kernel/linux.git/block/elevator.h, branch v6.12.80

block: Prevent deadlocks when switching elevators

2024-09-10T19:43:42+00:00

Commit af2814149883 ("block: freeze the queue in queue_attr_store") changed queue_attr_store() to always freeze a sysfs attribute queue before calling the attribute store() method, to ensure that no IOs are in-flight when an attribute value is being updated. However, this change created a potential deadlock situation for the scheduler queue attribute as changing the queue elevator with elv_iosched_store() can result in a call to request_module() if the user requested module is not already registered. If the file of the requested module is stored on the block device of the frozen queue, a deadlock will happen as the read operations triggered by request_module() will wait for the queue freeze to end. Solve this issue by introducing the load_module method in struct queue_sysfs_entry, and to calling this method function in queue_attr_store() before freezing the attribute queue. The macro definition QUEUE_RW_LOAD_MODULE_ENTRY() is added to define a queue sysfs attribute that needs loading a module. The definition of the scheduler atrribute is changed to using QUEUE_RW_LOAD_MODULE_ENTRY(), with the function elv_iosched_load_module() defined as the load_module method. elv_iosched_store() can then be simplified to remove the call to request_module(). Reported-by: Richard W.M. Jones Reported-by: Jiri Jaburek Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219166 Fixes: af2814149883 ("block: freeze the queue in queue_attr_store") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Tested-by: Richard W.M. Jones Link: https://lore.kernel.org/r/20240908000704.414538-1-dlemoal@kernel.org Signed-off-by: Jens Axboe

block: pass a gendisk to the queue_sysfs_entry methods

2024-06-28T21:06:16+00:00

The kobject for the queue entries is embedded into a struct gendisk. Pass it to the sysfs methods instead of the request_queue derived from it. Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/r/20240627111407.476276-4-hch@lst.de Signed-off-by: Jens Axboe

block: Remove elevator required features

2024-04-17T14:44:03+00:00

The only elevator feature ever implemented is ELEVATOR_F_ZBD_SEQ_WRITE for signaling that a scheduler implements zone write locking to tightly control the dispatching order of write operations to zoned block devices. With the removal of zone write locking support in mq-deadline and the reliance of all block device drivers on the block layer zone write plugging to control ordering of write operations to zones, the elevator feature ELEVATOR_F_ZBD_SEQ_WRITE is completely unused. Remove it, and also remove the now unused code for filtering the possible schedulers for a block device based on required features. Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Reviewed-by: Christoph Hellwig Reviewed-by: Bart Van Assche Tested-by: Hans Holmberg Tested-by: Dennis Maisenbacher Reviewed-by: Martin K. Petersen Link: https://lore.kernel.org/r/20240408014128.205141-23-dlemoal@kernel.org Signed-off-by: Jens Axboe

blk-mq: pass a flags argument to elevator_type->insert_requests

2023-04-13T12:52:30+00:00

Instead of passing a bool at_head, pass down the full flags from the blk_mq_insert_request interface. Signed-off-by: Christoph Hellwig Reviewed-by: Bart Van Assche Reviewed-by: Damien Le Moal Link: https://lore.kernel.org/r/20230413064057.707578-20-hch@lst.de Signed-off-by: Jens Axboe

block: add proper helpers for elevator_type module refcount management

2022-10-24T00:59:17+00:00

Make sure we have helpers for all relevant module refcount operations on the elevator_type in elevator.h, and use them. Move the call to the get helper in blk_mq_elv_switch_none a bit so that it is obvious with a less verbose comment. Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/r/20221020064819.1469928-2-hch@lst.de Signed-off-by: Jens Axboe

blk-wbt: don't enable throttling if default elevator is bfq

2022-10-24T00:59:17+00:00

Commit b5dc5d4d1f4f ("block,bfq: Disable writeback throttling") tries to disable wbt for bfq, it's done by calling wbt_disable_default() in bfq_init_queue(). However, wbt is still enabled if default elevator is bfq: device_add_disk elevator_init_mq bfq_init_queue wbt_disable_default -> done nothing blk_register_queue wbt_enable_default -> wbt is enabled Fix the problem by adding a new flag ELEVATOR_FLAG_DISBALE_WBT, bfq will set the flag in bfq_init_queue, and following wbt_enable_default() won't enable wbt while the flag is set. Signed-off-by: Yu Kuai Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20221019121518.3865235-7-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

elevator: add new field flags in struct elevator_queue

2022-10-24T00:59:17+00:00

There are only one flag to indicate that elevator is registered currently, prepare to add a flag to disable wbt if default elevator is bfq. Signed-off-by: Yu Kuai Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20221019121518.3865235-6-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe

block: Use the new blk_opf_t type

2022-07-14T18:14:30+00:00

Use the new blk_opf_t type for arguments and variables that represent request flags or a bitwise combination of a request operation and request flags. Rename the function arguments and also a structure member that hold a request operation and flags from 'rw' into 'opf'. This patch does not change any functionality. Cc: Christoph Hellwig Cc: Ming Lei Cc: Hannes Reinecke Cc: Damien Le Moal Cc: Johannes Thumshirn Signed-off-by: Bart Van Assche Link: https://lore.kernel.org/r/20220714180729.1065367-7-bvanassche@acm.org Signed-off-by: Jens Axboe

block: move elevator.h to block/

2021-10-18T12:17:01+00:00

Except for the features passed to blk_queue_required_elevator_features, elevator.h is only needed internally to the block layer. Move the ELEVATOR_F_* definitions to blkdev.h, and the move elevator.h to block/, dropping all the spurious includes outside of that. Signed-off-by: Christoph Hellwig Reviewed-by: Johannes Thumshirn Link: https://lore.kernel.org/r/20210920123328.1399408-13-hch@lst.de Signed-off-by: Jens Axboe