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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
	Mike Snitzer <snitzer@redhat.com>,
	Oleksii Kurochko <olkuroch@cisco.com>,
	Dongsheng Yang <dongsheng.yang@easystack.cn>,
	linux-block@vger.kernel.org, dm-devel@redhat.com,
	linux-nvme@lists.infradead.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Ilya Dryomov <idryomov@gmail.com>,
	ceph-devel@vger.kernel.org
Subject: Re: [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions
Date: Tue, 8 Dec 2020 18:29:23 +0800	[thread overview]
Message-ID: <20201208102923.GD1202995@T590> (raw)
In-Reply-To: <20201207131918.2252553-5-hch@lst.de>

On Mon, Dec 07, 2020 at 02:19:16PM +0100, 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:
> 
> permits writes. But:
> 
> <something triggers revalidate>
> 
> doesn't.
> 
> And a subsequent:
> 
> doesn't work either since sda1's read-only policy has been inherited
> from the whole-disk device.
> 
> You need to do:
> 
> 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>
> ---
>  block/genhd.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 878f94727aaa96..c214fcd25a05c9 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1449,8 +1449,7 @@ EXPORT_SYMBOL(set_disk_ro);
>  
>  int bdev_read_only(struct block_device *bdev)
>  {
> -	return bdev->bd_read_only ||
> -		test_bit(GD_READ_ONLY, &bdev->bd_disk->state);
> +	return bdev->bd_read_only || get_disk_ro(bdev->bd_disk);
>  }
>  EXPORT_SYMBOL(bdev_read_only);

I think this patch should be folded into previous one, otherwise
bdev_read_only(part) may return false even though ioctl(BLKROSET)
has been done on the whole disk.

-- 
Ming


WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
	Mike Snitzer <snitzer@redhat.com>,
	Oleksii Kurochko <olkuroch@cisco.com>,
	Dongsheng Yang <dongsheng.yang@easystack.cn>,
	linux-block@vger.kernel.org, dm-devel@redhat.com,
	linux-nvme@lists.infradead.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Ilya Dryomov <idryomov@gmail.com>,
	ceph-devel@vger.kernel.org
Subject: Re: [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions
Date: Tue, 8 Dec 2020 18:29:23 +0800	[thread overview]
Message-ID: <20201208102923.GD1202995@T590> (raw)
In-Reply-To: <20201207131918.2252553-5-hch@lst.de>

On Mon, Dec 07, 2020 at 02:19:16PM +0100, 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:
> 
> permits writes. But:
> 
> <something triggers revalidate>
> 
> doesn't.
> 
> And a subsequent:
> 
> doesn't work either since sda1's read-only policy has been inherited
> from the whole-disk device.
> 
> You need to do:
> 
> 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>
> ---
>  block/genhd.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 878f94727aaa96..c214fcd25a05c9 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1449,8 +1449,7 @@ EXPORT_SYMBOL(set_disk_ro);
>  
>  int bdev_read_only(struct block_device *bdev)
>  {
> -	return bdev->bd_read_only ||
> -		test_bit(GD_READ_ONLY, &bdev->bd_disk->state);
> +	return bdev->bd_read_only || get_disk_ro(bdev->bd_disk);
>  }
>  EXPORT_SYMBOL(bdev_read_only);

I think this patch should be folded into previous one, otherwise
bdev_read_only(part) may return false even though ioctl(BLKROSET)
has been done on the whole disk.

-- 
Ming


_______________________________________________
Linux-nvme mailing list
Linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
	Mike Snitzer <snitzer@redhat.com>,
	Oleksii Kurochko <olkuroch@cisco.com>,
	Dongsheng Yang <dongsheng.yang@easystack.cn>,
	linux-block@vger.kernel.org, dm-devel@redhat.com,
	linux-nvme@lists.infradead.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Ilya Dryomov <idryomov@gmail.com>,
	ceph-devel@vger.kernel.org
Subject: Re: [dm-devel] [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions
Date: Tue, 8 Dec 2020 18:29:23 +0800	[thread overview]
Message-ID: <20201208102923.GD1202995@T590> (raw)
In-Reply-To: <20201207131918.2252553-5-hch@lst.de>

On Mon, Dec 07, 2020 at 02:19:16PM +0100, 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:
> 
> permits writes. But:
> 
> <something triggers revalidate>
> 
> doesn't.
> 
> And a subsequent:
> 
> doesn't work either since sda1's read-only policy has been inherited
> from the whole-disk device.
> 
> You need to do:
> 
> 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>
> ---
>  block/genhd.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 878f94727aaa96..c214fcd25a05c9 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1449,8 +1449,7 @@ EXPORT_SYMBOL(set_disk_ro);
>  
>  int bdev_read_only(struct block_device *bdev)
>  {
> -	return bdev->bd_read_only ||
> -		test_bit(GD_READ_ONLY, &bdev->bd_disk->state);
> +	return bdev->bd_read_only || get_disk_ro(bdev->bd_disk);
>  }
>  EXPORT_SYMBOL(bdev_read_only);

I think this patch should be folded into previous one, otherwise
bdev_read_only(part) may return false even though ioctl(BLKROSET)
has been done on the whole disk.

