xfs: flush for older, xfs specific ioctls

837a6e7 ("fs: add generic UNRESVSP and ZERO_RANGE ioctl handlers") changed
ioctls XFS_IOC_UNRESVSP XFS_IOC_UNRESVSP64 and XFS_IOC_ZERO_RANGE to be generic
instead of xfs specific.

Because of this change, 36f1177 ("xfs: properly serialise fallocate against
AIO+DIO") needed adaptation, as 5.4 still uses the xfs specific ioctls.

Without this, xfstests xfs/242 and xfs/290 fail. Both of these tests test
XFS_IOC_ZERO_RANGE.

Fixes: 36f1177 ("xfs: properly serialise fallocate against AIO+DIO")
Tested-by: Andy Strohman <astroh@amazon.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Andy Strohman

fs/xfs/xfs_ioctl.c

@@ -622,7 +622,6 @@ xfs_ioc_space(
 	error = xfs_break_layouts(inode, &iolock, BREAK_UNMAP);
 	if (error)
 		goto out_unlock;
-	inode_dio_wait(inode);
 
 	switch (bf->l_whence) {
 	case 0: /*SEEK_SET*/
@@ -668,6 +667,31 @@ xfs_ioc_space(
 		goto out_unlock;
 	}
 
+	/*
+	 * Must wait for all AIO to complete before we continue as AIO can
+	 * change the file size on completion without holding any locks we
+	 * currently hold. We must do this first because AIO can update both
+	 * the on disk and in memory inode sizes, and the operations that follow
+	 * require the in-memory size to be fully up-to-date.
+	 */
+	inode_dio_wait(inode);
+
+	/*
+	 * Now that AIO and DIO has drained we can flush and (if necessary)
+	 * invalidate the cached range over the first operation we are about to
+	 * run. We include zero range here because it starts with a hole punch
+	 * over the target range.
+	 */
+	switch (cmd) {
+	case XFS_IOC_ZERO_RANGE:
+	case XFS_IOC_UNRESVSP:
+	case XFS_IOC_UNRESVSP64:
+		error = xfs_flush_unmap_range(ip, bf->l_start, bf->l_len);
+		if (error)
+			goto out_unlock;
+		break;
+	}
+
 	switch (cmd) {
 	case XFS_IOC_ZERO_RANGE:
 		flags |= XFS_PREALLOC_SET;