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![Kirill A. Shutemov](/assets/img/avatar_default.png)
PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
214 lines
5.5 KiB
C
214 lines
5.5 KiB
C
/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@squashfs.org.uk>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2,
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* or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* block.c
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*/
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/*
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* This file implements the low-level routines to read and decompress
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* datablocks and metadata blocks.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/buffer_head.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs.h"
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#include "decompressor.h"
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#include "page_actor.h"
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/*
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* Read the metadata block length, this is stored in the first two
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* bytes of the metadata block.
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*/
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static struct buffer_head *get_block_length(struct super_block *sb,
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u64 *cur_index, int *offset, int *length)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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struct buffer_head *bh;
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bh = sb_bread(sb, *cur_index);
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if (bh == NULL)
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return NULL;
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if (msblk->devblksize - *offset == 1) {
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*length = (unsigned char) bh->b_data[*offset];
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put_bh(bh);
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bh = sb_bread(sb, ++(*cur_index));
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if (bh == NULL)
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return NULL;
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*length |= (unsigned char) bh->b_data[0] << 8;
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*offset = 1;
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} else {
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*length = (unsigned char) bh->b_data[*offset] |
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(unsigned char) bh->b_data[*offset + 1] << 8;
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*offset += 2;
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if (*offset == msblk->devblksize) {
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put_bh(bh);
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bh = sb_bread(sb, ++(*cur_index));
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if (bh == NULL)
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return NULL;
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*offset = 0;
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}
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}
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return bh;
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}
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/*
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* Read and decompress a metadata block or datablock. Length is non-zero
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* if a datablock is being read (the size is stored elsewhere in the
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* filesystem), otherwise the length is obtained from the first two bytes of
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* the metadata block. A bit in the length field indicates if the block
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* is stored uncompressed in the filesystem (usually because compression
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* generated a larger block - this does occasionally happen with compression
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* algorithms).
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*/
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int squashfs_read_data(struct super_block *sb, u64 index, int length,
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u64 *next_index, struct squashfs_page_actor *output)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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struct buffer_head **bh;
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int offset = index & ((1 << msblk->devblksize_log2) - 1);
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u64 cur_index = index >> msblk->devblksize_log2;
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int bytes, compressed, b = 0, k = 0, avail, i;
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bh = kcalloc(((output->length + msblk->devblksize - 1)
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>> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
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if (bh == NULL)
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return -ENOMEM;
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if (length) {
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/*
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* Datablock.
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*/
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bytes = -offset;
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compressed = SQUASHFS_COMPRESSED_BLOCK(length);
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length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
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if (next_index)
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*next_index = index + length;
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TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
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index, compressed ? "" : "un", length, output->length);
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if (length < 0 || length > output->length ||
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(index + length) > msblk->bytes_used)
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goto read_failure;
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for (b = 0; bytes < length; b++, cur_index++) {
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bh[b] = sb_getblk(sb, cur_index);
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if (bh[b] == NULL)
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goto block_release;
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bytes += msblk->devblksize;
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}
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ll_rw_block(READ, b, bh);
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} else {
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/*
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* Metadata block.
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*/
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if ((index + 2) > msblk->bytes_used)
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goto read_failure;
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bh[0] = get_block_length(sb, &cur_index, &offset, &length);
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if (bh[0] == NULL)
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goto read_failure;
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b = 1;
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bytes = msblk->devblksize - offset;
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compressed = SQUASHFS_COMPRESSED(length);
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length = SQUASHFS_COMPRESSED_SIZE(length);
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if (next_index)
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*next_index = index + length + 2;
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TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
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compressed ? "" : "un", length);
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if (length < 0 || length > output->length ||
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(index + length) > msblk->bytes_used)
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goto block_release;
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for (; bytes < length; b++) {
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bh[b] = sb_getblk(sb, ++cur_index);
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if (bh[b] == NULL)
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goto block_release;
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bytes += msblk->devblksize;
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}
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ll_rw_block(READ, b - 1, bh + 1);
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}
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for (i = 0; i < b; i++) {
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wait_on_buffer(bh[i]);
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if (!buffer_uptodate(bh[i]))
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goto block_release;
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}
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if (compressed) {
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length = squashfs_decompress(msblk, bh, b, offset, length,
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output);
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if (length < 0)
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goto read_failure;
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} else {
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/*
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* Block is uncompressed.
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*/
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int in, pg_offset = 0;
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void *data = squashfs_first_page(output);
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for (bytes = length; k < b; k++) {
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in = min(bytes, msblk->devblksize - offset);
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bytes -= in;
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while (in) {
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if (pg_offset == PAGE_SIZE) {
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data = squashfs_next_page(output);
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pg_offset = 0;
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}
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avail = min_t(int, in, PAGE_SIZE -
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pg_offset);
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memcpy(data + pg_offset, bh[k]->b_data + offset,
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avail);
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in -= avail;
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pg_offset += avail;
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offset += avail;
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}
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offset = 0;
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put_bh(bh[k]);
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}
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squashfs_finish_page(output);
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}
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kfree(bh);
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return length;
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block_release:
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for (; k < b; k++)
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put_bh(bh[k]);
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read_failure:
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ERROR("squashfs_read_data failed to read block 0x%llx\n",
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(unsigned long long) index);
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kfree(bh);
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return -EIO;
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}
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