-- 
Ming

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel


  parent reply	other threads:[~2020-12-08 10:32 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-07 13:19 split hard read-only vs read-only policy v2 Christoph Hellwig
2020-12-07 13:19 ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19 ` Christoph Hellwig
2020-12-07 13:19 ` [PATCH 1/6] dm: use bdev_read_only to check if a device is read-only Christoph Hellwig
2020-12-07 13:19   ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19   ` Christoph Hellwig
2020-12-08  5:23   ` Martin K. Petersen
2020-12-08  5:23     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:23     ` Martin K. Petersen
2020-12-08  9:59   ` Ming Lei
2020-12-08  9:59     ` [dm-devel] " Ming Lei
2020-12-08  9:59     ` Ming Lei
2020-12-07 13:19 ` [PATCH 2/6] block: remove the NULL bdev check in bdev_read_only Christoph Hellwig
2020-12-07 13:19   ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19   ` Christoph Hellwig
2020-12-08  5:23   ` Martin K. Petersen
2020-12-08  5:23     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:23     ` Martin K. Petersen
2020-12-08 10:06   ` Ming Lei
2020-12-08 10:06     ` [dm-devel] " Ming Lei
2020-12-08 10:06     ` Ming Lei
2020-12-07 13:19 ` [PATCH 3/6] block: add a hard-readonly flag to struct gendisk Christoph Hellwig
2020-12-07 13:19   ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19   ` Christoph Hellwig
2020-12-08  5:24   ` Martin K. Petersen
2020-12-08  5:24     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:24     ` Martin K. Petersen
2020-12-08  5:28   ` Martin K. Petersen
2020-12-08  5:28     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:28     ` Martin K. Petersen
2020-12-08 10:22   ` Ming Lei
2020-12-08 10:22     ` [dm-devel] " Ming Lei
2020-12-08 10:22     ` Ming Lei
2020-12-08 10:57     ` Christoph Hellwig
2020-12-08 10:57       ` [dm-devel] " Christoph Hellwig
2020-12-08 10:57       ` Christoph Hellwig
2020-12-07 13:19 ` [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions Christoph Hellwig
2020-12-07 13:19   ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19   ` Christoph Hellwig
2020-12-08  5:27   ` Martin K. Petersen
2020-12-08  5:27     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:27     ` Martin K. Petersen
2020-12-08  9:25     ` Christoph Hellwig
2020-12-08  9:25       ` [dm-devel] " Christoph Hellwig
2020-12-08  9:25       ` Christoph Hellwig
2020-12-08 12:41       ` Johannes Thumshirn
2020-12-08 12:41         ` [dm-devel] " Johannes Thumshirn
2020-12-08 12:41         ` Johannes Thumshirn
2020-12-08 10:29   ` Ming Lei [this message]
2020-12-08 10:29     ` [dm-devel] " Ming Lei
2020-12-08 10:29     ` Ming Lei
2020-12-08 10:59     ` Christoph Hellwig
2020-12-08 10:59       ` [dm-devel] " Christoph Hellwig
2020-12-08 10:59       ` Christoph Hellwig
2020-12-09  1:23       ` Ming Lei
2020-12-09  1:23         ` [dm-devel] " Ming Lei
2020-12-09  1:23         ` Ming Lei
2020-12-07 13:19 ` [PATCH 5/6] rbd: remove the ->set_read_only method Christoph Hellwig
2020-12-07 13:19   ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19   ` Christoph Hellwig
2020-12-07 14:57   ` Ilya Dryomov
2020-12-07 14:57     ` [dm-devel] " Ilya Dryomov
2020-12-07 14:57     ` Ilya Dryomov
2020-12-08  5:30   ` Martin K. Petersen
2020-12-08  5:30     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:30     ` Martin K. Petersen
2020-12-07 13:19 ` [PATCH 6/6] nvme: allow revalidate to set a namespace read-only Christoph Hellwig
2020-12-07 13:19   ` [dm-devel] " Christoph Hellwig
2020-12-07 13:19   ` Christoph Hellwig
2020-12-07 18:13   ` Keith Busch
2020-12-07 18:13     ` [dm-devel] " Keith Busch
2020-12-07 18:13     ` Keith Busch
2020-12-08  5:29   ` Martin K. Petersen
2020-12-08  5:29     ` [dm-devel] " Martin K. Petersen
2020-12-08  5:29     ` Martin K. Petersen
2020-12-10  7:50 ` split hard read-only vs read-only policy v2 Christoph Hellwig
2020-12-10  7:50   ` [dm-devel] " Christoph Hellwig
2020-12-10  7:50   ` Christoph Hellwig
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 16:28   ` Christoph Hellwig
2020-12-08 16:47   ` Hannes Reinecke
2020-12-08 16:47     ` Hannes Reinecke
2020-12-09  2:51   ` Ming Lei
2020-12-09  2:51     ` Ming Lei
2021-01-09 10:42 split hard read-only vs read-only policy v3 (resend) Christoph Hellwig
2021-01-09 10:42 ` [PATCH 4/6] block: propagate BLKROSET on the whole device to all partitions Christoph Hellwig
2021-01-09 10:42   ` Christoph Hellwig
2021-01-10 15:00   ` Hannes Reinecke
2021-01-10 15:00     ` Hannes Reinecke

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