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Date: Tue, 8 Sep 2026 08:15:49 +0800
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Cc: chao@kernel.org, linux-f2fs-devel@lists.sourceforge.net,
 linux-kernel@vger.kernel.org, stable@vger.kernel.org,
 jianxin.pan@amlogic.com, tao.zeng@amlogic.com, tuan.zhang@amlogic.com
Subject: Re: [PATCH] f2fs: force out-place update for all writes on compressed
 file
To: jiucheng.xu@amlogic.com, Jaegeuk Kim <jaegeuk@kernel.org>
References: <20260907-origin-dev-v1-1-85ae7ebc8c98@amlogic.com>
Content-Language: en-US
From: Chao Yu <chao@kernel.org>
In-Reply-To: <20260907-origin-dev-v1-1-85ae7ebc8c98@amlogic.com>
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On 9/7/26 19:35, Jiucheng Xu via B4 Relay wrote:
> From: Jiucheng Xu <jiucheng.xu@amlogic.com>
> 
> For compressed file, compressed write may fail and fall back to raw
> write.
> 
> -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 small-capacity storage devices (< 16GB),
> 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: disk data is raw, yet metadata treats it as a
> compressed cluster, leading to decompression failure.
> 
> To eliminate this risk completely, force out-place update for all
> write operations on compressed file.
> 

Cc: stable@kernel.org
Fixes: 4c8ff7095bef ("f2fs: support data compression")

> Signed-off-by: Jiucheng Xu <jiucheng.xu@amlogic.com>

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

Thanks,