From: Luis Chamberlain <mcgrof@kernel.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk,
gregkh@linuxfoundation.org, rostedt@goodmis.org,
mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com,
nstange@suse.de, akpm@linux-foundation.org, mhocko@suse.com,
yukuai3@huawei.com, linux-block@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Omar Sandoval <osandov@fb.com>,
Hannes Reinecke <hare@suse.com>, Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v2 04/10] block: revert back to synchronous request_queue removal
Date: Mon, 20 Apr 2020 21:51:47 +0000 [thread overview]
Message-ID: <20200420215147.GP11244@42.do-not-panic.com> (raw)
In-Reply-To: <eba2a91b-62a6-839d-df54-2a1cf8262652@acm.org>
On Mon, Apr 20, 2020 at 02:11:13PM -0700, Bart Van Assche wrote:
> On 4/20/20 11:59 AM, Luis Chamberlain wrote:
> > On Sun, Apr 19, 2020 at 03:23:31PM -0700, Bart Van Assche wrote:
> > > On 4/19/20 12:45 PM, Luis Chamberlain wrote:
> > > > + * Decrements the refcount to the request_queue kobject, when this reaches
> > > > + * 0 we'll have blk_release_queue() called. You should avoid calling
> > > > + * this function in atomic context but if you really have to ensure you
> > > > + * first refcount the block device with bdgrab() / bdput() so that the
> > > > + * last decrement happens in blk_cleanup_queue().
> > > > + */
> > >
> > > Is calling bdgrab() and bdput() an option from a context in which it is not
> > > guaranteed that the block device is open?
> >
> > If the block device is not open, nope. For that blk_get_queue() can
> > be used, and is used by the block layer. This begs the question:
> >
> > Do we have *drivers* which requires access to the request_queue from
> > atomic context when the block device is not open?
>
> Instead of trying to answer that question, how about changing the references
> to bdgrab() and bdput() into references to blk_get_queue() and
> blk_put_queue()? I think if that change is made that we won't have to
> research what the answer to the bdgrab()/bdput() question is.
Yeah that's fine, now at least we'd have documented what should be avoided.
Luis
next prev parent reply other threads:[~2020-04-20 21:51 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-19 19:45 [PATCH v2 00/10] block: fix blktrace debugfs use after free Luis Chamberlain
2020-04-19 19:45 ` [PATCH v2 01/10] block: move main block debugfs initialization to its own file Luis Chamberlain
2020-04-19 21:06 ` Bart Van Assche
2020-04-19 19:45 ` [PATCH v2 02/10] blktrace: move blktrace debugfs creation to helper function Luis Chamberlain
2020-04-19 21:11 ` Bart Van Assche
2020-04-22 7:12 ` Christoph Hellwig
2020-04-19 19:45 ` [PATCH v2 03/10] blktrace: fix debugfs use after free Luis Chamberlain
2020-04-19 21:55 ` Bart Van Assche
2020-04-20 0:04 ` Luis Chamberlain
2020-04-20 0:38 ` Bart Van Assche
2020-04-20 18:46 ` Luis Chamberlain
2020-04-20 20:16 ` Greg KH
2020-04-20 20:41 ` Luis Chamberlain
2020-04-21 7:00 ` Greg KH
2020-04-22 7:28 ` Luis Chamberlain
2020-04-22 9:43 ` Ming Lei
2020-04-22 10:31 ` Luis Chamberlain
2020-04-24 23:47 ` Luis Chamberlain
2020-04-22 7:29 ` Christoph Hellwig
2020-04-22 7:34 ` Luis Chamberlain
2020-04-22 7:27 ` Christoph Hellwig
2020-04-22 7:48 ` Luis Chamberlain
2020-04-22 8:10 ` Christoph Hellwig
2020-04-22 8:26 ` Luis Chamberlain
2020-04-19 19:45 ` [PATCH v2 04/10] block: revert back to synchronous request_queue removal Luis Chamberlain
2020-04-19 22:23 ` Bart Van Assche
2020-04-20 18:59 ` Luis Chamberlain
2020-04-20 21:11 ` Bart Van Assche
2020-04-20 21:51 ` Luis Chamberlain [this message]
2020-04-19 19:45 ` [PATCH v2 05/10] blktrace: upgrade warns to BUG_ON() on unexpected circmunstances Luis Chamberlain
2020-04-19 22:50 ` Bart Van Assche
2020-04-19 23:07 ` Luis Chamberlain
2020-04-20 23:20 ` Steven Rostedt
2020-04-19 19:45 ` [PATCH v2 06/10] blk-debugfs: upgrade warns to BUG_ON() if directory is already found Luis Chamberlain
2020-04-20 11:36 ` Greg KH
2020-04-25 11:43 ` [blk] 90d38c0e30: kernel_BUG_at_block/blk-debugfs.c kernel test robot
2020-04-19 19:45 ` [PATCH v2 07/10] blktrace: move debugfs file creation to its own function Luis Chamberlain
2020-04-19 22:55 ` Bart Van Assche
2020-04-20 11:37 ` Greg KH
2020-04-19 19:45 ` [PATCH v2 08/10] blktrace: add checks for created debugfs files on setup Luis Chamberlain
2020-04-19 22:57 ` Bart Van Assche
2020-04-19 23:05 ` Luis Chamberlain
2020-04-19 23:17 ` Bart Van Assche
2020-04-20 11:40 ` Greg KH
2020-04-20 18:44 ` Luis Chamberlain
2020-04-20 20:11 ` Greg KH
2020-04-20 20:20 ` Luis Chamberlain
2020-04-21 6:55 ` Greg KH
2020-04-20 11:39 ` Greg KH
2020-04-19 19:45 ` [PATCH v2 09/10] block: panic if block debugfs dir is not created Luis Chamberlain
2020-04-19 23:08 ` Bart Van Assche
2020-04-20 11:38 ` Greg KH
2020-04-19 19:45 ` [PATCH v2 10/10] block: put_device() if device_add() fails Luis Chamberlain
2020-04-19 23:40 ` Bart Van Assche
2020-04-24 22:32 ` Luis Chamberlain
2020-04-25 1:58 ` Bart Van Assche
2020-04-25 2:12 ` Luis Chamberlain
2020-04-19 19:48 ` [PATCH v2 00/10] block: fix blktrace debugfs use after free Luis Chamberlain
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