linux-ext4 - Re: [PATCH 23/50] fs: update find_inode_*rcu to check the i

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Message-ID: <20250825-ameisen-reaktion-4898c02dd545@brauner>
Date: Mon, 25 Aug 2025 13:27:08 +0200
From: Christian Brauner <brauner@...nel.org>
To: Josef Bacik <josef@...icpanda.com>
Cc: linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org, 
	kernel-team@...com, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, 
	viro@...iv.linux.org.uk
Subject: Re: [PATCH 23/50] fs: update find_inode_*rcu to check the i_count
 count

On Thu, Aug 21, 2025 at 04:18:34PM -0400, Josef Bacik wrote:
> These two helpers are always used under the RCU and don't appear to mind
> if the inode state changes in between time of check and time of use.
> Update them to use the i_count refcount instead of I_WILL_FREE or
> I_FREEING.
> 
> Signed-off-by: Josef Bacik <josef@...icpanda.com>
> ---
>  fs/inode.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 893ac902268b..63ccd32fa221 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1839,7 +1839,7 @@ struct inode *find_inode_rcu(struct super_block *sb, unsigned long hashval,
>  
>  	hlist_for_each_entry_rcu(inode, head, i_hash) {
>  		if (inode->i_sb == sb &&
> -		    !(READ_ONCE(inode->i_state) & (I_FREEING | I_WILL_FREE)) &&
> +		    refcount_read(&inode->i_count) > 0 &&

No direct i_count access, otherwise another nice change. Not having to
look at these terribly named flags anymore is wonderful.

>  		    test(inode, data))
>  			return inode;
>  	}
> @@ -1878,8 +1878,8 @@ struct inode *find_inode_by_ino_rcu(struct super_block *sb,
>  	hlist_for_each_entry_rcu(inode, head, i_hash) {
>  		if (inode->i_ino == ino &&
>  		    inode->i_sb == sb &&
> -		    !(READ_ONCE(inode->i_state) & (I_FREEING | I_WILL_FREE)))
> -		    return inode;
> +		    refcount_read(&inode->i_count) > 0)
> +			return inode;
>  	}
>  	return NULL;
>  }
> -- 
> 2.49.0
>