xfs: move generic_write_sync calls inwards

To prepare for iomap iinfrastructure based DSYNC optimisations.

While moving the code araound, move the XFS write bytes metric
update for direct IO into xfs_dio_write_end_io callback so that we
always capture the amount of data written via AIO+DIO. This fixes
the problem where queued AIO+DIO writes are not accounted to this
metric.
Signed-Off-By: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_file.c

@@ -414,6 +414,12 @@ xfs_dio_write_end_io(
 	if (size <= 0)
 		return size;
 
+	/*
+	 * Capture amount written on completion as we can't reliably account
+	 * for it on submission.
+	 */
+	XFS_STATS_ADD(ip->i_mount, xs_write_bytes, size);
+
 	if (flags & IOMAP_DIO_COW) {
 		error = xfs_reflink_end_cow(ip, offset, size);
 		if (error)
@@ -562,6 +568,11 @@ xfs_file_dio_aio_write(
 	 * complete fully or fail.
 	 */
 	ASSERT(ret < 0 || ret == count);
+
+	if (ret > 0) {
+		/* Handle various SYNC-type writes */
+		ret = generic_write_sync(iocb, ret);
+	}
 	return ret;
 }
 
@@ -599,7 +610,16 @@ xfs_file_dax_write(
 	}
 out:
 	xfs_iunlock(ip, iolock);
-	return error ? error : ret;
+	if (error)
+		return error;
+
+	if (ret > 0) {
+		XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);
+
+		/* Handle various SYNC-type writes */
+		ret = generic_write_sync(iocb, ret);
+	}
+	return ret;
 }
 
 STATIC ssize_t
@@ -669,6 +689,12 @@ xfs_file_buffered_aio_write(
 out:
 	if (iolock)
 		xfs_iunlock(ip, iolock);
+
+	if (ret > 0) {
+		XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);
+		/* Handle various SYNC-type writes */
+		ret = generic_write_sync(iocb, ret);
+	}
 	return ret;
 }
 
@@ -693,8 +719,9 @@ xfs_file_write_iter(
 		return -EIO;
 
 	if (IS_DAX(inode))
-		ret = xfs_file_dax_write(iocb, from);
-	else if (iocb->ki_flags & IOCB_DIRECT) {
+		return xfs_file_dax_write(iocb, from);
+
+	if (iocb->ki_flags & IOCB_DIRECT) {
 		/*
 		 * Allow a directio write to fall back to a buffered
 		 * write *only* in the case that we're doing a reflink
@@ -702,20 +729,11 @@ xfs_file_write_iter(
 		 * allow an operation to fall back to buffered mode.
 		 */
 		ret = xfs_file_dio_aio_write(iocb, from);
-		if (ret == -EREMCHG)
-			goto buffered;
-	} else {
-buffered:
-		ret = xfs_file_buffered_aio_write(iocb, from);
+		if (ret != -EREMCHG)
+			return ret;
 	}
 
-	if (ret > 0) {
-		XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);
-
-		/* Handle various SYNC-type writes */
-		ret = generic_write_sync(iocb, ret);
-	}
-	return ret;
+	return xfs_file_buffered_aio_write(iocb, from);
 }
 
 #define	XFS_FALLOC_FL_SUPPORTED						\