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 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
  *
  * Copyright (c) 2001-2015 Anton Altaparmakov and Tuxera Inc.
  */
 
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/buffer_head.h>
 #include <linux/gfp.h>
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
 #include <linux/sched/signal.h>
 #include <linux/swap.h>
 #include <linux/uio.h>
 #include <linux/writeback.h>
 
 #include <asm/page.h>
 #include <linux/uaccess.h>
 
 #include "attrib.h"
 #include "bitmap.h"
 #include "inode.h"
 #include "debug.h"
 #include "lcnalloc.h"
 #include "malloc.h"
 #include "mft.h"
 #include "ntfs.h"
 
 /**
  * ntfs_file_open - called when an inode is about to be opened
  * @vi:     inode to be opened
  * @filp:   file structure describing the inode
  *
  * Limit file size to the page cache limit on architectures where unsigned long
  * is 32-bits. This is the most we can do for now without overflowing the page
  * cache page index. Doing it this way means we don't run into problems because
  * of existing too large files. It would be better to allow the user to read
  * the beginning of the file but I doubt very much anyone is going to hit this
  * check on a 32-bit architecture, so there is no point in adding the extra
  * complexity required to support this.
  *
  * On 64-bit architectures, the check is hopefully optimized away by the
  * compiler.
  *
  * After the check passes, just call generic_file_open() to do its work.
  */
 static int ntfs_file_open(struct inode *vi, struct file *filp)
 {
     if (sizeof(unsigned long) < 8) {
         if (i_size_read(vi) > MAX_LFS_FILESIZE)
             return -EOVERFLOW;
     }
     return generic_file_open(vi, filp);
 }
 
 #ifdef NTFS_RW
 
 /**
  * ntfs_attr_extend_initialized - extend the initialized size of an attribute
  * @ni:         ntfs inode of the attribute to extend
  * @new_init_size:  requested new initialized size in bytes
  *
  * Extend the initialized size of an attribute described by the ntfs inode @ni
  * to @new_init_size bytes.  This involves zeroing any non-sparse space between
  * the old initialized size and @new_init_size both in the page cache and on
  * disk (if relevant complete pages are already uptodate in the page cache then
  * these are simply marked dirty).
  *
  * As a side-effect, the file size (vfs inode->i_size) may be incremented as,
  * in the resident attribute case, it is tied to the initialized size and, in
  * the non-resident attribute case, it may not fall below the initialized size.
  *
  * Note that if the attribute is resident, we do not need to touch the page
  * cache at all.  This is because if the page cache page is not uptodate we
  * bring it uptodate later, when doing the write to the mft record since we
  * then already have the page mapped.  And if the page is uptodate, the
  * non-initialized region will already have been zeroed when the page was
  * brought uptodate and the region may in fact already have been overwritten
  * with new data via mmap() based writes, so we cannot just zero it.  And since
  * POSIX specifies that the behaviour of resizing a file whilst it is mmap()ped
  * is unspecified, we choose not to do zeroing and thus we do not need to touch
  * the page at all.  For a more detailed explanation see ntfs_truncate() in
  * fs/ntfs/inode.c.
  *
  * Return 0 on success and -errno on error.  In the case that an error is
  * encountered it is possible that the initialized size will already have been
  * incremented some way towards @new_init_size but it is guaranteed that if
  * this is the case, the necessary zeroing will also have happened and that all
  * metadata is self-consistent.
  *
  * Locking: i_mutex on the vfs inode corrseponsind to the ntfs inode @ni must be
  *      held by the caller.
  */
 static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size)
 {
     s64 old_init_size;
     loff_t old_i_size;
     pgoff_t index, end_index;
     unsigned long flags;
     struct inode *vi = VFS_I(ni);
     ntfs_inode *base_ni;
     MFT_RECORD *m = NULL;
     ATTR_RECORD *a;
     ntfs_attr_search_ctx *ctx = NULL;
     struct address_space *mapping;
     struct page *page = NULL;
     u8 *kattr;
     int err;
     u32 attr_len;
 
     read_lock_irqsave(&ni->size_lock, flags);
     old_init_size = ni->initialized_size;
     old_i_size = i_size_read(vi);
     BUG_ON(new_init_size > ni->allocated_size);
     read_unlock_irqrestore(&ni->size_lock, flags);
     ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
             "old_initialized_size 0x%llx, "
             "new_initialized_size 0x%llx, i_size 0x%llx.",
             vi->i_ino, (unsigned)le32_to_cpu(ni->type),
             (unsigned long long)old_init_size,
             (unsigned long long)new_init_size, old_i_size);
     if (!NInoAttr(ni))
         base_ni = ni;
     else
         base_ni = ni->ext.base_ntfs_ino;
     /* Use goto to reduce indentation and we need the label below anyway. */
     if (NInoNonResident(ni))
         goto do_non_resident_extend;
     BUG_ON(old_init_size != old_i_size);
     m = map_mft_record(base_ni);
     if (IS_ERR(m)) {
         err = PTR_ERR(m);
         m = 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(a->non_resident);
     /* The total length of the attribute value. */
     attr_len = le32_to_cpu(a->data.resident.value_length);
     BUG_ON(old_i_size != (loff_t)attr_len);
     /*
      * Do the zeroing in the mft record and update the attribute size in
      * the mft record.
      */
     kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
     memset(kattr + attr_len, 0, new_init_size - attr_len);
     a->data.resident.value_length = cpu_to_le32((u32)new_init_size);
     /* Finally, update the sizes in the vfs and ntfs inodes. */
     write_lock_irqsave(&ni->size_lock, flags);
     i_size_write(vi, new_init_size);
     ni->initialized_size = new_init_size;
     write_unlock_irqrestore(&ni->size_lock, flags);
     goto done;
 do_non_resident_extend:
     /*
      * If the new initialized size @new_init_size exceeds the current file
      * size (vfs inode->i_size), we need to extend the file size to the
      * new initialized size.
      */
     if (new_init_size > old_i_size) {
         m = map_mft_record(base_ni);
         if (IS_ERR(m)) {
             err = PTR_ERR(m);
             m = 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(!a->non_resident);
         BUG_ON(old_i_size != (loff_t)
                 sle64_to_cpu(a->data.non_resident.data_size));
         a->data.non_resident.data_size = cpu_to_sle64(new_init_size);
         flush_dcache_mft_record_page(ctx->ntfs_ino);
         mark_mft_record_dirty(ctx->ntfs_ino);
         /* Update the file size in the vfs inode. */
         i_size_write(vi, new_init_size);
         ntfs_attr_put_search_ctx(ctx);
         ctx = NULL;
         unmap_mft_record(base_ni);
         m = NULL;
     }
     mapping = vi->i_mapping;
     index = old_init_size >> PAGE_SHIFT;
     end_index = (new_init_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
     do {
         /*
          * Read the page.  If the page is not present, this will zero
          * the uninitialized regions for us.
          */
         page = read_mapping_page(mapping, index, NULL);
         if (IS_ERR(page)) {
             err = PTR_ERR(page);
             goto init_err_out;
         }
         /*
          * Update the initialized size in the ntfs inode.  This is
          * enough to make ntfs_writepage() work.
          */
         write_lock_irqsave(&ni->size_lock, flags);
         ni->initialized_size = (s64)(index + 1) << PAGE_SHIFT;
         if (ni->initialized_size > new_init_size)
             ni->initialized_size = new_init_size;
         write_unlock_irqrestore(&ni->size_lock, flags);
         /* Set the page dirty so it gets written out. */
         set_page_dirty(page);
         put_page(page);
         /*
          * Play nice with the vm and the rest of the system.  This is
          * very much needed as we can potentially be modifying the
          * initialised size from a very small value to a really huge
          * value, e.g.
          *  f = open(somefile, O_TRUNC);
          *  truncate(f, 10GiB);
          *  seek(f, 10GiB);
          *  write(f, 1);
          * And this would mean we would be marking dirty hundreds of
          * thousands of pages or as in the above example more than
          * two and a half million pages!
          *
          * TODO: For sparse pages could optimize this workload by using
          * the FsMisc / MiscFs page bit as a "PageIsSparse" bit.  This
          * would be set in read_folio for sparse pages and here we would
          * not need to mark dirty any pages which have this bit set.
          * The only caveat is that we have to clear the bit everywhere
          * where we allocate any clusters that lie in the page or that
          * contain the page.
          *
          * TODO: An even greater optimization would be for us to only
          * call read_folio() on pages which are not in sparse regions as
          * determined from the runlist.  This would greatly reduce the
          * number of pages we read and make dirty in the case of sparse
          * files.
          */
         balance_dirty_pages_ratelimited(mapping);
         cond_resched();
     } while (++index < end_index);
     read_lock_irqsave(&ni->size_lock, flags);
     BUG_ON(ni->initialized_size != new_init_size);
     read_unlock_irqrestore(&ni->size_lock, flags);
     /* Now bring in sync the initialized_size in the mft record. */
     m = map_mft_record(base_ni);
     if (IS_ERR(m)) {
         err = PTR_ERR(m);
         m = NULL;
         goto init_err_out;
     }
     ctx = ntfs_attr_get_search_ctx(base_ni, m);
     if (unlikely(!ctx)) {
         err = -ENOMEM;
         goto init_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 init_err_out;
     }
     m = ctx->mrec;
     a = ctx->attr;
     BUG_ON(!a->non_resident);
     a->data.non_resident.initialized_size = cpu_to_sle64(new_init_size);
 done:
     flush_dcache_mft_record_page(ctx->ntfs_ino);
     mark_mft_record_dirty(ctx->ntfs_ino);
     if (ctx)
         ntfs_attr_put_search_ctx(ctx);
     if (m)
         unmap_mft_record(base_ni);
     ntfs_debug("Done, initialized_size 0x%llx, i_size 0x%llx.",
             (unsigned long long)new_init_size, i_size_read(vi));
     return 0;
 init_err_out:
     write_lock_irqsave(&ni->size_lock, flags);
     ni->initialized_size = old_init_size;
     write_unlock_irqrestore(&ni->size_lock, flags);
 err_out:
     if (ctx)
         ntfs_attr_put_search_ctx(ctx);
     if (m)
         unmap_mft_record(base_ni);
     ntfs_debug("Failed.  Returning error code %i.", err);
     return err;
 }
 
