On 9/6/21 3:58 AM, Damien Le Moal wrote:
The Concurrent Positioning Ranges VPD page (for SCSI) and data log page
(for ATA) contain parameters describing the set of contiguous LBAs that
can be served independently by a single LUN multi-actuator hard-disk.
Similarly, a logically defined block device composed of multiple disks
can in some cases execute requests directed at different sector ranges
in parallel. A dm-linear device aggregating 2 block devices together is
an example.
This patch implements support for exposing a block device independent
access ranges to the user through sysfs to allow optimizing device
accesses to increase performance.
To describe the set of independent sector ranges of a device (actuators
of a multi-actuator HDDs or table entries of a dm-linear device),
The type struct blk_independent_access_ranges is introduced. This
structure describes the sector ranges using an array of
struct blk_independent_access_range structures. This range structure
defines the start sector and number of sectors of the access range.
The ranges in the array cannot overlap and must contain all sectors
within the device capacity.
The function disk_set_iaranges() allows a device driver to signal to
the block layer that a device has multiple independent access ranges.
In this case, a struct blk_independent_access_ranges is attached to
the device request queue by the function disk_set_iaranges(). The
function disk_alloc_iaranges() is provided for drivers to allocate this
structure.
struct blk_independent_access_ranges contains kobjects (struct kobject)
to expose to the user through sysfs the set of independent access ranges
supported by a device. When the device is initialized, sysfs
registration of the ranges information is done from blk_register_queue()
using the block layer internal function disk_register_iaranges(). If a
driver calls disk_set_iaranges() for a registered queue, e.g. when a
device is revalidated, disk_set_iaranges() will execute
disk_register_iaranges() to update the sysfs attribute files.
The sysfs file structure created starts from the
independent_access_ranges sub-directory and contains the start sector
and number of sectors of each range, with the information for each
range grouped in numbered sub-directories.
E.g. for a dual actuator HDD, the user sees:
$ tree /sys/block/sdk/queue/independent_access_ranges/
/sys/block/sdk/queue/independent_access_ranges/
|-- 0
| |-- nr_sectors
| `-- sector
`-- 1
|-- nr_sectors
`-- sector
For a regular device with a single access range, the
independent_access_ranges sysfs directory does not exist.
Device revalidation may lead to changes to this structure and to the
attribute values. When manipulated, the queue sysfs_lock and
sysfs_dir_lock mutexes are held for atomicity, similarly to how the
blk-mq and elevator sysfs queue sub-directories are protected.
The code related to the management of independent access ranges is
added in the new file block/blk-iaranges.c.
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
block/Makefile | 2 +-
block/blk-iaranges.c | 345 +++++++++++++++++++++++++++++++++++++++++
block/blk-sysfs.c | 26 +++-
block/blk.h | 4 +
include/linux/blkdev.h | 39 +++++
5 files changed, 407 insertions(+), 9 deletions(-)
create mode 100644 block/blk-iaranges.c
One feels a bit in a HP Lovecraft tale with these names, but I'll guess
that's fine :-)
So:
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
