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Re: next-20090220: XFS: inconsistent lock state

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: next-20090220: XFS: inconsistent lock state
From: Felix Blyakher <felixb@xxxxxxx>
Date: Tue, 3 Mar 2009 10:45:28 -0600
Cc: Alexander Beregalov <a.beregalov@xxxxxxxxx>, "linux-next@xxxxxxxxxxxxxxx" <linux-next@xxxxxxxxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20090224200740.GA9266@xxxxxxxxxxxxx>
References: <a4423d670902200952v5dc2fd91w3b54ab1db51a7fe2@xxxxxxxxxxxxxx> <20090224200740.GA9266@xxxxxxxxxxxxx>
On Feb 24, 2009, at 2:07 PM, Christoph Hellwig wrote:

On Fri, Feb 20, 2009 at 08:52:59PM +0300, Alexander Beregalov wrote:
Hi

[ INFO: inconsistent lock state ]
2.6.29-rc5-next-20090220 #2
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-R} usage.
kswapd0/324 [HC0[0]:SC0[0]:HE1:SE1] takes:
(&(&ip->i_lock)->mr_lock){+++++?}, at: [<ffffffff803ca60a>]
xfs_ilock+0xaa/0x120
{RECLAIM_FS-ON-W} state was registered at:

That's a false positive.  While the ilock can be taken in reclaim the
allocation here is done before the inode is added to the inode cache.

The patch below should help avoiding the warning:


Index: xfs/fs/xfs/xfs_iget.c
===================================================================
--- xfs.orig/fs/xfs/xfs_iget.c  2009-02-24 20:56:00.716027739 +0100
+++ xfs/fs/xfs/xfs_iget.c       2009-02-24 20:56:46.089031360 +0100
@@ -246,9 +246,6 @@ xfs_iget_cache_miss(
                goto out_destroy;
        }

-       if (lock_flags)
-               xfs_ilock(ip, lock_flags);
-
        /*
         * Preload the radix tree so we can insert safely under the
         * write spinlock. Note that we cannot sleep inside the preload
@@ -259,6 +256,15 @@ xfs_iget_cache_miss(
                goto out_unlock;

Since we removed call to xfs_ilock() above, this should change
to 'goto out_destroy;'
Otherwise, seems goot to me.

Reviewed-by: Felix Blyakher <felixb@xxxxxxx>



        }

+       /*
+ * Because the inode hasn't been added to the radix-tree yet it can't + * be found by another thread, so we can do the non-sleeping lock here.
+        */
+       if (lock_flags) {
+               if (!xfs_ilock_nowait(ip, lock_flags))
+                       BUG();


+       }
+
        mask = ~(((XFS_INODE_CLUSTER_SIZE(mp) >> mp->m_sb.sb_inodelog)) - 1);
        first_index = agino & mask;
        write_lock(&pag->pag_ici_lock);
--
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