diff options
| author | Yu Kuai <yukuai3@huawei.com> | 2022-10-12 11:40:33 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-10-24 02:59:16 +0200 |
| commit | 2c0647988433c3d7120542a3c42e12c152dd7afc (patch) | |
| tree | cef849c727459bc92fa9d114d9cd0fe53285d7ee /block | |
| parent | blk-iocost: disable writeback throttling (diff) | |
| download | linux-2c0647988433c3d7120542a3c42e12c152dd7afc.tar.xz linux-2c0647988433c3d7120542a3c42e12c152dd7afc.zip | |
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 <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20221012094035.390056-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to '')
| -rw-r--r-- | block/blk-iocost.c | 7 |
1 files 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); |