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From: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	Jens Axboe <axboe@fb.com>
Subject: Re: [PATCH 4/4] block: expose devt for GENHD_FL_HIDDEN disks
Date: Wed, 12 Dec 2018 10:39:06 -0200	[thread overview]
Message-ID: <20181212123906.GI4269@calabresa> (raw)
In-Reply-To: <20181206202200.GA32080@lst.de>

On Thu, Dec 06, 2018 at 09:22:00PM +0100, Christoph Hellwig wrote:
> On Thu, Dec 06, 2018 at 02:48:12PM -0200, Thadeu Lima de Souza Cascardo wrote:
> > Without this exposure, lsblk will fail as it tries to find out the
> > device's dev_t numbers. This causes a real problem for nvme multipath
> > devices, as their slaves are hidden.
> > 
> > Exposing them fixes the problem, even though trying to open the devices
> > returns an error in the case of nvme multipath. So, right now, it's the
> > driver's responsibility to return a failure to open hidden devices.
> 
> So the problem with this is that it will cause udev to actually create
> the /dev/nvmeXcYnZ nodes, which due to the previous patch will always
> fail to open, which is a bit confusing.  I guess we could live with this
> if we add udev rules to supress the creation or something, but in general
> it is a bit ugly.

Well, udev could just look at the hidden attribute. At least to some, the fact
that lsblk would fail was reason enough to revert the patches, so I would
rather apply the entire set.

We could add a message to the log when users try to open them, but given that
some programs (udev is one) would open them without any user interaction, maybe
we shouldn't.

Cascardo.

WARNING: multiple messages have this Message-ID (diff)
From: cascardo@canonical.com (Thadeu Lima de Souza Cascardo)
Subject: [PATCH 4/4] block: expose devt for GENHD_FL_HIDDEN disks
Date: Wed, 12 Dec 2018 10:39:06 -0200	[thread overview]
Message-ID: <20181212123906.GI4269@calabresa> (raw)
In-Reply-To: <20181206202200.GA32080@lst.de>

On Thu, Dec 06, 2018@09:22:00PM +0100, Christoph Hellwig wrote:
> On Thu, Dec 06, 2018@02:48:12PM -0200, Thadeu Lima de Souza Cascardo wrote:
> > Without this exposure, lsblk will fail as it tries to find out the
> > device's dev_t numbers. This causes a real problem for nvme multipath
> > devices, as their slaves are hidden.
> > 
> > Exposing them fixes the problem, even though trying to open the devices
> > returns an error in the case of nvme multipath. So, right now, it's the
> > driver's responsibility to return a failure to open hidden devices.
> 
> So the problem with this is that it will cause udev to actually create
> the /dev/nvmeXcYnZ nodes, which due to the previous patch will always
> fail to open, which is a bit confusing.  I guess we could live with this
> if we add udev rules to supress the creation or something, but in general
> it is a bit ugly.

Well, udev could just look at the hidden attribute. At least to some, the fact
that lsblk would fail was reason enough to revert the patches, so I would
rather apply the entire set.

We could add a message to the log when users try to open them, but given that
some programs (udev is one) would open them without any user interaction, maybe
we shouldn't.

Cascardo.

  parent reply	other threads:[~2018-12-12 12:39 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-06 16:48 [PATCH 0/4] nvme multipath: expose slaves/holders Thadeu Lima de Souza Cascardo
2018-12-06 16:48 ` Thadeu Lima de Souza Cascardo
2018-12-06 16:48 ` [PATCH 1/4] block: move holder tracking from struct block_device to hd_struct Thadeu Lima de Souza Cascardo
2018-12-06 16:48   ` Thadeu Lima de Souza Cascardo
2018-12-13  9:14   ` Hannes Reinecke
2018-12-13  9:14     ` Hannes Reinecke
2018-12-06 16:48 ` [PATCH 2/4] nvme: create slaves/holder entries for multipath devices Thadeu Lima de Souza Cascardo
2018-12-06 16:48   ` Thadeu Lima de Souza Cascardo
2018-12-13  9:15   ` Hannes Reinecke
2018-12-13  9:15     ` Hannes Reinecke
2018-12-06 16:48 ` [PATCH 3/4] nvme: Should not warn when a disk path is opened Thadeu Lima de Souza Cascardo
2018-12-06 16:48   ` Thadeu Lima de Souza Cascardo
2018-12-13  9:16   ` Hannes Reinecke
2018-12-13  9:16     ` Hannes Reinecke
2018-12-06 16:48 ` [PATCH 4/4] block: expose devt for GENHD_FL_HIDDEN disks Thadeu Lima de Souza Cascardo
2018-12-06 16:48   ` Thadeu Lima de Souza Cascardo
2018-12-06 20:22   ` Christoph Hellwig
2018-12-06 20:22     ` Christoph Hellwig
2018-12-12  8:32     ` Christoph Hellwig
2018-12-12  8:32       ` Christoph Hellwig
2018-12-12 12:39     ` Thadeu Lima de Souza Cascardo [this message]
2018-12-12 12:39       ` Thadeu Lima de Souza Cascardo
2018-12-13  9:18   ` Hannes Reinecke
2018-12-13  9:18     ` Hannes Reinecke
2018-12-13 11:41     ` Thadeu Lima de Souza Cascardo
2018-12-13 11:41       ` Thadeu Lima de Souza Cascardo
2018-12-13 12:19       ` Hannes Reinecke
2018-12-13 12:19         ` Hannes Reinecke
2018-12-13 16:08         ` Thadeu Lima de Souza Cascardo
2018-12-13 16:08           ` Thadeu Lima de Souza Cascardo
2018-12-13 14:32     ` Christoph Hellwig
2018-12-13 14:32       ` Christoph Hellwig
2018-12-13 15:25       ` Thadeu Lima de Souza Cascardo
2018-12-13 15:25         ` Thadeu Lima de Souza Cascardo
2018-12-13 20:20         ` Christoph Hellwig
2018-12-13 20:20           ` Christoph Hellwig
2018-12-13 21:00           ` Thadeu Lima de Souza Cascardo
2018-12-13 21:00             ` Thadeu Lima de Souza Cascardo
2018-12-14  7:47         ` Hannes Reinecke
2018-12-14  7:47           ` Hannes Reinecke
2018-12-14  8:56           ` Thadeu Lima de Souza Cascardo
2018-12-14  8:56             ` Thadeu Lima de Souza Cascardo
2018-12-14  9:06             ` Thadeu Lima de Souza Cascardo
2018-12-14  9:06               ` Thadeu Lima de Souza Cascardo
2018-12-14  9:54               ` Hannes Reinecke
2018-12-14  9:54                 ` Hannes Reinecke
2018-12-14 10:18                 ` Hannes Reinecke
2018-12-14 10:18                   ` Hannes Reinecke
2018-12-14 11:09                 ` Thadeu Lima de Souza Cascardo
2018-12-14 11:09                   ` Thadeu Lima de Souza Cascardo
2018-12-14  9:44             ` Hannes Reinecke
2018-12-14  9:44               ` Hannes Reinecke
2018-12-13  9:33 ` [PATCH 0/4] nvme multipath: expose slaves/holders Johannes Thumshirn
2018-12-13  9:33   ` Johannes Thumshirn
2018-12-13 11:35   ` Thadeu Lima de Souza Cascardo
2018-12-13 11:35     ` Thadeu Lima de Souza Cascardo

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