On 08/18/2011 02:34 AM, Li Dongyang wrote:
> This adds the BLKIF_OP_TRIM for blkfront and blkback, also 2 flags telling
> us the type of the backend, used in blkback to determine what to do when we
> see a trim request.
> Part of the patch is just taken from Owen Smith, Thanks
>
> Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
> Signed-off-by: Li Dongyang <lidongyang@xxxxxxxxxx>
> ---
> include/xen/interface/io/blkif.h | 21 +++++++++++++++++++++
> 1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/include/xen/interface/io/blkif.h
> b/include/xen/interface/io/blkif.h
> index 3d5d6db..b92cf23 100644
> --- a/include/xen/interface/io/blkif.h
> +++ b/include/xen/interface/io/blkif.h
> @@ -57,6 +57,19 @@ typedef uint64_t blkif_sector_t;
> * "feature-flush-cache" node!
> */
> #define BLKIF_OP_FLUSH_DISKCACHE 3
> +
> +/*
> + * Recognised only if "feature-trim" is present in backend xenbus info.
> + * The "feature-trim" node contains a boolean indicating whether barrier
> + * requests are likely to succeed or fail. Either way, a trim request
Barrier requests?
> + * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
> + * the underlying block-device hardware. The boolean simply indicates whether
> + * or not it is worthwhile for the frontend to attempt trim requests.
> + * If a backend does not recognise BLKIF_OP_TRIM, it should *not*
> + * create the "feature-trim" node!
Is all this necessary? What happens if guests just send OP_TRIM
requests, and if the host doesn't understand them then it will fails
them with EOPNOTSUPP? Is a TRIM request ever anything more than a hint
to the backend that certain blocks are no longer needed?
> + */
> +#define BLKIF_OP_TRIM 5
> +
> /*
> * Maximum scatter/gather segments per request.
> * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
> @@ -74,6 +87,11 @@ struct blkif_request_rw {
> } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> };
>
> +struct blkif_request_trim {
> + blkif_sector_t sector_number;
> + uint64_t nr_sectors;
> +};
> +
> struct blkif_request {
> uint8_t operation; /* BLKIF_OP_??? */
> uint8_t nr_segments; /* number of segments */
> @@ -81,6 +99,7 @@ struct blkif_request {
> uint64_t id; /* private guest value, echoed in resp */
> union {
> struct blkif_request_rw rw;
> + struct blkif_request_trim trim;
> } u;
> };
>
> @@ -109,6 +128,8 @@ DEFINE_RING_TYPES(blkif, struct blkif_request, struct
> blkif_response);
> #define VDISK_CDROM 0x1
> #define VDISK_REMOVABLE 0x2
> #define VDISK_READONLY 0x4
> +#define VDISK_FILE_BACKEND 0x8
> +#define VDISK_PHY_BACKEND 0x10
What are these for? Why does a frontend care about these?
J
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