From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: john.hubbard@gmail.com To: linux-mm@kvack.org Cc: Andrew Morton , LKML , linux-rdma , linux-fsdevel@vger.kernel.org, John Hubbard , Matthew Wilcox , Michal Hocko , Christopher Lameter , Jason Gunthorpe , Dan Williams , Jan Kara Subject: [PATCH v2 5/6] mm: introduce zone_gup_lock, for dma-pinned pages Date: Sat, 10 Nov 2018 00:50:40 -0800 Message-Id: <20181110085041.10071-6-jhubbard@nvidia.com> In-Reply-To: <20181110085041.10071-1-jhubbard@nvidia.com> References: <20181110085041.10071-1-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: 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. Cc: Matthew Wilcox Cc: Michal Hocko Cc: Christopher Lameter Cc: Jason Gunthorpe Cc: Dan Williams Cc: Jan Kara 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 847705a6d0ec..125a6f34f6ba 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -660,6 +660,7 @@ 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; @@ -729,6 +730,11 @@ 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 a919ba5cb3c8..7cc0d9bdba17 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6305,6 +6305,7 @@ 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