Re: [f2fs-dev] [PATCH v3] f2fs: fix compressed file start atomic write may cause data corruption

[Chao Yu <chao@kernel.org>]

On 2022/3/10 19:05, Fengnan Chang wrote:
> When compressed file has blocks, f2fs_ioc_start_atomic_write will succeed,
> but compressed flag will be remained in inode. If write partial compreseed
> cluster and commit atomic write will cause data corruption.
> 
> This is the reproduction process:
> Step 1:
> create a compressed file ,write 64K data , call fsync(), then the blocks
> are write as compressed cluster.
> Step2:
> iotcl(F2FS_IOC_START_ATOMIC_WRITE)  --- this should be fail, but not.
> write page 0 and page 3.
> iotcl(F2FS_IOC_COMMIT_ATOMIC_WRITE)  -- page 0 and 3 write as normal file,
> Step3:
> drop cache.
> read page 0-4   -- Since page 0 has a valid block address, read as
> non-compressed cluster, page 1 and 2 will be filled with compressed data
> or zero.
> 
> The root cause is, after commit 7eab7a696827 ("f2fs: compress: remove
> unneeded read when rewrite whole cluster"), in step 2, f2fs_write_begin()
> only set target page dirty, and in f2fs_commit_inmem_pages(), we will write
> partial raw pages into compressed cluster, result in corrupting compressed
> cluster layout.
> 
> Fixes: 4c8ff7095bef ("f2fs: support data compression")
> Fixes: 7eab7a696827 ("f2fs: compress: remove unneeded read when rewrite whole cluster")
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


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