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[157.230.128.187]) by smtp.gmail.com with ESMTPSA id z63sm13828068pfb.20.2020.04.15.06.25.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2020 06:25:04 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 757A040277; Wed, 15 Apr 2020 13:25:03 +0000 (UTC) Date: Wed, 15 Apr 2020 13:25:03 +0000 From: Luis Chamberlain To: Christoph Hellwig Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.org, 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 , Hannes Reinecke , Michal Hocko Subject: Re: [PATCH 3/5] blktrace: refcount the request_queue during ioctl Message-ID: <20200415132503.GX11244@42.do-not-panic.com> References: <20200414041902.16769-1-mcgrof@kernel.org> <20200414041902.16769-4-mcgrof@kernel.org> <20200414154044.GB25765@infradead.org> <20200415061649.GS11244@42.do-not-panic.com> <20200415071425.GA21099@infradead.org> <20200415123434.GU11244@42.do-not-panic.com> <20200415123925.GA14925@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200415123925.GA14925@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Apr 15, 2020 at 05:39:25AM -0700, Christoph Hellwig wrote: > On Wed, Apr 15, 2020 at 12:34:34PM +0000, Luis Chamberlain wrote: > > I'll pile up a fix. I've also considered doing a full review of callers > > outside of the core block layer using it, and maybe just unexporting > > this. It was originally exported due to commit d86e0e83b ("block: export > > blk_{get,put}_queue()") to fix a scsi bug, but I can't find such > > respective fix. I suspec that using bdgrab()/bdput() seems more likely > > what drivers should be using. That would allow us to keep this > > functionality internal. > > > > Think that's worthy review? > > Probably. I did in fact very quickly look into that but then gave > up due to the fair amount of modular users. Alright, then might as well then verify if the existing practice of bdgrab()/bdput() is indeed valid logic, as otherwise we'd be puting the atomic context / sleep concern to bdput(). As noted earlier I am able to confirm easily that bdgrab() can be called in atomic contex, however I cannot easily yet vet for *why* this was a safe assumption for bdput(). Luis