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authorChristoph Hellwig <hch@lst.de>2017-12-29 08:54:00 +0100
committerDan Williams <dan.j.williams@intel.com>2018-01-08 11:46:23 -0800
commit0822acb86cf340cd45b3af6436cec7e3bb24ebd2 (patch)
treec6faf43ac3d78e1bd91334e9e94feb7d6b939c30 /kernel/memremap.c
parenteb8045335c70ef8b272d2888a225b81344423139 (diff)
downloadop-kernel-dev-0822acb86cf340cd45b3af6436cec7e3bb24ebd2.zip
op-kernel-dev-0822acb86cf340cd45b3af6436cec7e3bb24ebd2.tar.gz
mm: move get_dev_pagemap out of line
This is a pretty big function, which should be out of line in general, and a no-op stub if CONFIG_ZONE_DEVICЕ is not set. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Logan Gunthorpe <logang@deltatee.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'kernel/memremap.c')
-rw-r--r--kernel/memremap.c36
1 files changed, 34 insertions, 2 deletions
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 64b12c8..3df6cd4 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -314,7 +314,7 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
}
/* assumes rcu_read_lock() held at entry */
-struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
+static struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
{
struct page_map *page_map;
@@ -501,8 +501,40 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
return pgmap ? pgmap->altmap : NULL;
}
-#endif /* CONFIG_ZONE_DEVICE */
+/**
+ * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
+ * @pfn: page frame number to lookup page_map
+ * @pgmap: optional known pgmap that already has a reference
+ *
+ * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the
+ * same mapping.
+ */
+struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
+ struct dev_pagemap *pgmap)
+{
+ const struct resource *res = pgmap ? pgmap->res : NULL;
+ resource_size_t phys = PFN_PHYS(pfn);
+
+ /*
+ * In the cached case we're already holding a live reference so
+ * we can simply do a blind increment
+ */
+ if (res && phys >= res->start && phys <= res->end) {
+ percpu_ref_get(pgmap->ref);
+ return pgmap;
+ }
+
+ /* fall back to slow path lookup */
+ rcu_read_lock();
+ pgmap = find_dev_pagemap(phys);
+ if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
+ pgmap = NULL;
+ rcu_read_unlock();
+
+ return pgmap;
+}
+#endif /* CONFIG_ZONE_DEVICE */
#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
void put_zone_device_private_or_public_page(struct page *page)
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