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bh=BpmeT6y9tW0E7A7tMHDfugGCZQ+kerTepO7ow0UTtMo=; b=GcE01FZIqNAhmjKaR6nu4cKDdAVYaBgBMNoIAcSua6qeEka1ZURwHGDwNx4Otb+zNHp+3w Uz91lJVLG9dNW6BA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 641421348A; Sat, 4 Sep 2021 10:50:11 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 6ATYF2NPM2HoUQAAMHmgww (envelope-from ); Sat, 04 Sep 2021 10:50:11 +0000 From: Vlastimil Babka To: linux-mm@kvack.org, Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim Cc: Andrew Morton , linux-kernel@vger.kernel.org, Mike Galbraith , Sebastian Andrzej Siewior , Thomas Gleixner , Mel Gorman , Vlastimil Babka Subject: [PATCH v6 12/33] mm, slub: do initial checks in ___slab_alloc() with irqs enabled Date: Sat, 4 Sep 2021 12:49:42 +0200 Message-Id: <20210904105003.11688-13-vbabka@suse.cz> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210904105003.11688-1-vbabka@suse.cz> References: <20210904105003.11688-1-vbabka@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4916; h=from:subject; bh=87FE9OnRJNS0hJN/F6onzd/dcCcpGvQurTw98yB4lQ4=; b=owEBbQGS/pANAwAIAeAhynPxiakQAcsmYgBhM08layrbhE7BGZ9g7S//qCc3uINZLuKCPbVCTiBb NbCquwOJATMEAAEIAB0WIQSNS5MBqTXjGL5IXszgIcpz8YmpEAUCYTNPJQAKCRDgIcpz8YmpEOtMCA CDILOVEKEfYJTvmrsDTaROd13M9ONiFoLUR52lXtaDBErcc2QMW6FXzLUOi3iWQFHAp5LPWTrt9NgK Np+Z+F+IZyQ0aDPhIfCDPjYBH8r0Gph8m+BBUZDrRJX8736/lsoBgPfIHt0DX49bocb/CmP9Kt0llU O8R6uDo6ClD3vlQdN1gxiv59HizvJfocs69xESjAeFc3jGanCMiHCM9QumpGElzRv9CYDZi9F+ZUmn aO68evD/w6eOF3KPB7d77WiVDZ4f43c4IBAGBdMP4ga5srnUmSY5PdXtlme09hror8WfcN+yuASfLl jU9zyAzz6RFy2nLrjr/nln6gwftZiI X-Developer-Key: i=vbabka@suse.cz; a=openpgp; fpr=A940D434992C2E8E99103D50224FA7E7CC82A664 Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=oa+dZdny; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=GcE01FZI; dmarc=none; spf=pass (imf25.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: BFE18B00008E X-Stat-Signature: 8beet94r7c5hb3wm1ychwr3ipypw61ym X-HE-Tag: 1630752612-523118 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: As another step of shortening irq disabled sections in ___slab_alloc(), delay disabling irqs until we pass the initial checks if there is a cached percpu slab and it's suitable for our allocation. Now we have to recheck c->page after actually disabling irqs as an allocation in irq handler might have replaced it. Because we call pfmemalloc_match() as one of the checks, we might hit VM_BUG_ON_PAGE(!PageSlab(page)) in PageSlabPfmemalloc in case we get interrupted and the page is freed. Thus introduce a pfmemalloc_match_unsafe() variant that lacks the PageSlab check. Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman --- include/linux/page-flags.h | 9 +++++++ mm/slub.c | 54 +++++++++++++++++++++++++++++++------- 2 files changed, 54 insertions(+), 9 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 5922031ffab6..7fda4fb85bdc 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -815,6 +815,15 @@ static inline int PageSlabPfmemalloc(struct page *page) return PageActive(page); } +/* + * A version of PageSlabPfmemalloc() for opportunistic checks where the page + * might have been freed under us and not be a PageSlab anymore. + */ +static inline int __PageSlabPfmemalloc(struct page *page) +{ + return PageActive(page); +} + static inline void SetPageSlabPfmemalloc(struct page *page) { VM_BUG_ON_PAGE(!PageSlab(page), page); diff --git a/mm/slub.c b/mm/slub.c index dda05cc83eef..6295695d8515 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2620,6 +2620,19 @@ static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags) return true; } +/* + * A variant of pfmemalloc_match() that tests page flags without asserting + * PageSlab. Intended for opportunistic checks before taking a lock and + * rechecking that nobody else freed the page under us. + */ +static inline bool pfmemalloc_match_unsafe(struct page *page, gfp_t gfpflags) +{ + if (unlikely(__PageSlabPfmemalloc(page))) + return gfp_pfmemalloc_allowed(gfpflags); + + return true; +} + /* * Check the page->freelist of a page and either transfer the freelist to the * per cpu freelist or deactivate the page. @@ -2682,8 +2695,9 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, stat(s, ALLOC_SLOWPATH); - local_irq_save(flags); - page = c->page; +reread_page: + + page = READ_ONCE(c->page); if (!page) { /* * if the node is not online or has no normal memory, just @@ -2692,6 +2706,11 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, if (unlikely(node != NUMA_NO_NODE && !node_isset(node, slab_nodes))) node = NUMA_NO_NODE; + local_irq_save(flags); + if (unlikely(c->page)) { + local_irq_restore(flags); + goto reread_page; + } goto new_slab; } redo: @@ -2706,8 +2725,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, goto redo; } else { stat(s, ALLOC_NODE_MISMATCH); - deactivate_slab(s, page, c->freelist, c); - goto new_slab; + goto deactivate_slab; } } @@ -2716,12 +2734,15 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, * PFMEMALLOC but right now, we are losing the pfmemalloc * information when the page leaves the per-cpu allocator */ - if (unlikely(!pfmemalloc_match(page, gfpflags))) { - deactivate_slab(s, page, c->freelist, c); - goto new_slab; - } + if (unlikely(!pfmemalloc_match_unsafe(page, gfpflags))) + goto deactivate_slab; - /* must check again c->freelist in case of cpu migration or IRQ */ + /* must check again c->page in case IRQ handler changed it */ + local_irq_save(flags); + if (unlikely(page != c->page)) { + local_irq_restore(flags); + goto reread_page; + } freelist = c->freelist; if (freelist) goto load_freelist; @@ -2737,6 +2758,9 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, stat(s, ALLOC_REFILL); load_freelist: + + lockdep_assert_irqs_disabled(); + /* * freelist is pointing to the list of objects to be used. * page is pointing to the page from which the objects are obtained. @@ -2748,11 +2772,23 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, local_irq_restore(flags); return freelist; +deactivate_slab: + + local_irq_save(flags); + if (page != c->page) { + local_irq_restore(flags); + goto reread_page; + } + deactivate_slab(s, page, c->freelist, c); + new_slab: + lockdep_assert_irqs_disabled(); + if (slub_percpu_partial(c)) { page = c->page = slub_percpu_partial(c); slub_set_percpu_partial(c, page); + local_irq_restore(flags); stat(s, CPU_PARTIAL_ALLOC); goto redo; }