From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 30 May 2018 08:49:33 -0700 From: Tejun Heo To: Josef Bacik Cc: axboe@kernel.dk, kernel-team@fb.com, linux-block@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Josef Bacik Subject: Re: [PATCH 01/13] block: add bi_blkg to the bio for cgroups Message-ID: <20180530154933.GI1351649@devbig577.frc2.facebook.com> References: <20180529211724.4531-1-josef@toxicpanda.com> <20180529211724.4531-2-josef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180529211724.4531-2-josef@toxicpanda.com> Sender: owner-linux-mm@kvack.org List-ID: On Tue, May 29, 2018 at 05:17:12PM -0400, Josef Bacik wrote: > From: Josef Bacik > > Currently io.low uses a bi_cg_private to stash its private data for the > blkg, however other blkcg policies may want to use this as well. Since > we can get the private data out of the blkg, move this to bi_blkg in the > bio and make it generic, then we can use bio_associate_blkg() to attach > the blkg to the bio. > > Theoretically we could simply replace the bi_css with this since we can > get to all the same information from the blkg, however you have to > lookup the blkg, so for example wbc_init_bio() would have to lookup and > possibly allocate the blkg for the css it was trying to attach to the > bio. This could be problematic and result in us either not attaching > the css at all to the bio, or falling back to the root blkcg if we are > unable to allocate the corresponding blkg. > > So for now do this, and in the future if possible we could just replace > the bi_css with bi_blkg and update the helpers to do the correct > translation. > > Signed-off-by: Josef Bacik Acked-by: Tejun Heo Thanks. -- tejun