From 7c8a3679e3d8e9d92d58f282161760a0e247df97 Mon Sep 17 00:00:00 2001 From: Tomoki Sekiyama Date: Tue, 15 Oct 2013 16:42:19 -0600 Subject: [PATCH] elevator: acquire q->sysfs_lock in elevator_change() 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 --- block/elevator.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/block/elevator.c b/block/elevator.c index 249cc5e1090692..b7ff2861b6bdc0 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -965,7 +965,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) /* * 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; @@ -987,6 +987,18 @@ int elevator_change(struct request_queue *q, const char *name) 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, @@ -997,7 +1009,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name, if (!q->elevator) return count; - ret = elevator_change(q, name); + ret = __elevator_change(q, name); if (!ret) return count;