f2fs: compress: don't redirty sparse cluster during {,de}compress

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In f2fs_do_write_data_page, when the data block is NULL_ADDR, it skips
writepage considering that it has been already truncated.
This results in an infinite loop as the PAGECACHE_TAG_TOWRITE tag is not
cleared during the writeback process for a compressed file including
NULL_ADDR in compress_mode=user.

This is the reproduction process:

1. dd if=/dev/zero bs=4096 count=1024 seek=1024 of=testfile
2. f2fs_io compress testfile
3. dd if=/dev/zero bs=4096 count=1 conv=notrunc of=testfile
4. f2fs_io decompress testfile

To prevent the problem, let's check whether the cluster is fully
allocated before redirty its pages.

Fixes: 5fdb322ff2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Sunmin Jeong <s_min.jeong@samsung.com>
Tested-by: Jaewook Kim <jw5454.kim@samsung.com>
Signed-off-by: Yeongjin Gil <youngjin.gil@samsung.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

...

This commit is contained in:

Yeongjin Gil 2024-08-19 17:34:30 +09:00 • committed by Jaegeuk Kim

parent 43aec4d01b

commit f785cec298

3 changed files with 61 additions and 26 deletions

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36

fs/f2fs/compress.c

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12

fs/f2fs/f2fs.h

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39

fs/f2fs/file.c

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