OSCL-LXR linux-6.0.1/​fs/​ntfs/​compress.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /**
  * compress.c - NTFS kernel compressed attributes handling.
  *      Part of the Linux-NTFS project.
  *
  * Copyright (c) 2001-2004 Anton Altaparmakov
  * Copyright (c) 2002 Richard Russon
  */
 
 #include <linux/fs.h>
 #include <linux/buffer_head.h>
 #include <linux/blkdev.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
 
 #include "attrib.h"
 #include "inode.h"
 #include "debug.h"
 #include "ntfs.h"
 
 /**
  * ntfs_compression_constants - enum of constants used in the compression code
  */
 typedef enum {
     /* Token types and access mask. */
     NTFS_SYMBOL_TOKEN   =   0,
     NTFS_PHRASE_TOKEN   =   1,
     NTFS_TOKEN_MASK     =   1,
 
     /* Compression sub-block constants. */
     NTFS_SB_SIZE_MASK   =   0x0fff,
     NTFS_SB_SIZE        =   0x1000,
     NTFS_SB_IS_COMPRESSED   =   0x8000,
 
     /*
      * The maximum compression block size is by definition 16 * the cluster
      * size, with the maximum supported cluster size being 4kiB. Thus the
      * maximum compression buffer size is 64kiB, so we use this when
      * initializing the compression buffer.
      */
     NTFS_MAX_CB_SIZE    = 64 * 1024,
 } ntfs_compression_constants;
 
 /**
  * ntfs_compression_buffer - one buffer for the decompression engine
  */
 static u8 *ntfs_compression_buffer;
 
 /**
  * ntfs_cb_lock - spinlock which protects ntfs_compression_buffer
  */
 static DEFINE_SPINLOCK(ntfs_cb_lock);
 
 /**
  * allocate_compression_buffers - allocate the decompression buffers
  *
  * Caller has to hold the ntfs_lock mutex.
  *
  * Return 0 on success or -ENOMEM if the allocations failed.
  */
 int allocate_compression_buffers(void)
 {
     BUG_ON(ntfs_compression_buffer);
 
     ntfs_compression_buffer = vmalloc(NTFS_MAX_CB_SIZE);
     if (!ntfs_compression_buffer)
         return -ENOMEM;
     return 0;
 }
 
 /**
  * free_compression_buffers - free the decompression buffers
  *
  * Caller has to hold the ntfs_lock mutex.
  */
 void free_compression_buffers(void)
 {
     BUG_ON(!ntfs_compression_buffer);
     vfree(ntfs_compression_buffer);
     ntfs_compression_buffer = NULL;
 }
 
 /**
  * zero_partial_compressed_page - zero out of bounds compressed page region
  */
 static void zero_partial_compressed_page(struct page *page,
         const s64 initialized_size)
 {
     u8 *kp = page_address(page);
     unsigned int kp_ofs;
 
     ntfs_debug("Zeroing page region outside initialized size.");
     if (((s64)page->index << PAGE_SHIFT) >= initialized_size) {
         clear_page(kp);
         return;
     }
     kp_ofs = initialized_size & ~PAGE_MASK;
     memset(kp + kp_ofs, 0, PAGE_SIZE - kp_ofs);
     return;
 }
 
 /**
  * handle_bounds_compressed_page - test for&handle out of bounds compressed page
  */
 static inline void handle_bounds_compressed_page(struct page *page,
         const loff_t i_size, const s64 initialized_size)
 {
     if ((page->index >= (initialized_size >> PAGE_SHIFT)) &&
             (initialized_size < i_size))
         zero_partial_compressed_page(page, initialized_size);
     return;
 }
 
