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From: Matthew Wilcox <willy@infradead.org>
To: linux-mm@kvack.org
Cc: "Matthew Wilcox" <mawilcox@microsoft.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	"Christoph Lameter" <cl@linux.com>,
	"Lai Jiangshan" <jiangshanlai@gmail.com>,
	"Pekka Enberg" <penberg@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>
Subject: [PATCH v6 14/17] slab,slub: Remove rcu_head size checks
Date: Fri, 18 May 2018 12:45:16 -0700
Message-ID: <20180518194519.3820-15-willy@infradead.org> (raw)
In-Reply-To: <20180518194519.3820-1-willy@infradead.org>

From: Matthew Wilcox <mawilcox@microsoft.com>

rcu_head may now grow larger than list_head without affecting slab or
slub.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slab.c |  2 --
 mm/slub.c | 27 ++-------------------------
 2 files changed, 2 insertions(+), 27 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index e387a17d6d56..e6ab1327db25 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1235,8 +1235,6 @@ void __init kmem_cache_init(void)
 {
 	int i;
 
-	BUILD_BUG_ON(sizeof(((struct page *)NULL)->lru) <
-					sizeof(struct rcu_head));
 	kmem_cache = &kmem_cache_boot;
 
 	if (!IS_ENABLED(CONFIG_NUMA) || num_possible_nodes() == 1)
diff --git a/mm/slub.c b/mm/slub.c
index 57a20f995220..8e2407f69855 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1681,17 +1681,9 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
 	__free_pages(page, order);
 }
 
-#define need_reserve_slab_rcu						\
-	(sizeof(((struct page *)NULL)->lru) < sizeof(struct rcu_head))
-
 static void rcu_free_slab(struct rcu_head *h)
 {
-	struct page *page;
-
-	if (need_reserve_slab_rcu)
-		page = virt_to_head_page(h);
-	else
-		page = container_of((struct list_head *)h, struct page, lru);
+	struct page *page = container_of(h, struct page, rcu_head);
 
 	__free_slab(page->slab_cache, page);
 }
@@ -1699,19 +1691,7 @@ static void rcu_free_slab(struct rcu_head *h)
 static void free_slab(struct kmem_cache *s, struct page *page)
 {
 	if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) {
-		struct rcu_head *head;
-
-		if (need_reserve_slab_rcu) {
-			int order = compound_order(page);
-			int offset = (PAGE_SIZE << order) - s->reserved;
-
-			VM_BUG_ON(s->reserved != sizeof(*head));
-			head = page_address(page) + offset;
-		} else {
-			head = &page->rcu_head;
-		}
-
-		call_rcu(head, rcu_free_slab);
+		call_rcu(&page->rcu_head, rcu_free_slab);
 	} else
 		__free_slab(s, page);
 }
@@ -3578,9 +3558,6 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
 	s->random = get_random_long();
 #endif
 
-	if (need_reserve_slab_rcu && (s->flags & SLAB_TYPESAFE_BY_RCU))
-		s->reserved = sizeof(struct rcu_head);
-
 	if (!calculate_sizes(s, -1))
 		goto error;
 	if (disable_higher_order_debug) {
-- 
2.17.0

  parent reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-18 19:45 [PATCH v6 00/17] Rearrange struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 01/17] s390: Use _refcount for pgtables Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 02/17] mm: Split page_type out from _mapcount Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 03/17] mm: Mark pages in use for page tables Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 04/17] mm: Switch s_mem and slab_cache in struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 05/17] mm: Move 'private' union within " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 06/17] mm: Move _refcount out of struct page union Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 07/17] mm: Combine first three unions in struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 08/17] mm: Use page->deferred_list Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 09/17] mm: Move lru union within struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 10/17] mm: Combine LRU and main union in " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 11/17] mm: Improve struct page documentation Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 12/17] mm: Add pt_mm to struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 13/17] mm: Add hmm_data " Matthew Wilcox
2018-05-18 19:45 ` Matthew Wilcox [this message]
2018-05-18 19:45 ` [PATCH v6 15/17] slub: Remove kmem_cache->reserved Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 16/17] slub: Remove 'reserved' file from sysfs Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 17/17] mm: Distinguish VMalloc pages Matthew Wilcox
2018-05-22 16:10   ` Andrey Ryabinin
2018-05-22 17:58     ` Matthew Wilcox
2018-05-22 19:49       ` Andrew Morton
2018-05-22 19:57       ` Andrey Ryabinin
2018-05-22 20:19         ` Matthew Wilcox
2018-05-22 20:48           ` Andrew Morton
2018-05-22 21:45             ` Matthew Wilcox
2018-05-22 23:02               ` Andrew Morton
2018-05-23  6:36           ` Michal Hocko
2018-05-23  6:34         ` Michal Hocko
2018-05-23  9:14           ` Andrey Ryabinin
2018-05-23  9:25             ` Michal Hocko
2018-05-23  9:28               ` Andrey Ryabinin
2018-05-23  9:52                 ` Michal Hocko

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