we cannot reinitialize the search
      * context using ntfs_attr_reinit_search_ctx() as this would set
      * @ctx->al_entry to NULL.  Thus we do the necessary bits manually (see
      * ntfs_attr_init_search_ctx() below).  Note, we _only_ preserve
      * @ctx->al_entry as the remaining fields (base_*) are identical to
      * their non base_ counterparts and we cannot set @ctx->base_attr
      * correctly yet as we do not know what @ctx->attr will be set to by
      * the call to ntfs_attr_find() below.
      */
     if (ni != base_ni)
         unmap_extent_mft_record(ni);
     ctx->mrec = ctx->base_mrec;
     ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
             le16_to_cpu(ctx->mrec->attrs_offset));
     ctx->is_first = true;
     ctx->ntfs_ino = base_ni;
     ctx->base_ntfs_ino = NULL;
     ctx->base_mrec = NULL;
     ctx->base_attr = NULL;
     /*
      * In case there are multiple matches in the base mft record, need to
      * keep enumerating until we get an attribute not found response (or
      * another error), otherwise we would keep returning the same attribute
      * over and over again and all programs using us for enumeration would
      * lock up in a tight loop.
      */
     do {
         err = ntfs_attr_find(type, name, name_len, ic, val, val_len,
                 ctx);
     } while (!err);
     ntfs_debug("Done, not found.");
     return err;
 }
 
 /**
  * ntfs_attr_lookup - find an attribute in an ntfs inode
  * @type:   attribute type to find
  * @name:   attribute name to find (optional, i.e. NULL means don't care)
  * @name_len:   attribute name length (only needed if @name present)
  * @ic:     IGNORE_CASE or CASE_SENSITIVE (ignored if @name not present)
  * @lowest_vcn: lowest vcn to find (optional, non-resident attributes only)
  * @val:    attribute value to find (optional, resident attributes only)
  * @val_len:    attribute value length
  * @ctx:    search context with mft record and attribute to search from
  *
  * Find an attribute in an ntfs inode.  On first search @ctx->ntfs_ino must
  * be the base mft record and @ctx must have been obtained from a call to
  * ntfs_attr_get_search_ctx().
  *
  * This function transparently handles attribute lists and @ctx is used to
  * continue searches where they were left off at.
  *
  * After finishing with the attribute/mft record you need to call
  * ntfs_attr_put_search_ctx() to cleanup the search context (unmapping any
  * mapped inodes, etc).
  *
  * Return 0 if the search was successful and -errno if not.
  *
  * When 0, @ctx->attr is the found attribute and it is in mft record
  * @ctx->mrec.  If an attribute list attribute is present, @ctx->al_entry is
  * the attribute list entry of the found attribute.
  *
  * When -ENOENT, @ctx->attr is the attribute which collates just after the
  * attribute being searched for, i.e. if one wants to add the attribute to the
  * mft record this is the correct place to insert it into.  If an attribute
  * list attribute is present, @ctx->al_entry is the attribute list entry which
  * collates just after the attribute list entry of the attribute being searched
  * for, i.e. if one wants to add the attribute to the mft record this is the
  * correct place to insert its attribute list entry into.
  *
  * When -errno != -ENOENT, an error occurred during the lookup.  @ctx->attr is
  * then undefined and in particular you should not rely on it not changing.
  */
 int ntfs_attr_lookup(const ATTR_TYPE type, const ntfschar *name,
         const u32 name_len, const IGNORE_CASE_BOOL ic,
         const VCN lowest_vcn, const u8 *val, const u32 val_len,
         ntfs_attr_search_ctx *ctx)
 {
     ntfs_inode *base_ni;
 
     ntfs_debug("Entering.");
     BUG_ON(IS_ERR(ctx->mrec));
     if (ctx->base_ntfs_ino)
         base_ni = ctx->base_ntfs_ino;
     else
         base_ni = ctx->ntfs_ino;
     /* Sanity check, just for debugging really. */
     BUG_ON(!base_ni);
     if (!NInoAttrList(base_ni) || type == AT_ATTRIBUTE_LIST)
         return ntfs_attr_find(type, name, name_len, ic, val, val_len,
                 ctx);
     return ntfs_external_attr_find(type, name, name_len, ic, lowest_vcn,
             val, val_len, ctx);
 }
 
 /**
  * ntfs_attr_init_search_ctx - initialize an attribute search context
  * @ctx:    attribute search context to initialize
  * @ni:     ntfs inode with which to initialize the search context
  * @mrec:   mft record with which to initialize the search context
  *
  * Initialize the attribute search context @ctx with @ni and @mrec.
  */
 static inline void ntfs_attr_init_search_ctx(ntfs_attr_search_ctx *ctx,
         ntfs_inode *ni, MFT_RECORD *mrec)
 {
     *ctx = (ntfs_attr_search_ctx) {
         .mrec = mrec,
         /* Sanity checks are performed elsewhere. */
         .attr = (ATTR_RECORD*)((u8*)mrec +
                 le16_to_cpu(mrec->attrs_offset)),
         .is_first = true,
         .ntfs_ino = ni,
     };
 }
 
 /**
  * ntfs_attr_reinit_search_ctx - reinitialize an attribute search context
  * @ctx:    attribute search context to reinitialize
  *
  * Reinitialize the attribute search context @ctx, unmapping an associated
  * extent mft record if present, and initialize the search context again.
  *
  * This is used when a search for a new attribute is being started to reset
  * the search context to the beginning.
  */
 void ntfs_attr_reinit_search_ctx(ntfs_attr_search_ctx *ctx)
 {
     if (likely(!ctx->base_ntfs_ino)) {
         /* No attribute list. */
         ctx->is_first = true;
         /* Sanity checks are performed elsewhere. */
         ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
                 le16_to_cpu(ctx->mrec->attrs_offset));
         /*
          * This needs resetting due to ntfs_external_attr_find() which
          * can leave it set despite having zeroed ctx->base_ntfs_ino.
          */
         ctx->al_entry = NULL;
         return;
     } /* Attribute list. */
     if (ctx->ntfs_ino != ctx->base_ntfs_ino)
         unmap_extent_mft_record(ctx->ntfs_ino);
     ntfs_attr_init_search_ctx(ctx, ctx->base_ntfs_ino, ctx->base_mrec);
     return;
 }
 
 /**
  * ntfs_attr_get_search_ctx - allocate/initialize a new attribute search context
  * @ni:     ntfs inode with which to initialize the search context
  * @mrec:   mft record with which to initialize the search context
  *
  * Allocate a new attribute search context, initialize it with @ni and @mrec,
  * and return it. Return NULL if allocation failed.
  */
 ntfs_attr_search_ctx *ntfs_attr_get_search_ctx(ntfs_inode *ni, MFT_RECORD *mrec)
 {
     ntfs_attr_search_ctx *ctx;
 
     ctx = kmem_cache_alloc(ntfs_attr_ctx_cache, GFP_NOFS);
     if (ctx)
         ntfs_attr_init_search_ctx(ctx, ni, mrec);
     return ctx;
 }
 
 /**
  * ntfs_attr_put_search_ctx - release an attribute search context
  * @ctx:    attribute search context to free
  *
  * Release the attribute search context @ctx, unmapping an associated extent
  * mft record if present.
  */
 void ntfs_attr_put_search_ctx(ntfs_attr_search_ctx *ctx)
 {
     if (ctx->base_ntfs_ino && ctx->ntfs_ino != ctx->base_ntfs_ino)
         unmap_extent_mft_record(ctx->ntfs_ino);
     kmem_cache_free(ntfs_attr_ctx_cache, ctx);
     return;
 }
 