 /**
  * ntfs_decompress - decompress a compression block into an array of pages
  * @dest_pages:     destination array of pages
  * @completed_pages:    scratch space to track completed pages
  * @dest_index:     current index into @dest_pages (IN/OUT)
  * @dest_ofs:       current offset within @dest_pages[@dest_index] (IN/OUT)
  * @dest_max_index: maximum index into @dest_pages (IN)
  * @dest_max_ofs:   maximum offset within @dest_pages[@dest_max_index] (IN)
  * @xpage:      the target page (-1 if none) (IN)
  * @xpage_done:     set to 1 if xpage was completed successfully (IN/OUT)
  * @cb_start:       compression block to decompress (IN)
  * @cb_size:        size of compression block @cb_start in bytes (IN)
  * @i_size:     file size when we started the read (IN)
  * @initialized_size:   initialized file size when we started the read (IN)
  *
  * The caller must have disabled preemption. ntfs_decompress() reenables it when
  * the critical section is finished.
  *
  * This decompresses the compression block @cb_start into the array of
  * destination pages @dest_pages starting at index @dest_index into @dest_pages
  * and at offset @dest_pos into the page @dest_pages[@dest_index].
  *
  * When the page @dest_pages[@xpage] is completed, @xpage_done is set to 1.
  * If xpage is -1 or @xpage has not been completed, @xpage_done is not modified.
  *
  * @cb_start is a pointer to the compression block which needs decompressing
  * and @cb_size is the size of @cb_start in bytes (8-64kiB).
  *
  * Return 0 if success or -EOVERFLOW on error in the compressed stream.
  * @xpage_done indicates whether the target page (@dest_pages[@xpage]) was
  * completed during the decompression of the compression block (@cb_start).
  *
  * Warning: This function *REQUIRES* PAGE_SIZE >= 4096 or it will blow up
  * unpredicatbly! You have been warned!
  *
  * Note to hackers: This function may not sleep until it has finished accessing
  * the compression block @cb_start as it is a per-CPU buffer.
  */
 static int ntfs_decompress(struct page *dest_pages[], int completed_pages[],
         int *dest_index, int *dest_ofs, const int dest_max_index,
         const int dest_max_ofs, const int xpage, char *xpage_done,
         u8 *const cb_start, const u32 cb_size, const loff_t i_size,
         const s64 initialized_size)
 {
     /*
      * Pointers into the compressed data, i.e. the compression block (cb),
      * and the therein contained sub-blocks (sb).
      */
     u8 *cb_end = cb_start + cb_size; /* End of cb. */
     u8 *cb = cb_start;  /* Current position in cb. */
     u8 *cb_sb_start = cb;   /* Beginning of the current sb in the cb. */
     u8 *cb_sb_end;      /* End of current sb / beginning of next sb. */
 
     /* Variables for uncompressed data / destination. */
     struct page *dp;    /* Current destination page being worked on. */
     u8 *dp_addr;        /* Current pointer into dp. */
     u8 *dp_sb_start;    /* Start of current sub-block in dp. */
     u8 *dp_sb_end;      /* End of current sb in dp (dp_sb_start +
                    NTFS_SB_SIZE). */
     u16 do_sb_start;    /* @dest_ofs when starting this sub-block. */
     u16 do_sb_end;      /* @dest_ofs of end of this sb (do_sb_start +
                    NTFS_SB_SIZE). */
 
     /* Variables for tag and token parsing. */
     u8 tag;         /* Current tag. */
     int token;      /* Loop counter for the eight tokens in tag. */
     int nr_completed_pages = 0;
 
     /* Default error code. */
     int err = -EOVERFLOW;
 
     ntfs_debug("Entering, cb_size = 0x%x.", cb_size);
 do_next_sb:
     ntfs_debug("Beginning sub-block at offset = 0x%zx in the cb.",
             cb - cb_start);
     /*
      * Have we reached the end of the compression block or the end of the
      * decompressed data?  The latter can happen for example if the current
      * position in the compression block is one byte before its end so the
      * first two checks do not detect it.
      */
     if (cb == cb_end || !le16_to_cpup((le16*)cb) ||
             (*dest_index == dest_max_index &&
             *dest_ofs == dest_max_ofs)) {
         int i;
 
         ntfs_debug("Completed. Returning success (0).");
         err = 0;
 return_error:
         /* We can sleep from now on, so we drop lock. */
         spin_unlock(&ntfs_cb_lock);
         /* Second stage: finalize completed pages. */
         if (nr_completed_pages > 0) {
             for (i = 0; i < nr_completed_pages; i++) {
                 int di = completed_pages[i];
 
                 dp = dest_pages[di];
                 /*
                  * If we are outside the initialized size, zero
                  * the out of bounds page range.
                  */
                 handle_bounds_compressed_page(dp, i_size,
                         initialized_size);
                 flush_dcache_page(dp);
                 kunmap(dp);
                 SetPageUptodate(dp);
                 unlock_page(dp);
                 if (di == xpage)
                     *xpage_done = 1;
                 else
                     put_page(dp);
                 dest_pages[di] = NULL;
             }
         }
         return err;
     }
 
