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RE: [PATCH] xfs: check for not fully initialized inodes in xfs_ireclaim

To: "Christoph Hellwig" <hch@xxxxxxxxxxxxx>
Subject: RE: [PATCH] xfs: check for not fully initialized inodes in xfs_ireclaim
From: "Alex Elder" <aelder@xxxxxxx>
Date: Mon, 30 Nov 2009 14:07:40 -0600
Cc: <xfs@xxxxxxxxxxx>
In-reply-to: <20091112190657.GA32110@xxxxxxxxxxxxx>
Thread-index: Acpjzq5hU3ICrxt+TTSEhPMfSpVhZgOKUKAw
Thread-topic: [PATCH] xfs: check for not fully initialized inodes in xfs_ireclaim
Christoph Hellwig wrote:
> Add an assert for inodes not added to the inode cache in xfs_ireclaim, to make
> sure we're not going to introduce something like the famous nfsd inode cache
> bug again.

I confess I have not looked at the radix tree
code in detail yet, but radix_tree_delete()
returns a value that is ignored here.  It reportedly
will return a null pointer if the index has no
corresponding item in the tree, so this could be
used in the assertion rather than doing a separate
lookup.

I think the change is fine, but would rather see
it done without the extra lookup (though there may
be a good reason for doing it anyway).

                                        -Alex

> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> 
> Index: xfs/fs/xfs/xfs_iget.c
> ===================================================================
> --- xfs.orig/fs/xfs/xfs_iget.c        2009-11-12 17:10:20.216276486 +0100
> +++ xfs/fs/xfs/xfs_iget.c     2009-11-12 17:13:27.565003964 +0100
> @@ -514,17 +514,21 @@ xfs_ireclaim(
>  {
>       struct xfs_mount        *mp = ip->i_mount;
>       struct xfs_perag        *pag;
> +     xfs_agino_t             agino = XFS_INO_TO_AGINO(mp, ip->i_ino);
> 
>       XFS_STATS_INC(xs_ig_reclaims);
> 
>       /*
> -      * Remove the inode from the per-AG radix tree.  It doesn't matter
> -      * if it was never added to it because radix_tree_delete can deal
> -      * with that case just fine.
> +      * Remove the inode from the per-AG radix tree.
> +      *
> +      * Because radix_tree_delete won't complain even if the item was never
> +      * added to the tree assert that it's been there before to catch
> +      * problems with the inode life time early on.
>        */
>       pag = xfs_get_perag(mp, ip->i_ino);
>       write_lock(&pag->pag_ici_lock);
> -     radix_tree_delete(&pag->pag_ici_root, XFS_INO_TO_AGINO(mp, ip->i_ino));
> +     ASSERT(radix_tree_lookup(&pag->pag_ici_root, agino));
> +     radix_tree_delete(&pag->pag_ici_root, agino);
>       write_unlock(&pag->pag_ici_lock);
>       xfs_put_perag(mp, pag);
> 
> 
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