linux-kernel - Re: [PATCH 2/3] xfs: move some code out of xfs_iget

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251114170402.GJ196370@frogsfrogsfrogs>
Date: Fri, 14 Nov 2025 09:04:02 -0800
From: "Darrick J. Wong" <djwong@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: Carlos Maiolino <cem@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
	Chris Li <sparse@...isli.org>, linux-sparse@...r.kernel.org,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] xfs: move some code out of xfs_iget_recycle

On Fri, Nov 14, 2025 at 06:52:24AM +0100, Christoph Hellwig wrote:
> Having a function drop locks, reacquire them and release them again
> seems to confuse the clang lock analysis even more than it confuses
> humans.  Keep the humans and machines sanity by moving a chunk of
> code into the caller to simplify the lock tracking.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/xfs/xfs_icache.c | 31 +++++++++++++------------------
>  1 file changed, 13 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index e44040206851..546efa6cec72 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -358,7 +358,7 @@ xfs_reinit_inode(
>  static int
>  xfs_iget_recycle(
>  	struct xfs_perag	*pag,
> -	struct xfs_inode	*ip) __releases(&ip->i_flags_lock)
> +	struct xfs_inode	*ip)
>  {
>  	struct xfs_mount	*mp = ip->i_mount;
>  	struct inode		*inode = VFS_I(ip);
> @@ -366,20 +366,6 @@ xfs_iget_recycle(
>  
>  	trace_xfs_iget_recycle(ip);
>  
> -	if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
> -		return -EAGAIN;
> -
> -	/*
> -	 * We need to make it look like the inode is being reclaimed to prevent
> -	 * the actual reclaim workers from stomping over us while we recycle
> -	 * the inode.  We can't clear the radix tree tag yet as it requires
> -	 * pag_ici_lock to be held exclusive.
> -	 */
> -	ip->i_flags |= XFS_IRECLAIM;
> -
> -	spin_unlock(&ip->i_flags_lock);
> -	rcu_read_unlock();
> -
>  	ASSERT(!rwsem_is_locked(&inode->i_rwsem));
>  	error = xfs_reinit_inode(mp, inode);
>  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
> @@ -576,10 +562,19 @@ xfs_iget_cache_hit(
>  
>  	/* The inode fits the selection criteria; process it. */
>  	if (ip->i_flags & XFS_IRECLAIMABLE) {
> -		/* Drops i_flags_lock and RCU read lock. */
> -		error = xfs_iget_recycle(pag, ip);
> -		if (error == -EAGAIN)
> +		/*
> +		 * We need to make it look like the inode is being reclaimed to
> +		 * prevent the actual reclaim workers from stomping over us
> +		 * while we recycle the inode.  We can't clear the radix tree
> +		 * tag yet as it requires pag_ici_lock to be held exclusive.
> +		 */
> +		if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
>  			goto out_skip;
> +		ip->i_flags |= XFS_IRECLAIM;
> +		spin_unlock(&ip->i_flags_lock);
> +		rcu_read_unlock();

I wonder, does sparse get confused by rcu_read_lock having been taken by
the caller but unlocked here?

The code move looks correct though.
Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>

--D


> +
> +		error = xfs_iget_recycle(pag, ip);
>  		if (error)
>  			return error;
>  	} else {
> -- 
> 2.47.3
> 
>