diff mbox series

[v3,4/4] doc: document sysfs queue/cranges attributes

Message ID 20210726013806.84815-5-damien.lemoal@wdc.com
State New
Headers show
Series Initial support for multi-actuator HDDs | expand

Commit Message

Damien Le Moal July 26, 2021, 1:38 a.m. UTC 
Update the file Documentation/block/queue-sysfs.rst to add a description
of a device queue sysfs entries related to concurrent sector ranges
(e.g. concurrent positioning ranges for multi-actuator hard-disks).

While at it, also fix a typo in this file introduction paragraph.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 Documentation/block/queue-sysfs.rst | 30 ++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Aug. 10, 2021, 8:27 a.m. UTC | #1 
On Mon, Jul 26, 2021 at 10:38:06AM +0900, Damien Le Moal wrote:
> Update the file Documentation/block/queue-sysfs.rst to add a description

> of a device queue sysfs entries related to concurrent sector ranges

> (e.g. concurrent positioning ranges for multi-actuator hard-disks).

> 

> While at it, also fix a typo in this file introduction paragraph.


That should really be a separate patch.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
Damien Le Moal Aug. 10, 2021, 11:04 a.m. UTC | #2 
On 2021/08/10 17:28, Christoph Hellwig wrote:
> On Mon, Jul 26, 2021 at 10:38:06AM +0900, Damien Le Moal wrote:
>> Update the file Documentation/block/queue-sysfs.rst to add a description
>> of a device queue sysfs entries related to concurrent sector ranges
>> (e.g. concurrent positioning ranges for multi-actuator hard-disks).
>>
>> While at it, also fix a typo in this file introduction paragraph.
> 
> That should really be a separate patch.

OK. Will split that part out in a different patch (and cc stable maybe).

> 
> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
>
diff mbox series

Patch

diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
index 4dc7f0d499a8..25f4a768f450 100644
--- a/Documentation/block/queue-sysfs.rst
+++ b/Documentation/block/queue-sysfs.rst
@@ -4,7 +4,7 @@  Queue sysfs files
 
 This text file will detail the queue files that are located in the sysfs tree
 for each block device. Note that stacked devices typically do not export
-any settings, since their queue merely functions are a remapping target.
+any settings, since their queue merely functions as a remapping target.
 These files are the ones found in the /sys/block/xxx/queue/ directory.
 
 Files denoted with a RO postfix are readonly and the RW postfix means
@@ -286,4 +286,32 @@  sequential zones of zoned block devices (devices with a zoned attributed
 that reports "host-managed" or "host-aware"). This value is always 0 for
 regular block devices.
 
+cranges (RO)
+------------
+
+The presence of this sub-directory of the /sys/block/xxx/queue/ directory
+indicates that the device is capable of executing requests targeting
+different sector ranges in parallel. For instance, single LUN multi-actuator
+hard-disks will likely have a cranges directory if the device correctly
+advertizes the sector ranges of its actuators.
+
+The cranges directory contains one directory per concurrent range, with each
+range described using the sector (RO) attribute file to indicate the first
+sector of the range and the nr_sectors (RO) attribute file to indicate the
+total number of sector in the range starting from the first sector.
+For example, a dual-actuator hard disk will have the following cranges
+entries.::
+
+        $ tree /sys/block/<device>/queue/cranges/
+        /sys/block/<device>/queue/cranges/
+        |-- 0
+        |   |-- nr_sectors
+        |   `-- sector
+        `-- 1
+            |-- nr_sectors
+            `-- sector
+
+The sector and nr_sectors attributes use 512B sector unit, regardless of
+the actual block size of the device.
+
 Jens Axboe <jens.axboe@oracle.com>, February 2009