Re: [Xen-devel] [PATCH] blkif.h: enhance comments related to the discard feature

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Jan 17, 2014 at 03:09:13PM +0000, Jan Beulich wrote:
> >>> On 14.01.14 at 22:57, Olaf Hering <olaf@xxxxxxxxx> wrote:
> > Also fix the name of the discard-alignment property, add the missing 'n'.
> > 
> > Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> 
> Konrad,
> 
> you have been working on the discard stuff quite a bit iirc - any
> chance you could take a look and send and ack/review?
> 
> Jan
> 
> > ---
> >  xen/include/public/io/blkif.h | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> > 
> > diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
> > index 84eb7fd..515ea90 100644
> > --- a/xen/include/public/io/blkif.h
> > +++ b/xen/include/public/io/blkif.h
> > @@ -175,7 +175,7 @@
> >   *
> >   *------------------------- Backend Device Properties 
> > -------------------------
> >   *
> > - * discard-aligment
> > + * discard-alignment
> >   *      Values:         <uint32_t>
> >   *      Default Value:  0
> >   *      Notes:          4, 5
> > @@ -194,6 +194,7 @@
> >   * discard-secure
> >   *      Values:         0/1 (boolean)
> >   *      Default Value:  0
> > + *      Notes:          10
> >   *
> >   *      A value of "1" indicates that the backend can process 
> > BLKIF_OP_DISCARD
> >   *      requests with the BLKIF_DISCARD_SECURE flag set.
> > @@ -323,9 +324,14 @@
> >   *     For full interoperability, block front and backends should publish
> >   *     identical ring parameters, adjusted for unit differences, to the
> >   *     XenStore nodes used in both schemes.
> > - * (4) Devices that support discard functionality may internally allocate
> > - *     space (discardable extents) in units that are larger than the
> > - *     exported logical block size.
> > + * (4) Devices that support discard functionality may internally allocate 
> > space
> > + *     (discardable extents) in units that are larger than the exported 
> > logical
> > + *     block size. If the backing device has such discardable extents the
> > + *     backend must provide both discard-granularity and discard-alignment.
                    ^^^^ - MAY

> > + *     Backends supporting discard should include discard-granularity and
                                        ^^^^^ - MAY
> > + *     discard-alignment even if it supports discarding individual sectors.
> > + *     Frontends should assume discard-alignment == 0 and 
> > discard-granularity 
> > ==
> > + *     sector size if these keys are missing.
> >   * (5) The discard-alignment parameter allows a physical device to be
> >   *     partitioned into virtual devices that do not necessarily begin or
> >   *     end on a discardable extent boundary.
> > @@ -344,6 +350,8 @@
> >   *     grants that can be persistently mapped in the frontend driver, but
> >   *     due to the frontent driver implementation it should never be bigger
> >   *     than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
> > + *(10) The discard-secure property may be present and will be set to 1 if 
> > the
> > + *     backing device supports secure discard.
> >   */
> >  
> >  /*
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx 
> > http://lists.xen.org/xen-devel 
> 
> 
> 

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