From: David Teigland <teigland@redhat.com>
To: Itai Handler <itai.handler@gmail.com>
Cc: Zdenek Kabelac <zkabelac@redhat.com>, lvm-devel@lists.linux.dev
Subject: Re: [PATCH] label: fix writes when the logical block size is not 512 or 4096
Date: Thu, 29 Oct 2026 13:45:36 -0500 [thread overview]
Message-ID: <auOUULF672SkVzt8@redhat.com> (raw)
In-Reply-To: <20261029135355.3690645-1-itai.handler@gmail.com>
On Thu, Oct 29, 2026 at 03:53:55PM +0200, Itai Handler wrote:
> Whichever size is used, the cost to LVM is small. Only LVM's own
> writes, such as metadata updates, are rounded up to whole blocks,
> which adds less than one block to each, and they happen only when LVM
> changes something. LV data does not go through this code, and the
> default 1MiB pe_start keeps extents aligned for any of these sizes.
This last line touches on the main concern I have with the rouding up.
dev_set_last_byte was added by aecf542126640faa17c240afbb1ea61f11355c39
which addressed a very subtle data corruption bug that was introduced
by the bcache (now blkio) layer. In order to safely round up, we need
to be certain that no VGs exist in which that rounded up space could
be used by LV extents. In the past (less so today), the pe_start value
could be highly variable due to several config settings or command
line options. We'll need to prove that current and past versions of
lvm would not have placed pe_start within the rounded-up space.
Dave
prev parent reply other threads:[~2026-10-29 18:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-29 12:53 [PATCH] label: fix writes when the logical block size is not 512 or 4096 Itai Handler
2026-10-29 13:12 ` Zdenek Kabelac
2026-10-29 13:53 ` Itai Handler
2026-10-29 18:45 ` David Teigland [this message]
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