From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 3662B6B0031 for ; Mon, 23 Sep 2013 04:24:32 -0400 (EDT) Received: by mail-pa0-f46.google.com with SMTP id fa1so3273849pad.19 for ; Mon, 23 Sep 2013 01:24:31 -0700 (PDT) Received: from epcpsbgm1.samsung.com (epcpsbgm1 [203.254.230.26]) by mailout3.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0MTK0034GKNU3CY0@mailout3.samsung.com> for linux-mm@kvack.org; Mon, 23 Sep 2013 17:24:23 +0900 (KST) From: Weijie Yang Subject: [PATCH v3 2/3] mm/zswap: bugfix: memory leak when invalidate and reclaim occur concurrently Date: Mon, 23 Sep 2013 16:21:49 +0800 Message-id: <000201ceb836$4c549740$e4fdc5c0$%yang@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit Content-language: zh-cn Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: sjenning@linux.vnet.ibm.com, bob.liu@oracle.com, minchan@kernel.org, weijie.yang.kh@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, d.j.shin@samsung.com, heesub.shin@samsung.com, kyungmin.park@samsung.com, hau.chen@samsung.com, bifeng.tong@samsung.com, rui.xie@samsung.com Consider the following scenario: thread 0: reclaim entry x (get refcount, but not call zswap_get_swap_cache_page) thread 1: call zswap_frontswap_invalidate_page to invalidate entry x. finished, entry x and its zbud is not freed as its refcount != 0 now, the swap_map[x] = 0 thread 0: now call zswap_get_swap_cache_page swapcache_prepare return -ENOENT because entry x is not used any more zswap_get_swap_cache_page return ZSWAP_SWAPCACHE_NOMEM zswap_writeback_entry do nothing except put refcount Now, the memory of zswap_entry x and its zpage leak. Modify: - check the refcount in fail path, free memory if it is not referenced. - use ZSWAP_SWAPCACHE_FAIL instead of ZSWAP_SWAPCACHE_NOMEM as the fail path can be not only caused by nomem but also by invalidate. Signed-off-by: Weijie Yang Reviewed-by: Bob Liu Cc: Minchan Kim Cc: stable@vger.kernel.org Acked-by: Seth Jennings --- mm/zswap.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index cbd9578..1be7b90 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -387,7 +387,7 @@ static void zswap_free_entry(struct zswap_tree *tree, struct zswap_entry *entry) enum zswap_get_swap_ret { ZSWAP_SWAPCACHE_NEW, ZSWAP_SWAPCACHE_EXIST, - ZSWAP_SWAPCACHE_NOMEM + ZSWAP_SWAPCACHE_FAIL, }; /* @@ -401,9 +401,9 @@ enum zswap_get_swap_ret { * added to the swap cache, and returned in retpage. * * If success, the swap cache page is returned in retpage - * Returns 0 if page was already in the swap cache, page is not locked - * Returns 1 if the new page needs to be populated, page is locked - * Returns <0 on error + * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache + * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated, page is locked + * Returns ZSWAP_SWAPCACHE_FAIL on error */ static int zswap_get_swap_cache_page(swp_entry_t entry, struct page **retpage) @@ -475,7 +475,7 @@ static int zswap_get_swap_cache_page(swp_entry_t entry, if (new_page) page_cache_release(new_page); if (!found_page) - return ZSWAP_SWAPCACHE_NOMEM; + return ZSWAP_SWAPCACHE_FAIL; *retpage = found_page; return ZSWAP_SWAPCACHE_EXIST; } @@ -529,11 +529,11 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle) /* try to allocate swap cache page */ switch (zswap_get_swap_cache_page(swpentry, &page)) { - case ZSWAP_SWAPCACHE_NOMEM: /* no memory */ + case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */ ret = -ENOMEM; goto fail; - case ZSWAP_SWAPCACHE_EXIST: /* page is unlocked */ + case ZSWAP_SWAPCACHE_EXIST: /* page is already in the swap cache, ignore for now */ page_cache_release(page); ret = -EEXIST; @@ -591,7 +591,12 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle) fail: spin_lock(&tree->lock); - zswap_entry_put(entry); + refcount = zswap_entry_put(entry); + if (refcount <= 0) { + /* invalidate happened, consider writeback as success */ + zswap_free_entry(tree, entry); + ret = 0; + } spin_unlock(&tree->lock); return ret; } -- 1.7.10.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org