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Subject: Re: [virtio-dev] [PATCH v3 5/5] virtio-blk: clarify semantics of multi-segment discard/write zeroes commands
On Thu, Feb 21, 2019 at 04:22:19PM +0000, Stefan Hajnoczi wrote: > Describe the failure case and maximum number of segments in a > multi-segment discard/write zeroes command. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> OK so just making sure. Patches 1-4 have already been approved, so I should apply them. Patch 5 needs another vote. Is that right? > --- > content.tex | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/content.tex b/content.tex > index c5fdc34..7bfcc78 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 > -- > 2.20.1 > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
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