Re: [Xen-devel] [PATCH V3 1/3] xen-blkback: add BLKIF_OP_TRIM and backend types

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 24.08.11 at 11:23, Li Dongyang <lidongyang@xxxxxxxxxx> wrote:
> This adds the BLKIF_OP_TRIM for blkfront and blkback, also 2 enums telling
> us the type of the backend, used in blkback to determine what to do when we
> see a trim request.
> The BLKIF_OP_TRIM part is just taken from Owen Smith, Thanks
> 
> Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
> Signed-off-by: Li Dongyang <lidongyang@xxxxxxxxxx>
> ---
>  drivers/block/xen-blkback/common.h |   10 +++++++++-
>  include/xen/interface/io/blkif.h   |   19 +++++++++++++++++++
>  2 files changed, 28 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/common.h 
> b/drivers/block/xen-blkback/common.h
> index 9e40b28..146d325 100644
> --- a/drivers/block/xen-blkback/common.h
> +++ b/drivers/block/xen-blkback/common.h
> @@ -113,6 +113,11 @@ enum blkif_protocol {
>       BLKIF_PROTOCOL_X86_64 = 3,
>  };
>  
> +enum blkif_backend_type {
> +     BLKIF_BACKEND_PHY  = 1,
> +     BLKIF_BACKEND_FILE = 2,
> +};
> +
>  struct xen_vbd {
>       /* What the domain refers to this vbd as. */
>       blkif_vdev_t            handle;
> @@ -138,6 +143,7 @@ struct xen_blkif {
>       unsigned int            irq;
>       /* Comms information. */
>       enum blkif_protocol     blk_protocol;
> +     enum blkif_backend_type blk_backend_type;
>       union blkif_back_rings  blk_rings;
>       struct vm_struct        *blk_ring_area;
>       /* The VBD attached to this interface. */
> @@ -159,8 +165,10 @@ struct xen_blkif {
>       int                     st_wr_req;
>       int                     st_oo_req;
>       int                     st_f_req;
> +     int                     st_tr_req;
>       int                     st_rd_sect;
>       int                     st_wr_sect;
> +     int                     st_tr_sect;

Just to repeat - I don't think this piece of statistic is very useful, the
more that you use "int" here while ...

>  
>       wait_queue_head_t       waiting_to_free;
>  
> @@ -182,7 +190,7 @@ struct xen_blkif {
>  
>  struct phys_req {
>       unsigned short          dev;
> -     unsigned short          nr_sects;
> +     blkif_sector_t          nr_sects;

... you specifically widen the field to 64 bits here.

Also, all of the changes to this header look somewhat misplaced, they
should rather be part of the backend patch.

Jan

>       struct block_device     *bdev;
>       blkif_sector_t          sector_number;
>  };
> diff --git a/include/xen/interface/io/blkif.h 
> b/include/xen/interface/io/blkif.h
> index 3d5d6db..43762dd 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 trim
> + * requests are likely to succeed or fail. Either way, a trim request
> + * 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!
> + */
> +#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;
>  };
>  





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