block, documentation: Document discard_zeroes_data, fua, max_discard_segments and write_zeroes_max_bytes
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>
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@ -52,6 +52,16 @@ large discards are issued, setting this value lower will make Linux issue
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smaller discards and potentially help reduce latencies induced by large
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discard operations.
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discard_zeroes_data (RO)
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------------------------
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Obsolete. Always zero.
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fua (RO)
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--------
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Whether or not the block driver supports the FUA flag for write requests.
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FUA stands for Force Unit Access. If the FUA flag is set that means that
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write requests must bypass the volatile cache of the storage device.
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hw_sector_size (RO)
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-------------------
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This is the hardware sector size of the device, in bytes.
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@ -92,6 +102,10 @@ logical_block_size (RO)
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-----------------------
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This is the logical block size of the device, in bytes.
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max_discard_segments (RO)
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-------------------------
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The maximum number of DMA scatter/gather entries in a discard request.
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max_hw_sectors_kb (RO)
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----------------------
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This is the maximum number of kilobytes supported in a single data transfer.
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@ -218,6 +232,12 @@ blk-throttle makes decision based on the samplings. Lower time means cgroups
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have more smooth throughput, but higher CPU overhead. This exists only when
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CONFIG_BLK_DEV_THROTTLING_LOW is enabled.
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write_zeroes_max_bytes (RO)
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---------------------------
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For block drivers that support REQ_OP_WRITE_ZEROES, the maximum number of
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bytes that can be zeroed at once. The value 0 means that REQ_OP_WRITE_ZEROES
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is not supported.
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zoned (RO)
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----------
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This indicates if the device is a zoned block device and the zone model of the
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