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Ming Lei 01b91bf14f block: don't grab elevator lock during queue initialization
->elevator_lock depends on queue freeze lock, see block/blk-sysfs.c.

queue freeze lock depends on fs_reclaim.

So don't grab elevator lock during queue initialization which needs to
call kmalloc(GFP_KERNEL), and we can cut the dependency between
->elevator_lock and fs_reclaim, then the lockdep warning can be killed.

This way is safe because elevator setting isn't ready to run during
queue initialization.

There isn't such issue in __blk_mq_update_nr_hw_queues() because
memalloc_noio_save() is called before acquiring elevator lock.

Fixes the following lockdep warning:

https://lore.kernel.org/linux-block/67e6b425.050a0220.2f068f.007b.GAE@google.com/

Reported-by: syzbot+4c7e0f9b94ad65811efb@syzkaller.appspotmail.com
Cc: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250403105402.1334206-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
History 2025-04-03 08:32:03 -06:00
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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.