 static ssize_t ntfs_prepare_file_for_write(struct kiocb *iocb,
         struct iov_iter *from)
 {
     loff_t pos;
     s64 end, ll;
     ssize_t err;
     unsigned long flags;
     struct file *file = iocb->ki_filp;
     struct inode *vi = file_inode(file);
     ntfs_inode *ni = NTFS_I(vi);
     ntfs_volume *vol = ni->vol;
 
     ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, pos "
             "0x%llx, count 0x%zx.", vi->i_ino,
             (unsigned)le32_to_cpu(ni->type),
             (unsigned long long)iocb->ki_pos,
             iov_iter_count(from));
     err = generic_write_checks(iocb, from);
     if (unlikely(err <= 0))
         goto out;
     /*
      * All checks have passed.  Before we start doing any writing we want
      * to abort any totally illegal writes.
      */
     BUG_ON(NInoMstProtected(ni));
     BUG_ON(ni->type != AT_DATA);
     /* If file is encrypted, deny access, just like NT4. */
     if (NInoEncrypted(ni)) {
         /* Only $DATA attributes can be encrypted. */
         /*
          * Reminder for later: Encrypted files are _always_
          * non-resident so that the content can always be encrypted.
          */
         ntfs_debug("Denying write access to encrypted file.");
         err = -EACCES;
         goto out;
     }
     if (NInoCompressed(ni)) {
         /* Only unnamed $DATA attribute can be compressed. */
         BUG_ON(ni->name_len);
         /*
          * Reminder for later: If resident, the data is not actually
          * compressed.  Only on the switch to non-resident does
          * compression kick in.  This is in contrast to encrypted files
          * (see above).
          */
         ntfs_error(vi->i_sb, "Writing to compressed files is not "
                 "implemented yet.  Sorry.");
         err = -EOPNOTSUPP;
         goto out;
     }
     err = file_remove_privs(file);
     if (unlikely(err))
         goto out;
     /*
      * Our ->update_time method always succeeds thus file_update_time()
      * cannot fail either so there is no need to check the return code.
      */
     file_update_time(file);
     pos = iocb->ki_pos;
     /* The first byte after the last cluster being written to. */
     end = (pos + iov_iter_count(from) + vol->cluster_size_mask) &
             ~(u64)vol->cluster_size_mask;
     /*
      * If the write goes beyond the allocated size, extend the allocation
      * to cover the whole of the write, rounded up to the nearest cluster.
      */
     read_lock_irqsave(&ni->size_lock, flags);
     ll = ni->allocated_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     if (end > ll) {
         /*
          * Extend the allocation without changing the data size.
          *
          * Note we ensure the allocation is big enough to at least
          * write some data but we do not require the allocation to be
          * complete, i.e. it may be partial.
          */
         ll = ntfs_attr_extend_allocation(ni, end, -1, pos);
         if (likely(ll >= 0)) {
             BUG_ON(pos >= ll);
             /* If the extension was partial truncate the write. */
             if (end > ll) {
                 ntfs_debug("Truncating write to inode 0x%lx, "
                         "attribute type 0x%x, because "
                         "the allocation was only "
                         "partially extended.",
                         vi->i_ino, (unsigned)
                         le32_to_cpu(ni->type));
                 iov_iter_truncate(from, ll - pos);
             }
         } else {
             err = ll;
             read_lock_irqsave(&ni->size_lock, flags);
             ll = ni->allocated_size;
             read_unlock_irqrestore(&ni->size_lock, flags);
             /* Perform a partial write if possible or fail. */
             if (pos < ll) {
                 ntfs_debug("Truncating write to inode 0x%lx "
                         "attribute type 0x%x, because "
                         "extending the allocation "
                         "failed (error %d).",
                         vi->i_ino, (unsigned)
                         le32_to_cpu(ni->type),
                         (int)-err);
                 iov_iter_truncate(from, ll - pos);
             } else {
                 if (err != -ENOSPC)
                     ntfs_error(vi->i_sb, "Cannot perform "
                             "write to inode "
                             "0x%lx, attribute "
                             "type 0x%x, because "
                             "extending the "
                             "allocation failed "
                             "(error %ld).",
                             vi->i_ino, (unsigned)
                             le32_to_cpu(ni->type),
                             (long)-err);
                 else
                     ntfs_debug("Cannot perform write to "
                             "inode 0x%lx, "
                             "attribute type 0x%x, "
                             "because there is not "
                             "space left.",
                             vi->i_ino, (unsigned)
                             le32_to_cpu(ni->type));
                 goto out;
             }
         }
     }
     /*
      * If the write starts beyond the initialized size, extend it up to the
      * beginning of the write and initialize all non-sparse space between
      * the old initialized size and the new one.  This automatically also
      * increments the vfs inode->i_size to keep it above or equal to the
      * initialized_size.
      */
     read_lock_irqsave(&ni->size_lock, flags);
     ll = ni->initialized_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     if (pos > ll) {
         /*
          * Wait for ongoing direct i/o to complete before proceeding.
          * New direct i/o cannot start as we hold i_mutex.
          */
         inode_dio_wait(vi);
         err = ntfs_attr_extend_initialized(ni, pos);
         if (unlikely(err < 0))
             ntfs_error(vi->i_sb, "Cannot perform write to inode "
                     "0x%lx, attribute type 0x%x, because "
                     "extending the initialized size "
                     "failed (error %d).", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type),
                     (int)-err);
     }
 out:
     return err;
 }
 
 /**
  * __ntfs_grab_cache_pages - obtain a number of locked pages
  * @mapping:    address space mapping from which to obtain page cache pages
  * @index:  starting index in @mapping at which to begin obtaining pages
  * @nr_pages:   number of page cache pages to obtain
  * @pages:  array of pages in which to return the obtained page cache pages
  * @cached_page: allocated but as yet unused page
  *
  * Obtain @nr_pages locked page cache pages from the mapping @mapping and
  * starting at index @index.
  *
  * If a page is newly created, add it to lru list
  *
  * Note, the page locks are obtained in ascending page index order.
  */
 static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
         pgoff_t index, const unsigned nr_pages, struct page **pages,
         struct page **cached_page)
 {
     int err, nr;
 
