linux-ext4 - [patch 13/19] vfs: fix possible deadlock in ext2, ext3, ext4 when using xattrs

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Date:	Tue, 15 Apr 2008 14:34:43 -0700
From:	akpm@...ux-foundation.org
To:	torvalds@...ux-foundation.org
Cc:	akpm@...ux-foundation.org, jack@...e.cz, davej@...hat.com,
	linux-ext4@...r.kernel.org
Subject: [patch 13/19] vfs: fix possible deadlock in ext2, ext3, ext4 when using xattrs

From: Jan Kara <jack@...e.cz>

mb_cache_entry_alloc() was allocating cache entries with GFP_KERNEL.  But
filesystems are calling this function while holding xattr_sem so possible
recursion into the fs violates locking ordering of xattr_sem and transaction
start / i_mutex for ext2-4.  Change mb_cache_entry_alloc() so that filesystems
can specify desired gfp mask and use GFP_NOFS from all of them.

Signed-off-by: Jan Kara <jack@...e.cz>
Reported-by: Dave Jones <davej@...hat.com>
Cc: <linux-ext4@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/ext2/xattr.c         |    2 +-
 fs/ext3/xattr.c         |    2 +-
 fs/ext4/xattr.c         |    2 +-
 fs/mbcache.c            |    4 ++--
 include/linux/mbcache.h |    2 +-
 5 files changed, 6 insertions(+), 6 deletions(-)

diff -puN fs/ext2/xattr.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs fs/ext2/xattr.c
--- a/fs/ext2/xattr.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs
+++ a/fs/ext2/xattr.c
@@ -835,7 +835,7 @@ ext2_xattr_cache_insert(struct buffer_he
 	struct mb_cache_entry *ce;
 	int error;
 
-	ce = mb_cache_entry_alloc(ext2_xattr_cache);
+	ce = mb_cache_entry_alloc(ext2_xattr_cache, GFP_NOFS);
 	if (!ce)
 		return -ENOMEM;
 	error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
diff -puN fs/ext3/xattr.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs fs/ext3/xattr.c
--- a/fs/ext3/xattr.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs
+++ a/fs/ext3/xattr.c
@@ -1126,7 +1126,7 @@ ext3_xattr_cache_insert(struct buffer_he
 	struct mb_cache_entry *ce;
 	int error;
 
-	ce = mb_cache_entry_alloc(ext3_xattr_cache);
+	ce = mb_cache_entry_alloc(ext3_xattr_cache, GFP_NOFS);
 	if (!ce) {
 		ea_bdebug(bh, "out of memory");
 		return;
diff -puN fs/ext4/xattr.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs fs/ext4/xattr.c
--- a/fs/ext4/xattr.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs
+++ a/fs/ext4/xattr.c
@@ -1386,7 +1386,7 @@ ext4_xattr_cache_insert(struct buffer_he
 	struct mb_cache_entry *ce;
 	int error;
 
-	ce = mb_cache_entry_alloc(ext4_xattr_cache);
+	ce = mb_cache_entry_alloc(ext4_xattr_cache, GFP_NOFS);
 	if (!ce) {
 		ea_bdebug(bh, "out of memory");
 		return;
diff -puN fs/mbcache.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs fs/mbcache.c
--- a/fs/mbcache.c~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs
+++ a/fs/mbcache.c
@@ -399,11 +399,11 @@ mb_cache_destroy(struct mb_cache *cache)
  * if no more memory was available.
  */
 struct mb_cache_entry *
-mb_cache_entry_alloc(struct mb_cache *cache)
+mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
 {
 	struct mb_cache_entry *ce;
 
-	ce = kmem_cache_alloc(cache->c_entry_cache, GFP_KERNEL);
+	ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
 	if (ce) {
 		atomic_inc(&cache->c_entry_count);
 		INIT_LIST_HEAD(&ce->e_lru_list);
diff -puN include/linux/mbcache.h~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs include/linux/mbcache.h
--- a/include/linux/mbcache.h~vfs-fix-possible-deadlock-in-ext2-ext3-ext4-when-using-xattrs
+++ a/include/linux/mbcache.h
@@ -34,7 +34,7 @@ void mb_cache_destroy(struct mb_cache *)
 
 /* Functions on cache entries */
 
-struct mb_cache_entry *mb_cache_entry_alloc(struct mb_cache *);
+struct mb_cache_entry *mb_cache_entry_alloc(struct mb_cache *, gfp_t);
 int mb_cache_entry_insert(struct mb_cache_entry *, struct block_device *,
 			  sector_t, unsigned int[]);
 void mb_cache_entry_release(struct mb_cache_entry *);
_
--
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