Re: [f2fs-dev] [PING][PATCH] f2fs: force out‑place update for all writes on compressed file

[Jiucheng Xu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 9/7/2026 3:08 PM, Chao Yu wrote:
> [ EXTERNAL EMAIL ]
> 
> On 9/2/26 11:18, Jiucheng Xu wrote:
> 
> Jiucheng,
> 
> Sorry for delay reply.
> 
> 
> I didn't get it, can you please describe the issue w/ call stack in race
> condition?
>
Hi Chao,

Thanks for your time, The call stack is shown as below:

-Thread A                                         - Thread B
 - f2fs_write_multi_pages                          -
f2fs_down_write(&sbi->cp_rwsem);
  - f2fs_write_compressed_pages                    - ...
   - f2fs_trylock_op                               - ...
    - f2fs_down_read_trylock(&sbi->cp_rwsem);      - ...
  - f2fs_write_raw_pages                           - ...

Thread B acquires the lock first, which causes Thread A to fail lock
acquisition and fall back to raw‑data write.
IPU_FORCE is enabled on 16G eMMC platforms, so f2fs_write_raw_pages()
overwrites the original compressed data in‑place.
The in‑memory node has been updated with raw‑data addresses, while the
node metadata stored on eMMC still remains in compressed state.
If a power‑cut occurs before the node is flushed to disk, on‑disk
inconsistency arises: The data on disk is raw, but metadata
still treats it as a compressed cluster and decompression will fail.




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