 #ifdef NTFS_RW
 
 /**
  * ntfs_attr_find_in_attrdef - find an attribute in the $AttrDef system file
  * @vol:    ntfs volume to which the attribute belongs
  * @type:   attribute type which to find
  *
  * Search for the attribute definition record corresponding to the attribute
  * @type in the $AttrDef system file.
  *
  * Return the attribute type definition record if found and NULL if not found.
  */
 static ATTR_DEF *ntfs_attr_find_in_attrdef(const ntfs_volume *vol,
         const ATTR_TYPE type)
 {
     ATTR_DEF *ad;
 
     BUG_ON(!vol->attrdef);
     BUG_ON(!type);
     for (ad = vol->attrdef; (u8*)ad - (u8*)vol->attrdef <
             vol->attrdef_size && ad->type; ++ad) {
         /* We have not found it yet, carry on searching. */
         if (likely(le32_to_cpu(ad->type) < le32_to_cpu(type)))
             continue;
         /* We found the attribute; return it. */
         if (likely(ad->type == type))
             return ad;
         /* We have gone too far already.  No point in continuing. */
         break;
     }
     /* Attribute not found. */
     ntfs_debug("Attribute type 0x%x not found in $AttrDef.",
             le32_to_cpu(type));
     return NULL;
 }
 
 /**
  * ntfs_attr_size_bounds_check - check a size of an attribute type for validity
  * @vol:    ntfs volume to which the attribute belongs
  * @type:   attribute type which to check
  * @size:   size which to check
  *
  * Check whether the @size in bytes is valid for an attribute of @type on the
  * ntfs volume @vol.  This information is obtained from $AttrDef system file.
  *
  * Return 0 if valid, -ERANGE if not valid, or -ENOENT if the attribute is not
  * listed in $AttrDef.
  */
 int ntfs_attr_size_bounds_check(const ntfs_volume *vol, const ATTR_TYPE type,
         const s64 size)
 {
     ATTR_DEF *ad;
 
     BUG_ON(size < 0);
     /*
      * $ATTRIBUTE_LIST has a maximum size of 256kiB, but this is not
      * listed in $AttrDef.
      */
     if (unlikely(type == AT_ATTRIBUTE_LIST && size > 256 * 1024))
         return -ERANGE;
     /* Get the $AttrDef entry for the attribute @type. */
     ad = ntfs_attr_find_in_attrdef(vol, type);
     if (unlikely(!ad))
         return -ENOENT;
     /* Do the bounds check. */
     if (((sle64_to_cpu(ad->min_size) > 0) &&
             size < sle64_to_cpu(ad->min_size)) ||
             ((sle64_to_cpu(ad->max_size) > 0) && size >
             sle64_to_cpu(ad->max_size)))
         return -ERANGE;
     return 0;
 }
 
 /**
  * ntfs_attr_can_be_non_resident - check if an attribute can be non-resident
  * @vol:    ntfs volume to which the attribute belongs
  * @type:   attribute type which to check
  *
  * Check whether the attribute of @type on the ntfs volume @vol is allowed to
  * be non-resident.  This information is obtained from $AttrDef system file.
  *
  * Return 0 if the attribute is allowed to be non-resident, -EPERM if not, and
  * -ENOENT if the attribute is not listed in $AttrDef.
  */
 int ntfs_attr_can_be_non_resident(const ntfs_volume *vol, const ATTR_TYPE type)
 {
     ATTR_DEF *ad;
 
     /* Find the attribute definition record in $AttrDef. */
     ad = ntfs_attr_find_in_attrdef(vol, type);
     if (unlikely(!ad))
         return -ENOENT;
     /* Check the flags and return the result. */
     if (ad->flags & ATTR_DEF_RESIDENT)
         return -EPERM;
     return 0;
 }
 
 /**
  * ntfs_attr_can_be_resident - check if an attribute can be resident
  * @vol:    ntfs volume to which the attribute belongs
  * @type:   attribute type which to check
  *
  * Check whether the attribute of @type on the ntfs volume @vol is allowed to
  * be resident.  This information is derived from our ntfs knowledge and may
  * not be completely accurate, especially when user defined attributes are
  * present.  Basically we allow everything to be resident except for index
  * allocation and $EA attributes.
  *
  * Return 0 if the attribute is allowed to be non-resident and -EPERM if not.
  *
  * Warning: In the system file $MFT the attribute $Bitmap must be non-resident
  *      otherwise windows will not boot (blue screen of death)!  We cannot
  *      check for this here as we do not know which inode's $Bitmap is
  *      being asked about so the caller needs to special case this.
  */
 int ntfs_attr_can_be_resident(const ntfs_volume *vol, const ATTR_TYPE type)
 {
     if (type == AT_INDEX_ALLOCATION)
         return -EPERM;
     return 0;
 }
 
 /**
  * ntfs_attr_record_resize - resize an attribute record
  * @m:      mft record containing attribute record
  * @a:      attribute record to resize
  * @new_size:   new size in bytes to which to resize the attribute record @a
  *
  * Resize the attribute record @a, i.e. the resident part of the attribute, in
  * the mft record @m to @new_size bytes.
  *
  * Return 0 on success and -errno on error.  The following error codes are
  * defined:
  *  -ENOSPC - Not enough space in the mft record @m to perform the resize.
  *
  * Note: On error, no modifications have been performed whatsoever.
  *
  * Warning: If you make a record smaller without having copied all the data you
  *      are interested in the data may be overwritten.
  */
 int ntfs_attr_record_resize(MFT_RECORD *m, ATTR_RECORD *a, u32 new_size)
 {
     ntfs_debug("Entering for new_size %u.", new_size);
     /* Align to 8 bytes if it is not already done. */
     if (new_size & 7)
         new_size = (new_size + 7) & ~7;
     /* If the actual attribute length has changed, move things around. */
     if (new_size != le32_to_cpu(a->length)) {
         u32 new_muse = le32_to_cpu(m->bytes_in_use) -
                 le32_to_cpu(a->length) + new_size;
         /* Not enough space in this mft record. */
         if (new_muse > le32_to_cpu(m->bytes_allocated))
             return -ENOSPC;
         /* Move attributes following @a to their new location. */
         memmove((u8*)a + new_size, (u8*)a + le32_to_cpu(a->length),
                 le32_to_cpu(m->bytes_in_use) - ((u8*)a -
                 (u8*)m) - le32_to_cpu(a->length));
         /* Adjust @m to reflect the change in used space. */
         m->bytes_in_use = cpu_to_le32(new_muse);
         /* Adjust @a to reflect the new size. */
         if (new_size >= offsetof(ATTR_REC, length) + sizeof(a->length))
             a->length = cpu_to_le32(new_size);
     }
     return 0;
 }
 
 /**
  * ntfs_resident_attr_value_resize - resize the value of a resident attribute
  * @m:      mft record containing attribute record
  * @a:      attribute record whose value to resize
  * @new_size:   new size in bytes to which to resize the attribute value of @a
  *
  * Resize the value of the attribute @a in the mft record @m to @new_size bytes.
  * If the value is made bigger, the newly allocated space is cleared.
  *
  * Return 0 on success and -errno on error.  The following error codes are
  * defined:
  *  -ENOSPC - Not enough space in the mft record @m to perform the resize.
  *
  * Note: On error, no modifications have been performed whatsoever.
  *
  * Warning: If you make a record smaller without having copied all the data you
  *      are interested in the data may be overwritten.
  */
 int ntfs_resident_attr_value_resize(MFT_RECORD *m, ATTR_RECORD *a,
         const u32 new_size)
 {
     u32 old_size;
 
