xfs: factor out a xfs_update_prealloc_flags() helper

This logic is duplicated in xfs_file_fallocate and xfs_ioc_space, and
we'll need another copy of it for pNFS block support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 4ed2ba9..bc220bc 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -377,6 +377,15 @@
 int		xfs_bumplink(struct xfs_trans *, struct xfs_inode *);
 
 /* from xfs_file.c */
+enum xfs_prealloc_flags {
+	XFS_PREALLOC_SET	= (1 << 1),
+	XFS_PREALLOC_CLEAR	= (1 << 2),
+	XFS_PREALLOC_SYNC	= (1 << 3),
+	XFS_PREALLOC_INVISIBLE	= (1 << 4),
+};
+
+int		xfs_update_prealloc_flags(struct xfs_inode *,
+			enum xfs_prealloc_flags);
 int		xfs_zero_eof(struct xfs_inode *, xfs_off_t, xfs_fsize_t);
 int		xfs_iozero(struct xfs_inode *, loff_t, size_t);