Re: [Nbd] [PATCHv3] Improve the documentation of NBD_CMD_FLUSH and NBD_CMD_FLAG_FUA.
On 05/04/2016 14:07, Alex Bligh wrote:
> Improve the documentation of NBD_CMD_FLUSH and NBD_CMD_FLAG_FUA. Specifically
> the latter may be set on any command, and its semantics on commands other
> than NBD_CMD_WRITE need explaining. Further, explain how these relate to
> reordering of commands.
>
> Signed-off-by: Alex Bligh <alex-rWA27mgs/Jz10XsdtD+oqA@...953...>
> ---
> doc/proto.md | 51 +++++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 41 insertions(+), 10 deletions(-)
>
> ARRRGH - this time with a proper commit header.
>
> Changes since version 2:
>
> * Rebase on master
>
> * Remove bogus 'SHOULD' for FLUSH in relation to writes that are in flight
> but not yet completed
>
> * After consultation with lkml etc., document that FUA on things that do not
> write does nothing
>
> * Document that sending FUA for commands that do nothing is permissible, but
> 'SHOULD NOT' be done; an existing client does this.
Can you send a pointer to the discussion? FUA on reads definitely does
*something* in SCSI (it ensures that the data is moved out of the
volatile cache prior to the read, similar to what QEMU implements).
Paolo
> * Document that FUA on TRIM should do something after all, per Kevin Wolf's
> comment
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