[PATCH] xfs: use KM_NOFS for allocations during attribute list operations

[PATCH] xfs: use KM_NOFS for allocations during attribute list operations

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

When listing attributes, we are doiing memory allocations under the
inode ilock using only KM_SLEEP. This allows memory allocation to
recurse back into the filesystem and do writeback, which may the
ilock we already hold on the current inode. THis will deadlock.
Hence use KM_NOFS for such allocations outside of transaction
context to ensure that reclaim recursion does not occur.

Reported-by: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_attr_leaf.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_attr_leaf.c b/fs/xfs/xfs_attr_leaf.c
index a6cff8e..71e90dc2 100644
--- a/fs/xfs/xfs_attr_leaf.c
+++ b/fs/xfs/xfs_attr_leaf.c
@@ -637,7 +637,7 @@ xfs_attr_shortform_list(xfs_attr_list_context_t *context)
 	 * It didn't all fit, so we have to sort everything on hashval.
 	 */
 	sbsize = sf->hdr.count * sizeof(*sbuf);
-	sbp = sbuf = kmem_alloc(sbsize, KM_SLEEP);
+	sbp = sbuf = kmem_alloc(sbsize, KM_SLEEP | KM_NOFS);
 
 	/*
 	 * Scan the attribute list for the rest of the entries, storing
@@ -2386,7 +2386,7 @@ xfs_attr_leaf_list_int(xfs_dabuf_t *bp, xfs_attr_list_context_t *context)
 				args.dp = context->dp;
 				args.whichfork = XFS_ATTR_FORK;
 				args.valuelen = valuelen;
-				args.value = kmem_alloc(valuelen, KM_SLEEP);
+				args.value = kmem_alloc(valuelen, KM_SLEEP | KM_NOFS);
 				args.rmtblkno = be32_to_cpu(name_rmt->valueblk);
 				args.rmtblkcnt = XFS_B_TO_FSB(args.dp->i_mount, valuelen);
 				retval = xfs_attr_rmtval_get(&args);
-- 
1.7.2.3

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Re: [PATCH] xfs: use KM_NOFS for allocations during attribute list operations

[Christoph Hellwig]

On Tue, Dec 21, 2010 at 11:56:33AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> When listing attributes, we are doiing memory allocations under the
> inode ilock using only KM_SLEEP. This allows memory allocation to
> recurse back into the filesystem and do writeback, which may the
> ilock we already hold on the current inode. THis will deadlock.
> Hence use KM_NOFS for such allocations outside of transaction
> context to ensure that reclaim recursion does not occur.
> 
> Reported-by: Nick Piggin <npiggin@gmail.com>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Looks good,

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

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