[PATCH] xfs: fix might_sleep() warning when initialising per-ag tree

[PATCH] xfs: fix might_sleep() warning when initialising per-ag tree

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

The use of radix_tree_preload() only works if the radix tree was initialised
without the __GFP_WAIT flag. The per-ag tree uses GFP_NOFS, so does not trigger
allocation of new tree nodes from the preloaded array. Hence it enters the
allocator with a spinlock held and triggers the might_sleep() warnings.

Reported-by; Chris Mason <chris.mason@oracle.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_mount.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index ace795f..c901283 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1251,7 +1251,7 @@ xfs_mountfs(
 	 * Allocate and initialize the per-ag data.
 	 */
 	spin_lock_init(&mp->m_perag_lock);
-	INIT_RADIX_TREE(&mp->m_perag_tree, GFP_NOFS);
+	INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
 	error = xfs_initialize_perag(mp, sbp->sb_agcount, &mp->m_maxagi);
 	if (error) {
 		cmn_err(CE_WARN, "XFS: Failed per-ag init: %d", error);
-- 
1.5.6.5

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Re: [PATCH] xfs: fix might_sleep() warning when initialising per-ag tree

[Christoph Hellwig]

On Thu, May 27, 2010 at 11:58:13AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> The use of radix_tree_preload() only works if the radix tree was initialised
> without the __GFP_WAIT flag. The per-ag tree uses GFP_NOFS, so does not trigger
> allocation of new tree nodes from the preloaded array. Hence it enters the
> allocator with a spinlock held and triggers the might_sleep() warnings.
> 
> Reported-by; Chris Mason <chris.mason@oracle.com>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Looks good,


Reviewed-by: Christoph Hellwig <hch@lst.de>

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