Re: [PATCH v2] f2fs: compress: don't redirty sparse cluster during {,de}compress

[Chao Yu]

On 2024/8/19 16:34, Yeongjin Gil wrote:
> 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: 5fdb322ff2c2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
> Reviewed-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>
> Reviewed-by: Sunmin Jeong <s_min.jeong@xxxxxxxxxxx>
> Tested-by: Jaewook Kim <jw5454.kim@xxxxxxxxxxx>
> Signed-off-by: Yeongjin Gil <youngjin.gil@xxxxxxxxxxx>

Reviewed-by: Chao Yu <chao@xxxxxxxxxx>

Thanks,