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    SubjectRe: [Xen-devel] [PATCH 3/3] xen/blk[front|back]: Enhance discard support with secure erasing support.
    On Mon, Oct 10, 2011 at 05:13:07PM +0100, Ian Campbell wrote:
    > On Mon, 2011-10-10 at 16:28 +0100, Konrad Rzeszutek Wilk wrote:
    > > diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
    > > index 9324488..04f60b0 100644
    > > --- a/include/xen/interface/io/blkif.h
    > > +++ b/include/xen/interface/io/blkif.h
    > > @@ -84,6 +84,10 @@ typedef uint64_t blkif_sector_t;
    > > * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
    > > * http://www.seagate.com/staticfiles/support/disc/manuals/
    > > * Interface%20manuals/100293068c.pdf
    > > + * We also provide three extra XenBus options to the discard operation:
    > > + * 'discard-granularity' - Max amount of sectors that can be discarded.
    > > + * 'discard-alignment' - 4K, 128K, etc aligment on sectors to erased.
    > > + * 'discard-secure' - whether the discard can also securely erase data.
    > > */
    > > #define BLKIF_OP_DISCARD 5
    > >
    > > @@ -107,6 +111,7 @@ struct blkif_request_rw {
    > > struct blkif_request_discard {
    > > blkif_sector_t sector_number;
    > > uint64_t nr_sectors;
    > > + uint8_t secure:1;
    > > };
    > >
    > > struct blkif_request {
    >
    > Which tree/branch is this? I don't see BLKIF_OP_DISCARD in mainline or
    > your linux-next branch.

    Uh, that is not good. I must have forgotten to merge it in - that is the
    #stable/for-jens-3.2 branch.

    Let me do that right now.
    >
    > Since this changes an inter-guest ABI we may need to consider backwards
    > compatibility (I suspect this interface is new enough that no one has
    > actually implemented it in anger and we can get away with changing it).

    <nods>
    > In any case it should also be posted against the canonical inter-guest
    > interface definition in the xen tree for review with that in mind.

    Yes! But I was thinking to first let this one rattle a bit and see what
    folks thought about it before submitting the xen-devel.
    >
    > I think an explicit flag variable is likely to be less trouble WRT
    > maintaining compatibility in the future than a bit-field. Also I think
    > you may as well align the struct size to something larger than a byte,
    > either 4 or 8 bytes would make sense.

    Ok. Will change it and make it an uint64_t secure_flag
    variable. Later on if there are any "other" flags we can chop it down.


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