kernel/git/stable/linux-stable.git/block/blk-sysfs.c, branch linux-6.15.y

block: fix kobject leak in blk_unregister_queue

2025-07-24T06:58:34+00:00

[ Upstream commit 3051247e4faa32a3d90c762a243c2c62dde310db ] The kobject for the queue, `disk->queue_kobj`, is initialized with a reference count of 1 via `kobject_init()` in `blk_register_queue()`. While `kobject_del()` is called during the unregister path to remove the kobject from sysfs, the initial reference is never released. Add a call to `kobject_put()` in `blk_unregister_queue()` to properly decrement the reference count and fix the leak. Fixes: 2bd85221a625 ("block: untangle request_queue refcounting from sysfs") Cc: Christoph Hellwig Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20250711083009.2574432-1-ming.lei@redhat.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

block: fix resource leak in blk_register_queue() error path

2025-04-14T14:28:26+00:00

When registering a queue fails after blk_mq_sysfs_register() is successful but the function later encounters an error, we need to clean up the blk_mq_sysfs resources. Add the missing blk_mq_sysfs_unregister() call in the error path to properly clean up these resources and prevent a memory leak. Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism") Signed-off-by: Zheng Qixing Reviewed-by: Christoph Hellwig Reviewed-by: Yu Kuai Link: https://lore.kernel.org/r/20250412092554.475218-1-zhengqixing@huaweicloud.com Signed-off-by: Jens Axboe

block: fix a comment in the queue_attrs[] array

2025-03-18T13:54:50+00:00

queue_ra_entry uses limits_lock just like the attributes above it. Signed-off-by: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Reviewed-by: Nilay Shroff Link: https://lore.kernel.org/r/20250312150127.703534-1-hch@lst.de Signed-off-by: Jens Axboe

block: protect read_ahead_kb using q->limits_lock

2025-03-10T13:30:19+00:00

The bdi->ra_pages could be updated under q->limits_lock because it's usually calculated from the queue limits by queue_limits_commit_update. So protect reading/writing the sysfs attribute read_ahead_kb using q->limits_lock instead of q->sysfs_lock. Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-8-nilay@linux.ibm.com Signed-off-by: Jens Axboe

block: protect wbt_lat_usec using q->elevator_lock

2025-03-10T13:30:18+00:00

The wbt latency and state could be updated while initializing the elevator or exiting the elevator. It could be also updated while configuring IO latency QoS parameters using cgroup. The elevator code path is now protected with q->elevator_lock. So we should protect the access to sysfs attribute wbt_lat_usec using q->elevator _lock instead of q->sysfs_lock. White we're at it, also protect ioc_qos_write(), which configures wbt parameters via cgroup, using q->elevator_lock. Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-7-nilay@linux.ibm.com Signed-off-by: Jens Axboe

block: protect nr_requests update using q->elevator_lock

2025-03-10T13:30:18+00:00

The sysfs attribute nr_requests could be simultaneously updated from elevator switch/update or nr_hw_queue update code path. The update to nr_requests for each of those code paths runs holding q->elevator_lock. So we should protect access to sysfs attribute nr_requests using q-> elevator_lock instead of q->sysfs_lock. Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-6-nilay@linux.ibm.com Signed-off-by: Jens Axboe

block: introduce a dedicated lock for protecting queue elevator updates

2025-03-10T13:30:18+00:00

A queue's elevator can be updated either when modifying nr_hw_queues or through the sysfs scheduler attribute. Currently, elevator switching/ updating is protected using q->sysfs_lock, but this has led to lockdep splats[1] due to inconsistent lock ordering between q->sysfs_lock and the freeze-lock in multiple block layer call sites. As the scope of q->sysfs_lock is not well-defined, its (mis)use has resulted in numerous lockdep warnings. To address this, introduce a new q->elevator_lock, dedicated specifically for protecting elevator switches/updates. And we'd now use this new q->elevator_lock instead of q->sysfs_lock for protecting elevator switches/updates. While at it, make elv_iosched_load_module() a static function, as it is only called from elv_iosched_store(). Also, remove redundant parameters from elv_iosched_load_module() function signature. [1] https://lore.kernel.org/all/67637e70.050a0220.3157ee.000c.GAE@google.com/ Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-5-nilay@linux.ibm.com Signed-off-by: Jens Axboe