     BUG_ON(!nr_pages);
     err = nr = 0;
     do {
         pages[nr] = find_get_page_flags(mapping, index, FGP_LOCK |
                 FGP_ACCESSED);
         if (!pages[nr]) {
             if (!*cached_page) {
                 *cached_page = page_cache_alloc(mapping);
                 if (unlikely(!*cached_page)) {
                     err = -ENOMEM;
                     goto err_out;
                 }
             }
             err = add_to_page_cache_lru(*cached_page, mapping,
                    index,
                    mapping_gfp_constraint(mapping, GFP_KERNEL));
             if (unlikely(err)) {
                 if (err == -EEXIST)
                     continue;
                 goto err_out;
             }
             pages[nr] = *cached_page;
             *cached_page = NULL;
         }
         index++;
         nr++;
     } while (nr < nr_pages);
 out:
     return err;
 err_out:
     while (nr > 0) {
         unlock_page(pages[--nr]);
         put_page(pages[nr]);
     }
     goto out;
 }
 
 static inline int ntfs_submit_bh_for_read(struct buffer_head *bh)
 {
     lock_buffer(bh);
     get_bh(bh);
     bh->b_end_io = end_buffer_read_sync;
     return submit_bh(REQ_OP_READ, bh);
 }
 
 /**
  * ntfs_prepare_pages_for_non_resident_write - prepare pages for receiving data
  * @pages:  array of destination pages
  * @nr_pages:   number of pages in @pages
  * @pos:    byte position in file at which the write begins
  * @bytes:  number of bytes to be written
  *
  * This is called for non-resident attributes from ntfs_file_buffered_write()
  * with i_mutex held on the inode (@pages[0]->mapping->host).  There are
  * @nr_pages pages in @pages which are locked but not kmap()ped.  The source
  * data has not yet been copied into the @pages.
  * 
  * Need to fill any holes with actual clusters, allocate buffers if necessary,
  * ensure all the buffers are mapped, and bring uptodate any buffers that are
  * only partially being written to.
  *
  * If @nr_pages is greater than one, we are guaranteed that the cluster size is
  * greater than PAGE_SIZE, that all pages in @pages are entirely inside
  * the same cluster and that they are the entirety of that cluster, and that
  * the cluster is sparse, i.e. we need to allocate a cluster to fill the hole.
  *
  * i_size is not to be modified yet.
  *
  * Return 0 on success or -errno on error.
  */
 static int ntfs_prepare_pages_for_non_resident_write(struct page **pages,
         unsigned nr_pages, s64 pos, size_t bytes)
 {
     VCN vcn, highest_vcn = 0, cpos, cend, bh_cpos, bh_cend;
     LCN lcn;
     s64 bh_pos, vcn_len, end, initialized_size;
     sector_t lcn_block;
     struct page *page;
     struct inode *vi;
     ntfs_inode *ni, *base_ni = NULL;
     ntfs_volume *vol;
     runlist_element *rl, *rl2;
     struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
     ntfs_attr_search_ctx *ctx = NULL;
     MFT_RECORD *m = NULL;
     ATTR_RECORD *a = NULL;
     unsigned long flags;
     u32 attr_rec_len = 0;
     unsigned blocksize, u;
     int err, mp_size;
     bool rl_write_locked, was_hole, is_retry;
     unsigned char blocksize_bits;
     struct {
         u8 runlist_merged:1;
         u8 mft_attr_mapped:1;
         u8 mp_rebuilt:1;
         u8 attr_switched:1;
     } status = { 0, 0, 0, 0 };
 
     BUG_ON(!nr_pages);
     BUG_ON(!pages);
     BUG_ON(!*pages);
     vi = pages[0]->mapping->host;
     ni = NTFS_I(vi);
     vol = ni->vol;
     ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
             "index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
             vi->i_ino, ni->type, pages[0]->index, nr_pages,
             (long long)pos, bytes);
     blocksize = vol->sb->s_blocksize;
     blocksize_bits = vol->sb->s_blocksize_bits;
     u = 0;
     do {
         page = pages[u];
         BUG_ON(!page);
         /*
          * create_empty_buffers() will create uptodate/dirty buffers if
          * the page is uptodate/dirty.
          */
         if (!page_has_buffers(page)) {
             create_empty_buffers(page, blocksize, 0);
             if (unlikely(!page_has_buffers(page)))
                 return -ENOMEM;
         }
     } while (++u < nr_pages);
     rl_write_locked = false;
     rl = NULL;
     err = 0;
     vcn = lcn = -1;
     vcn_len = 0;
     lcn_block = -1;
     was_hole = false;
     cpos = pos >> vol->cluster_size_bits;
     end = pos + bytes;
     cend = (end + vol->cluster_size - 1) >> vol->cluster_size_bits;
     /*
      * Loop over each page and for each page over each buffer.  Use goto to
      * reduce indentation.
      */
     u = 0;
 do_next_page:
     page = pages[u];
     bh_pos = (s64)page->index << PAGE_SHIFT;
     bh = head = page_buffers(page);
     do {
         VCN cdelta;
         s64 bh_end;
         unsigned bh_cofs;
 
         /* Clear buffer_new on all buffers to reinitialise state. */
         if (buffer_new(bh))
             clear_buffer_new(bh);
         bh_end = bh_pos + blocksize;
         bh_cpos = bh_pos >> vol->cluster_size_bits;
         bh_cofs = bh_pos & vol->cluster_size_mask;
         if (buffer_mapped(bh)) {
             /*
              * The buffer is already mapped.  If it is uptodate,
              * ignore it.
              */
             if (buffer_uptodate(bh))
                 continue;
             /*
              * The buffer is not uptodate.  If the page is uptodate
              * set the buffer uptodate and otherwise ignore it.
              */
             if (PageUptodate(page)) {
                 set_buffer_uptodate(bh);
                 continue;
             }
             /*
              * Neither the page nor the buffer are uptodate.  If
              * the buffer is only partially being written to, we
              * need to read it in before the write, i.e. now.
              */
             if ((bh_pos < pos && bh_end > pos) ||
                     (bh_pos < end && bh_end > end)) {
                 /*
                  * If the buffer is fully or partially within
                  * the initialized size, do an actual read.
                  * Otherwise, simply zero the buffer.
                  */
                 read_lock_irqsave(&ni->size_lock, flags);
                 initialized_size = ni->initialized_size;
                 read_unlock_irqrestore(&ni->size_lock, flags);
                 if (bh_pos < initialized_size) {
                     ntfs_submit_bh_for_read(bh);
                     *wait_bh++ = bh;
                 } else {
                     zero_user(page, bh_offset(bh),
                             blocksize);
                     set_buffer_uptodate(bh);
                 }
             }
             continue;
         }
         /* Unmapped buffer.  Need to map it. */
         bh->b_bdev = vol->sb->s_bdev;
         /*
          * If the current buffer is in the same clusters as the map
          * cache, there is no need to check the runlist again.  The
          * map cache is made up of @vcn, which is the first cached file
          * cluster, @vcn_len which is the number of cached file
          * clusters, @lcn is the device cluster corresponding to @vcn,
          * and @lcn_block is the block number corresponding to @lcn.
          */
         cdelta = bh_cpos - vcn;
         if (likely(!cdelta || (cdelta > 0 && cdelta < vcn_len))) {
 map_buffer_cached:
             BUG_ON(lcn < 0);
             bh->b_blocknr = lcn_block +
                     (cdelta << (vol->cluster_size_bits -
                     blocksize_bits)) +
                     (bh_cofs >> blocksize_bits);
             set_buffer_mapped(bh);
             /*
              * If the page is uptodate so is the buffer.  If the
              * buffer is fully outside the write, we ignore it if
              * it was already allocated and we mark it dirty so it
              * gets written out if we allocated it.  On the other
              * hand, if we allocated the buffer but we are not
              * marking it dirty we set buffer_new so we can do
              * error recovery.
              */
             if (PageUptodate(page)) {
                 if (!buffer_uptodate(bh))
                     set_buffer_uptodate(bh);
                 if (unlikely(was_hole)) {
                     /* We allocated the buffer. */
                     clean_bdev_bh_alias(bh);
                     if (bh_end <= pos || bh_pos >= end)
                         mark_buffer_dirty(bh);
                     else
                         set_buffer_new(bh);
                 }
                 continue;
             }
             /* Page is _not_ uptodate. */
             if (likely(!was_hole)) {
                 /*
                  * Buffer was already allocated.  If it is not
                  * uptodate and is only partially being written
                  * to, we need to read it in before the write,
                  * i.e. now.
                  */
                 if (!buffer_uptodate(bh) && bh_pos < end &&
                         bh_end > pos &&
                         (bh_pos < pos ||
                         bh_end > end)) {
                     /*
                      * If the buffer is fully or partially
                      * within the initialized size, do an
                      * actual read.  Otherwise, simply zero
                      * the buffer.
                      */
                     read_lock_irqsave(&ni->size_lock,
                             flags);
                     initialized_size = ni->initialized_size;
                     read_unlock_irqrestore(&ni->size_lock,
                             flags);
                     if (bh_pos < initialized_size) {
                         ntfs_submit_bh_for_read(bh);
                         *wait_bh++ = bh;
                     } else {
                         zero_user(page, bh_offset(bh),
                                 blocksize);
                         set_buffer_uptodate(bh);
                     }
                 }
                 continue;
             }
             /* We allocated the buffer. */
             clean_bdev_bh_alias(bh);
             /*
              * If the buffer is fully outside the write, zero it,
              * set it uptodate, and mark it dirty so it gets
              * written out.  If it is partially being written to,
              * zero region surrounding the write but leave it to
              * commit write to do anything else.  Finally, if the
              * buffer is fully being overwritten, do nothing.
              */
             if (bh_end <= pos || bh_pos >= end) {
                 if (!buffer_uptodate(bh)) {
                     zero_user(page, bh_offset(bh),
                             blocksize);
                     set_buffer_uptodate(bh);
                 }
                 mark_buffer_dirty(bh);
                 continue;
             }
             set_buffer_new(bh);
             if (!buffer_uptodate(bh) &&
                     (bh_pos < pos || bh_end > end)) {
                 u8 *kaddr;
                 unsigned pofs;
                     
