linux/fs/ntfs/compress.c
Christoph Lameter eebd2aa355 Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user
Simplify page cache zeroing of segments of pages through 3 functions

zero_user_segments(page, start1, end1, start2, end2)

        Zeros two segments of the page. It takes the position where to
        start and end the zeroing which avoids length calculations and
	makes code clearer.

zero_user_segment(page, start, end)

        Same for a single segment.

zero_user(page, start, length)

        Length variant for the case where we know the length.

We remove the zero_user_page macro. Issues:

1. Its a macro. Inline functions are preferable.

2. The KM_USER0 macro is only defined for HIGHMEM.

   Having to treat this special case everywhere makes the
   code needlessly complex. The parameter for zeroing is always
   KM_USER0 except in one single case that we open code.

Avoiding KM_USER0 makes a lot of code not having to be dealing
with the special casing for HIGHMEM anymore. Dealing with
kmap is only necessary for HIGHMEM configurations. In those
configurations we use KM_USER0 like we do for a series of other
functions defined in highmem.h.

Since KM_USER0 is depends on HIGHMEM the existing zero_user_page
function could not be a macro. zero_user_* functions introduced
here can be be inline because that constant is not used when these
functions are called.

Also extract the flushing of the caches to be outside of the kmap.

[akpm@linux-foundation.org: fix nfs and ntfs build]
[akpm@linux-foundation.org: fix ntfs build some more]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Steven French <sfrench@us.ibm.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Anton Altaparmakov <aia21@cantab.net>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Cc: David Chinner <dgc@sgi.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Steven French <sfrench@us.ibm.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:13 -08:00

969 lines
29 KiB
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 "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 (minumum 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 (unlikely(test_set_buffer_locked(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);
blk_run_address_space(mapping);
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" : "unkown 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;
}