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[PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d_alloc.

To: linux-mm@xxxxxxxxx, linux-nfs@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d_alloc.
From: NeilBrown <neilb@xxxxxxx>
Date: Wed, 16 Apr 2014 14:03:37 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140416033623.10604.69237.stgit@xxxxxxxxxxxxxx>
References: <20140416033623.10604.69237.stgit@xxxxxxxxxxxxxx>
User-agent: StGit/0.16
__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@xxxxxxx>
---
 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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