                 kaddr = kmap_atomic(page);
                 if (bh_pos < pos) {
                     pofs = bh_pos & ~PAGE_MASK;
                     memset(kaddr + pofs, 0, pos - bh_pos);
                 }
                 if (bh_end > end) {
                     pofs = end & ~PAGE_MASK;
                     memset(kaddr + pofs, 0, bh_end - end);
                 }
                 kunmap_atomic(kaddr);
                 flush_dcache_page(page);
             }
             continue;
         }
         /*
          * Slow path: this is the first buffer in the cluster.  If it
          * is outside allocated size and is not uptodate, zero it and
          * set it uptodate.
          */
         read_lock_irqsave(&ni->size_lock, flags);
         initialized_size = ni->allocated_size;
         read_unlock_irqrestore(&ni->size_lock, flags);
         if (bh_pos > initialized_size) {
             if (PageUptodate(page)) {
                 if (!buffer_uptodate(bh))
                     set_buffer_uptodate(bh);
             } else if (!buffer_uptodate(bh)) {
                 zero_user(page, bh_offset(bh), blocksize);
                 set_buffer_uptodate(bh);
             }
             continue;
         }
         is_retry = false;
         if (!rl) {
             down_read(&ni->runlist.lock);
 retry_remap:
             rl = ni->runlist.rl;
         }
         if (likely(rl != NULL)) {
             /* Seek to element containing target cluster. */
             while (rl->length && rl[1].vcn <= bh_cpos)
                 rl++;
             lcn = ntfs_rl_vcn_to_lcn(rl, bh_cpos);
             if (likely(lcn >= 0)) {
                 /*
                  * Successful remap, setup the map cache and
                  * use that to deal with the buffer.
                  */
                 was_hole = false;
                 vcn = bh_cpos;
                 vcn_len = rl[1].vcn - vcn;
                 lcn_block = lcn << (vol->cluster_size_bits -
                         blocksize_bits);
                 cdelta = 0;
                 /*
                  * If the number of remaining clusters touched
                  * by the write is smaller or equal to the
                  * number of cached clusters, unlock the
                  * runlist as the map cache will be used from
                  * now on.
                  */
                 if (likely(vcn + vcn_len >= cend)) {
                     if (rl_write_locked) {
                         up_write(&ni->runlist.lock);
                         rl_write_locked = false;
                     } else
                         up_read(&ni->runlist.lock);
                     rl = NULL;
                 }
                 goto map_buffer_cached;
             }
         } else
             lcn = LCN_RL_NOT_MAPPED;
         /*
          * If it is not a hole and not out of bounds, the runlist is
          * probably unmapped so try to map it now.
          */
         if (unlikely(lcn != LCN_HOLE && lcn != LCN_ENOENT)) {
             if (likely(!is_retry && lcn == LCN_RL_NOT_MAPPED)) {
                 /* Attempt to map runlist. */
                 if (!rl_write_locked) {
                     /*
                      * We need the runlist locked for
                      * writing, so if it is locked for
                      * reading relock it now and retry in
                      * case it changed whilst we dropped
                      * the lock.
                      */
                     up_read(&ni->runlist.lock);
                     down_write(&ni->runlist.lock);
                     rl_write_locked = true;
                     goto retry_remap;
                 }
                 err = ntfs_map_runlist_nolock(ni, bh_cpos,
                         NULL);
                 if (likely(!err)) {
                     is_retry = true;
                     goto retry_remap;
                 }
                 /*
                  * If @vcn is out of bounds, pretend @lcn is
                  * LCN_ENOENT.  As long as the buffer is out
                  * of bounds this will work fine.
                  */
                 if (err == -ENOENT) {
                     lcn = LCN_ENOENT;
                     err = 0;
                     goto rl_not_mapped_enoent;
                 }
             } else
                 err = -EIO;
             /* Failed to map the buffer, even after retrying. */
             bh->b_blocknr = -1;
             ntfs_error(vol->sb, "Failed to write to inode 0x%lx, "
                     "attribute type 0x%x, vcn 0x%llx, "
                     "vcn offset 0x%x, because its "
                     "location on disk could not be "
                     "determined%s (error code %i).",
                     ni->mft_no, ni->type,
                     (unsigned long long)bh_cpos,
                     (unsigned)bh_pos &
                     vol->cluster_size_mask,
                     is_retry ? " even after retrying" : "",
                     err);
             break;
         }
 rl_not_mapped_enoent:
         /*
          * The buffer is in a hole or out of bounds.  We need to fill
          * the hole, unless the buffer is in a cluster which is not
          * touched by the write, in which case we just leave the buffer
          * unmapped.  This can only happen when the cluster size is
          * less than the page cache size.
          */
         if (unlikely(vol->cluster_size < PAGE_SIZE)) {
             bh_cend = (bh_end + vol->cluster_size - 1) >>
                     vol->cluster_size_bits;
             if ((bh_cend <= cpos || bh_cpos >= cend)) {
                 bh->b_blocknr = -1;
                 /*
                  * If the buffer is uptodate we skip it.  If it
                  * is not but the page is uptodate, we can set
                  * the buffer uptodate.  If the page is not
                  * uptodate, we can clear the buffer and set it
                  * uptodate.  Whether this is worthwhile is
                  * debatable and this could be removed.
                  */
                 if (PageUptodate(page)) {
                     if (!buffer_uptodate(bh))
                         set_buffer_uptodate(bh);
                 } else if (!buffer_uptodate(bh)) {
                     zero_user(page, bh_offset(bh),
                         blocksize);
                     set_buffer_uptodate(bh);
                 }
                 continue;
             }
         }
         /*
          * Out of bounds buffer is invalid if it was not really out of
          * bounds.
          */
         BUG_ON(lcn != LCN_HOLE);
         /*
          * We need the runlist locked for writing, so if it is locked
          * for reading relock it now and retry in case it changed
          * whilst we dropped the lock.
          */
         BUG_ON(!rl);
         if (!rl_write_locked) {
             up_read(&ni->runlist.lock);
             down_write(&ni->runlist.lock);
             rl_write_locked = true;
             goto retry_remap;
         }
         /* Find the previous last allocated cluster. */
         BUG_ON(rl->lcn != LCN_HOLE);
         lcn = -1;
         rl2 = rl;
         while (--rl2 >= ni->runlist.rl) {
             if (rl2->lcn >= 0) {
                 lcn = rl2->lcn + rl2->length;
                 break;
             }
         }
         rl2 = ntfs_cluster_alloc(vol, bh_cpos, 1, lcn, DATA_ZONE,
                 false);
         if (IS_ERR(rl2)) {
             err = PTR_ERR(rl2);
             ntfs_debug("Failed to allocate cluster, error code %i.",
                     err);
             break;
         }
         lcn = rl2->lcn;
         rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
         if (IS_ERR(rl)) {
             err = PTR_ERR(rl);
             if (err != -ENOMEM)
                 err = -EIO;
             if (ntfs_cluster_free_from_rl(vol, rl2)) {
                 ntfs_error(vol->sb, "Failed to release "
                         "allocated cluster in error "
                         "code path.  Run chkdsk to "
                         "recover the lost cluster.");
                 NVolSetErrors(vol);
             }
             ntfs_free(rl2);
             break;
         }
         ni->runlist.rl = rl;
         status.runlist_merged = 1;
         ntfs_debug("Allocated cluster, lcn 0x%llx.",
                 (unsigned long long)lcn);
         /* Map and lock the mft record and get the attribute record. */
         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);
             break;
         }
         ctx = ntfs_attr_get_search_ctx(base_ni, m);
         if (unlikely(!ctx)) {
             err = -ENOMEM;
             unmap_mft_record(base_ni);
             break;
         }
         status.mft_attr_mapped = 1;
         err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                 CASE_SENSITIVE, bh_cpos, NULL, 0, ctx);
         if (unlikely(err)) {
             if (err == -ENOENT)
                 err = -EIO;
             break;
         }
         m = ctx->mrec;
         a = ctx->attr;
         /*
          * Find the runlist element with which the attribute extent
          * starts.  Note, we cannot use the _attr_ version because we
          * have mapped the mft record.  That is ok because we know the
          * runlist fragment must be mapped already to have ever gotten
          * here, so we can just use the _rl_ version.
          */
         vcn = sle64_to_cpu(a->data.non_resident.lowest_vcn);
         rl2 = ntfs_rl_find_vcn_nolock(rl, vcn);
         BUG_ON(!rl2);
         BUG_ON(!rl2->length);
         BUG_ON(rl2->lcn < LCN_HOLE);
         highest_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
         /*
          * If @highest_vcn is zero, calculate the real highest_vcn
          * (which can really be zero).
          */
         if (!highest_vcn)
             highest_vcn = (sle64_to_cpu(
                     a->data.non_resident.allocated_size) >>
                     vol->cluster_size_bits) - 1;
         /*
          * Determine the size of the mapping pairs array for the new
          * extent, i.e. the old extent with the hole filled.
          */
         mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, vcn,
                 highest_vcn);
         if (unlikely(mp_size <= 0)) {
             if (!(err = mp_size))
                 err = -EIO;
             ntfs_debug("Failed to get size for mapping pairs "
                     "array, error code %i.", err);
             break;
         }
         /*
          * Resize the attribute record to fit the new mapping pairs
          * array.
          */
         attr_rec_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 using the current attribute
             // and fill it with as much of the mapping pairs
             // array as possible.  Then loop over each attribute
             // extent rewriting the mapping pairs arrays as we go
             // along and if when we reach the end we have not
             // enough space, try to resize the last attribute
             // extent and if even that fails, add a new attribute
             // extent.
             // We could also try to resize at each step in the hope
             // that we will not need to rewrite every single extent.
             // Note, we may need to decompress some extents to fill
             // the runlist as we are walking the extents...
             ntfs_error(vol->sb, "Not enough space in the mft "
                     "record for the extended attribute "
                     "record.  This case is not "
                     "implemented yet.");
             err = -EOPNOTSUPP;
             break ;
         }
         status.mp_rebuilt = 1;
         /*
          * Generate the mapping pairs array directly into the attribute
          * record.
          */
         err = ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
                 a->data.non_resident.mapping_pairs_offset),
                 mp_size, rl2, vcn, highest_vcn, NULL);
         if (unlikely(err)) {
             ntfs_error(vol->sb, "Cannot fill hole in 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;
             break;
         }
         /* Update the highest_vcn but only if it was not set. */
         if (unlikely(!a->data.non_resident.highest_vcn))
             a->data.non_resident.highest_vcn =
                     cpu_to_sle64(highest_vcn);
         /*
          * If the attribute is sparse/compressed, update the compressed
          * size in the ntfs_inode structure and the attribute record.
          */
         if (likely(NInoSparse(ni) || NInoCompressed(ni))) {
             /*
              * If we are not in the first attribute extent, switch
              * to it, but first ensure the changes will make it to
              * disk later.
              */
             if (a->data.non_resident.lowest_vcn) {
                 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)) {
                     status.attr_switched = 1;
                     break;
                 }
                 /* @m is not used any more so do not set it. */
                 a = ctx->attr;
             }
             write_lock_irqsave(&ni->size_lock, flags);
             ni->itype.compressed.size += vol->cluster_size;
             a->data.non_resident.compressed_size =
                     cpu_to_sle64(ni->itype.compressed.size);
             write_unlock_irqrestore(&ni->size_lock, flags);
         }
         /* Ensure the changes make it to disk. */
         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);
         /* Successfully filled the hole. */
         status.runlist_merged = 0;
         status.mft_attr_mapped = 0;
         status.mp_rebuilt = 0;
         /* Setup the map cache and use that to deal with the buffer. */
         was_hole = true;
         vcn = bh_cpos;
         vcn_len = 1;
         lcn_block = lcn << (vol->cluster_size_bits - blocksize_bits);
         cdelta = 0;
         /*
          * If the number of remaining clusters in the @pages is smaller
          * or equal to the number of cached clusters, unlock the
          * runlist as the map cache will be used from now on.
          */
         if (likely(vcn + vcn_len >= cend)) {
             up_write(&ni->runlist.lock);
             rl_write_locked = false;
             rl = NULL;
         }
         goto map_buffer_cached;
     } while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
     /* If there are no errors, do the next page. */
     if (likely(!err && ++u < nr_pages))
         goto do_next_page;
     /* If there are no errors, release the runlist lock if we took it. */
     if (likely(!err)) {
         if (unlikely(rl_write_locked)) {
             up_write(&ni->runlist.lock);
             rl_write_locked = false;
         } else if (unlikely(rl))
             up_read(&ni->runlist.lock);
         rl = NULL;
     }
     /* If we issued read requests, let them complete. */
     read_lock_irqsave(&ni->size_lock, flags);
     initialized_size = ni->initialized_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     while (wait_bh > wait) {
         bh = *--wait_bh;
         wait_on_buffer(bh);
         if (likely(buffer_uptodate(bh))) {
             page = bh->b_page;
             bh_pos = ((s64)page->index << PAGE_SHIFT) +
                     bh_offset(bh);
             /*
              * If the buffer overflows the initialized size, need
              * to zero the overflowing region.
              */
             if (unlikely(bh_pos + blocksize > initialized_size)) {
                 int ofs = 0;
 