     /* Resize the resident part of the attribute record. */
     if (ntfs_attr_record_resize(m, a,
             le16_to_cpu(a->data.resident.value_offset) + new_size))
         return -ENOSPC;
     /*
      * The resize succeeded!  If we made the attribute value bigger, clear
      * the area between the old size and @new_size.
      */
     old_size = le32_to_cpu(a->data.resident.value_length);
     if (new_size > old_size)
         memset((u8*)a + le16_to_cpu(a->data.resident.value_offset) +
                 old_size, 0, new_size - old_size);
     /* Finally update the length of the attribute value. */
     a->data.resident.value_length = cpu_to_le32(new_size);
     return 0;
 }
 
 /**
  * ntfs_attr_make_non_resident - convert a resident to a non-resident attribute
  * @ni:     ntfs inode describing the attribute to convert
  * @data_size:  size of the resident data to copy to the non-resident attribute
  *
  * Convert the resident ntfs attribute described by the ntfs inode @ni to a
  * non-resident one.
  *
  * @data_size must be equal to the attribute value size.  This is needed since
  * we need to know the size before we can map the mft record and our callers
  * always know it.  The reason we cannot simply read the size from the vfs
  * inode i_size is that this is not necessarily uptodate.  This happens when
  * ntfs_attr_make_non_resident() is called in the ->truncate call path(s).
  *
  * Return 0 on success and -errno on error.  The following error return codes
  * are defined:
  *  -EPERM  - The attribute is not allowed to be non-resident.
  *  -ENOMEM - Not enough memory.
  *  -ENOSPC - Not enough disk space.
  *  -EINVAL - Attribute not defined on the volume.
  *  -EIO    - I/o error or other error.
  * Note that -ENOSPC is also returned in the case that there is not enough
  * space in the mft record to do the conversion.  This can happen when the mft
  * record is already very full.  The caller is responsible for trying to make
  * space in the mft record and trying again.  FIXME: Do we need a separate
  * error return code for this kind of -ENOSPC or is it always worth trying
  * again in case the attribute may then fit in a resident state so no need to
  * make it non-resident at all?  Ho-hum...  (AIA)
  *
  * NOTE to self: No changes in the attribute list are required to move from
  *       a resident to a non-resident attribute.
  *
  * Locking: - The caller must hold i_mutex on the inode.
  */
 int ntfs_attr_make_non_resident(ntfs_inode *ni, const u32 data_size)
 {
     s64 new_size;
     struct inode *vi = VFS_I(ni);
     ntfs_volume *vol = ni->vol;
     ntfs_inode *base_ni;
     MFT_RECORD *m;
     ATTR_RECORD *a;
     ntfs_attr_search_ctx *ctx;
     struct page *page;
     runlist_element *rl;
     u8 *kaddr;
     unsigned long flags;
     int mp_size, mp_ofs, name_ofs, arec_size, err, err2;
     u32 attr_size;
     u8 old_res_attr_flags;
 