     /* Setup offsets for the current sub-block destination. */
     do_sb_start = *dest_ofs;
     do_sb_end = do_sb_start + NTFS_SB_SIZE;
 
     /* Check that we are still within allowed boundaries. */
     if (*dest_index == dest_max_index && do_sb_end > dest_max_ofs)
         goto return_overflow;
 
     /* Does the minimum size of a compressed sb overflow valid range? */
     if (cb + 6 > cb_end)
         goto return_overflow;
 
     /* Setup the current sub-block source pointers and validate range. */
     cb_sb_start = cb;
     cb_sb_end = cb_sb_start + (le16_to_cpup((le16*)cb) & NTFS_SB_SIZE_MASK)
             + 3;
     if (cb_sb_end > cb_end)
         goto return_overflow;
 
     /* Get the current destination page. */
     dp = dest_pages[*dest_index];
     if (!dp) {
         /* No page present. Skip decompression of this sub-block. */
         cb = cb_sb_end;
 
         /* Advance destination position to next sub-block. */
         *dest_ofs = (*dest_ofs + NTFS_SB_SIZE) & ~PAGE_MASK;
         if (!*dest_ofs && (++*dest_index > dest_max_index))
             goto return_overflow;
         goto do_next_sb;
     }
 
     /* We have a valid destination page. Setup the destination pointers. */
     dp_addr = (u8*)page_address(dp) + do_sb_start;
 
     /* Now, we are ready to process the current sub-block (sb). */
     if (!(le16_to_cpup((le16*)cb) & NTFS_SB_IS_COMPRESSED)) {
         ntfs_debug("Found uncompressed sub-block.");
         /* This sb is not compressed, just copy it into destination. */
 
         /* Advance source position to first data byte. */
         cb += 2;
 
         /* An uncompressed sb must be full size. */
         if (cb_sb_end - cb != NTFS_SB_SIZE)
             goto return_overflow;
 
         /* Copy the block and advance the source position. */
         memcpy(dp_addr, cb, NTFS_SB_SIZE);
         cb += NTFS_SB_SIZE;
 
         /* Advance destination position to next sub-block. */
         *dest_ofs += NTFS_SB_SIZE;
         if (!(*dest_ofs &= ~PAGE_MASK)) {
 finalize_page:
             /*
              * First stage: add current page index to array of
              * completed pages.
              */
             completed_pages[nr_completed_pages++] = *dest_index;
             if (++*dest_index > dest_max_index)
                 goto return_overflow;
         }
         goto do_next_sb;
     }
     ntfs_debug("Found compressed sub-block.");
     /* This sb is compressed, decompress it into destination. */
 
     /* Setup destination pointers. */
     dp_sb_start = dp_addr;
     dp_sb_end = dp_sb_start + NTFS_SB_SIZE;
 
     /* Forward to the first tag in the sub-block. */
     cb += 2;
 do_next_tag:
     if (cb == cb_sb_end) {
         /* Check if the decompressed sub-block was not full-length. */
         if (dp_addr < dp_sb_end) {
             int nr_bytes = do_sb_end - *dest_ofs;
 
             ntfs_debug("Filling incomplete sub-block with "
                     "zeroes.");
             /* Zero remainder and update destination position. */
             memset(dp_addr, 0, nr_bytes);
             *dest_ofs += nr_bytes;
         }
         /* We have finished the current sub-block. */
         if (!(*dest_ofs &= ~PAGE_MASK))
             goto finalize_page;
         goto do_next_sb;
     }
 
     /* Check we are still in range. */
     if (cb > cb_sb_end || dp_addr > dp_sb_end)
         goto return_overflow;
 
     /* Get the next tag and advance to first token. */
     tag = *cb++;
 
     /* Parse the eight tokens described by the tag. */
     for (token = 0; token < 8; token++, tag >>= 1) {
         u16 lg, pt, length, max_non_overlap;
         register u16 i;
         u8 *dp_back_addr;
 
         /* Check if we are done / still in range. */
         if (cb >= cb_sb_end || dp_addr > dp_sb_end)
             break;
 
         /* Determine token type and parse appropriately.*/
         if ((tag & NTFS_TOKEN_MASK) == NTFS_SYMBOL_TOKEN) {
             /*
              * We have a symbol token, copy the symbol across, and
              * advance the source and destination positions.
              */
             *dp_addr++ = *cb++;
             ++*dest_ofs;
 
