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f983622ae6
scsi_host_block() calls scsi_internal_device_block() for each scsi_device and scsi_internal_device_block() calls blk_mq_quiesce_queue() for each LUN. Since synchronize_rcu() is called from blk_mq_quiesce_queue(), this can cause substantial slowdowns on systems with many LUNs. Use scsi_internal_device_block_nowait() to implement scsi_host_block() so it is sufficient to run synchronize_rcu() once. This is safe since SCSI does not set the BLK_MQ_F_BLOCKING flag. [mkp: commit desc and comment tweaks] Link: https://lore.kernel.org/r/20200423020713.332743-1-ming.lei@redhat.com Cc: Steffen Maier <maier@linux.ibm.com> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Dexuan Cui <decui@microsoft.com> Cc: Hannes Reinecke <hare@suse.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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.