From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tomoki Sekiyama , Jens Axboe , Josh Boyer Subject: [PATCH 3.4 30/32] elevator: acquire q->sysfs_lock in elevator_change() Date: Fri, 6 Dec 2013 13:52:40 -0800 Message-Id: <20131206214959.588722356@linuxfoundation.org> In-Reply-To: <20131206214956.830407026@linuxfoundation.org> References: <20131206214956.830407026@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tomoki Sekiyama commit 7c8a3679e3d8e9d92d58f282161760a0e247df97 upstream. Add locking of q->sysfs_lock into elevator_change() (an exported function) to ensure it is held to protect q->elevator from elevator_init(), even if elevator_change() is called from non-sysfs paths. sysfs path (elv_iosched_store) uses __elevator_change(), non-locking version, as the lock is already taken by elv_iosched_store(). Signed-off-by: Tomoki Sekiyama Signed-off-by: Jens Axboe Cc: Josh Boyer Signed-off-by: Greg Kroah-Hartman --- block/elevator.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/block/elevator.c +++ b/block/elevator.c @@ -961,7 +961,7 @@ fail_register: /* * Switch this queue to the given IO scheduler. */ -int elevator_change(struct request_queue *q, const char *name) +static int __elevator_change(struct request_queue *q, const char *name) { char elevator_name[ELV_NAME_MAX]; struct elevator_type *e; @@ -983,6 +983,18 @@ int elevator_change(struct request_queue return elevator_switch(q, e); } + +int elevator_change(struct request_queue *q, const char *name) +{ + int ret; + + /* Protect q->elevator from elevator_init() */ + mutex_lock(&q->sysfs_lock); + ret = __elevator_change(q, name); + mutex_unlock(&q->sysfs_lock); + + return ret; +} EXPORT_SYMBOL(elevator_change); ssize_t elv_iosched_store(struct request_queue *q, const char *name, @@ -993,7 +1005,7 @@ ssize_t elv_iosched_store(struct request if (!q->elevator) return count; - ret = elevator_change(q, name); + ret = __elevator_change(q, name); if (!ret) return count;