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![Phillip Lougher](/assets/img/avatar_default.png)
Further generalise the decompressors by adding a page handler abstraction. This adds helpers to allow the decompressors to access and process the output buffers in an implementation independant manner. This allows different types of output buffer to be passed to the decompressors, with the implementation specific aspects handled at decompression time, but without the knowledge being held in the decompressor wrapper code. This will allow the decompressors to handle Squashfs cache buffers, and page cache pages. This patch adds the abstraction and an implementation for the caches. Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk> Reviewed-by: Minchan Kim <minchan@kernel.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_CACHE_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_CACHE_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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