From: Hannes Reinecke <hare@suse.de>
To: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
Oleksii Kurochko <olkuroch@cisco.com>,
Sagi Grimberg <sagi@grimberg.me>,
Mike Snitzer <snitzer@redhat.com>,
Ilya Dryomov <idryomov@gmail.com>,
Dongsheng Yang <dongsheng.yang@easystack.cn>,
ceph-devel@vger.kernel.org, dm-devel@redhat.com,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org
Subject: Re: [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions
Date: Sun, 10 Jan 2021 16:00:48 +0100 [thread overview]
Message-ID: <81a37585-bf6e-9ab5-993e-e9a0881ce996@suse.de> (raw)
In-Reply-To: <20210109104254.1077093-5-hch@lst.de>
On 1/9/21 11:42 AM, Christoph Hellwig wrote:
> Change the policy so that a BLKROSET on the whole device also affects
> partitions. To quote Martin K. Petersen:
>
> It's very common for database folks to twiddle the read-only state of
> block devices and partitions. I know that our users will find it very
> counter-intuitive that setting /dev/sda read-only won't prevent writes
> to /dev/sda1.
>
> The existing behavior is inconsistent in the sense that doing:
>
> # blockdev --setro /dev/sda
> # echo foo > /dev/sda1
>
> permits writes. But:
>
> # blockdev --setro /dev/sda
> <something triggers revalidate>
> # echo foo > /dev/sda1
>
> doesn't.
>
> And a subsequent:
>
> # blockdev --setrw /dev/sda
> # echo foo > /dev/sda1
>
> doesn't work either since sda1's read-only policy has been inherited
> from the whole-disk device.
>
> You need to do:
>
> # blockdev --rereadpt
>
> after setting the whole-disk device rw to effectuate the same change on
> the partitions, otherwise they are stuck being read-only indefinitely.
>
> However, setting the read-only policy on a partition does *not* require
> the revalidate step. As a matter of fact, doing the revalidate will blow
> away the policy setting you just made.
>
> So the user needs to take different actions depending on whether they
> are trying to read-protect a whole-disk device or a partition. Despite
> using the same ioctl. That is really confusing.
>
> I have lost count how many times our customers have had data clobbered
> because of ambiguity of the existing whole-disk device policy. The
> current behavior violates the principle of least surprise by letting the
> user think they write protected the whole disk when they actually
> didn't.
>
> Suggested-by: Martin K. Petersen <martin.petersen@oracle.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
> block/genhd.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
next prev parent reply other threads:[~2021-01-10 15:01 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-09 10:42 split hard read-only vs read-only policy v3 (resend) Christoph Hellwig
2021-01-09 10:42 ` [PATCH 1/6] dm: use bdev_read_only to check if a device is read-only Christoph Hellwig
2021-01-09 10:42 ` [PATCH 2/6] block: remove the NULL bdev check in bdev_read_only Christoph Hellwig
2021-01-09 20:14 ` Chaitanya Kulkarni
2021-01-10 14:59 ` Hannes Reinecke
2021-01-09 10:42 ` [PATCH 3/6] block: add a hard-readonly flag to struct gendisk Christoph Hellwig
2021-01-09 10:42 ` [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions Christoph Hellwig
2021-01-10 15:00 ` Hannes Reinecke [this message]
2021-01-09 10:42 ` [PATCH 5/6] rbd: remove the ->set_read_only method Christoph Hellwig
2021-01-09 10:42 ` [PATCH 6/6] nvme: allow revalidate to set a namespace read-only Christoph Hellwig
2021-01-09 20:27 ` Chaitanya Kulkarni
2021-01-10 15:01 ` Hannes Reinecke
-- strict thread matches above, loose matches on Subject: below --
2020-12-08 16:28 split hard read-only vs read-only policy v3 Christoph Hellwig
2020-12-08 16:28 ` [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions Christoph Hellwig
2020-12-08 16:47 ` Hannes Reinecke
2020-12-09 2:51 ` Ming Lei
2020-12-07 13:19 split hard read-only vs read-only policy v2 Christoph Hellwig
2020-12-07 13:19 ` [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions Christoph Hellwig
2020-12-08 5:27 ` Martin K. Petersen
2020-12-08 9:25 ` Christoph Hellwig
2020-12-08 12:41 ` Johannes Thumshirn
2020-12-08 10:29 ` Ming Lei
2020-12-08 10:59 ` Christoph Hellwig
2020-12-09 1:23 ` Ming Lei
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=81a37585-bf6e-9ab5-993e-e9a0881ce996@suse.de \
--to=hare@suse.de \
--cc=axboe@kernel.dk \
--cc=ceph-devel@vger.kernel.org \
--cc=dm-devel@redhat.com \
--cc=dongsheng.yang@easystack.cn \
--cc=hch@lst.de \
--cc=idryomov@gmail.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-nvme@lists.infradead.org \
--cc=martin.petersen@oracle.com \
--cc=olkuroch@cisco.com \
--cc=sagi@grimberg.me \
--cc=snitzer@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).