block: remove q->sysfs_lock for attributes which don't need it

2025-03-10T13:30:18+00:00

There're few sysfs attributes in block layer which don't really need acquiring q->sysfs_lock while accessing it. The reason being, reading/ writing a value from/to such attributes are either atomic or could be easily protected using READ_ONCE()/WRITE_ONCE(). Moreover, sysfs attributes are inherently protected with sysfs/kernfs internal locking. So this change help segregate all existing sysfs attributes for which we could avoid acquiring q->sysfs_lock. For all read-only attributes we removed the q->sysfs_lock from show method of such attributes. In case attribute is read/write then we removed the q->sysfs_lock from both show and store methods of these attributes. We audited all block sysfs attributes and found following list of attributes which shouldn't require q->sysfs_lock protection: 1. io_poll: Write to this attribute is ignored. So, we don't need q->sysfs_lock. 2. io_poll_delay: Write to this attribute is NOP, so we don't need q->sysfs_lock. 3. io_timeout: Write to this attribute updates q->rq_timeout and read of this attribute returns the value stored in q->rq_timeout Moreover, the q->rq_timeout is set only once when we init the queue (under blk_mq_ init_allocated_queue()) even before disk is added. So that means that we don't need to protect it with q->sysfs_lock. As this attribute is not directly correlated with anything else simply using READ_ONCE/WRITE_ONCE should be enough. 4. nomerges: Write to this attribute file updates two q->flags : QUEUE_FLAG_ NOMERGES and QUEUE_FLAG_NOXMERGES. These flags are accessed during bio-merge which anyways doesn't run with q->sysfs_lock held. Moreover, the q->flags are updated/accessed with bitops which are atomic. So, protecting it with q->sysfs_lock is not necessary. 5. rq_affinity: Write to this attribute file makes atomic updates to q->flags: QUEUE_FLAG_SAME_COMP and QUEUE_FLAG_SAME_FORCE. These flags are also accessed from blk_mq_complete_need_ipi() using test_bit macro. As read/write to q->flags uses bitops which are atomic, protecting it with q->stsys_lock is not necessary. 6. nr_zones: Write to this attribute happens in the driver probe method (except nvme) before disk is added and outside of q->sysfs_lock or any other lock. Moreover nr_zones is defined as "unsigned int" and so reading this attribute, even when it's simultaneously being updated on other cpu, should not return torn value on any architecture supported by linux. So we can avoid using q->sysfs_lock or any other lock/ protection while reading this attribute. 7. discard_zeroes_data: Reading of this attribute always returns 0, so we don't require holding q->sysfs_lock. 8. write_same_max_bytes Reading of this attribute always returns 0, so we don't require holding q->sysfs_lock. Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-4-nilay@linux.ibm.com Signed-off-by: Jens Axboe

block: move q->sysfs_lock and queue-freeze under show/store method

2025-03-10T13:30:18+00:00

In preparation to further simplify and group sysfs attributes which don't require locking or require some form of locking other than q-> limits_lock, move acquire/release of q->sysfs_lock and queue freeze/ unfreeze under each attributes' respective show/store method. While we are at it, also remove ->load_module() as it's used to load the module before queue is freezed. Now as we moved queue-freeze under ->store(), we could load module directly from the attributes' store method before we actually start freezing the queue. Currently, the ->load_module() is only used by "scheduler" attribute, so we now load the relevant elevator module before we start freezing the queue in elv_iosched_store(). Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-3-nilay@linux.ibm.com Signed-off-by: Jens Axboe

block: acquire q->limits_lock while reading sysfs attributes

2025-03-10T13:30:18+00:00

There're few sysfs attributes(RW) whose store method is protected with q->limits_lock, however the corresponding show method of these attributes run holding q->sysfs_lock and that doesn't make sense as ideally the show method of these attributes should also run holding q->limits_lock instead of q->sysfs_lock. Hence update the show method of these sysfs attributes so that reading of these attributes acquire q->limits_lock instead of q->sysfs_lock. Similarly, there're few sysfs attributes(RO) whose show method is currently protected with q->sysfs_lock however updates to these attributes could occur using atomic limit update APIs such as queue_ limits_start_update() and queue_limits_commit_update() which run holding q->limits_lock. So that means that reading these attributes holding q->sysfs_lock doesn't make sense. Hence update the show method of these sysfs attributes(RO) such that they run with holding q-> limits_lock instead of q->sysfs_lock. We have defined a new macro QUEUE_LIM_RO_ENTRY() which uses new ->show_ limit() method and it runs holding q->limits_lock. All existing sysfs attributes(RO) which needs protection using q->limits_lock while reading have been now updated to use this new macro for initialization. Also, the existing QUEUE_LIM_RW_ENTRY() is updated to use new ->show_ limit() method for reading attributes instead of existing ->show() method. As ->show_limit() runs holding q->limits_lock, the existing sysfs attributes(RW) requiring protection are now inherently protected using q->limits_lock instead of q->sysfs_lock. Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: Nilay Shroff Link: https://lore.kernel.org/r/20250304102551.2533767-2-nilay@linux.ibm.com Signed-off-by: Jens Axboe