From: Filipe Manana <fdmanana@suse.com>
Date: Thu, 13 Dec 2018 21:16:56 +0000
Git-commit: a0873490660246db587849a9e172f2b7b21fa88a
Patch-mainline: 5.1
References: bsc#1172127
Subject: [PATCH] Btrfs: setup a nofs context for memory allocation at
 __btrfs_set_acl

We are holding a transaction handle when setting an acl, therefore we can
not allocate the xattr value buffer using GFP_KERNEL, as we could deadlock
if reclaim is triggered by the allocation, therefore setup a nofs context.

Fixes: 39a27ec1004e8 ("btrfs: use GFP_KERNEL for xattr and acl allocations")
CC: stable@vger.kernel.org # 4.9+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/acl.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 1ba49ebe67da..1c42d9f1d6c8 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -22,6 +22,7 @@
 #include <linux/posix_acl_xattr.h>
 #include <linux/posix_acl.h>
 #include <linux/sched.h>
+#include <linux/sched/mm.h>
 #include <linux/slab.h>
 
 #include "ctree.h"
@@ -89,8 +90,16 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
 	}
 
 	if (acl) {
+		unsigned int nofs_flag;
+
 		size = posix_acl_xattr_size(acl->a_count);
+		/*
+		 * We're holding a transaction handle, so use a NOFS memory
+		 * allocation context to avoid deadlock if reclaim happens.
+		 */
+		nofs_flag = memalloc_nofs_save();
 		value = kmalloc(size, GFP_KERNEL);
+		memalloc_nofs_restore(nofs_flag);
 		if (!value) {
 			ret = -ENOMEM;
 			goto out;
-- 
2.16.4