[PATCH 17/19] ext4: Add support for MAP_SYNC flag

[Jan Kara <jack@suse.cz>]

Now when everything is prepared, add support in ext4 to accept MAP_SYNC
as an mmap(2) flag.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/file.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 61a8788168f3..f013cda84b3d 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -364,6 +364,25 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 	return 0;
 }
 
+#define EXT4_SUPPORTED_MAP_FLAGS (LEGACY_MAP_MASK | MAP_SYNC)
+
+static int ext4_file_mmap_validate(struct file *file,
+				   struct vm_area_struct *vma,
+				   unsigned long map_flags)
+{
+	if (map_flags & ~EXT4_SUPPORTED_MAP_FLAGS)
+		return -EOPNOTSUPP;
+
+	/*
+	 * We don't support synchronous mappings for non-DAX files. At least
+	 * until someone comes with a sensible use case.
+	 */
+	if (!IS_DAX(file_inode(file)) && (map_flags & MAP_SYNC))
+		return -EOPNOTSUPP;
+
+	return ext4_file_mmap(file, vma);
+}
+
 static int ext4_file_open(struct inode * inode, struct file * filp)
 {
 	struct super_block *sb = inode->i_sb;
@@ -723,6 +742,7 @@ const struct file_operations ext4_file_operations = {
 	.compat_ioctl	= ext4_compat_ioctl,
 #endif
 	.mmap		= ext4_file_mmap,
+	.mmap_validate	= ext4_file_mmap_validate,
 	.open		= ext4_file_open,
 	.release	= ext4_release_file,
 	.fsync		= ext4_sync_file,
-- 
2.12.3