From: Milan Broz <gmazyland@gmail.com>
To: Eric Wheeler <linux-integrity@lists.ewheeler.net>,
linux-integrity@vger.kernel.org
Cc: "dm-devel@lists.linux.dev" <dm-devel@lists.linux.dev>,
Mikulas Patocka <mpatocka@redhat.com>
Subject: Re: dm-integrity: 4k devices report 512b discard alignment
Date: Sun, 14 Apr 2024 17:43:56 +0200 [thread overview]
Message-ID: <acd54b09-c5b9-4548-a24f-95c503e20139@gmail.com> (raw)
In-Reply-To: <447e2027-bfe2-9c21-a5ad-291e16b78f28@ewheeler.net>
On 4/14/24 3:05 AM, Eric Wheeler wrote:
> 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
Hi,
this looks wrong. But you should send it to dm-devel list (added to cc) ...
Maybe also add lsblk -D (and lsblk -t for block sizes)
(where you can see inherited values for all layers).
And I see similar problem in dm-crypt with 4k sector but 512B discard granularity
(on 6.8.4 - LUKS with forced 4k sector and alllow_discards).
What is interesting, for current Linus' tree I see discard granularity 0 (?), but
with Mike's DM for-next (with use queue_limits_set fixes) it correctly shows 4k.
(Ditto for your integrity case. So perhaps linux-next is fixed.)
Milan
>
> 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 parent reply other threads:[~2024-04-14 15:43 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <447e2027-bfe2-9c21-a5ad-291e16b78f28@ewheeler.net>
2024-04-14 15:43 ` Milan Broz [this message]
2024-04-15 1:56 ` dm-integrity: 4k devices report 512b discard alignment Eric Wheeler
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