mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-03 20:34:23 -04:00
b5718d6c00
Commit7520872c0c("block: don't defer flushes on blk-mq + scheduling") tried to fix deadlock for cycled wait between flush requests and data request into flush_data_in_flight. The former holded all driver tags and wait for data request completion, but the latter can not complete for waiting free driver tags. After commit923218f616("blk-mq: don't allocate driver tag upfront for flush rq"), flush requests will not get driver tag before queuing into flush queue. * With elevator, flush request just get sched_tags before inserting flush queue. It will not get driver tag until issue them to driver. data request on list fq->flush_data_in_flight will complete in the end. * Without elevator, each flush request will get a driver tag when allocate request. Then data request on fq->flush_data_in_flight don't worry about lacking driver tag. In both of these cases, cycled wait cannot be true. So we may allow to defer flush request. Signed-off-by: Yufen Yu <yuyufen@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.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 Restructured Text 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.