[4/4] block, documentation: Document discard_zeroes_data, fua, max_discard_segments and write_zeroes_max_bytes
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Message ID 20190628200745.206110-5-bvanassche@acm.org
State New
Headers show
  • Improve block layer request queue sysfs parameter documentation
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Commit Message

Bart Van Assche June 28, 2019, 8:07 p.m. UTC
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
 Documentation/block/queue-sysfs.txt | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)


Martin K. Petersen June 28, 2019, 8:23 p.m. UTC | #1

Looks fine.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

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diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 1515dcf3dec4..b40b5b7cebd9 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -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
 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)
 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.
+max_discard_segments (RO)
+The maximum number of DMA scatter/gather entries in a discard request.
 max_hw_sectors_kb (RO)
 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
+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)
 This indicates if the device is a zoned block device and the zone model of the