4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Filipe Manana <fdmanana@xxxxxxxx>
commit b89f6d1fcb30a8cbdc18ce00c7d93792076af453 upstream.
We are holding a transaction handle when creating a tree, therefore we can
not allocate the root using GFP_KERNEL, as we could deadlock if reclaim is
triggered by the allocation, therefore setup a nofs context.
Fixes: 74e4d82757f74 ("btrfs: let callers of btrfs_alloc_root pass gfp flags")
CC: stable@xxxxxxxxxxxxxxx # 4.9+
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/disk-io.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -17,6 +17,7 @@
#include <linux/semaphore.h>
#include <linux/error-injection.h>
#include <linux/crc32c.h>
+#include <linux/sched/mm.h>
#include <asm/unaligned.h>
#include "ctree.h"
#include "disk-io.h"
@@ -1236,10 +1237,17 @@ struct btrfs_root *btrfs_create_tree(str
struct btrfs_root *tree_root = fs_info->tree_root;
struct btrfs_root *root;
struct btrfs_key key;
+ unsigned int nofs_flag;
int ret = 0;
uuid_le uuid = NULL_UUID_LE;
+ /*
+ * We're holding a transaction handle, so use a NOFS memory allocation
+ * context to avoid deadlock if reclaim happens.
+ */
+ nofs_flag = memalloc_nofs_save();
root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+ memalloc_nofs_restore(nofs_flag);
if (!root)
return ERR_PTR(-ENOMEM);
