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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 <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Link: https://lore.kernel.org/r/20250304102551.2533767-5-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.