     /* Check that the attribute is allowed to be non-resident. */
     err = ntfs_attr_can_be_non_resident(vol, ni->type);
     if (unlikely(err)) {
         if (err == -EPERM)
             ntfs_debug("Attribute is not allowed to be "
                     "non-resident.");
         else
             ntfs_debug("Attribute not defined on the NTFS "
                     "volume!");
         return err;
     }
     /*
      * FIXME: Compressed and encrypted attributes are not supported when
      * writing and we should never have gotten here for them.
      */
     BUG_ON(NInoCompressed(ni));
     BUG_ON(NInoEncrypted(ni));
     /*
      * The size needs to be aligned to a cluster boundary for allocation
      * purposes.
      */
     new_size = (data_size + vol->cluster_size - 1) &
             ~(vol->cluster_size - 1);
     if (new_size > 0) {
         /*
          * Will need the page later and since the page lock nests
          * outside all ntfs locks, we need to get the page now.
          */
         page = find_or_create_page(vi->i_mapping, 0,
                 mapping_gfp_mask(vi->i_mapping));
         if (unlikely(!page))
             return -ENOMEM;
         /* Start by allocating clusters to hold the attribute value. */
         rl = ntfs_cluster_alloc(vol, 0, new_size >>
                 vol->cluster_size_bits, -1, DATA_ZONE, true);
         if (IS_ERR(rl)) {
             err = PTR_ERR(rl);
             ntfs_debug("Failed to allocate cluster%s, error code "
                     "%i.", (new_size >>
                     vol->cluster_size_bits) > 1 ? "s" : "",
                     err);
             goto page_err_out;
         }
     } else {
         rl = NULL;
         page = NULL;
     }
     /* Determine the size of the mapping pairs array. */
     mp_size = ntfs_get_size_for_mapping_pairs(vol, rl, 0, -1);
     if (unlikely(mp_size < 0)) {
         err = mp_size;
         ntfs_debug("Failed to get size for mapping pairs array, error "
                 "code %i.", err);
         goto rl_err_out;
     }
     down_write(&ni->runlist.lock);
     if (!NInoAttr(ni))
         base_ni = ni;
     else
         base_ni = ni->ext.base_ntfs_ino;
     m = map_mft_record(base_ni);
     if (IS_ERR(m)) {
         err = PTR_ERR(m);
         m = NULL;
         ctx = NULL;
         goto err_out;
     }
     ctx = ntfs_attr_get_search_ctx(base_ni, m);
     if (unlikely(!ctx)) {
         err = -ENOMEM;
         goto err_out;
     }
     err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
             CASE_SENSITIVE, 0, NULL, 0, ctx);
     if (unlikely(err)) {
         if (err == -ENOENT)
             err = -EIO;
         goto err_out;
     }
     m = ctx->mrec;
     a = ctx->attr;
     BUG_ON(NInoNonResident(ni));
     BUG_ON(a->non_resident);
     /*
      * Calculate new offsets for the name and the mapping pairs array.
      */
     if (NInoSparse(ni) || NInoCompressed(ni))
         name_ofs = (offsetof(ATTR_REC,
                 data.non_resident.compressed_size) +
                 sizeof(a->data.non_resident.compressed_size) +
                 7) & ~7;
     else
         name_ofs = (offsetof(ATTR_REC,
                 data.non_resident.compressed_size) + 7) & ~7;
     mp_ofs = (name_ofs + a->name_length * sizeof(ntfschar) + 7) & ~7;
     /*
      * Determine the size of the resident part of the now non-resident
      * attribute record.
      */
     arec_size = (mp_ofs + mp_size + 7) & ~7;
     /*
      * If the page is not uptodate bring it uptodate by copying from the
      * attribute value.
      */
     attr_size = le32_to_cpu(a->data.resident.value_length);
     BUG_ON(attr_size != data_size);
     if (page && !PageUptodate(page)) {
         kaddr = kmap_atomic(page);
         memcpy(kaddr, (u8*)a +
                 le16_to_cpu(a->data.resident.value_offset),
                 attr_size);
         memset(kaddr + attr_size, 0, PAGE_SIZE - attr_size);
         kunmap_atomic(kaddr);
         flush_dcache_page(page);
         SetPageUptodate(page);
     }
     /* Backup the attribute flag. */
     old_res_attr_flags = a->data.resident.flags;
     /* Resize the resident part of the attribute record. */
     err = ntfs_attr_record_resize(m, a, arec_size);
     if (unlikely(err))
         goto err_out;
     /*
      * Convert the resident part of the attribute record to describe a
      * non-resident attribute.
      */
     a->non_resident = 1;
     /* Move the attribute name if it exists and update the offset. */
     if (a->name_length)
         memmove((u8*)a + name_ofs, (u8*)a + le16_to_cpu(a->name_offset),
                 a->name_length * sizeof(ntfschar));
     a->name_offset = cpu_to_le16(name_ofs);
     /* Setup the fields specific to non-resident attributes. */
     a->data.non_resident.lowest_vcn = 0;
     a->data.non_resident.highest_vcn = cpu_to_sle64((new_size - 1) >>
             vol->cluster_size_bits);
     a->data.non_resident.mapping_pairs_offset = cpu_to_le16(mp_ofs);
     memset(&a->data.non_resident.reserved, 0,
             sizeof(a->data.non_resident.reserved));
     a->data.non_resident.allocated_size = cpu_to_sle64(new_size);
     a->data.non_resident.data_size =
             a->data.non_resident.initialized_size =
             cpu_to_sle64(attr_size);
     if (NInoSparse(ni) || NInoCompressed(ni)) {
         a->data.non_resident.compression_unit = 0;
         if (NInoCompressed(ni) || vol->major_ver < 3)
             a->data.non_resident.compression_unit = 4;
         a->data.non_resident.compressed_size =
                 a->data.non_resident.allocated_size;
     } else
         a->data.non_resident.compression_unit = 0;
     /* Generate the mapping pairs array into the attribute record. */
     err = ntfs_mapping_pairs_build(vol, (u8*)a + mp_ofs,
             arec_size - mp_ofs, rl, 0, -1, NULL);
     if (unlikely(err)) {
         ntfs_debug("Failed to build mapping pairs, error code %i.",
                 err);
         goto undo_err_out;
     }
     /* Setup the in-memory attribute structure to be non-resident. */
     ni->runlist.rl = rl;
     write_lock_irqsave(&ni->size_lock, flags);
     ni->allocated_size = new_size;
     if (NInoSparse(ni) || NInoCompressed(ni)) {
         ni->itype.compressed.size = ni->allocated_size;
         if (a->data.non_resident.compression_unit) {
             ni->itype.compressed.block_size = 1U << (a->data.
                     non_resident.compression_unit +
                     vol->cluster_size_bits);
             ni->itype.compressed.block_size_bits =
                     ffs(ni->itype.compressed.block_size) -
                     1;
             ni->itype.compressed.block_clusters = 1U <<
                     a->data.non_resident.compression_unit;
         } else {
             ni->itype.compressed.block_size = 0;
             ni->itype.compressed.block_size_bits = 0;
             ni->itype.compressed.block_clusters = 0;
         }
         vi->i_blocks = ni->itype.compressed.size >> 9;
     } else
         vi->i_blocks = ni->allocated_size >> 9;
     write_unlock_irqrestore(&ni->size_lock, flags);
     /*
      * This needs to be last since the address space operations ->read_folio
      * and ->writepage can run concurrently with us as they are not
      * serialized on i_mutex.  Note, we are not allowed to fail once we flip
      * this switch, which is another reason to do this last.
      */
     NInoSetNonResident(ni);
     /* Mark the mft record dirty, so it gets written back. */
     flush_dcache_mft_record_page(ctx->ntfs_ino);
     mark_mft_record_dirty(ctx->ntfs_ino);
     ntfs_attr_put_search_ctx(ctx);
     unmap_mft_record(base_ni);
     up_write(&ni->runlist.lock);
     if (page) {
         set_page_dirty(page);
         unlock_page(page);
         put_page(page);
     }
     ntfs_debug("Done.");
     return 0;
 undo_err_out:
     /* Convert the attribute back into a resident attribute. */
     a->non_resident = 0;
     /* Move the attribute name if it exists and update the offset. */
     name_ofs = (offsetof(ATTR_RECORD, data.resident.reserved) +
             sizeof(a->data.resident.reserved) + 7) & ~7;
     if (a->name_length)
         memmove((u8*)a + name_ofs, (u8*)a + le16_to_cpu(a->name_offset),
                 a->name_length * sizeof(ntfschar));
     mp_ofs = (name_ofs + a->name_length * sizeof(ntfschar) + 7) & ~7;
     a->name_offset = cpu_to_le16(name_ofs);
     arec_size = (mp_ofs + attr_size + 7) & ~7;
     /* Resize the resident part of the attribute record. */
     err2 = ntfs_attr_record_resize(m, a, arec_size);
     if (unlikely(err2)) {
         /*
          * This cannot happen (well if memory corruption is at work it
          * could happen in theory), but deal with it as well as we can.
          * If the old size is too small, truncate the attribute,
          * otherwise simply give it a larger allocated size.
          * FIXME: Should check whether chkdsk complains when the
          * allocated size is much bigger than the resident value size.
          */
         arec_size = le32_to_cpu(a->length);
         if ((mp_ofs + attr_size) > arec_size) {
             err2 = attr_size;
             attr_size = arec_size - mp_ofs;
             ntfs_error(vol->sb, "Failed to undo partial resident "
                     "to non-resident attribute "
                     "conversion.  Truncating inode 0x%lx, "
                     "attribute type 0x%x from %i bytes to "
                     "%i bytes to maintain metadata "
                     "consistency.  THIS MEANS YOU ARE "
                     "LOSING %i BYTES DATA FROM THIS %s.",
                     vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type),
                     err2, attr_size, err2 - attr_size,
                     ((ni->type == AT_DATA) &&
                     !ni->name_len) ? "FILE": "ATTRIBUTE");
             write_lock_irqsave(&ni->size_lock, flags);
             ni->initialized_size = attr_size;
             i_size_write(vi, attr_size);
             write_unlock_irqrestore(&ni->size_lock, flags);
         }
     }
     /* Setup the fields specific to resident attributes. */
     a->data.resident.value_length = cpu_to_le32(attr_size);
     a->data.resident.value_offset = cpu_to_le16(mp_ofs);
     a->data.resident.flags = old_res_attr_flags;
     memset(&a->data.resident.reserved, 0,
             sizeof(a->data.resident.reserved));
     /* Copy the data from the page back to the attribute value. */
     if (page) {
         kaddr = kmap_atomic(page);
         memcpy((u8*)a + mp_ofs, kaddr, attr_size);
         kunmap_atomic(kaddr);
     }
     /* Setup the allocated size in the ntfs inode in case it changed. */
     write_lock_irqsave(&ni->size_lock, flags);
     ni->allocated_size = arec_size - mp_ofs;
     write_unlock_irqrestore(&ni->size_lock, flags);
     /* Mark the mft record dirty, so it gets written back. */
     flush_dcache_mft_record_page(ctx->ntfs_ino);
     mark_mft_record_dirty(ctx->ntfs_ino);
 err_out:
     if (ctx)
         ntfs_attr_put_search_ctx(ctx);
     if (m)
         unmap_mft_record(base_ni);
     ni->runlist.rl = NULL;
     up_write(&ni->runlist.lock);
 rl_err_out:
     if (rl) {
         if (ntfs_cluster_free_from_rl(vol, rl) < 0) {
             ntfs_error(vol->sb, "Failed to release allocated "
                     "cluster(s) in error code path.  Run "
                     "chkdsk to recover the lost "
                     "cluster(s).");
             NVolSetErrors(vol);
         }
         ntfs_free(rl);
 page_err_out:
         unlock_page(page);
         put_page(page);
     }
     if (err == -EINVAL)
         err = -EIO;
     return err;
 }
 