             /* Continue with the next token. */
             continue;
         }
 
         /*
          * We have a phrase token. Make sure it is not the first tag in
          * the sb as this is illegal and would confuse the code below.
          */
         if (dp_addr == dp_sb_start)
             goto return_overflow;
 
         /*
          * Determine the number of bytes to go back (p) and the number
          * of bytes to copy (l). We use an optimized algorithm in which
          * we first calculate log2(current destination position in sb),
          * which allows determination of l and p in O(1) rather than
          * O(n). We just need an arch-optimized log2() function now.
          */
         lg = 0;
         for (i = *dest_ofs - do_sb_start - 1; i >= 0x10; i >>= 1)
             lg++;
 
         /* Get the phrase token into i. */
         pt = le16_to_cpup((le16*)cb);
 
         /*
          * Calculate starting position of the byte sequence in
          * the destination using the fact that p = (pt >> (12 - lg)) + 1
          * and make sure we don't go too far back.
          */
         dp_back_addr = dp_addr - (pt >> (12 - lg)) - 1;
         if (dp_back_addr < dp_sb_start)
             goto return_overflow;
 
         /* Now calculate the length of the byte sequence. */
         length = (pt & (0xfff >> lg)) + 3;
 
         /* Advance destination position and verify it is in range. */
         *dest_ofs += length;
         if (*dest_ofs > do_sb_end)
             goto return_overflow;
 
         /* The number of non-overlapping bytes. */
         max_non_overlap = dp_addr - dp_back_addr;
 
         if (length <= max_non_overlap) {
             /* The byte sequence doesn't overlap, just copy it. */
             memcpy(dp_addr, dp_back_addr, length);
 
             /* Advance destination pointer. */
             dp_addr += length;
         } else {
             /*
              * The byte sequence does overlap, copy non-overlapping
              * part and then do a slow byte by byte copy for the
              * overlapping part. Also, advance the destination
              * pointer.
              */
             memcpy(dp_addr, dp_back_addr, max_non_overlap);
             dp_addr += max_non_overlap;
             dp_back_addr += max_non_overlap;
             length -= max_non_overlap;
             while (length--)
                 *dp_addr++ = *dp_back_addr++;
         }
 
         /* Advance source position and continue with the next token. */
         cb += 2;
     }
 
     /* No tokens left in the current tag. Continue with the next tag. */
     goto do_next_tag;
 
 return_overflow:
     ntfs_error(NULL, "Failed. Returning -EOVERFLOW.");
     goto return_error;
 }
 
