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btrfs: do nofs allocations when adding and removing qgroup relations 

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>
This commit is contained in:
Filipe Manana 2020-11-23 18:30:54 +00:00 committed by David Sterba
parent 3d05cad3c3
commit 7aa6d35984
1 changed files with 9 additions and 0 deletions
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9
fs/btrfs/qgroup.c
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@ -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;