diff options
Diffstat (limited to 'content.tex')
| -rw-r--r-- | content.tex | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/content.tex b/content.tex index 445f26f..ede0ef6 100644 --- a/content.tex +++ b/content.tex @@ -3967,8 +3967,10 @@ read from the block device (in multiples of 512 bytes). VIRTIO_BLK_T_OUT requests write the contents of \field{data} to the block device (in multiples of 512 bytes). -The \field{data} used for discard or write zeroes command is described -by one or more virtio_blk_discard_write_zeroes structs: +The \field{data} used for discard or write zeroes commands consists of one or +more segments. The maximum number of segments is \field{max_discard_seg} for +discard commands and \field{max_write_zeroes_seg} for write zeroes commands. +Each segment is of form: \begin{lstlisting} struct virtio_blk_discard_write_zeroes { @@ -3997,6 +3999,10 @@ error or VIRTIO_BLK_S_UNSUPP for a request unsupported by device: #define VIRTIO_BLK_S_UNSUPP 2 \end{lstlisting} +The status of individual segments is indeterminate when a discard or write zero +command produces VIRTIO_BLK_S_IOERR. A segment may have completed +successfully, failed, or not been processed by the device. + \drivernormative{\subsubsection}{Device Operation}{Device Types / Block Device / Device Operation} A driver MUST NOT submit a request which would cause a read or write @@ -4014,6 +4020,14 @@ The length of \field{data} MUST be a multiple of the size of struct virtio_blk_discard_write_zeroes for VIRTIO_BLK_T_DISCARD and VIRTIO_BLK_T_WRITE_ZEROES requests. +VIRTIO_BLK_T_DISCARD requests MUST NOT contain more than +\field{max_discard_seg} struct virtio_blk_discard_write_zeroes segments in +\field{data}. + +VIRTIO_BLK_T_WRITE_ZEROES requests MUST NOT contain more than +\field{max_write_zeroes_seg} struct virtio_blk_discard_write_zeroes segments in +\field{data}. + If the VIRTIO_BLK_F_CONFIG_WCE feature is negotiated, the driver MAY switch to writethrough or writeback mode by writing respectively 0 and 1 to the \field{writeback} field. After writing a 0 to \field{writeback}, @@ -4024,6 +4038,11 @@ The \field{unmap} bit MUST be zero for discard commands. The driver MUST NOT assume anything about the data returned by read requests after a range of sectors has been discarded. +A driver MUST NOT assume that individual segments in a multi-segment +VIRTIO_BLK_T_DISCARD or VIRTIO_BLK_T_WRITE_ZEROES request completed +successfully, failed, or were processed by the device at all if the request +failed with VIRTIO_BLK_S_IOERR. + \devicenormative{\subsubsection}{Device Operation}{Device Types / Block Device / Device Operation} A device MUST set the \field{status} byte to VIRTIO_BLK_S_IOERR |