linux-kernel - [PATCH] cma: allow concurrent cma pages allocation for multi-cma areas

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Date:	Fri, 05 Jun 2015 16:01:56 +0800
From:	Weijie Yang <weijie.yang@...sung.com>
To:	iamjoonsoo.kim@....com
Cc:	mina86@...a86.com, m.szyprowski@...sung.com,
	'Andrew Morton' <akpm@...ux-foundation.org>,
	'Weijie Yang' <weijie.yang.kh@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] cma: allow concurrent cma pages allocation for multi-cma areas

Currently we have to hold the single cma_mutex when alloc cma pages,
it is ok when there is only one cma area in system.
However, when there are several cma areas, such as in our Android smart
phone, the single cma_mutex prevents concurrent cma page allocation.

This patch removes the single cma_mutex and uses per-cma area alloc_lock,
this allows concurrent cma pages allocation for different cma areas while
protects access to the same pageblocks.

Signed-off-by: Weijie Yang <weijie.yang@...sung.com>
---
 mm/cma.c |    6 +++---
 mm/cma.h |    1 +
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 3a7a67b..eaf1afe 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -41,7 +41,6 @@
 
 struct cma cma_areas[MAX_CMA_AREAS];
 unsigned cma_area_count;
-static DEFINE_MUTEX(cma_mutex);
 
 phys_addr_t cma_get_base(const struct cma *cma)
 {
@@ -128,6 +127,7 @@ static int __init cma_activate_area(struct cma *cma)
 	} while (--i);
 
 	mutex_init(&cma->lock);
+	mutex_init(&cma->alloc_lock);
 
 #ifdef CONFIG_CMA_DEBUGFS
 	INIT_HLIST_HEAD(&cma->mem_head);
@@ -398,9 +398,9 @@ struct page *cma_alloc(struct cma *cma, unsigned int count, unsigned int align)
 		mutex_unlock(&cma->lock);
 
 		pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
-		mutex_lock(&cma_mutex);
+		mutex_lock(&cma->alloc_lock);
 		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
-		mutex_unlock(&cma_mutex);
+		mutex_unlock(&cma->alloc_lock);
 		if (ret == 0) {
 			page = pfn_to_page(pfn);
 			break;
diff --git a/mm/cma.h b/mm/cma.h
index 1132d73..2084c9f 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -7,6 +7,7 @@ struct cma {
 	unsigned long   *bitmap;
 	unsigned int order_per_bit; /* Order of pages represented by one bit */
 	struct mutex    lock;
+	struct mutex    alloc_lock;
 #ifdef CONFIG_CMA_DEBUGFS
 	struct hlist_head mem_head;
 	spinlock_t mem_head_lock;
-- 
1.7.10.4


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