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[216.228.112.21]) by smtp.gmail.com with ESMTPSA id z3-v6sm368579pfm.150.2018.10.11.23.00.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Oct 2018 23:00:34 -0700 (PDT) From: john.hubbard@gmail.com X-Google-Original-From: jhubbard@nvidia.com To: Matthew Wilcox , Michal Hocko , Christopher Lameter , Jason Gunthorpe , Dan Williams , Jan Kara Cc: linux-mm@kvack.org, Andrew Morton , LKML , linux-rdma , linux-fsdevel@vger.kernel.org, John Hubbard Subject: [PATCH 5/6] mm: introduce zone_gup_lock, for dma-pinned pages Date: Thu, 11 Oct 2018 23:00:13 -0700 Message-Id: <20181012060014.10242-6-jhubbard@nvidia.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181012060014.10242-1-jhubbard@nvidia.com> References: <20181012060014.10242-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: John Hubbard The page->dma_pinned_flags and _count fields require lock protection. A lock at approximately the granularity of the zone_lru_lock is called for, but adding to the locking contention of zone_lru_lock is undesirable, because that is a pre-existing hot spot. Fortunately, these new dma_pinned_* fields can use an independent lock, so this patch creates an entirely new lock, right next to the zone_lru_lock. Why "zone_gup_lock"? Most of the naming refers to "DMA-pinned pages", but "zone DMA lock" has other meanings already, so this is called zone_gup_lock instead. The "dma pinning" is a result of get_user_pages (gup) being called, so the name still helps explain its use. Signed-off-by: John Hubbard --- include/linux/mmzone.h | 6 ++++++ mm/page_alloc.c | 1 + 2 files changed, 7 insertions(+) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index d4b0c79d2924..971a63f84ad5 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -661,6 +661,7 @@ typedef struct pglist_data { enum zone_type kswapd_classzone_idx; int kswapd_failures; /* Number of 'reclaimed == 0' runs */ + spinlock_t pinned_dma_lock; #ifdef CONFIG_COMPACTION int kcompactd_max_order; @@ -730,6 +731,11 @@ static inline spinlock_t *zone_lru_lock(struct zone *zone) return &zone->zone_pgdat->lru_lock; } +static inline spinlock_t *zone_gup_lock(struct zone *zone) +{ + return &zone->zone_pgdat->pinned_dma_lock; +} + static inline struct lruvec *node_lruvec(struct pglist_data *pgdat) { return &pgdat->lruvec; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e2ef1c17942f..850f90223cc7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6225,6 +6225,7 @@ static void __meminit pgdat_init_internals(struct pglist_data *pgdat) pgdat_page_ext_init(pgdat); spin_lock_init(&pgdat->lru_lock); + spin_lock_init(&pgdat->pinned_dma_lock); lruvec_init(node_lruvec(pgdat)); } -- 2.19.1