linux-kernel - Re: [PATCH] f2fs: don't call iput() from f2fs_drop

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Message-ID: <aN1LM3C3Dc1TrQTq@google.com>
Date: Wed, 1 Oct 2025 15:39:31 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: brauner@...nel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, josef@...icpanda.com,
	oe-lkp@...ts.linux.dev, linux-f2fs-devel@...ts.sourceforge.net,
	ltp@...ts.linux.it, oliver.sang@...el.com
Subject: Re: [PATCH] f2fs: don't call iput() from f2fs_drop_inode()

On 10/01, Mateusz Guzik wrote:
> iput() calls the problematic routine, which does a ->i_count inc/dec
> cycle. Undoing it with iput() recurses into the problem.
> 
> Note f2fs should not be playing games with the refcount to begin with,
> but that will be handled later. Right now solve the immediate
> regression.
> 
> Fixes: bc986b1d756482a ("fs: stop accessing ->i_count directly in f2fs and gfs2")
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Closes: https://lore.kernel.org/oe-lkp/202509301450.138b448f-lkp@intel.com
> Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
> ---
>  fs/f2fs/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 2619cbbd7d2d..26ec31eb8c80 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -1769,7 +1769,7 @@ static int f2fs_drop_inode(struct inode *inode)
>  			sb_end_intwrite(inode->i_sb);
>  
>  			spin_lock(&inode->i_lock);
> -			iput(inode);
> +			atomic_dec(&inode->i_count);

It seems this was applied by Josef [1], added in 6.18-rc1. Let me apply this fix
after my f2fs pull request, since I don't have this issue in my -next tree yet.

[1] https://lore.kernel.org/all/b8e6eb8a3e690ce082828d3580415bf70dfa93aa.1755806649.git.josef@toxicpanda.com/

>  		}
>  		trace_f2fs_drop_inode(inode, 0);
>  		return 0;
> -- 
> 2.43.0
>