 /**
  * ntfs_read_compressed_block - read a compressed block into the page cache
  * @page:   locked page in the compression block(s) we need to read
  *
  * When we are called the page has already been verified to be locked and the
  * attribute is known to be non-resident, not encrypted, but compressed.
  *
  * 1. Determine which compression block(s) @page is in.
  * 2. Get hold of all pages corresponding to this/these compression block(s).
  * 3. Read the (first) compression block.
  * 4. Decompress it into the corresponding pages.
  * 5. Throw the compressed data away and proceed to 3. for the next compression
  *    block or return success if no more compression blocks left.
  *
  * Warning: We have to be careful what we do about existing pages. They might
  * have been written to so that we would lose data if we were to just overwrite
  * them with the out-of-date uncompressed data.
  *
  * FIXME: For PAGE_SIZE > cb_size we are not doing the Right Thing(TM) at
  * the end of the file I think. We need to detect this case and zero the out
  * of bounds remainder of the page in question and mark it as handled. At the
  * moment we would just return -EIO on such a page. This bug will only become
  * apparent if pages are above 8kiB and the NTFS volume only uses 512 byte
  * clusters so is probably not going to be seen by anyone. Still this should
  * be fixed. (AIA)
  *
  * FIXME: Again for PAGE_SIZE > cb_size we are screwing up both in
  * handling sparse and compressed cbs. (AIA)
  *
  * FIXME: At the moment we don't do any zeroing out in the case that
  * initialized_size is less than data_size. This should be safe because of the
  * nature of the compression algorithm used. Just in case we check and output
  * an error message in read inode if the two sizes are not equal for a
  * compressed file. (AIA)
  */
 int ntfs_read_compressed_block(struct page *page)
 {
     loff_t i_size;
     s64 initialized_size;
     struct address_space *mapping = page->mapping;
     ntfs_inode *ni = NTFS_I(mapping->host);
     ntfs_volume *vol = ni->vol;
     struct super_block *sb = vol->sb;
     runlist_element *rl;
     unsigned long flags, block_size = sb->s_blocksize;
     unsigned char block_size_bits = sb->s_blocksize_bits;
     u8 *cb, *cb_pos, *cb_end;
     struct buffer_head **bhs;
     unsigned long offset, index = page->index;
     u32 cb_size = ni->itype.compressed.block_size;
     u64 cb_size_mask = cb_size - 1UL;
     VCN vcn;
     LCN lcn;
     /* The first wanted vcn (minimum alignment is PAGE_SIZE). */
     VCN start_vcn = (((s64)index << PAGE_SHIFT) & ~cb_size_mask) >>
             vol->cluster_size_bits;
     /*
      * The first vcn after the last wanted vcn (minimum alignment is again
      * PAGE_SIZE.
      */
     VCN end_vcn = ((((s64)(index + 1UL) << PAGE_SHIFT) + cb_size - 1)
             & ~cb_size_mask) >> vol->cluster_size_bits;
     /* Number of compression blocks (cbs) in the wanted vcn range. */
     unsigned int nr_cbs = (end_vcn - start_vcn) << vol->cluster_size_bits
             >> ni->itype.compressed.block_size_bits;
     /*
      * Number of pages required to store the uncompressed data from all
      * compression blocks (cbs) overlapping @page. Due to alignment
      * guarantees of start_vcn and end_vcn, no need to round up here.
      */
     unsigned int nr_pages = (end_vcn - start_vcn) <<
             vol->cluster_size_bits >> PAGE_SHIFT;
     unsigned int xpage, max_page, cur_page, cur_ofs, i;
     unsigned int cb_clusters, cb_max_ofs;
     int block, max_block, cb_max_page, bhs_size, nr_bhs, err = 0;
     struct page **pages;
     int *completed_pages;
     unsigned char xpage_done = 0;
 
     ntfs_debug("Entering, page->index = 0x%lx, cb_size = 0x%x, nr_pages = "
             "%i.", index, cb_size, nr_pages);
     /*
      * Bad things happen if we get here for anything that is not an
      * unnamed $DATA attribute.
      */
     BUG_ON(ni->type != AT_DATA);
     BUG_ON(ni->name_len);
 
     pages = kmalloc_array(nr_pages, sizeof(struct page *), GFP_NOFS);
     completed_pages = kmalloc_array(nr_pages + 1, sizeof(int), GFP_NOFS);
 
     /* Allocate memory to store the buffer heads we need. */
     bhs_size = cb_size / block_size * sizeof(struct buffer_head *);
     bhs = kmalloc(bhs_size, GFP_NOFS);
 
     if (unlikely(!pages || !bhs || !completed_pages)) {
         kfree(bhs);
         kfree(pages);
         kfree(completed_pages);
         unlock_page(page);
         ntfs_error(vol->sb, "Failed to allocate internal buffers.");
         return -ENOMEM;
     }
 
     /*
      * We have already been given one page, this is the one we must do.
      * Once again, the alignment guarantees keep it simple.
      */
     offset = start_vcn << vol->cluster_size_bits >> PAGE_SHIFT;
     xpage = index - offset;
     pages[xpage] = page;
     /*
      * The remaining pages need to be allocated and inserted into the page
      * cache, alignment guarantees keep all the below much simpler. (-8
      */
     read_lock_irqsave(&ni->size_lock, flags);
     i_size = i_size_read(VFS_I(ni));
     initialized_size = ni->initialized_size;
     read_unlock_irqrestore(&ni->size_lock, flags);
     max_page = ((i_size + PAGE_SIZE - 1) >> PAGE_SHIFT) -
             offset;
     /* Is the page fully outside i_size? (truncate in progress) */
     if (xpage >= max_page) {
         kfree(bhs);
         kfree(pages);
         kfree(completed_pages);
         zero_user(page, 0, PAGE_SIZE);
         ntfs_debug("Compressed read outside i_size - truncated?");
         SetPageUptodate(page);
         unlock_page(page);
         return 0;
     }
     if (nr_pages < max_page)
         max_page = nr_pages;
     for (i = 0; i < max_page; i++, offset++) {
         if (i != xpage)
             pages[i] = grab_cache_page_nowait(mapping, offset);
         page = pages[i];
         if (page) {
             /*
              * We only (re)read the page if it isn't already read
              * in and/or dirty or we would be losing data or at
              * least wasting our time.
              */
             if (!PageDirty(page) && (!PageUptodate(page) ||
                     PageError(page))) {
                 ClearPageError(page);
                 kmap(page);
                 continue;
             }
             unlock_page(page);
             put_page(page);
             pages[i] = NULL;
         }
     }
 
