[PATCH AUTOSEL 5.9 24/39] btrfs: do nofs allocations when adding and removing qgroup relations

Sasha Levin
2020-12-03T13:39:06Z

From: Filipe Manana <fdmanana@suse.com>

[ Upstream commit 7aa6d359845a9dbf7ad90b0b1b6347ef4764621f ]

When adding or removing a qgroup relation we are doing a GFP_KERNEL
allocation which is not safe because we are holding a transaction
handle open and that can make us deadlock if the allocator needs to
recurse into the filesystem. So just surround those calls with a
nofs context.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/qgroup.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 9205a88f2a881..15c38803576ce 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -11,6 +11,7 @@
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/btrfs.h>
+#include <linux/sched/mm.h>

#include "ctree.h"
#include "transaction.h"
@@ -1324,13 +1325,17 @@ int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
struct btrfs_qgroup *member;
struct btrfs_qgroup_list *list;
struct ulist *tmp;
+ unsigned int nofs_flag;
int ret = 0;

/* Check the level of src and dst first */
if (btrfs_qgroup_level(src) >= btrfs_qgroup_level(dst))
return -EINVAL;

+ /* We hold a transaction handle open, must do a NOFS allocation. */
+ nofs_flag = memalloc_nofs_save();
tmp = ulist_alloc(GFP_KERNEL);
+ memalloc_nofs_restore(nofs_flag);
if (!tmp)
return -ENOMEM;

@@ -1387,10 +1392,14 @@ static int __del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
struct btrfs_qgroup_list *list;
struct ulist *tmp;
bool found = false;
+ unsigned int nofs_flag;
int ret = 0;
int ret2;

+ /* We hold a transaction handle open, must do a NOFS allocation. */
+ nofs_flag = memalloc_nofs_save();
tmp = ulist_alloc(GFP_KERNEL);
+ memalloc_nofs_restore(nofs_flag);
if (!tmp)
return -ENOMEM;

--
2.27.0