 /**
  * ntfs_attr_extend_allocation - extend the allocated space of an attribute
  * @ni:         ntfs inode of the attribute whose allocation to extend
  * @new_alloc_size: new size in bytes to which to extend the allocation to
  * @new_data_size:  new size in bytes to which to extend the data to
  * @data_start:     beginning of region which is required to be non-sparse
  *
  * Extend the allocated space of an attribute described by the ntfs inode @ni
  * to @new_alloc_size bytes.  If @data_start is -1, the whole extension may be
  * implemented as a hole in the file (as long as both the volume and the ntfs
  * inode @ni have sparse support enabled).  If @data_start is >= 0, then the
  * region between the old allocated size and @data_start - 1 may be made sparse
  * but the regions between @data_start and @new_alloc_size must be backed by
  * actual clusters.
  *
  * If @new_data_size is -1, it is ignored.  If it is >= 0, then the data size
  * of the attribute is extended to @new_data_size.  Note that the i_size of the
  * vfs inode is not updated.  Only the data size in the base attribute record
  * is updated.  The caller has to update i_size separately if this is required.
  * WARNING: It is a BUG() for @new_data_size to be smaller than the old data
  * size as well as for @new_data_size to be greater than @new_alloc_size.
  *
  * For resident attributes this involves resizing the attribute record and if
  * necessary moving it and/or other attributes into extent mft records and/or
  * converting the attribute to a non-resident attribute which in turn involves
  * extending the allocation of a non-resident attribute as described below.
  *
  * For non-resident attributes this involves allocating clusters in the data
  * zone on the volume (except for regions that are being made sparse) and
  * extending the run list to describe the allocated clusters as well as
  * updating the mapping pairs array of the attribute.  This in turn involves
  * resizing the attribute record and if necessary moving it and/or other
  * attributes into extent mft records and/or splitting the attribute record
  * into multiple extent attribute records.
  *
  * Also, the attribute list attribute is updated if present and in some of the
  * above cases (the ones where extent mft records/attributes come into play),
  * an attribute list attribute is created if not already present.
  *
  * Return the new allocated size on success and -errno on error.  In the case
  * that an error is encountered but a partial extension at least up to
  * @data_start (if present) is possible, the allocation is partially extended
  * and this is returned.  This means the caller must check the returned size to
  * determine if the extension was partial.  If @data_start is -1 then partial
  * allocations are not performed.
  *
  * WARNING: Do not call ntfs_attr_extend_allocation() for $MFT/$DATA.
  *
  * Locking: This function takes the runlist lock of @ni for writing as well as
  * locking the mft record of the base ntfs inode.  These locks are maintained
  * throughout execution of the function.  These locks are required so that the
  * attribute can be resized safely and so that it can for example be converted
  * from resident to non-resident safely.
  *
  * TODO: At present attribute list attribute handling is not implemented.
  *
  * TODO: At present it is not safe to call this function for anything other
  * than the $DATA attribute(s) of an uncompressed and unencrypted file.
  */
 s64 ntfs_attr_extend_allocation(ntfs_inode *ni, s64 new_alloc_size,
         const s64 new_data_size, const s64 data_start)
 {
     VCN vcn;
     s64 ll, allocated_size, start = data_start;
     struct inode *vi = VFS_I(ni);
     ntfs_volume *vol = ni->vol;
     ntfs_inode *base_ni;
     MFT_RECORD *m;
     ATTR_RECORD *a;
     ntfs_attr_search_ctx *ctx;
     runlist_element *rl, *rl2;
     unsigned long flags;
     int err, mp_size;
     u32 attr_len = 0; /* Silence stupid gcc warning. */
     bool mp_rebuilt;
 
