linux-kernel - Re: [PATCH V2 2/2] f2fs: compress: fix reserve_cblocks counting error when out of space

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Date: Wed, 6 Mar 2024 14:01:44 +0800
From: Chao Yu <chao@...nel.org>
To: Xiuhong Wang <xiuhong.wang@...soc.com>, jaegeuk@...nel.org,
 linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Cc: hongyu.jin.cn@...il.com, niuzhiguo84@...il.com, ke.wang@...soc.com,
 xiuhong.wang.cn@...il.com
Subject: Re: [PATCH V2 2/2] f2fs: compress: fix reserve_cblocks counting error
 when out of space

On 2024/3/6 11:47, Xiuhong Wang wrote:
> When a file only needs one direct_node, performing the following
> operations will cause the file to be unrepairable:
> 
> unisoc # ./f2fs_io compress test.apk
> unisoc #df -h | grep dm-48
> /dev/block/dm-48 112G 112G 1.2M 100% /data
> 
> unisoc # ./f2fs_io release_cblocks test.apk
> 924
> unisoc # df -h | grep dm-48
> /dev/block/dm-48 112G 112G 4.8M 100% /data
> 
> unisoc # dd if=/dev/random of=file4 bs=1M count=3
> 3145728 bytes (3.0 M) copied, 0.025 s, 120 M/s
> unisoc # df -h | grep dm-48
> /dev/block/dm-48 112G 112G 1.8M 100% /data
> 
> unisoc # ./f2fs_io reserve_cblocks test.apk
> F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device
> 
> adb reboot
> unisoc # df -h  | grep dm-48
> /dev/block/dm-48             112G 112G   11M 100% /data
> unisoc # ./f2fs_io reserve_cblocks test.apk
> 0
> 
> This is because the file has only one direct_node. After returning
> to -ENOSPC, reserved_blocks += ret will not be executed. As a result,
> the reserved_blocks at this time is still 0, which is not the real
> number of reserved blocks. Therefore, fsck cannot be set to repair
> the file.
> 
> After this patch, the fsck flag will be set to fix this problem.
> 
> unisoc # df -h | grep dm-48
> /dev/block/dm-48             112G 112G  1.8M 100% /data
> unisoc # ./f2fs_io reserve_cblocks test.apk
> F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device
> 
> adb reboot then fsck will be executed
> unisoc # df -h  | grep dm-48
> /dev/block/dm-48             112G 112G   11M 100% /data
> unisoc # ./f2fs_io reserve_cblocks test.apk
> 924
> 
> Fixes: c75488fb4d82 ("f2fs: introduce F2FS_IOC_RESERVE_COMPRESS_BLOCKS")
> Signed-off-by: Xiuhong Wang <xiuhong.wang@...soc.com>
> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>

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

Thanks,