diff options
| author | Nilay Shroff <nilay@linux.ibm.com> | 2025-03-06 15:09:53 +0530 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2025-03-10 07:31:06 -0600 |
| commit | 5abba4cebec0a591ca7e7f55701e42cd5dc059af (patch) | |
| tree | 4a316ee6217a9ac1ab559b040508d94ef077c75d | |
| parent | 5e40f4452dc9a3fb44d13bb6bc7032f3911a2675 (diff) | |
block: protect hctx attributes/params using q->elevator_lock
Currently, hctx attributes (nr_tags, nr_reserved_tags, and cpu_list)
are protected using `q->sysfs_lock`. However, these attributes can be
updated in multiple scenarios:
- During the driver's probe method.
- When updating nr_hw_queues.
- When writing to the sysfs attribute nr_requests,
which can modify nr_tags.
The nr_requests attribute is already protected using q->elevator_lock,
but none of the update paths actually use q->sysfs_lock to protect hctx
attributes. So to ensure proper synchronization, replace q->sysfs_lock
with q->elevator_lock when reading hctx attributes through sysfs.
Additionally, blk_mq_update_nr_hw_queues allocates and updates hctx.
The allocation of hctx is protected using q->elevator_lock, however,
updating hctx params happens without any protection, so safeguard hctx
param update path by also using q->elevator_lock.
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250306093956.2818808-1-nilay@linux.ibm.com
[axboe: wrap comment at 80 chars]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-mq-sysfs.c | 4 | ||||
| -rw-r--r-- | block/blk-mq.c | 4 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 14 |
3 files changed, 14 insertions, 8 deletions
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 3feeeccf8a99..24656980f443 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -61,9 +61,9 @@ static ssize_t blk_mq_hw_sysfs_show(struct kobject *kobj, if (!entry->show) return -EIO; - mutex_lock(&q->sysfs_lock); + mutex_lock(&q->elevator_lock); res = entry->show(hctx, page); - mutex_unlock(&q->sysfs_lock); + mutex_unlock(&q->elevator_lock); return res; } diff --git a/block/blk-mq.c b/block/blk-mq.c index 5a2d63927525..b9550a127c8e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4094,6 +4094,8 @@ static void blk_mq_map_swqueue(struct request_queue *q) struct blk_mq_ctx *ctx; struct blk_mq_tag_set *set = q->tag_set; + mutex_lock(&q->elevator_lock); + queue_for_each_hw_ctx(q, hctx, i) { cpumask_clear(hctx->cpumask); hctx->nr_ctx = 0; @@ -4198,6 +4200,8 @@ static void blk_mq_map_swqueue(struct request_queue *q) hctx->next_cpu = blk_mq_first_mapped_cpu(hctx); hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH; } + + mutex_unlock(&q->elevator_lock); } /* diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 3bee1b4858b6..dcf8fce15e23 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -561,12 +561,14 @@ struct request_queue { struct list_head flush_list; /* - * Protects against I/O scheduler switching, particularly when - * updating q->elevator. Since the elevator update code path may - * also modify q->nr_requests and wbt latency, this lock also - * protects the sysfs attributes nr_requests and wbt_lat_usec. - * To ensure proper locking order during an elevator update, first - * freeze the queue, then acquire ->elevator_lock. + * Protects against I/O scheduler switching, particularly when updating + * q->elevator. Since the elevator update code path may also modify q-> + * nr_requests and wbt latency, this lock also protects the sysfs attrs + * nr_requests and wbt_lat_usec. Additionally the nr_hw_queues update + * may modify hctx tags, reserved-tags and cpumask, so this lock also + * helps protect the hctx attrs. To ensure proper locking order during + * an elevator or nr_hw_queue update, first freeze the queue, then + * acquire ->elevator_lock. */ struct mutex elevator_lock; |