netdev - [PATCH v4 43/48] drm/ttm: introduce pool_shrink

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230807110936.21819-44-zhengqi.arch@bytedance.com>
Date: Mon,  7 Aug 2023 19:09:31 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: akpm@...ux-foundation.org,
	david@...morbit.com,
	tkhai@...ru,
	vbabka@...e.cz,
	roman.gushchin@...ux.dev,
	djwong@...nel.org,
	brauner@...nel.org,
	paulmck@...nel.org,
	tytso@....edu,
	steven.price@....com,
	cel@...nel.org,
	senozhatsky@...omium.org,
	yujie.liu@...el.com,
	gregkh@...uxfoundation.org,
	muchun.song@...ux.dev,
	simon.horman@...igine.com,
	dlemoal@...nel.org
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	x86@...nel.org,
	kvm@...r.kernel.org,
	xen-devel@...ts.xenproject.org,
	linux-erofs@...ts.ozlabs.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	cluster-devel@...hat.com,
	linux-nfs@...r.kernel.org,
	linux-mtd@...ts.infradead.org,
	rcu@...r.kernel.org,
	netdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-arm-msm@...r.kernel.org,
	dm-devel@...hat.com,
	linux-raid@...r.kernel.org,
	linux-bcache@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	linux-btrfs@...r.kernel.org,
	Qi Zheng <zhengqi.arch@...edance.com>,
	Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v4 43/48] drm/ttm: introduce pool_shrink_rwsem

Currently, the synchronize_shrinkers() is only used by TTM pool. It only
requires that no shrinkers run in parallel.

After we use RCU+refcount method to implement the lockless slab shrink,
we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all
shrinker invocations have seen an update before freeing memory.

So we introduce a new pool_shrink_rwsem to implement a private
synchronize_shrinkers(), so as to achieve the same purpose.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
Reviewed-by: Muchun Song <songmuchun@...edance.com>
---
 drivers/gpu/drm/ttm/ttm_pool.c | 15 +++++++++++++++
 include/linux/shrinker.h       |  2 --
 mm/shrinker.c                  | 15 ---------------
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index c9c9618c0dce..38b4c280725c 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -74,6 +74,7 @@ static struct ttm_pool_type global_dma32_uncached[MAX_ORDER + 1];
 static spinlock_t shrinker_lock;
 static struct list_head shrinker_list;
 static struct shrinker *mm_shrinker;
+static DECLARE_RWSEM(pool_shrink_rwsem);
 
 /* Allocate pages of size 1 << order with the given gfp_flags */
 static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
@@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void)
 	unsigned int num_pages;
 	struct page *p;
 
+	down_read(&pool_shrink_rwsem);
 	spin_lock(&shrinker_lock);
 	pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
 	list_move_tail(&pt->shrinker_list, &shrinker_list);
@@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void)
 	} else {
 		num_pages = 0;
 	}
+	up_read(&pool_shrink_rwsem);
 
 	return num_pages;
 }
@@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
 }
 EXPORT_SYMBOL(ttm_pool_init);
 
+/**
+ * synchronize_shrinkers - Wait for all running shrinkers to complete.
+ *
+ * This is useful to guarantee that all shrinker invocations have seen an
+ * update, before freeing memory, similar to rcu.
+ */
+static void synchronize_shrinkers(void)
+{
+	down_write(&pool_shrink_rwsem);
+	up_write(&pool_shrink_rwsem);
+}
+
 /**
  * ttm_pool_fini - Cleanup a pool
  *
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index c55c07c3f0cb..025c8070dd86 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -103,8 +103,6 @@ struct shrinker *shrinker_alloc(unsigned int flags, const char *fmt, ...);
 void shrinker_register(struct shrinker *shrinker);
 void shrinker_free(struct shrinker *shrinker);
 
-extern void synchronize_shrinkers(void);
-
 #ifdef CONFIG_SHRINKER_DEBUG
 extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker,
 						  const char *fmt, ...);
diff --git a/mm/shrinker.c b/mm/shrinker.c
index 3ab301ff122d..a27779ed3798 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -650,18 +650,3 @@ void shrinker_free(struct shrinker *shrinker)
 	kfree(shrinker);
 }
 EXPORT_SYMBOL_GPL(shrinker_free);
-
-/**
- * synchronize_shrinkers - Wait for all running shrinkers to complete.
- *
- * This is equivalent to calling unregister_shrink() and register_shrinker(),
- * but atomically and with less overhead. This is useful to guarantee that all
- * shrinker invocations have seen an update, before freeing memory, similar to
- * rcu.
- */
-void synchronize_shrinkers(void)
-{
-	down_write(&shrinker_rwsem);
-	up_write(&shrinker_rwsem);
-}
-EXPORT_SYMBOL(synchronize_shrinkers);
-- 
2.30.2