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Harding" , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 0/4] mm: Use slab_list list_head instead of lru Message-ID: <20190311231633.GF19508@bombadil.infradead.org> References: <20190311010744.5862-1-tobin@kernel.org> <20190311204919.GA20002@tower.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190311204919.GA20002@tower.DHCP.thefacebook.com> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Mon, Mar 11, 2019 at 08:49:23PM +0000, Roman Gushchin wrote: > The patchset looks good to me, however I'd add some clarifications > why switching from lru to slab_list is safe. > > My understanding is that the slab_list fields isn't currently in use, > but it's not that obvious that putting slab_list and next/pages/pobjects > fields into a union is safe (for the slub case). It's already in a union. struct page { union { struct { /* Page cache and anonymous pages */ struct list_head lru; ... struct { /* slab, slob and slub */ union { struct list_head slab_list; /* uses lru */ struct { /* Partial pages */ struct page *next; slab_list and lru are in the same bits. Once this patch set is in, we can remove the enigmatic 'uses lru' comment that I added.