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| author | Stefan Hajnoczi <stefanha@redhat.com> | 2019-02-21 16:22:17 +0000 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2019-03-07 23:59:18 -0500 |
| commit | caffe5caf73b4052fae8f7ff1aa3af18fa4f7395 (patch) | |
| tree | f8f2adbdd4f6ea0da05f73fd197e9ca45c4e5fd0 /content.tex | |
| parent | c5c0ce75aba6461b6fe42368bbdcbf459a94d62d (diff) | |
| download | virtio-spec-caffe5caf73b4052fae8f7ff1aa3af18fa4f7395.tar.gz | |
virtio-blk: describe write zeroes unmap semantics
Explain the meaning of the unmap flag. The details are already covered
in the device normative section but mentioning it here makes the text
easier to understand.
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'content.tex')
| -rw-r--r-- | content.tex | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/content.tex b/content.tex index 2adeb62..47f0ef5 100644 --- a/content.tex +++ b/content.tex @@ -3983,7 +3983,9 @@ struct virtio_blk_discard_write_zeroes { \field{sector} indicates the starting offset (in 512-byte units) of the segment, while \field{num_sectors} indicates the number of sectors in each -discarded range. \field{unmap} is only used for write zeroes command. +discarded range. \field{unmap} is only used in write zeroes commands and allows +the device to discard the specified range, provided that following reads return +zeroes. The final \field{status} byte is written by the device: either VIRTIO_BLK_S_OK for success, VIRTIO_BLK_S_IOERR for device or driver |