[PATCH] btrfs: allow MAP_SYNC mmap

[Adam Borowski]

Used by userspace to detect DAX.

Signed-off-by: Adam Borowski <kilob...@angband.pl>
---
 fs/btrfs/file.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 196c8f37ff9d..8efdb040bc1d 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -16,6 +16,7 @@
 #include <linux/btrfs.h>
 #include <linux/uio.h>
 #include <linux/iversion.h>
+#include <linux/mman.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -3320,6 +3321,7 @@ const struct file_operations btrfs_file_operations = {
        .splice_read    = generic_file_splice_read,
        .write_iter     = btrfs_file_write_iter,
        .mmap           = btrfs_file_mmap,
+       .mmap_supported_flags = MAP_SYNC,
        .open           = btrfs_file_open,
        .release        = btrfs_release_file,
        .fsync          = btrfs_sync_file,
-- 
2.20.1