From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f198.google.com (mail-qt0-f198.google.com [209.85.216.198]) by kanga.kvack.org (Postfix) with ESMTP id D26246B0253 for ; Thu, 26 Jan 2017 10:59:07 -0500 (EST) Received: by mail-qt0-f198.google.com with SMTP id f4so233681286qte.1 for ; Thu, 26 Jan 2017 07:59:07 -0800 (PST) Received: from mail-qt0-x242.google.com (mail-qt0-x242.google.com. [2607:f8b0:400d:c0d::242]) by mx.google.com with ESMTPS id f186si1417613qka.137.2017.01.26.07.59.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 26 Jan 2017 07:59:07 -0800 (PST) Received: by mail-qt0-x242.google.com with SMTP id n13so39425604qtc.0 for ; Thu, 26 Jan 2017 07:59:07 -0800 (PST) From: Dan Streetman Subject: [PATCH] zswap: don't param_set_charp while holding spinlock Date: Thu, 26 Jan 2017 10:58:21 -0500 Message-Id: <20170126155821.4545-1-ddstreet@ieee.org> Sender: owner-linux-mm@kvack.org List-ID: To: Linux-MM , Seth Jennings , Andrew Morton Cc: Dan Streetman , Sergey Senozhatsky , Michal Hocko , Minchan Kim , linux-kernel , Dan Streetman Change the zpool/compressor param callback function to release the zswap_pools_lock spinlock before calling param_set_charp, since that function may sleep when it calls kmalloc with GFP_KERNEL. While this problem has existed for a while, I wasn't able to trigger it using a tight loop changing either/both the zpool and compressor params; I think it's very unlikely to be an issue on the stable kernels, especially since most zswap users will change the compressor and/or zpool from sysfs only one time each boot - or zero times, if they add the params to the kernel boot. Fixes: c99b42c3529e ("zswap: use charp for zswap param strings") Reported-by: Sergey Senozhatsky Signed-off-by: Dan Streetman --- Andrew, I'll leave it up to you if you want to send this to -stable; personally I don't think it's needed. For the stable kernels, only the first hunk of the patch applies. mm/zswap.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index 9e8565d..eedc278 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -704,18 +704,22 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp, pool = zswap_pool_find_get(type, compressor); if (pool) { zswap_pool_debug("using existing", pool); + WARN_ON(pool == zswap_pool_current()); list_del_rcu(&pool->list); - } else { - spin_unlock(&zswap_pools_lock); - pool = zswap_pool_create(type, compressor); - spin_lock(&zswap_pools_lock); } + spin_unlock(&zswap_pools_lock); + + if (!pool) + pool = zswap_pool_create(type, compressor); + if (pool) ret = param_set_charp(s, kp); else ret = -EINVAL; + spin_lock(&zswap_pools_lock); + if (!ret) { put_pool = zswap_pool_current(); list_add_rcu(&pool->list, &zswap_pools); @@ -727,7 +731,11 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp, */ list_add_tail_rcu(&pool->list, &zswap_pools); put_pool = pool; - } else if (!zswap_has_pool) { + } + + spin_unlock(&zswap_pools_lock); + + if (!zswap_has_pool && !pool) { /* if initial pool creation failed, and this pool creation also * failed, maybe both compressor and zpool params were bad. * Allow changing this param, so pool creation will succeed @@ -738,8 +746,6 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp, ret = param_set_charp(s, kp); } - spin_unlock(&zswap_pools_lock); - /* drop the ref from either the old current pool, * or the new pool we failed to add */ -- 2.9.3 -- 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