mkfs.xfs: don't increase agblocks past maximum

RH QA discovered this bug:

Steps to Reproduce:
1. Create 4 TB - 1 B partition
    dd if=/dev/zero of=x.img bs=1 count=0 seek=4398046511103
2. Create xfs fs with 512 B block size on the partition
    mkfs.xfs -b size=512 xfs.img

Actual results:
Agsize is computed incorrectly resulting in fs creation fail:
agsize (2147483648b) too big, maximum is 2147483647 blocks

This is due to the "rounding up" at the very end of the calculations;
there may be other places to alleviate the problem, but it seems
most obvious to simply skip the rounding up if it would create too
many blocks in the AG.  Worst case, we lose 1 block per AG.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 9a96b8f06ab18edb6dbb4aa62d89f7486e59f816..f527f3d52ee1af4c21f385746aa09372bec4944c 100644 (file)
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -658,8 +658,11 @@ calc_default_ag_geometry(
         * last bit of the filesystem. The same principle applies
         * to the AG count, so we don't lose the last AG!
         */
-       blocks = (dblocks >> shift) + ((dblocks & xfs_mask32lo(shift)) != 0);
-
+       blocks = dblocks >> shift;
+       if (dblocks & xfs_mask32lo(shift)) {
+               if (blocks < XFS_AG_MAX_BLOCKS(blocklog))
+                   blocks++;
+       }
 done:
        *agsize = blocks;
        *agcount = dblocks / blocks + (dblocks % blocks != 0);