 #ifdef DEBUG
     read_lock_irqsave(&ni->size_lock, flags);
     allocated_size = ni->allocated_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
             "old_allocated_size 0x%llx, "
             "new_allocated_size 0x%llx, new_data_size 0x%llx, "
             "data_start 0x%llx.", vi->i_ino,
             (unsigned)le32_to_cpu(ni->type),
             (unsigned long long)allocated_size,
             (unsigned long long)new_alloc_size,
             (unsigned long long)new_data_size,
             (unsigned long long)start);
 #endif
 retry_extend:
     /*
      * For non-resident attributes, @start and @new_size need to be aligned
      * to cluster boundaries for allocation purposes.
      */
     if (NInoNonResident(ni)) {
         if (start > 0)
             start &= ~(s64)vol->cluster_size_mask;
         new_alloc_size = (new_alloc_size + vol->cluster_size - 1) &
                 ~(s64)vol->cluster_size_mask;
     }
     BUG_ON(new_data_size >= 0 && new_data_size > new_alloc_size);
     /* Check if new size is allowed in $AttrDef. */
     err = ntfs_attr_size_bounds_check(vol, ni->type, new_alloc_size);
     if (unlikely(err)) {
         /* Only emit errors when the write will fail completely. */
         read_lock_irqsave(&ni->size_lock, flags);
         allocated_size = ni->allocated_size;
         read_unlock_irqrestore(&ni->size_lock, flags);
         if (start < 0 || start >= allocated_size) {
             if (err == -ERANGE) {
                 ntfs_error(vol->sb, "Cannot extend allocation "
                         "of inode 0x%lx, attribute "
                         "type 0x%x, because the new "
                         "allocation would exceed the "
                         "maximum allowed size for "
                         "this attribute type.",
                         vi->i_ino, (unsigned)
                         le32_to_cpu(ni->type));
             } else {
                 ntfs_error(vol->sb, "Cannot extend allocation "
                         "of inode 0x%lx, attribute "
                         "type 0x%x, because this "
                         "attribute type is not "
                         "defined on the NTFS volume.  "
                         "Possible corruption!  You "
                         "should run chkdsk!",
                         vi->i_ino, (unsigned)
                         le32_to_cpu(ni->type));
             }
         }
         /* Translate error code to be POSIX conformant for write(2). */
         if (err == -ERANGE)
             err = -EFBIG;
         else
             err = -EIO;
         return err;
     }
     if (!NInoAttr(ni))
         base_ni = ni;
     else
         base_ni = ni->ext.base_ntfs_ino;
     /*
      * We will be modifying both the runlist (if non-resident) and the mft
      * record so lock them both down.
      */
     down_write(&ni->runlist.lock);
     m = map_mft_record(base_ni);
     if (IS_ERR(m)) {
         err = PTR_ERR(m);
         m = NULL;
         ctx = NULL;
         goto err_out;
     }
     ctx = ntfs_attr_get_search_ctx(base_ni, m);
     if (unlikely(!ctx)) {
         err = -ENOMEM;
         goto err_out;
     }
     read_lock_irqsave(&ni->size_lock, flags);
     allocated_size = ni->allocated_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     /*
      * If non-resident, seek to the last extent.  If resident, there is
      * only one extent, so seek to that.
      */
     vcn = NInoNonResident(ni) ? allocated_size >> vol->cluster_size_bits :
             0;
     /*
      * Abort if someone did the work whilst we waited for the locks.  If we
      * just converted the attribute from resident to non-resident it is
      * likely that exactly this has happened already.  We cannot quite
      * abort if we need to update the data size.
      */
     if (unlikely(new_alloc_size <= allocated_size)) {
         ntfs_debug("Allocated size already exceeds requested size.");
         new_alloc_size = allocated_size;
         if (new_data_size < 0)
             goto done;
         /*
          * We want the first attribute extent so that we can update the
          * data size.
          */
         vcn = 0;
     }
     err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
             CASE_SENSITIVE, vcn, NULL, 0, ctx);
     if (unlikely(err)) {
         if (err == -ENOENT)
             err = -EIO;
         goto err_out;
     }
     m = ctx->mrec;
     a = ctx->attr;
     /* Use goto to reduce indentation. */
     if (a->non_resident)
         goto do_non_resident_extend;
     BUG_ON(NInoNonResident(ni));
     /* The total length of the attribute value. */
     attr_len = le32_to_cpu(a->data.resident.value_length);
     /*
      * Extend the attribute record to be able to store the new attribute
      * size.  ntfs_attr_record_resize() will not do anything if the size is
      * not changing.
      */
     if (new_alloc_size < vol->mft_record_size &&
             !ntfs_attr_record_resize(m, a,
             le16_to_cpu(a->data.resident.value_offset) +
             new_alloc_size)) {
         /* The resize succeeded! */
         write_lock_irqsave(&ni->size_lock, flags);
         ni->allocated_size = le32_to_cpu(a->length) -
                 le16_to_cpu(a->data.resident.value_offset);
         write_unlock_irqrestore(&ni->size_lock, flags);
         if (new_data_size >= 0) {
             BUG_ON(new_data_size < attr_len);
             a->data.resident.value_length =
                     cpu_to_le32((u32)new_data_size);
         }
         goto flush_done;
     }
     /*
      * We have to drop all the locks so we can call
      * ntfs_attr_make_non_resident().  This could be optimised by try-
      * locking the first page cache page and only if that fails dropping
      * the locks, locking the page, and redoing all the locking and
      * lookups.  While this would be a huge optimisation, it is not worth
      * it as this is definitely a slow code path.
      */
     ntfs_attr_put_search_ctx(ctx);
     unmap_mft_record(base_ni);
     up_write(&ni->runlist.lock);
     /*
      * Not enough space in the mft record, try to make the attribute
      * non-resident and if successful restart the extension process.
      */
     err = ntfs_attr_make_non_resident(ni, attr_len);
     if (likely(!err))
         goto retry_extend;
     /*
      * Could not make non-resident.  If this is due to this not being
      * permitted for this attribute type or there not being enough space,
      * try to make other attributes non-resident.  Otherwise fail.
      */
     if (unlikely(err != -EPERM && err != -ENOSPC)) {
         /* Only emit errors when the write will fail completely. */
         read_lock_irqsave(&ni->size_lock, flags);
         allocated_size = ni->allocated_size;
         read_unlock_irqrestore(&ni->size_lock, flags);
         if (start < 0 || start >= allocated_size)
             ntfs_error(vol->sb, "Cannot extend allocation of "
                     "inode 0x%lx, attribute type 0x%x, "
                     "because the conversion from resident "
                     "to non-resident attribute failed "
                     "with error code %i.", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type), err);
         if (err != -ENOMEM)
             err = -EIO;
         goto conv_err_out;
     }
     /* TODO: Not implemented from here, abort. */
     read_lock_irqsave(&ni->size_lock, flags);
     allocated_size = ni->allocated_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     if (start < 0 || start >= allocated_size) {
         if (err == -ENOSPC)
             ntfs_error(vol->sb, "Not enough space in the mft "
                     "record/on disk for the non-resident "
                     "attribute value.  This case is not "
                     "implemented yet.");
         else /* if (err == -EPERM) */
             ntfs_error(vol->sb, "This attribute type may not be "
                     "non-resident.  This case is not "
                     "implemented yet.");
     }
     err = -EOPNOTSUPP;
     goto conv_err_out;
 #if 0
     // TODO: Attempt to make other attributes non-resident.
     if (!err)
         goto do_resident_extend;
     /*
      * Both the attribute list attribute and the standard information
      * attribute must remain in the base inode.  Thus, if this is one of
      * these attributes, we have to try to move other attributes out into
      * extent mft records instead.
      */
     if (ni->type == AT_ATTRIBUTE_LIST ||
             ni->type == AT_STANDARD_INFORMATION) {
         // TODO: Attempt to move other attributes into extent mft
         // records.
         err = -EOPNOTSUPP;
         if (!err)
             goto do_resident_extend;
         goto err_out;
     }
     // TODO: Attempt to move this attribute to an extent mft record, but
     // only if it is not already the only attribute in an mft record in
     // which case there would be nothing to gain.
     err = -EOPNOTSUPP;
     if (!err)
         goto do_resident_extend;
     /* There is nothing we can do to make enough space. )-: */
     goto err_out;
 #endif
 do_non_resident_extend:
     BUG_ON(!NInoNonResident(ni));
     if (new_alloc_size == allocated_size) {
         BUG_ON(vcn);
         goto alloc_done;
     }
     /*
      * If the data starts after the end of the old allocation, this is a
      * $DATA attribute and sparse attributes are enabled on the volume and
      * for this inode, then create a sparse region between the old
      * allocated size and the start of the data.  Otherwise simply proceed
      * with filling the whole space between the old allocated size and the
      * new allocated size with clusters.
      */
     if ((start >= 0 && start <= allocated_size) || ni->type != AT_DATA ||
             !NVolSparseEnabled(vol) || NInoSparseDisabled(ni))
         goto skip_sparse;
     // TODO: This is not implemented yet.  We just fill in with real
     // clusters for now...
     ntfs_debug("Inserting holes is not-implemented yet.  Falling back to "
             "allocating real clusters instead.");
 skip_sparse:
     rl = ni->runlist.rl;
     if (likely(rl)) {
         /* Seek to the end of the runlist. */
         while (rl->length)
             rl++;
     }
     /* If this attribute extent is not mapped, map it now. */
     if (unlikely(!rl || rl->lcn == LCN_RL_NOT_MAPPED ||
             (rl->lcn == LCN_ENOENT && rl > ni->runlist.rl &&
             (rl-1)->lcn == LCN_RL_NOT_MAPPED))) {
         if (!rl && !allocated_size)
             goto first_alloc;
         rl = ntfs_mapping_pairs_decompress(vol, a, ni->runlist.rl);
         if (IS_ERR(rl)) {
             err = PTR_ERR(rl);
             if (start < 0 || start >= allocated_size)
                 ntfs_error(vol->sb, "Cannot extend allocation "
                         "of inode 0x%lx, attribute "
                         "type 0x%x, because the "
                         "mapping of a runlist "
                         "fragment failed with error "
                         "code %i.", vi->i_ino,
                         (unsigned)le32_to_cpu(ni->type),
                         err);
             if (err != -ENOMEM)
                 err = -EIO;
             goto err_out;
         }
         ni->runlist.rl = rl;
         /* Seek to the end of the runlist. */
         while (rl->length)
             rl++;
     }
     /*
      * We now know the runlist of the last extent is mapped and @rl is at
      * the end of the runlist.  We want to begin allocating clusters
      * starting at the last allocated cluster to reduce fragmentation.  If
