iomap: split size and error for iomap_dio_rw ->end_io

Modify the calling convention for the iomap_dio_rw ->end_io() callback.
Rather than passing either dio->error or dio->size as the 'size' argument,
instead pass both the dio->error and the dio->size value separately.

In the instance that an error occurred during a write, we currently cannot
determine whether any blocks have been allocated beyond the current EOF and
data has subsequently been written to these blocks within the ->end_io()
callback. As a result, we cannot judge whether we should take the truncate
failed write path. Having both dio->error and dio->size will allow us to
perform such checks within this callback.

Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
[hch: minor cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

fs/iomap/direct-io.c

@@ -77,13 +77,10 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
 	loff_t offset = iocb->ki_pos;
 	ssize_t ret;
 
-	if (dio->end_io) {
-		ret = dio->end_io(iocb,
-				dio->error ? dio->error : dio->size,
-				dio->flags);
-	} else {
+	if (dio->end_io)
+		ret = dio->end_io(iocb, dio->size, dio->error, dio->flags);
+	else
 		ret = dio->error;
-	}
 
 	if (likely(!ret)) {
 		ret = dio->size;

fs/xfs/xfs_file.c

@@ -369,21 +369,23 @@ static int
 xfs_dio_write_end_io(
 	struct kiocb		*iocb,
 	ssize_t			size,
+	int			error,
 	unsigned		flags)
 {
 	struct inode		*inode = file_inode(iocb->ki_filp);
 	struct xfs_inode	*ip = XFS_I(inode);
 	loff_t			offset = iocb->ki_pos;
 	unsigned int		nofs_flag;
-	int			error = 0;
 
 	trace_xfs_end_io_direct_write(ip, offset, size);
 
 	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
 		return -EIO;
 
-	if (size <= 0)
-		return size;
+	if (error)
+		return error;
+	if (!size)
+		return 0;
 
 	/*
 	 * Capture amount written on completion as we can't reliably account

include/linux/iomap.h

@@ -188,8 +188,8 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
  */
 #define IOMAP_DIO_UNWRITTEN	(1 << 0)	/* covers unwritten extent(s) */
 #define IOMAP_DIO_COW		(1 << 1)	/* covers COW extent(s) */
-typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t ret,
-		unsigned flags);
+typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t size, int error,
+				 unsigned int flags);
 ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 		const struct iomap_ops *ops, iomap_dio_end_io_t end_io);
 int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);