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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id w18sm849280qtn.3.2020.06.24.05.10.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 05:10:54 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.93) (envelope-from ) id 1jo4Ev-00DK8g-K0; Wed, 24 Jun 2020 09:10:53 -0300 Date: Wed, 24 Jun 2020 09:10:53 -0300 From: Jason Gunthorpe To: Chris Wilson Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, Andrew Morton Subject: Re: [PATCH 1/2] mm/mmu_notifier: Mark up direct reclaim paths with MAYFAIL Message-ID: <20200624121053.GD6578@ziepe.ca> References: <20200624080248.3701-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624080248.3701-1-chris@chris-wilson.co.uk> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 24, 2020 at 09:02:47AM +0100, Chris Wilson wrote: > When direct reclaim enters the shrinker and tries to reclaim pages, it > has to opportunitically unmap them [try_to_unmap_one]. For direct > reclaim, the calling context is unknown and may include attempts to > unmap one page of a dma object while attempting to allocate more pages > for that object. Pass the information along that we are inside an > opportunistic unmap that can allow that page to remain referenced and > mapped, and let the callback opt in to avoiding a recursive wait. i915 should already not be holding locks shared with the notifiers across allocations that can trigger reclaim. This is already required to use notifiers correctly anyhow - why do we need something in the notifiers? I really don't like this patch, the purpose of notifiers is only to *track changes* not to influence policy of the callers. Jason