                 if (likely(bh_pos < initialized_size))
                     ofs = initialized_size - bh_pos;
                 zero_user_segment(page, bh_offset(bh) + ofs,
                         blocksize);
             }
         } else /* if (unlikely(!buffer_uptodate(bh))) */
             err = -EIO;
     }
     if (likely(!err)) {
         /* Clear buffer_new on all buffers. */
         u = 0;
         do {
             bh = head = page_buffers(pages[u]);
             do {
                 if (buffer_new(bh))
                     clear_buffer_new(bh);
             } while ((bh = bh->b_this_page) != head);
         } while (++u < nr_pages);
         ntfs_debug("Done.");
         return err;
     }
     if (status.attr_switched) {
         /* Get back to the attribute extent we modified. */
         ntfs_attr_reinit_search_ctx(ctx);
         if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                 CASE_SENSITIVE, bh_cpos, NULL, 0, ctx)) {
             ntfs_error(vol->sb, "Failed to find required "
                     "attribute extent of attribute in "
                     "error code path.  Run chkdsk to "
                     "recover.");
             write_lock_irqsave(&ni->size_lock, flags);
             ni->itype.compressed.size += vol->cluster_size;
             write_unlock_irqrestore(&ni->size_lock, flags);
             flush_dcache_mft_record_page(ctx->ntfs_ino);
             mark_mft_record_dirty(ctx->ntfs_ino);
             /*
              * The only thing that is now wrong is the compressed
              * size of the base attribute extent which chkdsk
              * should be able to fix.
              */
             NVolSetErrors(vol);
         } else {
             m = ctx->mrec;
             a = ctx->attr;
             status.attr_switched = 0;
         }
     }
     /*
      * If the runlist has been modified, need to restore it by punching a
      * hole into it and we then need to deallocate the on-disk cluster as
      * well.  Note, we only modify the runlist if we are able to generate a
      * new mapping pairs array, i.e. only when the mapped attribute extent
      * is not switched.
      */
     if (status.runlist_merged && !status.attr_switched) {
         BUG_ON(!rl_write_locked);
         /* Make the file cluster we allocated sparse in the runlist. */
         if (ntfs_rl_punch_nolock(vol, &ni->runlist, bh_cpos, 1)) {
             ntfs_error(vol->sb, "Failed to punch hole into "
                     "attribute runlist in error code "
                     "path.  Run chkdsk to recover the "
                     "lost cluster.");
             NVolSetErrors(vol);
         } else /* if (success) */ {
             status.runlist_merged = 0;
             /*
              * Deallocate the on-disk cluster we allocated but only
              * if we succeeded in punching its vcn out of the
              * runlist.
              */
             down_write(&vol->lcnbmp_lock);
             if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
                 ntfs_error(vol->sb, "Failed to release "
                         "allocated cluster in error "
                         "code path.  Run chkdsk to "
                         "recover the lost cluster.");
                 NVolSetErrors(vol);
             }
             up_write(&vol->lcnbmp_lock);
         }
     }
     /*
      * Resize the attribute record to its old size and rebuild the mapping
      * pairs array.  Note, we only can do this if the runlist has been
      * restored to its old state which also implies that the mapped
      * attribute extent is not switched.
      */
     if (status.mp_rebuilt && !status.runlist_merged) {
         if (ntfs_attr_record_resize(m, a, attr_rec_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_rec_len -
                     le16_to_cpu(a->data.non_resident.
                     mapping_pairs_offset), ni->runlist.rl,
                     vcn, highest_vcn, 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);
         }
     }
     /* Release the mft record and the attribute. */
     if (status.mft_attr_mapped) {
         ntfs_attr_put_search_ctx(ctx);
         unmap_mft_record(base_ni);
     }
     /* Release the runlist lock. */
     if (rl_write_locked)
         up_write(&ni->runlist.lock);
     else if (rl)
         up_read(&ni->runlist.lock);
     /*
      * Zero out any newly allocated blocks to avoid exposing stale data.
      * If BH_New is set, we know that the block was newly allocated above
      * and that it has not been fully zeroed and marked dirty yet.
      */
     nr_pages = u;
     u = 0;
     end = bh_cpos << vol->cluster_size_bits;
     do {
         page = pages[u];
         bh = head = page_buffers(page);
         do {
             if (u == nr_pages &&
                     ((s64)page->index << PAGE_SHIFT) +
                     bh_offset(bh) >= end)
                 break;
             if (!buffer_new(bh))
                 continue;
             clear_buffer_new(bh);
             if (!buffer_uptodate(bh)) {
                 if (PageUptodate(page))
                     set_buffer_uptodate(bh);
                 else {
                     zero_user(page, bh_offset(bh),
                             blocksize);
                     set_buffer_uptodate(bh);
                 }
             }
             mark_buffer_dirty(bh);
         } while ((bh = bh->b_this_page) != head);
     } while (++u <= nr_pages);
     ntfs_error(vol->sb, "Failed.  Returning error code %i.", err);
     return err;
 }
 
