linux-kernel - Re: [PATCH] f2fs: fix f2fs_bug_on when uninstalling filesystem call f2fs_evict

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Message-ID: <82e4a8bb-29d4-4ce8-bc04-985b08801aeb@kernel.org>
Date: Tue, 8 Oct 2024 11:25:45 +0800
From: Chao Yu <chao@...nel.org>
To: Qi Han <hanqi@...o.com>, jaegeuk@...nel.org
Cc: Chao Yu <chao@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: fix f2fs_bug_on when uninstalling filesystem call
 f2fs_evict_inode.

On 2024/9/18 16:44, Qi Han wrote:
> creating a large files during checkpoint disable until it runs out of
> space and then delete it, then remount to enable checkpoint again, and
> then unmount the filesystem triggers the f2fs_bug_on as below:
> 
> ------------[ cut here ]------------
> kernel BUG at fs/f2fs/inode.c:896!
> CPU: 2 UID: 0 PID: 1286 Comm: umount Not tainted 6.11.0-rc7-dirty #360
> Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
> RIP: 0010:f2fs_evict_inode+0x58c/0x610
> Call Trace:
>   __die_body+0x15/0x60
>   die+0x33/0x50
>   do_trap+0x10a/0x120
>   f2fs_evict_inode+0x58c/0x610
>   do_error_trap+0x60/0x80
>   f2fs_evict_inode+0x58c/0x610
>   exc_invalid_op+0x53/0x60
>   f2fs_evict_inode+0x58c/0x610
>   asm_exc_invalid_op+0x16/0x20
>   f2fs_evict_inode+0x58c/0x610
>   evict+0x101/0x260
>   dispose_list+0x30/0x50
>   evict_inodes+0x140/0x190
>   generic_shutdown_super+0x2f/0x150
>   kill_block_super+0x11/0x40
>   kill_f2fs_super+0x7d/0x140
>   deactivate_locked_super+0x2a/0x70
>   cleanup_mnt+0xb3/0x140
>   task_work_run+0x61/0x90
> 
> The root cause is: creating large files during disable checkpoint
> period results in not enough free segments, so when writing back root
> inode will failed in f2fs_enable_checkpoint. When umount the file
> system after enabling checkpoint, the root inode is dirty in
> f2fs_evict_inode function, which triggers BUG_ON. The steps to
> reproduce are as follows:
> 
> dd if=/dev/zero of=f2fs.img bs=1M count=55
> mount f2fs.img f2fs_dir -o checkpoint=disable:10%
> dd if=/dev/zero of=big bs=1M count=50
> sync
> rm big
> mount -o remount,checkpoint=enable f2fs_dir
> umount f2fs_dir
> 
> Let's redirty inode when there is not free segments during checkpoint
> is disable.
> 
> Signed-off-by: Qi Han <hanqi@...o.com>

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

Thanks,