From 2c0647988433c3d7120542a3c42e12c152dd7afc Mon Sep 17 00:00:00 2001 From: Yu Kuai Date: Wed, 12 Oct 2022 17:40:33 +0800 Subject: [PATCH] blk-iocost: don't release 'ioc->lock' while updating params ioc_qos_write() and ioc_cost_model_write() are the same: 1) hold lock to read 'ioc->params' to local variable; 2) update params to local variable without lock; 3) hold lock to write local variable to 'ioc->params'; In theroy, if user updates params concurrenty, the params might be lost: t1: update params a t2: update params b spin_lock_irq(&ioc->lock); memcpy(qos, ioc->params.qos, sizeof(qos)) spin_unlock_irq(&ioc->lock); qos[a] = xxx; spin_lock_irq(&ioc->lock); memcpy(qos, ioc->params.qos, sizeof(qos)) spin_unlock_irq(&ioc->lock); qos[b] = xxx; spin_lock_irq(&ioc->lock); memcpy(ioc->params.qos, qos, sizeof(qos)); ioc_refresh_params(ioc, true); spin_unlock_irq(&ioc->lock); spin_lock_irq(&ioc->lock); // updates of a will be lost memcpy(ioc->params.qos, qos, sizeof(qos)); ioc_refresh_params(ioc, true); spin_unlock_irq(&ioc->lock); Althrough this is not common case, the problem can by fixed easily by holding the lock through the read, update, write process. Signed-off-by: Yu Kuai Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20221012094035.390056-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe --- block/blk-iocost.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 08036476e6fa..6d36a4bd4382 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -3191,7 +3191,6 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, memcpy(qos, ioc->params.qos, sizeof(qos)); enable = ioc->enabled; user = ioc->user_qos_params; - spin_unlock_irq(&ioc->lock); while ((p = strsep(&input, " \t\n"))) { substring_t args[MAX_OPT_ARGS]; @@ -3258,8 +3257,6 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, if (qos[QOS_MIN] > qos[QOS_MAX]) goto einval; - spin_lock_irq(&ioc->lock); - if (enable) { blk_stat_enable_accounting(disk->queue); blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, disk->queue); @@ -3284,6 +3281,7 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, blkdev_put_no_open(bdev); return nbytes; einval: + spin_unlock_irq(&ioc->lock); ret = -EINVAL; err: blkdev_put_no_open(bdev); @@ -3359,7 +3357,6 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, spin_lock_irq(&ioc->lock); memcpy(u, ioc->params.i_lcoefs, sizeof(u)); user = ioc->user_cost_model; - spin_unlock_irq(&ioc->lock); while ((p = strsep(&input, " \t\n"))) { substring_t args[MAX_OPT_ARGS]; @@ -3396,7 +3393,6 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, user = true; } - spin_lock_irq(&ioc->lock); if (user) { memcpy(ioc->params.i_lcoefs, u, sizeof(u)); ioc->user_cost_model = true; @@ -3410,6 +3406,7 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, return nbytes; einval: + spin_unlock_irq(&ioc->lock); ret = -EINVAL; err: blkdev_put_no_open(bdev); -- 2.11.0