linux-kernel - Re: [PATCH v4] f2fs: prevent the current section from being selected as a victim during GC

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Message-ID: <d8dc7ba9-a46c-473c-aabf-90a417a300cc@kernel.org>
Date: Thu, 3 Apr 2025 15:19:36 +0800
From: Chao Yu <chao@...nel.org>
To: "yohan.joung" <yohan.joung@...com>, jaegeuk@...nel.org
Cc: chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org, pilhyun.kim@...com
Subject: Re: [PATCH v4] f2fs: prevent the current section from being selected
 as a victim during GC

On 2025/4/3 15:10, yohan.joung wrote:
> When selecting a victim using next_victim_seg in a large section, the
> selected section might already have been cleared and designated as the
> new current section, making it actively in use.
> This behavior causes inconsistency between the SIT and SSA.
> 
> F2FS-fs (dm-54): Inconsistent segment (70961) type [0, 1] in SSA and SIT
> Call trace:
> dump_backtrace+0xe8/0x10c
> show_stack+0x18/0x28
> dump_stack_lvl+0x50/0x6c
> dump_stack+0x18/0x28
> f2fs_stop_checkpoint+0x1c/0x3c
> do_garbage_collect+0x41c/0x271c
> f2fs_gc+0x27c/0x828
> gc_thread_func+0x290/0x88c
> kthread+0x11c/0x164
> ret_from_fork+0x10/0x20
> 
> issue scenario
> segs_per_sec=2
> - seg#0 and seg#1 are all dirty
> - all valid blocks are removed in seg#1
> - gc select this sec and next_victim_seg=seg#0
> - migrate seg#0, next_victim_seg=seg#1
> - checkpoint -> sec(seg#0, seg#1)  becomes free
> - allocator assigns sec(seg#0, seg#1) to curseg
> - gc tries to migrate seg#1
> 
> Signed-off-by: yohan.joung <yohan.joung@...com>
> Signed-off-by: Chao Yu <chao@...nel.org>

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

Thanks,