      * there are no valid LCNs in the attribute we let the cluster
      * allocator choose the starting cluster.
      */
     /* If the last LCN is a hole or simillar seek back to last real LCN. */
     while (rl->lcn < 0 && rl > ni->runlist.rl)
         rl--;
 first_alloc:
     // FIXME: Need to implement partial allocations so at least part of the
     // write can be performed when start >= 0.  (Needed for POSIX write(2)
     // conformance.)
     rl2 = ntfs_cluster_alloc(vol, allocated_size >> vol->cluster_size_bits,
             (new_alloc_size - allocated_size) >>
             vol->cluster_size_bits, (rl && (rl->lcn >= 0)) ?
             rl->lcn + rl->length : -1, DATA_ZONE, true);
     if (IS_ERR(rl2)) {
         err = PTR_ERR(rl2);
         if (start < 0 || start >= allocated_size)
             ntfs_error(vol->sb, "Cannot extend allocation of "
                     "inode 0x%lx, attribute type 0x%x, "
                     "because the allocation of clusters "
                     "failed with error code %i.", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type), err);
         if (err != -ENOMEM && err != -ENOSPC)
             err = -EIO;
         goto err_out;
     }
     rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
     if (IS_ERR(rl)) {
         err = PTR_ERR(rl);
         if (start < 0 || start >= allocated_size)
             ntfs_error(vol->sb, "Cannot extend allocation of "
                     "inode 0x%lx, attribute type 0x%x, "
                     "because the runlist merge failed "
                     "with error code %i.", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type), err);
         if (err != -ENOMEM)
             err = -EIO;
         if (ntfs_cluster_free_from_rl(vol, rl2)) {
             ntfs_error(vol->sb, "Failed to release allocated "
                     "cluster(s) in error code path.  Run "
                     "chkdsk to recover the lost "
                     "cluster(s).");
             NVolSetErrors(vol);
         }
         ntfs_free(rl2);
         goto err_out;
     }
     ni->runlist.rl = rl;
     ntfs_debug("Allocated 0x%llx clusters.", (long long)(new_alloc_size -
             allocated_size) >> vol->cluster_size_bits);
     /* Find the runlist element with which the attribute extent starts. */
     ll = sle64_to_cpu(a->data.non_resident.lowest_vcn);
     rl2 = ntfs_rl_find_vcn_nolock(rl, ll);
     BUG_ON(!rl2);
     BUG_ON(!rl2->length);
     BUG_ON(rl2->lcn < LCN_HOLE);
     mp_rebuilt = false;
     /* Get the size for the new mapping pairs array for this extent. */
     mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, ll, -1);
     if (unlikely(mp_size <= 0)) {
         err = mp_size;
         if (start < 0 || start >= allocated_size)
             ntfs_error(vol->sb, "Cannot extend allocation of "
                     "inode 0x%lx, attribute type 0x%x, "
                     "because determining the size for the "
                     "mapping pairs failed with error code "
                     "%i.", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type), err);
         err = -EIO;
         goto undo_alloc;
     }
     /* Extend the attribute record to fit the bigger mapping pairs array. */
     attr_len = le32_to_cpu(a->length);
     err = ntfs_attr_record_resize(m, a, mp_size +
             le16_to_cpu(a->data.non_resident.mapping_pairs_offset));
     if (unlikely(err)) {
         BUG_ON(err != -ENOSPC);
         // TODO: Deal with this by moving this extent to a new mft
         // record or by starting a new extent in a new mft record,
         // possibly by extending this extent partially and filling it
         // and creating a new extent for the remainder, or by making
         // other attributes non-resident and/or by moving other
         // attributes out of this mft record.
         if (start < 0 || start >= allocated_size)
             ntfs_error(vol->sb, "Not enough space in the mft "
                     "record for the extended attribute "
                     "record.  This case is not "
                     "implemented yet.");
         err = -EOPNOTSUPP;
         goto undo_alloc;
     }
     mp_rebuilt = true;
     /* Generate the mapping pairs array directly into the attr record. */
     err = ntfs_mapping_pairs_build(vol, (u8*)a +
             le16_to_cpu(a->data.non_resident.mapping_pairs_offset),
             mp_size, rl2, ll, -1, NULL);
     if (unlikely(err)) {
         if (start < 0 || start >= allocated_size)
             ntfs_error(vol->sb, "Cannot extend allocation of "
                     "inode 0x%lx, attribute type 0x%x, "
                     "because building the mapping pairs "
                     "failed with error code %i.", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type), err);
         err = -EIO;
         goto undo_alloc;
     }
     /* Update the highest_vcn. */
     a->data.non_resident.highest_vcn = cpu_to_sle64((new_alloc_size >>
             vol->cluster_size_bits) - 1);
     /*
      * We now have extended the allocated size of the attribute.  Reflect
      * this in the ntfs_inode structure and the attribute record.
      */
     if (a->data.non_resident.lowest_vcn) {
         /*
          * We are not in the first attribute extent, switch to it, but
          * first ensure the changes will make it to disk later.
          */
         flush_dcache_mft_record_page(ctx->ntfs_ino);
         mark_mft_record_dirty(ctx->ntfs_ino);
         ntfs_attr_reinit_search_ctx(ctx);
         err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                 CASE_SENSITIVE, 0, NULL, 0, ctx);
         if (unlikely(err))
             goto restore_undo_alloc;
         /* @m is not used any more so no need to set it. */
         a = ctx->attr;
     }
     write_lock_irqsave(&ni->size_lock, flags);
     ni->allocated_size = new_alloc_size;
     a->data.non_resident.allocated_size = cpu_to_sle64(new_alloc_size);
     /*
      * FIXME: This would fail if @ni is a directory, $MFT, or an index,
      * since those can have sparse/compressed set.  For example can be
      * set compressed even though it is not compressed itself and in that
      * case the bit means that files are to be created compressed in the
      * directory...  At present this is ok as this code is only called for
      * regular files, and only for their $DATA attribute(s).
      * FIXME: The calculation is wrong if we created a hole above.  For now
      * it does not matter as we never create holes.
      */
     if (NInoSparse(ni) || NInoCompressed(ni)) {
         ni->itype.compressed.size += new_alloc_size - allocated_size;
         a->data.non_resident.compressed_size =
                 cpu_to_sle64(ni->itype.compressed.size);
         vi->i_blocks = ni->itype.compressed.size >> 9;
     } else
         vi->i_blocks = new_alloc_size >> 9;
     write_unlock_irqrestore(&ni->size_lock, flags);
 alloc_done:
     if (new_data_size >= 0) {
         BUG_ON(new_data_size <
                 sle64_to_cpu(a->data.non_resident.data_size));
         a->data.non_resident.data_size = cpu_to_sle64(new_data_size);
     }
 flush_done:
     /* Ensure the changes make it to disk. */
     flush_dcache_mft_record_page(ctx->ntfs_ino);
     mark_mft_record_dirty(ctx->ntfs_ino);
 done:
     ntfs_attr_put_search_ctx(ctx);
     unmap_mft_record(base_ni);
     up_write(&ni->runlist.lock);
     ntfs_debug("Done, new_allocated_size 0x%llx.",
             (unsigned long long)new_alloc_size);
     return new_alloc_size;
 restore_undo_alloc:
     if (start < 0 || start >= allocated_size)
         ntfs_error(vol->sb, "Cannot complete extension of allocation "
                 "of inode 0x%lx, attribute type 0x%x, because "
                 "lookup of first attribute extent failed with "
                 "error code %i.", vi->i_ino,
                 (unsigned)le32_to_cpu(ni->type), err);
     if (err == -ENOENT)
         err = -EIO;
     ntfs_attr_reinit_search_ctx(ctx);
     if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len, CASE_SENSITIVE,
             allocated_size >> vol->cluster_size_bits, NULL, 0,
             ctx)) {
         ntfs_error(vol->sb, "Failed to find last attribute extent of "
                 "attribute in error code path.  Run chkdsk to "
                 "recover.");
         write_lock_irqsave(&ni->size_lock, flags);
         ni->allocated_size = new_alloc_size;
         /*
          * FIXME: This would fail if @ni is a directory...  See above.
          * FIXME: The calculation is wrong if we created a hole above.
          * For now it does not matter as we never create holes.
          */
         if (NInoSparse(ni) || NInoCompressed(ni)) {
             ni->itype.compressed.size += new_alloc_size -
                     allocated_size;
             vi->i_blocks = ni->itype.compressed.size >> 9;
         } else
             vi->i_blocks = new_alloc_size >> 9;
         write_unlock_irqrestore(&ni->size_lock, flags);
         ntfs_attr_put_search_ctx(ctx);
         unmap_mft_record(base_ni);
         up_write(&ni->runlist.lock);
         /*
          * The only thing that is now wrong is the allocated size of the
          * base attribute extent which chkdsk should be able to fix.
          */
         NVolSetErrors(vol);
         return err;
     }
     ctx->attr->data.non_resident.highest_vcn = cpu_to_sle64(
             (allocated_size >> vol->cluster_size_bits) - 1);
 undo_alloc:
     ll = allocated_size >> vol->cluster_size_bits;
     if (ntfs_cluster_free(ni, ll, -1, ctx) < 0) {
         ntfs_error(vol->sb, "Failed to release allocated cluster(s) "
                 "in error code path.  Run chkdsk to recover "
                 "the lost cluster(s).");
         NVolSetErrors(vol);
     }
     m = ctx->mrec;
     a = ctx->attr;
     /*
      * If the runlist truncation fails and/or the search context is no
      * longer valid, we cannot resize the attribute record or build the
      * mapping pairs array thus we mark the inode bad so that no access to
      * the freed clusters can happen.
      */
     if (ntfs_rl_truncate_nolock(vol, &ni->runlist, ll) || IS_ERR(m)) {
         ntfs_error(vol->sb, "Failed to %s in error code path.  Run "
                 "chkdsk to recover.", IS_ERR(m) ?
                 "restore attribute search context" :
                 "truncate attribute runlist");
         NVolSetErrors(vol);
     } else if (mp_rebuilt) {
         if (ntfs_attr_record_resize(m, a, attr_len)) {
             ntfs_error(vol->sb, "Failed to restore attribute "
                     "record in error code path.  Run "
                     "chkdsk to recover.");
             NVolSetErrors(vol);
         } else /* if (success) */ {
             if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
                     a->data.non_resident.
                     mapping_pairs_offset), attr_len -
                     le16_to_cpu(a->data.non_resident.
                     mapping_pairs_offset), rl2, ll, -1,
                     NULL)) {
                 ntfs_error(vol->sb, "Failed to restore "
                         "mapping pairs array in error "
                         "code path.  Run chkdsk to "
                         "recover.");
                 NVolSetErrors(vol);
             }
             flush_dcache_mft_record_page(ctx->ntfs_ino);
             mark_mft_record_dirty(ctx->ntfs_ino);
         }
     }
 err_out:
     if (ctx)
         ntfs_attr_put_search_ctx(ctx);
     if (m)
         unmap_mft_record(base_ni);
     up_write(&ni->runlist.lock);
 conv_err_out:
     ntfs_debug("Failed.  Returning error code %i.", err);
     return err;
 }
 
