doc: document sysfs queue/independent_access_ranges attributes
Update the file Documentation/block/queue-sysfs.rst to add a description of a device queue sysfs entries related to independent access ranges (e.g. concurrent positioning ranges for multi-actuator hard-disks). Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Keith Busch <kbusch@kernel.org> Link: https://lore.kernel.org/r/20211027022223.183838-5-damien.lemoal@wdc.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -286,4 +286,35 @@ sequential zones of zoned block devices (devices with a zoned attributed
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that reports "host-managed" or "host-aware"). This value is always 0 for
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that reports "host-managed" or "host-aware"). This value is always 0 for
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regular block devices.
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regular block devices.
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independent_access_ranges (RO)
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------------------------------
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The presence of this sub-directory of the /sys/block/xxx/queue/ directory
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indicates that the device is capable of executing requests targeting
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different sector ranges in parallel. For instance, single LUN multi-actuator
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hard-disks will have an independent_access_ranges directory if the device
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correctly advertizes the sector ranges of its actuators.
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The independent_access_ranges directory contains one directory per access
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range, with each range described using the sector (RO) attribute file to
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indicate the first sector of the range and the nr_sectors (RO) attribute file
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to indicate the total number of sectors in the range starting from the first
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sector of the range. For example, a dual-actuator hard-disk will have the
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following independent_access_ranges entries.::
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$ tree /sys/block/<device>/queue/independent_access_ranges/
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/sys/block/<device>/queue/independent_access_ranges/
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|-- 0
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| |-- nr_sectors
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| `-- sector
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`-- 1
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|-- nr_sectors
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`-- sector
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The sector and nr_sectors attributes use 512B sector unit, regardless of
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the actual block size of the device. Independent access ranges do not
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overlap and include all sectors within the device capacity. The access
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ranges are numbered in increasing order of the range start sector,
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that is, the sector attribute of range 0 always has the value 0.
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Jens Axboe <jens.axboe@oracle.com>, February 2009
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Jens Axboe <jens.axboe@oracle.com>, February 2009
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