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block, documentation: Document discard_zeroes_data, fua, max_discard_segments and write_zeroes_max_bytes

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Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2019-06-28 13:07:45 -07:00 committed by Jens Axboe
parent 0c766e78bd
commit fbbe7c86b4
1 changed files with 20 additions and 0 deletions
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20
Documentation/block/queue-sysfs.txt
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@ -52,6 +52,16 @@ large discards are issued, setting this value lower will make Linux issue
smaller discards and potentially help reduce latencies induced by large smaller discards and potentially help reduce latencies induced by large
discard operations. discard operations.
discard_zeroes_data (RO)
------------------------
Obsolete. Always zero.
fua (RO)
--------
Whether or not the block driver supports the FUA flag for write requests.
FUA stands for Force Unit Access. If the FUA flag is set that means that
write requests must bypass the volatile cache of the storage device.
hw_sector_size (RO) hw_sector_size (RO)
------------------- -------------------
This is the hardware sector size of the device, in bytes. This is the hardware sector size of the device, in bytes.
@ -92,6 +102,10 @@ logical_block_size (RO)
----------------------- -----------------------
This is the logical block size of the device, in bytes. This is the logical block size of the device, in bytes.
max_discard_segments (RO)
-------------------------
The maximum number of DMA scatter/gather entries in a discard request.
max_hw_sectors_kb (RO) max_hw_sectors_kb (RO)
---------------------- ----------------------
This is the maximum number of kilobytes supported in a single data transfer. This is the maximum number of kilobytes supported in a single data transfer.
@ -218,6 +232,12 @@ blk-throttle makes decision based on the samplings. Lower time means cgroups
have more smooth throughput, but higher CPU overhead. This exists only when have more smooth throughput, but higher CPU overhead. This exists only when
CONFIG_BLK_DEV_THROTTLING_LOW is enabled. CONFIG_BLK_DEV_THROTTLING_LOW is enabled.
write_zeroes_max_bytes (RO)
---------------------------
For block drivers that support REQ_OP_WRITE_ZEROES, the maximum number of
bytes that can be zeroed at once. The value 0 means that REQ_OP_WRITE_ZEROES
is not supported.
zoned (RO) zoned (RO)
---------- ----------
This indicates if the device is a zoned block device and the zone model of the This indicates if the device is a zoned block device and the zone model of the