 /**
  * ntfs_attr_set - fill (a part of) an attribute with a byte
  * @ni:     ntfs inode describing the attribute to fill
  * @ofs:    offset inside the attribute at which to start to fill
  * @cnt:    number of bytes to fill
  * @val:    the unsigned 8-bit value with which to fill the attribute
  *
  * Fill @cnt bytes of the attribute described by the ntfs inode @ni starting at
  * byte offset @ofs inside the attribute with the constant byte @val.
  *
  * This function is effectively like memset() applied to an ntfs attribute.
  * Note thie function actually only operates on the page cache pages belonging
  * to the ntfs attribute and it marks them dirty after doing the memset().
  * Thus it relies on the vm dirty page write code paths to cause the modified
  * pages to be written to the mft record/disk.
  *
  * Return 0 on success and -errno on error.  An error code of -ESPIPE means
  * that @ofs + @cnt were outside the end of the attribute and no write was
  * performed.
  */
 int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
 {
     ntfs_volume *vol = ni->vol;
     struct address_space *mapping;
     struct page *page;
     u8 *kaddr;
     pgoff_t idx, end;
     unsigned start_ofs, end_ofs, size;
 
     ntfs_debug("Entering for ofs 0x%llx, cnt 0x%llx, val 0x%hx.",
             (long long)ofs, (long long)cnt, val);
     BUG_ON(ofs < 0);
     BUG_ON(cnt < 0);
     if (!cnt)
         goto done;
     /*
      * FIXME: Compressed and encrypted attributes are not supported when
      * writing and we should never have gotten here for them.
      */
     BUG_ON(NInoCompressed(ni));
     BUG_ON(NInoEncrypted(ni));
     mapping = VFS_I(ni)->i_mapping;
     /* Work out the starting index and page offset. */
     idx = ofs >> PAGE_SHIFT;
     start_ofs = ofs & ~PAGE_MASK;
     /* Work out the ending index and page offset. */
     end = ofs + cnt;
     end_ofs = end & ~PAGE_MASK;
     /* If the end is outside the inode size return -ESPIPE. */
     if (unlikely(end > i_size_read(VFS_I(ni)))) {
         ntfs_error(vol->sb, "Request exceeds end of attribute.");
         return -ESPIPE;
     }
     end >>= PAGE_SHIFT;
     /* If there is a first partial page, need to do it the slow way. */
     if (start_ofs) {
         page = read_mapping_page(mapping, idx, NULL);
         if (IS_ERR(page)) {
             ntfs_error(vol->sb, "Failed to read first partial "
                     "page (error, index 0x%lx).", idx);
             return PTR_ERR(page);
         }
         /*
          * If the last page is the same as the first page, need to
          * limit the write to the end offset.
          */
         size = PAGE_SIZE;
         if (idx == end)
             size = end_ofs;
         kaddr = kmap_atomic(page);
         memset(kaddr + start_ofs, val, size - start_ofs);
         flush_dcache_page(page);
         kunmap_atomic(kaddr);
         set_page_dirty(page);
         put_page(page);
         balance_dirty_pages_ratelimited(mapping);
         cond_resched();
         if (idx == end)
             goto done;
         idx++;
     }
     /* Do the whole pages the fast way. */
     for (; idx < end; idx++) {
         /* Find or create the current page.  (The page is locked.) */
         page = grab_cache_page(mapping, idx);
         if (unlikely(!page)) {
             ntfs_error(vol->sb, "Insufficient memory to grab "
                     "page (index 0x%lx).", idx);
             return -ENOMEM;
         }
         kaddr = kmap_atomic(page);
         memset(kaddr, val, PAGE_SIZE);
         flush_dcache_page(page);
         kunmap_atomic(kaddr);
         /*
          * If the page has buffers, mark them uptodate since buffer
          * state and not page state is definitive in 2.6 kernels.
          */
         if (page_has_buffers(page)) {
             struct buffer_head *bh, *head;
 
             bh = head = page_buffers(page);
             do {
                 set_buffer_uptodate(bh);
             } while ((bh = bh->b_this_page) != head);
         }
         /* Now that buffers are uptodate, set the page uptodate, too. */
         SetPageUptodate(page);
         /*
          * Set the page and all its buffers dirty and mark the inode
          * dirty, too.  The VM will write the page later on.
          */
         set_page_dirty(page);
         /* Finally unlock and release the page. */
         unlock_page(page);
         put_page(page);
         balance_dirty_pages_ratelimited(mapping);
         cond_resched();
     }
     /* If there is a last partial page, need to do it the slow way. */
     if (end_ofs) {
         page = read_mapping_page(mapping, idx, NULL);
         if (IS_ERR(page)) {
             ntfs_error(vol->sb, "Failed to read last partial page "
                     "(error, index 0x%lx).", idx);
             return PTR_ERR(page);
         }
         kaddr = kmap_atomic(page);
         memset(kaddr, val, end_ofs);
         flush_dcache_page(page);
         kunmap_atomic(kaddr);
         set_page_dirty(page);
         put_page(page);
         balance_dirty_pages_ratelimited(mapping);
         cond_resched();
     }
 done:
     ntfs_debug("Done.");
     return 0;
 }
 
 #endif /* NTFS_RW */

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