     /*
      * We have the runlist, and all the destination pages we need to fill.
      * Now read the first compression block.
      */
     cur_page = 0;
     cur_ofs = 0;
     cb_clusters = ni->itype.compressed.block_clusters;
 do_next_cb:
     nr_cbs--;
     nr_bhs = 0;
 
     /* Read all cb buffer heads one cluster at a time. */
     rl = NULL;
     for (vcn = start_vcn, start_vcn += cb_clusters; vcn < start_vcn;
             vcn++) {
         bool is_retry = false;
 
         if (!rl) {
 lock_retry_remap:
             down_read(&ni->runlist.lock);
             rl = ni->runlist.rl;
         }
         if (likely(rl != NULL)) {
             /* Seek to element containing target vcn. */
             while (rl->length && rl[1].vcn <= vcn)
                 rl++;
             lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
         } else
             lcn = LCN_RL_NOT_MAPPED;
         ntfs_debug("Reading vcn = 0x%llx, lcn = 0x%llx.",
                 (unsigned long long)vcn,
                 (unsigned long long)lcn);
         if (lcn < 0) {
             /*
              * When we reach the first sparse cluster we have
              * finished with the cb.
              */
             if (lcn == LCN_HOLE)
                 break;
             if (is_retry || lcn != LCN_RL_NOT_MAPPED)
                 goto rl_err;
             is_retry = true;
             /*
              * Attempt to map runlist, dropping lock for the
              * duration.
              */
             up_read(&ni->runlist.lock);
             if (!ntfs_map_runlist(ni, vcn))
                 goto lock_retry_remap;
             goto map_rl_err;
         }
         block = lcn << vol->cluster_size_bits >> block_size_bits;
         /* Read the lcn from device in chunks of block_size bytes. */
         max_block = block + (vol->cluster_size >> block_size_bits);
         do {
             ntfs_debug("block = 0x%x.", block);
             if (unlikely(!(bhs[nr_bhs] = sb_getblk(sb, block))))
                 goto getblk_err;
             nr_bhs++;
         } while (++block < max_block);
     }
 
     /* Release the lock if we took it. */
     if (rl)
         up_read(&ni->runlist.lock);
 
     /* Setup and initiate io on all buffer heads. */
     for (i = 0; i < nr_bhs; i++) {
         struct buffer_head *tbh = bhs[i];
 
         if (!trylock_buffer(tbh))
             continue;
         if (unlikely(buffer_uptodate(tbh))) {
             unlock_buffer(tbh);
             continue;
         }
         get_bh(tbh);
         tbh->b_end_io = end_buffer_read_sync;
         submit_bh(REQ_OP_READ, tbh);
     }
 
     /* Wait for io completion on all buffer heads. */
     for (i = 0; i < nr_bhs; i++) {
         struct buffer_head *tbh = bhs[i];
 
         if (buffer_uptodate(tbh))
             continue;
         wait_on_buffer(tbh);
         /*
          * We need an optimization barrier here, otherwise we start
          * hitting the below fixup code when accessing a loopback
          * mounted ntfs partition. This indicates either there is a
          * race condition in the loop driver or, more likely, gcc
          * overoptimises the code without the barrier and it doesn't
          * do the Right Thing(TM).
          */
         barrier();
         if (unlikely(!buffer_uptodate(tbh))) {
             ntfs_warning(vol->sb, "Buffer is unlocked but not "
                     "uptodate! Unplugging the disk queue "
                     "and rescheduling.");
             get_bh(tbh);
             io_schedule();
             put_bh(tbh);
             if (unlikely(!buffer_uptodate(tbh)))
                 goto read_err;
             ntfs_warning(vol->sb, "Buffer is now uptodate. Good.");
         }
     }
 
     /*
      * Get the compression buffer. We must not sleep any more
      * until we are finished with it.
      */
     spin_lock(&ntfs_cb_lock);
     cb = ntfs_compression_buffer;
 
