From: Eric Wheeler <linux-integrity@lists.ewheeler.net>
To: linux-integrity@vger.kernel.org
Subject: dm-integrity: 4k devices report 512b discard alignment
Date: Sat, 13 Apr 2024 18:05:10 -0700 (PDT) [thread overview]
Message-ID: <447e2027-bfe2-9c21-a5ad-291e16b78f28@ewheeler.net> (raw)
Hello all,
I'm not sure if this is a bug or a feature, so thought I'd report it.
These are all for Linux 6.6.26:
If you start with a 512-byte backing device (logical and physical):
# blockdev --getss --getpbsz /dev/nvme9n9
512
512
then format+open with 4k sectors:
# integritysetup format -s 4096 /dev/nvme9n9
# integritysetup open /dev/nvme9n9 integrity-nvme9n9
and find the dm-X device:
# ls -l /dev/mapper/integrity-nvme9n9
lrwxrwxrwx. 1 root root 9 Apr 13 17:09 /dev/mapper/integrity-nvme9n9 -> ../dm-189
then check it's discard_granularity, it shows 512:
# tail /sys/block/dm-189/queue/discard_*
==> /sys/block/dm-189/queue/discard_granularity <==
512
The sector size is 4k, so supporting unaligned discards seems at least
strange, if not invalid, and dmesg complains too:
# blockdev --getss /dev/mapper/integrity-nvme9n9
4096
Relatedly, should the physical size of an integrity volume "properly"
report 512 to match the backing device, or is 4k correct in this case?
Presently it reports 4k:
# blockdev --getpbsz /dev/mapper/integrity-nvme2n1
4096
Finally, this is what made me go investiage: when you issue `blkdiscard`
on the integrity volume:
# blkdiscard /dev/mapper/integrity-nvme9n9
it causes dmesg spews the following:
[ 2508.364637] device-mapper: integrity: Bio not aligned on 8 sectors: 0x74ff8000, 0x7f0f
[ 2508.364856] device-mapper: integrity: Bio not aligned on 8 sectors: 0x74ffff16, 0xea
[ 2508.365070] device-mapper: integrity: Bio not aligned on 8 sectors: 0x757fff0e, 0x7
[ 2508.365973] device-mapper: integrity: Bio not aligned on 8 sectors: 0x757f8000, 0x7f0e
What do you think?
--
Eric Wheeler
next reply other threads:[~2024-04-14 1:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-14 1:05 Eric Wheeler [this message]
2024-04-14 15:43 ` dm-integrity: 4k devices report 512b discard alignment Milan Broz
2024-04-15 1:56 ` Eric Wheeler
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