linux-ext4 - Re: [PATCH] ext4: recheck buffer uptodate bit under buffer lock

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Date:   Thu, 16 Sep 2021 10:05:04 +0200
From:   Jan Kara <jack@...e.cz>
To:     Zhang Yi <yi.zhang@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, yukuai3@...wei.com
Subject: Re: [PATCH] ext4: recheck buffer uptodate bit under buffer lock

On Fri 10-09-21 16:03:16, Zhang Yi wrote:
> Commit 8e33fadf945a ("ext4: remove an unnecessary if statement in
> __ext4_get_inode_loc()") forget to recheck buffer's uptodate bit again
> under buffer lock, which may overwrite the buffer if someone else have
> already brought it uptodate and changed it.
> 
> Fixes: 8e33fadf945a ("ext4: remove an unnecessary if statement in __ext4_get_inode_loc()")
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Oh, right. Thanks for fixing this. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/inode.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index d18852d6029c..236adc647eb0 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4340,6 +4340,12 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
>  		goto has_buffer;
>  
>  	lock_buffer(bh);
> +	if (ext4_buffer_uptodate(bh)) {
> +		/* Someone brought it uptodate while we waited */
> +		unlock_buffer(bh);
> +		goto has_buffer;
> +	}
> +
>  	/*
>  	 * If we have all information of the inode in memory and this
>  	 * is the only valid inode in the block, we need not read the
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR