diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 4e8f0df82d025e6bc38615a94d254bf003c24972..8459b5d8cb71ceaa98ff64990cae8d4daaf6f1b1 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1334,6 +1334,12 @@ _xfs_buf_ioapply(
 	int		size;
 	int		i;
 
+	/*
+	 * Make sure we capture only current IO errors rather than stale errors
+	 * left over from previous use of the buffer (e.g. failed readahead).
+	 */
+	bp->b_error = 0;
+
 	if (bp->b_flags & XBF_WRITE) {
 		if (bp->b_flags & XBF_SYNCIO)
 			rw = WRITE_SYNC;
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 912d83d8860a984a938b604f3e2447c3e390ce89..5a30dd899d2b32c38dbc1fc552e323d233f33e50 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -325,7 +325,7 @@ xfs_iomap_eof_want_preallocate(
  * rather than falling short due to things like stripe unit/width alignment of
  * real extents.
  */
-STATIC int
+STATIC xfs_fsblock_t
 xfs_iomap_eof_prealloc_initial_size(
 	struct xfs_mount	*mp,
 	struct xfs_inode	*ip,
@@ -413,7 +413,7 @@ xfs_iomap_prealloc_size(
 		 * have a large file on a small filesystem and the above
 		 * lowspace thresholds are smaller than MAXEXTLEN.
 		 */
-		while (alloc_blocks >= freesp)
+		while (alloc_blocks && alloc_blocks >= freesp)
 			alloc_blocks >>= 4;
 	}