linux-kernel - [PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d

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Date:	Wed, 16 Apr 2014 14:03:37 +1000
From:	NeilBrown <neilb@...e.de>
To:	linux-mm@...ck.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	xfs@....sgi.com
Subject: [PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d_alloc.

__d_alloc can be called with i_mutex held, so it is safer to
use GFP_NOFS.

lockdep reports this can deadlock when loop-back NFS is in use,
as nfsd may be required to write out for reclaim, and nfsd certainly
takes i_mutex.

Signed-off-by: NeilBrown <neilb@...e.de>
---
 fs/dcache.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index ca02c13a84aa..3651ff6185b4 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1483,7 +1483,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	struct dentry *dentry;
 	char *dname;
 
-	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
+	dentry = kmem_cache_alloc(dentry_cache, GFP_NOFS);
 	if (!dentry)
 		return NULL;
 
@@ -1495,7 +1495,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	 */
 	dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
 	if (name->len > DNAME_INLINE_LEN-1) {
-		dname = kmalloc(name->len + 1, GFP_KERNEL);
+		dname = kmalloc(name->len + 1, GFP_NOFS);
 		if (!dname) {
 			kmem_cache_free(dentry_cache, dentry); 
 			return NULL;


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