 static inline void ntfs_flush_dcache_pages(struct page **pages,
         unsigned nr_pages)
 {
     BUG_ON(!nr_pages);
     /*
      * Warning: Do not do the decrement at the same time as the call to
      * flush_dcache_page() because it is a NULL macro on i386 and hence the
      * decrement never happens so the loop never terminates.
      */
     do {
         --nr_pages;
         flush_dcache_page(pages[nr_pages]);
     } while (nr_pages > 0);
 }
 
 /**
  * ntfs_commit_pages_after_non_resident_write - commit the received data
  * @pages:  array of destination pages
  * @nr_pages:   number of pages in @pages
  * @pos:    byte position in file at which the write begins
  * @bytes:  number of bytes to be written
  *
  * See description of ntfs_commit_pages_after_write(), below.
  */
 static inline int ntfs_commit_pages_after_non_resident_write(
         struct page **pages, const unsigned nr_pages,
         s64 pos, size_t bytes)
 {
     s64 end, initialized_size;
     struct inode *vi;
     ntfs_inode *ni, *base_ni;
     struct buffer_head *bh, *head;
     ntfs_attr_search_ctx *ctx;
     MFT_RECORD *m;
     ATTR_RECORD *a;
     unsigned long flags;
     unsigned blocksize, u;
     int err;
 
     vi = pages[0]->mapping->host;
     ni = NTFS_I(vi);
     blocksize = vi->i_sb->s_blocksize;
     end = pos + bytes;
     u = 0;
     do {
         s64 bh_pos;
         struct page *page;
         bool partial;
 
         page = pages[u];
         bh_pos = (s64)page->index << PAGE_SHIFT;
         bh = head = page_buffers(page);
         partial = false;
         do {
             s64 bh_end;
 
             bh_end = bh_pos + blocksize;
             if (bh_end <= pos || bh_pos >= end) {
                 if (!buffer_uptodate(bh))
                     partial = true;
             } else {
                 set_buffer_uptodate(bh);
                 mark_buffer_dirty(bh);
             }
         } while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
         /*
          * If all buffers are now uptodate but the page is not, set the
          * page uptodate.
          */
         if (!partial && !PageUptodate(page))
             SetPageUptodate(page);
     } while (++u < nr_pages);
     /*
      * Finally, if we do not need to update initialized_size or i_size we
      * are finished.
      */
     read_lock_irqsave(&ni->size_lock, flags);
     initialized_size = ni->initialized_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     if (end <= initialized_size) {
         ntfs_debug("Done.");
         return 0;
     }
     /*
      * Update initialized_size/i_size as appropriate, both in the inode and
      * the mft record.
      */
     if (!NInoAttr(ni))
         base_ni = ni;
     else
         base_ni = ni->ext.base_ntfs_ino;
     /* Map, pin, and lock the mft record. */
     m = map_mft_record(base_ni);
     if (IS_ERR(m)) {
         err = PTR_ERR(m);
         m = NULL;
         ctx = NULL;
         goto err_out;
     }
     BUG_ON(!NInoNonResident(ni));
     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;
     }
     a = ctx->attr;
     BUG_ON(!a->non_resident);
     write_lock_irqsave(&ni->size_lock, flags);
     BUG_ON(end > ni->allocated_size);
     ni->initialized_size = end;
     a->data.non_resident.initialized_size = cpu_to_sle64(end);
     if (end > i_size_read(vi)) {
         i_size_write(vi, end);
         a->data.non_resident.data_size =
                 a->data.non_resident.initialized_size;
     }
     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);
     ntfs_attr_put_search_ctx(ctx);
     unmap_mft_record(base_ni);
     ntfs_debug("Done.");
     return 0;
 err_out:
     if (ctx)
         ntfs_attr_put_search_ctx(ctx);
     if (m)
         unmap_mft_record(base_ni);
     ntfs_error(vi->i_sb, "Failed to update initialized_size/i_size (error "
             "code %i).", err);
     if (err != -ENOMEM)
         NVolSetErrors(ni->vol);
     return err;
 }
 