     BUG_ON(!cb);
 
     cb_pos = cb;
     cb_end = cb + cb_size;
 
     /* Copy the buffer heads into the contiguous buffer. */
     for (i = 0; i < nr_bhs; i++) {
         memcpy(cb_pos, bhs[i]->b_data, block_size);
         cb_pos += block_size;
     }
 
     /* Just a precaution. */
     if (cb_pos + 2 <= cb + cb_size)
         *(u16*)cb_pos = 0;
 
     /* Reset cb_pos back to the beginning. */
     cb_pos = cb;
 
     /* We now have both source (if present) and destination. */
     ntfs_debug("Successfully read the compression block.");
 
     /* The last page and maximum offset within it for the current cb. */
     cb_max_page = (cur_page << PAGE_SHIFT) + cur_ofs + cb_size;
     cb_max_ofs = cb_max_page & ~PAGE_MASK;
     cb_max_page >>= PAGE_SHIFT;
 
     /* Catch end of file inside a compression block. */
     if (cb_max_page > max_page)
         cb_max_page = max_page;
 
     if (vcn == start_vcn - cb_clusters) {
         /* Sparse cb, zero out page range overlapping the cb. */
         ntfs_debug("Found sparse compression block.");
         /* We can sleep from now on, so we drop lock. */
         spin_unlock(&ntfs_cb_lock);
         if (cb_max_ofs)
             cb_max_page--;
         for (; cur_page < cb_max_page; cur_page++) {
             page = pages[cur_page];
             if (page) {
                 if (likely(!cur_ofs))
                     clear_page(page_address(page));
                 else
                     memset(page_address(page) + cur_ofs, 0,
                             PAGE_SIZE -
                             cur_ofs);
                 flush_dcache_page(page);
                 kunmap(page);
                 SetPageUptodate(page);
                 unlock_page(page);
                 if (cur_page == xpage)
                     xpage_done = 1;
                 else
                     put_page(page);
                 pages[cur_page] = NULL;
             }
             cb_pos += PAGE_SIZE - cur_ofs;
             cur_ofs = 0;
             if (cb_pos >= cb_end)
                 break;
         }
         /* If we have a partial final page, deal with it now. */
         if (cb_max_ofs && cb_pos < cb_end) {
             page = pages[cur_page];
             if (page)
                 memset(page_address(page) + cur_ofs, 0,
                         cb_max_ofs - cur_ofs);
             /*
              * No need to update cb_pos at this stage:
              *  cb_pos += cb_max_ofs - cur_ofs;
              */
             cur_ofs = cb_max_ofs;
         }
     } else if (vcn == start_vcn) {
         /* We can't sleep so we need two stages. */
         unsigned int cur2_page = cur_page;
         unsigned int cur_ofs2 = cur_ofs;
         u8 *cb_pos2 = cb_pos;
 
         ntfs_debug("Found uncompressed compression block.");
         /* Uncompressed cb, copy it to the destination pages. */
         /*
          * TODO: As a big optimization, we could detect this case
          * before we read all the pages and use block_read_full_folio()
          * on all full pages instead (we still have to treat partial
          * pages especially but at least we are getting rid of the
          * synchronous io for the majority of pages.
          * Or if we choose not to do the read-ahead/-behind stuff, we
          * could just return block_read_full_folio(pages[xpage]) as long
          * as PAGE_SIZE <= cb_size.
          */
         if (cb_max_ofs)
             cb_max_page--;
         /* First stage: copy data into destination pages. */
         for (; cur_page < cb_max_page; cur_page++) {
             page = pages[cur_page];
             if (page)
                 memcpy(page_address(page) + cur_ofs, cb_pos,
                         PAGE_SIZE - cur_ofs);
             cb_pos += PAGE_SIZE - cur_ofs;
             cur_ofs = 0;
             if (cb_pos >= cb_end)
                 break;
         }
         /* If we have a partial final page, deal with it now. */
         if (cb_max_ofs && cb_pos < cb_end) {
             page = pages[cur_page];
             if (page)
                 memcpy(page_address(page) + cur_ofs, cb_pos,
                         cb_max_ofs - cur_ofs);
             cb_pos += cb_max_ofs - cur_ofs;
             cur_ofs = cb_max_ofs;
         }
         /* We can sleep from now on, so drop lock. */
         spin_unlock(&ntfs_cb_lock);
         /* Second stage: finalize pages. */
         for (; cur2_page < cb_max_page; cur2_page++) {
             page = pages[cur2_page];
             if (page) {
                 /*
                  * If we are outside the initialized size, zero
                  * the out of bounds page range.
                  */
                 handle_bounds_compressed_page(page, i_size,
                         initialized_size);
                 flush_dcache_page(page);
                 kunmap(page);
                 SetPageUptodate(page);
                 unlock_page(page);
                 if (cur2_page == xpage)
                     xpage_done = 1;
                 else
                     put_page(page);
                 pages[cur2_page] = NULL;
             }
             cb_pos2 += PAGE_SIZE - cur_ofs2;
             cur_ofs2 = 0;
             if (cb_pos2 >= cb_end)
                 break;
         }
     } else {
         /* Compressed cb, decompress it into the destination page(s). */
         unsigned int prev_cur_page = cur_page;
 
