growfs: workaround sfdisk + LUKS incompatibility on 512e disks #3033
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No functional change. Prep for next patch.
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More context on this in coreos/fedora-coreos-tracker#1384 (comment). |
On 512e disks, `sfdisk` (which is used by `growpart`) will end up growing the rootfs to a size not aligned to a 4K boundary. This is mostly fine because, well, the drive claims to be 512b-compatible. Issues arise however if one wants to also put LUKS on top: cryptsetup, trying to optimize performance, wants to set the sector size of the LUKS device to that of the physical value, which is 4K. But if the partition range itself isn't 4K-aligned, it will choke. Ideally, this should be fixed in sfdisk: util-linux/util-linux#2140 (Though cryptsetup could also learn to align the mapped area itself). Anyway, for now work aorund this by manually checking if the size of the partition is a multiple of 4k. If not, and the physical sector size is 4k, then trim off the edge of the partition to make it so. Note the partition start is always going to be aligned (they're 1M-aligned). Closes: coreos/fedora-coreos-tracker#1384 Closes: https://issues.redhat.com/browse/OCPBUGS-35410 See also: https://gitlab.com/cryptsetup/cryptsetup/-/issues/585
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On 512e disks,
sfdisk(which is used bygrowpart) will end upgrowing the rootfs to a size not aligned to a 4K boundary. This is
mostly fine because, well, the drive claims to be 512b-compatible.
Issues arise however if one wants to also put LUKS on top: cryptsetup,
trying to optimize performance, wants to set the sector size of the LUKS
device to that of the physical value, which is 4K. But if the partition
range itself isn't 4K-aligned, it will choke.
Ideally, this should be fixed in sfdisk:
util-linux/util-linux#2140
(Though cryptsetup could also learn to align the mapped area itself).
Anyway, for now work aorund this by manually checking if the size of
the partition is a multiple of 4k. If not, and the physical sector size
is 4k, then trim off the edge of the partition to make it so. Note the
partition start is always going to be aligned (they're 1M-aligned).
Closes: coreos/fedora-coreos-tracker#1384
Closes: https://issues.redhat.com/browse/OCPBUGS-35410
See also: https://gitlab.com/cryptsetup/cryptsetup/-/issues/585