The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From b89f6d1fcb30a8cbdc18ce00c7d93792076af453 Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@xxxxxxxx>
Date: Thu, 13 Dec 2018 21:16:45 +0000
Subject: [PATCH] Btrfs: setup a nofs context for memory allocation at
btrfs_create_tree()
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>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 6a2a2a951705..888d72dda794 100644
--- 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"
@@ -1258,10 +1259,17 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
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);