         ntfs_debug("Found compressed compression block.");
         err = ntfs_decompress(pages, completed_pages, &cur_page,
                 &cur_ofs, cb_max_page, cb_max_ofs, xpage,
                 &xpage_done, cb_pos, cb_size - (cb_pos - cb),
                 i_size, initialized_size);
         /*
          * We can sleep from now on, lock already dropped by
          * ntfs_decompress().
          */
         if (err) {
             ntfs_error(vol->sb, "ntfs_decompress() failed in inode "
                     "0x%lx with error code %i. Skipping "
                     "this compression block.",
                     ni->mft_no, -err);
             /* Release the unfinished pages. */
             for (; prev_cur_page < cur_page; prev_cur_page++) {
                 page = pages[prev_cur_page];
                 if (page) {
                     flush_dcache_page(page);
                     kunmap(page);
                     unlock_page(page);
                     if (prev_cur_page != xpage)
                         put_page(page);
                     pages[prev_cur_page] = NULL;
                 }
             }
         }
     }
 
     /* Release the buffer heads. */
     for (i = 0; i < nr_bhs; i++)
         brelse(bhs[i]);
 
     /* Do we have more work to do? */
     if (nr_cbs)
         goto do_next_cb;
 
     /* We no longer need the list of buffer heads. */
     kfree(bhs);
 
     /* Clean up if we have any pages left. Should never happen. */
     for (cur_page = 0; cur_page < max_page; cur_page++) {
         page = pages[cur_page];
         if (page) {
             ntfs_error(vol->sb, "Still have pages left! "
                     "Terminating them with extreme "
                     "prejudice.  Inode 0x%lx, page index "
                     "0x%lx.", ni->mft_no, page->index);
             flush_dcache_page(page);
             kunmap(page);
             unlock_page(page);
             if (cur_page != xpage)
                 put_page(page);
             pages[cur_page] = NULL;
         }
     }
 
     /* We no longer need the list of pages. */
     kfree(pages);
     kfree(completed_pages);
 
     /* If we have completed the requested page, we return success. */
     if (likely(xpage_done))
         return 0;
 
     ntfs_debug("Failed. Returning error code %s.", err == -EOVERFLOW ?
             "EOVERFLOW" : (!err ? "EIO" : "unknown error"));
     return err < 0 ? err : -EIO;
 
 read_err:
     ntfs_error(vol->sb, "IO error while reading compressed data.");
     /* Release the buffer heads. */
     for (i = 0; i < nr_bhs; i++)
         brelse(bhs[i]);
     goto err_out;
 
 map_rl_err:
     ntfs_error(vol->sb, "ntfs_map_runlist() failed. Cannot read "
             "compression block.");
     goto err_out;
 
 rl_err:
     up_read(&ni->runlist.lock);
     ntfs_error(vol->sb, "ntfs_rl_vcn_to_lcn() failed. Cannot read "
             "compression block.");
     goto err_out;
 
 getblk_err:
     up_read(&ni->runlist.lock);
     ntfs_error(vol->sb, "getblk() failed. Cannot read compression block.");
 
 err_out:
     kfree(bhs);
     for (i = cur_page; i < max_page; i++) {
         page = pages[i];
         if (page) {
             flush_dcache_page(page);
             kunmap(page);
             unlock_page(page);
             if (i != xpage)
                 put_page(page);
         }
     }
     kfree(pages);
     kfree(completed_pages);
     return -EIO;
 }

This page was automatically generated by the 2.1.0 LXR engine. The LXR team