d0985394e7
This reverts commit a72c5e5eb7.
The commit introduced alias for block devices which is intended to be
used during logging although actual usage hasn't been committed yet.
This approach adds very limited benefit (raw log might be easier to
follow) which can be trivially implemented in userland but has a lot
of problems.
It is much worse than netif renames because it doesn't rename the
actual device but just adds conveninence name which isn't used
universally or enforced. Everything internal including device lookup
and sysfs still uses the internal name and nothing prevents two
devices from using conflicting alias - ie. sda can have sdb as its
alias.
This has been nacked by people working on device driver core, block
layer and kernel-userland interface and shouldn't have been
upstreamed. Revert it.
http://thread.gmane.org/gmane.linux.kernel/1155104
http://thread.gmane.org/gmane.linux.scsi/68632
http://thread.gmane.org/gmane.linux.scsi/69776
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Nao Nishijima <nao.nishijima.xt@hitachi.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
208 lines
7.9 KiB
Text
208 lines
7.9 KiB
Text
What: /sys/block/<disk>/stat
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Date: February 2008
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Contact: Jerome Marchand <jmarchan@redhat.com>
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Description:
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The /sys/block/<disk>/stat files displays the I/O
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statistics of disk <disk>. They contain 11 fields:
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1 - reads completed successfully
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2 - reads merged
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3 - sectors read
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4 - time spent reading (ms)
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5 - writes completed
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6 - writes merged
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7 - sectors written
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8 - time spent writing (ms)
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9 - I/Os currently in progress
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10 - time spent doing I/Os (ms)
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11 - weighted time spent doing I/Os (ms)
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For more details refer Documentation/iostats.txt
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What: /sys/block/<disk>/<part>/stat
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Date: February 2008
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Contact: Jerome Marchand <jmarchan@redhat.com>
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Description:
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The /sys/block/<disk>/<part>/stat files display the
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I/O statistics of partition <part>. The format is the
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same as the above-written /sys/block/<disk>/stat
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format.
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What: /sys/block/<disk>/integrity/format
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Metadata format for integrity capable block device.
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E.g. T10-DIF-TYPE1-CRC.
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What: /sys/block/<disk>/integrity/read_verify
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Indicates whether the block layer should verify the
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integrity of read requests serviced by devices that
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support sending integrity metadata.
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What: /sys/block/<disk>/integrity/tag_size
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Number of bytes of integrity tag space available per
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512 bytes of data.
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What: /sys/block/<disk>/integrity/write_generate
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Indicates whether the block layer should automatically
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generate checksums for write requests bound for
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devices that support receiving integrity metadata.
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What: /sys/block/<disk>/alignment_offset
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report a physical block size that is
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bigger than the logical block size (for instance a drive
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with 4KB physical sectors exposing 512-byte logical
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blocks to the operating system). This parameter
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indicates how many bytes the beginning of the device is
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offset from the disk's natural alignment.
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What: /sys/block/<disk>/<partition>/alignment_offset
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report a physical block size that is
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bigger than the logical block size (for instance a drive
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with 4KB physical sectors exposing 512-byte logical
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blocks to the operating system). This parameter
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indicates how many bytes the beginning of the partition
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is offset from the disk's natural alignment.
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What: /sys/block/<disk>/queue/logical_block_size
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Date: May 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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This is the smallest unit the storage device can
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address. It is typically 512 bytes.
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What: /sys/block/<disk>/queue/physical_block_size
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Date: May 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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This is the smallest unit a physical storage device can
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write atomically. It is usually the same as the logical
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block size but may be bigger. One example is SATA
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drives with 4KB sectors that expose a 512-byte logical
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block size to the operating system. For stacked block
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devices the physical_block_size variable contains the
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maximum physical_block_size of the component devices.
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What: /sys/block/<disk>/queue/minimum_io_size
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report a granularity or preferred
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minimum I/O size which is the smallest request the
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device can perform without incurring a performance
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penalty. For disk drives this is often the physical
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block size. For RAID arrays it is often the stripe
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chunk size. A properly aligned multiple of
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minimum_io_size is the preferred request size for
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workloads where a high number of I/O operations is
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desired.
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What: /sys/block/<disk>/queue/optimal_io_size
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report an optimal I/O size, which is
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the device's preferred unit for sustained I/O. This is
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rarely reported for disk drives. For RAID arrays it is
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usually the stripe width or the internal track size. A
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properly aligned multiple of optimal_io_size is the
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preferred request size for workloads where sustained
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throughput is desired. If no optimal I/O size is
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reported this file contains 0.
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What: /sys/block/<disk>/queue/nomerges
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Date: January 2010
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Contact:
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Description:
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Standard I/O elevator operations include attempts to
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merge contiguous I/Os. For known random I/O loads these
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attempts will always fail and result in extra cycles
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being spent in the kernel. This allows one to turn off
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this behavior on one of two ways: When set to 1, complex
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merge checks are disabled, but the simple one-shot merges
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with the previous I/O request are enabled. When set to 2,
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all merge tries are disabled. The default value is 0 -
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which enables all types of merge tries.
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What: /sys/block/<disk>/discard_alignment
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Date: May 2011
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Devices that support discard functionality may
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internally allocate space in units that are bigger than
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the exported logical block size. The discard_alignment
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parameter indicates how many bytes the beginning of the
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device is offset from the internal allocation unit's
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natural alignment.
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What: /sys/block/<disk>/<partition>/discard_alignment
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Date: May 2011
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Devices that support discard functionality may
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internally allocate space in units that are bigger than
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the exported logical block size. The discard_alignment
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parameter indicates how many bytes the beginning of the
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partition is offset from the internal allocation unit's
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natural alignment.
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What: /sys/block/<disk>/queue/discard_granularity
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Date: May 2011
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Devices that support discard functionality may
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internally allocate space using units that are bigger
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than the logical block size. The discard_granularity
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parameter indicates the size of the internal allocation
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unit in bytes if reported by the device. Otherwise the
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discard_granularity will be set to match the device's
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physical block size. A discard_granularity of 0 means
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that the device does not support discard functionality.
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What: /sys/block/<disk>/queue/discard_max_bytes
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Date: May 2011
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Devices that support discard functionality may have
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internal limits on the number of bytes that can be
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trimmed or unmapped in a single operation. Some storage
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protocols also have inherent limits on the number of
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blocks that can be described in a single command. The
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discard_max_bytes parameter is set by the device driver
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to the maximum number of bytes that can be discarded in
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a single operation. Discard requests issued to the
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device must not exceed this limit. A discard_max_bytes
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value of 0 means that the device does not support
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discard functionality.
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What: /sys/block/<disk>/queue/discard_zeroes_data
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Date: May 2011
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Devices that support discard functionality may return
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stale or random data when a previously discarded block
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is read back. This can cause problems if the filesystem
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expects discarded blocks to be explicitly cleared. If a
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device reports that it deterministically returns zeroes
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when a discarded area is read the discard_zeroes_data
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parameter will be set to one. Otherwise it will be 0 and
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the result of reading a discarded area is undefined.
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