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btrfs: protect space cache inode alloc with GFP_NOFS

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commit 84de76a2fb217dc1b6bc2965cc397d1648aa1404 upstream.

If we're allocating a new space cache inode it's likely going to be
under a transaction handle, so we need to use memalloc_nofs_save() in
order to avoid deadlocks, and more importantly lockdep messages that
make xfstests fail.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josef Bacik 2018-09-28 07:17:49 -04:00 committed by Greg Kroah-Hartman
parent 0de8cf3f99
commit 9006ad16ef
1 changed files with 8 additions and 0 deletions
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8
fs/btrfs/free-space-cache.c
View file

@ -10,6 +10,7 @@
#include <linux/math64.h>
#include <linux/ratelimit.h>
#include <linux/error-injection.h>
#include <linux/sched/mm.h>
#include "ctree.h"
#include "free-space-cache.h"
#include "transaction.h"
@ -47,6 +48,7 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
struct btrfs_free_space_header *header;
struct extent_buffer *leaf;
struct inode *inode = NULL;
unsigned nofs_flag;
int ret;
key.objectid = BTRFS_FREE_SPACE_OBJECTID;
@ -68,7 +70,13 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
btrfs_disk_key_to_cpu(&location, &disk_key);
btrfs_release_path(path);
/*
* We are often under a trans handle at this point, so we need to make
* sure NOFS is set to keep us from deadlocking.
*/
nofs_flag = memalloc_nofs_save();
inode = btrfs_iget(fs_info->sb, &location, root, NULL);
memalloc_nofs_restore(nofs_flag);
if (IS_ERR(inode))
return inode;