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[3.0-stable PATCH 28/36] xfs: fix memory reclaim deadlock on agi buffer

To: stable@xxxxxxxxxxxxxxx
Subject: [3.0-stable PATCH 28/36] xfs: fix memory reclaim deadlock on agi buffer
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Mon, 03 Dec 2012 17:42:36 -0600
Cc: xfs@xxxxxxxxxxx
References: <20121203144208.143464631@xxxxxxx>
User-agent: quilt/0.51-1
From: Peter Watkins <treestem@xxxxxxxxx>

Upstream commit: 3ba316037470bbf98c8a16c2179c02794fb8862e

Note xfs_iget can be called while holding a locked agi buffer. If
it goes into memory reclaim then inode teardown may try to lock the
same buffer. Prevent the deadlock by calling radix_tree_preload
with GFP_NOFS.

Signed-off-by: Peter Watkins <treestem@xxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Ben Myers <bpm@xxxxxxx>
---
 fs/xfs/xfs_iget.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: b/fs/xfs/xfs_iget.c
===================================================================
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -340,9 +340,10 @@ xfs_iget_cache_miss(
        /*
         * Preload the radix tree so we can insert safely under the
         * write spinlock. Note that we cannot sleep inside the preload
-        * region.
+        * region. Since we can be called from transaction context, don't
+        * recurse into the file system.
         */
-       if (radix_tree_preload(GFP_KERNEL)) {
+       if (radix_tree_preload(GFP_NOFS)) {
                error = EAGAIN;
                goto out_destroy;
        }


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