- 根目录:
- fs
- ntfs
- compress.c
/**
* compress.c - NTFS kernel compressed attributes handling.
* Part of the Linux-NTFS project.
*
* Copyright (c) 2001-2004 Anton Altaparmakov
* Copyright (c) 2002 Richard Russon
*
* This program/include file is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as published
* by the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program/include file is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (in the main directory of the Linux-NTFS
* distribution in the file COPYING); if not, write to the Free Software
* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#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 = NULL;
/**
* 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_CACHE_SHIFT) >= initialized_size) {
/*
* FIXME: Using clear_page() will become wrong when we get
* PAGE_CACHE_SIZE != PAGE_SIZE but for now there is no problem.
*/
clear_page(kp);
return;
}
kp_ofs = initialized_size & ~PAGE_CACHE_MASK;
memset(kp + kp_ofs, 0, PAGE_CACHE_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_CACHE_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
* @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_CACHE_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 *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. */
/* Need this because we can't sleep, so need two stages. */
int completed_pages[dest_max_index - *dest_index + 1];
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
page_cache_release(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_CACHE_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_CACHE_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_CACHE_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_CACHE_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_CACHE_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_CACHE_SIZE). */
VCN start_vcn = (((s64)index << PAGE_CACHE_SHIFT) & ~cb_size_mask) >>
vol->cluster_size_bits;
/*
* The first vcn after the last wanted vcn (minimum alignment is again
* PAGE_CACHE_SIZE.
*/
VCN end_vcn = ((((s64)(index + 1UL) << PAGE_CACHE_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_CACHE_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;
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(nr_pages * sizeof(struct page *), 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)) {
kfree(bhs);
kfree(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_CACHE_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_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
offset;
/* Is the page fully outside i_size? (truncate in progress) */
if (xpage >= max_page) {
kfree(bhs);
kfree(pages);
zero_user(page, 0, PAGE_CACHE_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);
page_cache_release(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(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_CACHE_SHIFT) + cur_ofs + cb_size;
cb_max_ofs = cb_max_page & ~PAGE_CACHE_MASK;
cb_max_page >>= PAGE_CACHE_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) {
/*
* FIXME: Using clear_page() will become wrong
* when we get PAGE_CACHE_SIZE != PAGE_SIZE but
* for now there is no problem.
*/
if (likely(!cur_ofs))
clear_page(page_address(page));
else
memset(page_address(page) + cur_ofs, 0,
PAGE_CACHE_SIZE -
cur_ofs);
flush_dcache_page(page);
kunmap(page);
SetPageUptodate(page);
unlock_page(page);
if (cur_page == xpage)
xpage_done = 1;
else
page_cache_release(page);
pages[cur_page] = NULL;
}
cb_pos += PAGE_CACHE_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_page()
* 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_page(pages[xpage]) as long
* as PAGE_CACHE_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_CACHE_SIZE - cur_ofs);
cb_pos += PAGE_CACHE_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
page_cache_release(page);
pages[cur2_page] = NULL;
}
cb_pos2 += PAGE_CACHE_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, &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)
page_cache_release(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)
page_cache_release(page);
pages[cur_page] = NULL;
}
}
/* We no longer need the list of pages. */
kfree(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)
page_cache_release(page);
}
}
kfree(pages);
return -EIO;
}