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Subject[PATCH 4.20 57/57] Btrfs: use nofs context when initializing security xattrs to avoid deadlock
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Filipe Manana <fdmanana@suse.com>

commit 827aa18e7b903c5ff3b3cd8fec328a99b1dbd411 upstream.

When initializing the security xattrs, we are holding a transaction handle
therefore we need to use a GFP_NOFS context in order to avoid a deadlock
with reclaim in case it's triggered.

Fixes: 39a27ec1004e8 ("btrfs: use GFP_KERNEL for xattr and acl allocations")
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/xattr.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -11,6 +11,7 @@
#include <linux/security.h>
#include <linux/posix_acl_xattr.h>
#include <linux/iversion.h>
+#include <linux/sched/mm.h>
#include "ctree.h"
#include "btrfs_inode.h"
#include "transaction.h"
@@ -422,9 +423,15 @@ static int btrfs_initxattrs(struct inode
{
const struct xattr *xattr;
struct btrfs_trans_handle *trans = fs_info;
+ unsigned int nofs_flag;
char *name;
int err = 0;

+ /*
+ * We're holding a transaction handle, so use a NOFS memory allocation
+ * context to avoid deadlock if reclaim happens.
+ */
+ nofs_flag = memalloc_nofs_save();
for (xattr = xattr_array; xattr->name != NULL; xattr++) {
name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
strlen(xattr->name) + 1, GFP_KERNEL);
@@ -440,6 +447,7 @@ static int btrfs_initxattrs(struct inode
if (err < 0)
break;
}
+ memalloc_nofs_restore(nofs_flag);
return err;
}


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