1 files changed, 12 insertions, 7 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 55582bd66659..091d82b94c4d 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -101,11 +101,11 @@ xfs_iomap_eof_align_last_fsb(
 }
 
 STATIC int
-xfs_cmn_err_fsblock_zero(
+xfs_alert_fsblock_zero(
         xfs_inode_t     *ip,
         xfs_bmbt_irec_t *imap)
 {
-        xfs_cmn_err(XFS_PTAG_FSBLOCK_ZERO, CE_ALERT, ip->i_mount,
+        xfs_alert_tag(ip->i_mount, XFS_PTAG_FSBLOCK_ZERO,
                         "Access to block zero in inode %llu "
                         "start_block: %llx start_off: %llx "
                         "blkcnt: %llx extent-state: %x\n",
@@ -246,7 +246,7 @@ xfs_iomap_write_direct(
         }
 
         if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip))) {
-                error = xfs_cmn_err_fsblock_zero(ip, imap);
+                error = xfs_alert_fsblock_zero(ip, imap);
                 goto error_out;
         }
 
@@ -337,7 +337,12 @@ xfs_iomap_prealloc_size(
                 int shift = 0;
                 int64_t freesp;
 
-                alloc_blocks = XFS_B_TO_FSB(mp, ip->i_size);
+                /*
+                 * rounddown_pow_of_two() returns an undefined result
+                 * if we pass in alloc_blocks = 0. Hence the "+ 1" to
+                 * ensure we always pass in a non-zero value.
+                 */
+                alloc_blocks = XFS_B_TO_FSB(mp, ip->i_size) + 1;
                 alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
                                         rounddown_pow_of_two(alloc_blocks));
 
@@ -459,7 +464,7 @@ retry:
         }
 
         if (!(imap[0].br_startblock || XFS_IS_REALTIME_INODE(ip)))
-                return xfs_cmn_err_fsblock_zero(ip, &imap[0]);
+                return xfs_alert_fsblock_zero(ip, &imap[0]);
 
         *ret_imap = imap[0];
         return 0;
@@ -609,7 +614,7 @@ xfs_iomap_write_allocate(
                  * covers at least part of the callers request
                  */
                 if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip)))
-                        return xfs_cmn_err_fsblock_zero(ip, imap);
+                        return xfs_alert_fsblock_zero(ip, imap);
 
                 if ((offset_fsb >= imap->br_startoff) &&
                     (offset_fsb < (imap->br_startoff +
@@ -719,7 +724,7 @@ xfs_iomap_write_unwritten(
                         return XFS_ERROR(error);
 
                 if (!(imap.br_startblock || XFS_IS_REALTIME_INODE(ip)))
-                        return xfs_cmn_err_fsblock_zero(ip, &imap);
+                        return xfs_alert_fsblock_zero(ip, &imap);
 
                 if ((numblks_fsb = imap.br_blockcount) == 0) {
                         /*