 /**
  * ntfs_commit_pages_after_write - commit the received data
  * @pages:  array of destination pages
  * @nr_pages:   number of pages in @pages
  * @pos:    byte position in file at which the write begins
  * @bytes:  number of bytes to be written
  *
  * This is called from ntfs_file_buffered_write() with i_mutex held on the inode
  * (@pages[0]->mapping->host).  There are @nr_pages pages in @pages which are
  * locked but not kmap()ped.  The source data has already been copied into the
  * @page.  ntfs_prepare_pages_for_non_resident_write() has been called before
  * the data was copied (for non-resident attributes only) and it returned
  * success.
  *
  * Need to set uptodate and mark dirty all buffers within the boundary of the
  * write.  If all buffers in a page are uptodate we set the page uptodate, too.
  *
  * Setting the buffers dirty ensures that they get written out later when
  * ntfs_writepage() is invoked by the VM.
  *
  * Finally, we need to update i_size and initialized_size as appropriate both
  * in the inode and the mft record.
  *
  * This is modelled after fs/buffer.c::generic_commit_write(), which marks
  * buffers uptodate and dirty, sets the page uptodate if all buffers in the
  * page are uptodate, and updates i_size if the end of io is beyond i_size.  In
  * that case, it also marks the inode dirty.
  *
  * If things have gone as outlined in
  * ntfs_prepare_pages_for_non_resident_write(), we do not need to do any page
  * content modifications here for non-resident attributes.  For resident
  * attributes we need to do the uptodate bringing here which we combine with
  * the copying into the mft record which means we save one atomic kmap.
  *
  * Return 0 on success or -errno on error.
  */
 static int ntfs_commit_pages_after_write(struct page **pages,
         const unsigned nr_pages, s64 pos, size_t bytes)
 {
     s64 end, initialized_size;
     loff_t i_size;
     struct inode *vi;
     ntfs_inode *ni, *base_ni;
     struct page *page;
     ntfs_attr_search_ctx *ctx;
     MFT_RECORD *m;
     ATTR_RECORD *a;
     char *kattr, *kaddr;
     unsigned long flags;
     u32 attr_len;
     int err;
 
     BUG_ON(!nr_pages);
     BUG_ON(!pages);
     page = pages[0];
     BUG_ON(!page);
     vi = page->mapping->host;
     ni = NTFS_I(vi);
     ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
             "index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
             vi->i_ino, ni->type, page->index, nr_pages,
             (long long)pos, bytes);
     if (NInoNonResident(ni))
         return ntfs_commit_pages_after_non_resident_write(pages,
                 nr_pages, pos, bytes);
     BUG_ON(nr_pages > 1);
     /*
      * Attribute is resident, implying it is not compressed, encrypted, or
      * sparse.
      */
     if (!NInoAttr(ni))
         base_ni = ni;
     else
         base_ni = ni->ext.base_ntfs_ino;
     BUG_ON(NInoNonResident(ni));
     /* Map, pin, and lock the mft record. */
     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;
     }
     a = ctx->attr;
     BUG_ON(a->non_resident);
     /* The total length of the attribute value. */
     attr_len = le32_to_cpu(a->data.resident.value_length);
     i_size = i_size_read(vi);
     BUG_ON(attr_len != i_size);
     BUG_ON(pos > attr_len);
     end = pos + bytes;
     BUG_ON(end > le32_to_cpu(a->length) -
             le16_to_cpu(a->data.resident.value_offset));
     kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
     kaddr = kmap_atomic(page);
     /* Copy the received data from the page to the mft record. */
     memcpy(kattr + pos, kaddr + pos, bytes);
     /* Update the attribute length if necessary. */
     if (end > attr_len) {
         attr_len = end;
         a->data.resident.value_length = cpu_to_le32(attr_len);
     }
     /*
      * If the page is not uptodate, bring the out of bounds area(s)
      * uptodate by copying data from the mft record to the page.
      */
     if (!PageUptodate(page)) {
         if (pos > 0)
             memcpy(kaddr, kattr, pos);
         if (end < attr_len)
             memcpy(kaddr + end, kattr + end, attr_len - end);
         /* Zero the region outside the end of the attribute value. */
         memset(kaddr + attr_len, 0, PAGE_SIZE - attr_len);
         flush_dcache_page(page);
         SetPageUptodate(page);
     }
     kunmap_atomic(kaddr);
     /* Update initialized_size/i_size if necessary. */
     read_lock_irqsave(&ni->size_lock, flags);
     initialized_size = ni->initialized_size;
     BUG_ON(end > ni->allocated_size);
     read_unlock_irqrestore(&ni->size_lock, flags);
     BUG_ON(initialized_size != i_size);
     if (end > initialized_size) {
         write_lock_irqsave(&ni->size_lock, flags);
         ni->initialized_size = end;
         i_size_write(vi, end);
         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);
     ntfs_attr_put_search_ctx(ctx);
     unmap_mft_record(base_ni);
     ntfs_debug("Done.");
     return 0;
 err_out:
     if (err == -ENOMEM) {
         ntfs_warning(vi->i_sb, "Error allocating memory required to "
                 "commit the write.");
         if (PageUptodate(page)) {
             ntfs_warning(vi->i_sb, "Page is uptodate, setting "
                     "dirty so the write will be retried "
                     "later on by the VM.");
             /*
              * Put the page on mapping->dirty_pages, but leave its
              * buffers' dirty state as-is.
              */
             __set_page_dirty_nobuffers(page);
             err = 0;
         } else
             ntfs_error(vi->i_sb, "Page is not uptodate.  Written "
                     "data has been lost.");
     } else {
         ntfs_error(vi->i_sb, "Resident attribute commit write failed "
                 "with error %i.", err);
         NVolSetErrors(ni->vol);
     }
     if (ctx)
         ntfs_attr_put_search_ctx(ctx);
     if (m)
         unmap_mft_record(base_ni);
     return err;
 }
 
 /*
  * Copy as much as we can into the pages and return the number of bytes which
  * were successfully copied.  If a fault is encountered then clear the pages
  * out to (ofs + bytes) and return the number of bytes which were copied.
  */
 static size_t ntfs_copy_from_user_iter(struct page **pages, unsigned nr_pages,
         unsigned ofs, struct iov_iter *i, size_t bytes)
 {
     struct page **last_page = pages + nr_pages;
     size_t total = 0;
     unsigned len, copied;
 
     do {
         len = PAGE_SIZE - ofs;
         if (len > bytes)
             len = bytes;
         copied = copy_page_from_iter_atomic(*pages, ofs, len, i);
         total += copied;
         bytes -= copied;
         if (!bytes)
             break;
         if (copied < len)
             goto err;
         ofs = 0;
     } while (++pages < last_page);
 out:
     return total;
 err:
     /* Zero the rest of the target like __copy_from_user(). */
     len = PAGE_SIZE - copied;
     do {
         if (len > bytes)
             len = bytes;
         zero_user(*pages, copied, len);
         bytes -= len;
         copied = 0;
         len = PAGE_SIZE;
     } while (++pages < last_page);
     goto out;
 }
 
 /**
  * ntfs_perform_write - perform buffered write to a file
  * @file:   file to write to
  * @i:      iov_iter with data to write
  * @pos:    byte offset in file at which to begin writing to
  */
 static ssize_t ntfs_perform_write(struct file *file, struct iov_iter *i,
         loff_t pos)
 {
     struct address_space *mapping = file->f_mapping;
     struct inode *vi = mapping->host;
     ntfs_inode *ni = NTFS_I(vi);
     ntfs_volume *vol = ni->vol;
     struct page *pages[NTFS_MAX_PAGES_PER_CLUSTER];
     struct page *cached_page = NULL;
     VCN last_vcn;
     LCN lcn;
     size_t bytes;
     ssize_t status, written = 0;
     unsigned nr_pages;
 
     ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, pos "
             "0x%llx, count 0x%lx.", vi->i_ino,
             (unsigned)le32_to_cpu(ni->type),
             (unsigned long long)pos,
             (unsigned long)iov_iter_count(i));
     /*
      * If a previous ntfs_truncate() failed, repeat it and abort if it
      * fails again.
      */
     if (unlikely(NInoTruncateFailed(ni))) {
         int err;
 
         inode_dio_wait(vi);
         err = ntfs_truncate(vi);
         if (err || NInoTruncateFailed(ni)) {
             if (!err)
                 err = -EIO;
             ntfs_error(vol->sb, "Cannot perform write to inode "
                     "0x%lx, attribute type 0x%x, because "
                     "ntfs_truncate() failed (error code "
                     "%i).", vi->i_ino,
                     (unsigned)le32_to_cpu(ni->type), err);
             return err;
         }
     }
     /*
      * Determine the number of pages per cluster for non-resident
      * attributes.
      */
     nr_pages = 1;
     if (vol->cluster_size > PAGE_SIZE && NInoNonResident(ni))
         nr_pages = vol->cluster_size >> PAGE_SHIFT;
     last_vcn = -1;
     do {
         VCN vcn;
         pgoff_t start_idx;
         unsigned ofs, do_pages, u;
         size_t copied;
 
         start_idx = pos >> PAGE_SHIFT;
         ofs = pos & ~PAGE_MASK;
         bytes = PAGE_SIZE - ofs;
         do_pages = 1;
         if (nr_pages > 1) {
             vcn = pos >> vol->cluster_size_bits;
             if (vcn != last_vcn) {
                 last_vcn = vcn;
                 /*
                  * Get the lcn of the vcn the write is in.  If
                  * it is a hole, need to lock down all pages in
                  * the cluster.
                  */
                 down_read(&ni->runlist.lock);
                 lcn = ntfs_attr_vcn_to_lcn_nolock(ni, pos >>
                         vol->cluster_size_bits, false);
                 up_read(&ni->runlist.lock);
                 if (unlikely(lcn < LCN_HOLE)) {
                     if (lcn == LCN_ENOMEM)
                         status = -ENOMEM;
                     else {
                         status = -EIO;
                         ntfs_error(vol->sb, "Cannot "
                             "perform write to "
                             "inode 0x%lx, "
                             "attribute type 0x%x, "
                             "because the attribute "
                             "is corrupt.",
                             vi->i_ino, (unsigned)
                             le32_to_cpu(ni->type));
                     }
                     break;
                 }
                 if (lcn == LCN_HOLE) {
                     start_idx = (pos & ~(s64)
                             vol->cluster_size_mask)
                             >> PAGE_SHIFT;
                     bytes = vol->cluster_size - (pos &
                             vol->cluster_size_mask);
                     do_pages = nr_pages;
                 }
             }
         }
         if (bytes > iov_iter_count(i))
             bytes = iov_iter_count(i);
 again:
         /*
          * Bring in the user page(s) that we will copy from _first_.
          * Otherwise there is a nasty deadlock on copying from the same
          * page(s) as we are writing to, without it/them being marked
          * up-to-date.  Note, at present there is nothing to stop the
          * pages being swapped out between us bringing them into memory
          * and doing the actual copying.
          */
         if (unlikely(fault_in_iov_iter_readable(i, bytes))) {
             status = -EFAULT;
             break;
         }
         /* Get and lock @do_pages starting at index @start_idx. */
         status = __ntfs_grab_cache_pages(mapping, start_idx, do_pages,
                 pages, &cached_page);
         if (unlikely(status))
             break;
         /*
          * For non-resident attributes, we need to fill any holes with
          * actual clusters and ensure all bufferes are mapped.  We also
          * need to bring uptodate any buffers that are only partially
          * being written to.
          */
         if (NInoNonResident(ni)) {
             status = ntfs_prepare_pages_for_non_resident_write(
                     pages, do_pages, pos, bytes);
             if (unlikely(status)) {
                 do {
                     unlock_page(pages[--do_pages]);
                     put_page(pages[do_pages]);
                 } while (do_pages);
                 break;
             }
         }
         u = (pos >> PAGE_SHIFT) - pages[0]->index;
         copied = ntfs_copy_from_user_iter(pages + u, do_pages - u, ofs,
                     i, bytes);
         ntfs_flush_dcache_pages(pages + u, do_pages - u);
         status = 0;
         if (likely(copied == bytes)) {
             status = ntfs_commit_pages_after_write(pages, do_pages,
                     pos, bytes);
         }
         do {
             unlock_page(pages[--do_pages]);
             put_page(pages[do_pages]);
         } while (do_pages);
         if (unlikely(status < 0)) {
             iov_iter_revert(i, copied);
             break;
         }
         cond_resched();
         if (unlikely(copied < bytes)) {
             iov_iter_revert(i, copied);
             if (copied)
                 bytes = copied;
             else if (bytes > PAGE_SIZE - ofs)
                 bytes = PAGE_SIZE - ofs;
             goto again;
         }
         pos += copied;
         written += copied;
         balance_dirty_pages_ratelimited(mapping);
         if (fatal_signal_pending(current)) {
             status = -EINTR;
             break;
         }
     } while (iov_iter_count(i));
     if (cached_page)
         put_page(cached_page);
     ntfs_debug("Done.  Returning %s (written 0x%lx, status %li).",
             written ? "written" : "status", (unsigned long)written,
             (long)status);
     return written ? written : status;
 }
 
 /**
  * ntfs_file_write_iter - simple wrapper for ntfs_file_write_iter_nolock()
  * @iocb:   IO state structure
  * @from:   iov_iter with data to write
  *
  * Basically the same as generic_file_write_iter() except that it ends up
  * up calling ntfs_perform_write() instead of generic_perform_write() and that
  * O_DIRECT is not implemented.
  */
 static ssize_t ntfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
     struct file *file = iocb->ki_filp;
     struct inode *vi = file_inode(file);
     ssize_t written = 0;
     ssize_t err;
 
     inode_lock(vi);
     /* We can write back this queue in page reclaim. */
     current->backing_dev_info = inode_to_bdi(vi);
     err = ntfs_prepare_file_for_write(iocb, from);
     if (iov_iter_count(from) && !err)
         written = ntfs_perform_write(file, from, iocb->ki_pos);
     current->backing_dev_info = NULL;
     inode_unlock(vi);
     iocb->ki_pos += written;
     if (likely(written > 0))
         written = generic_write_sync(iocb, written);
     return written ? written : err;
 }
 
 /**
  * ntfs_file_fsync - sync a file to disk
  * @filp:   file to be synced
  * @datasync:   if non-zero only flush user data and not metadata
  *
  * Data integrity sync of a file to disk.  Used for fsync, fdatasync, and msync
  * system calls.  This function is inspired by fs/buffer.c::file_fsync().
  *
  * If @datasync is false, write the mft record and all associated extent mft
  * records as well as the $DATA attribute and then sync the block device.
  *
  * If @datasync is true and the attribute is non-resident, we skip the writing
  * of the mft record and all associated extent mft records (this might still
  * happen due to the write_inode_now() call).
  *
  * Also, if @datasync is true, we do not wait on the inode to be written out
  * but we always wait on the page cache pages to be written out.
  *
  * Locking: Caller must hold i_mutex on the inode.
  *
  * TODO: We should probably also write all attribute/index inodes associated
  * with this inode but since we have no simple way of getting to them we ignore
  * this problem for now.
  */
 static int ntfs_file_fsync(struct file *filp, loff_t start, loff_t end,
                int datasync)
 {
     struct inode *vi = filp->f_mapping->host;
     int err, ret = 0;
 
     ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 
     err = file_write_and_wait_range(filp, start, end);
     if (err)
         return err;
     inode_lock(vi);
 
     BUG_ON(S_ISDIR(vi->i_mode));
     if (!datasync || !NInoNonResident(NTFS_I(vi)))
         ret = __ntfs_write_inode(vi, 1);
     write_inode_now(vi, !datasync);
     /*
      * NOTE: If we were to use mapping->private_list (see ext2 and
      * fs/buffer.c) for dirty blocks then we could optimize the below to be
      * sync_mapping_buffers(vi->i_mapping).
      */
     err = sync_blockdev(vi->i_sb->s_bdev);
     if (unlikely(err && !ret))
         ret = err;
     if (likely(!ret))
         ntfs_debug("Done.");
     else
         ntfs_warning(vi->i_sb, "Failed to f%ssync inode 0x%lx.  Error "
                 "%u.", datasync ? "data" : "", vi->i_ino, -ret);
     inode_unlock(vi);
     return ret;
 }
 
 #endif /* NTFS_RW */
 
 const struct file_operations ntfs_file_ops = {
     .llseek     = generic_file_llseek,
     .read_iter  = generic_file_read_iter,
 #ifdef NTFS_RW
     .write_iter = ntfs_file_write_iter,
     .fsync      = ntfs_file_fsync,
 #endif /* NTFS_RW */
     .mmap       = generic_file_mmap,
     .open       = ntfs_file_open,
     .splice_read    = generic_file_splice_read,
 };
 
 const struct inode_operations ntfs_file_inode_ops = {
 #ifdef NTFS_RW
     .setattr    = ntfs_setattr,
 #endif /* NTFS_RW */
 };
 
 const struct file_operations ntfs_empty_file_ops = {};
 
 const struct inode_operations ntfs_empty_inode_ops = {};

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