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xfs: fix 32-bit truncation in xfs_compute_rextslog

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It's quite reasonable that some customer somewhere will want to
configure a realtime volume with more than 2^32 extents.  If they try to
do this, the highbit32() call will truncate the upper bits of the
xfs_rtbxlen_t and produce the wrong value for rextslog.  This in turn
causes the rsumlevels to be wrong, which results in a realtime summary
file that is the wrong length.  Fix that.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2023-12-03 09:19:44 -08:00
parent a6a38f309a
commit cf8f0e6c14
1 changed files with 5 additions and 3 deletions
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8
fs/xfs/libxfs/xfs_rtbitmap.c
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@ -1132,14 +1132,16 @@ xfs_rtbitmap_blockcount(
/*
* Compute the maximum level number of the realtime summary file, as defined by
* mkfs. The use of highbit32 on a 64-bit quantity is a historic artifact that
* prohibits correct use of rt volumes with more than 2^32 extents.
* mkfs. The historic use of highbit32 on a 64-bit quantity prohibited correct
* use of rt volumes with more than 2^32 extents.
*/
uint8_t
xfs_compute_rextslog(
xfs_rtbxlen_t rtextents)
{
return rtextents ? xfs_highbit32(rtextents) : 0;
if (!rtextents)
return 0;
return xfs_highbit64(rtextents);
}
/*