Commit bc37b06a authored by Vladimir Sementsov-Ogievskiy's avatar Vladimir Sementsov-Ogievskiy Committed by Eric Blake
Browse files

nbd/server: introduce NBD_CMD_CACHE 



Handle nbd CACHE command. Just do read, without sending read data back.
Cache mechanism should be done by exported node driver chain.

Signed-off-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180413143156.11409-1-vsementsov@virtuozzo.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
[eblake: fix two missing case labels in switch statements]
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
parent 3229a835

include/block/nbd.h

+2 −1
Original line number Diff line number Diff line
@@ -135,6 +135,7 @@ typedef struct NBDExtent { 
#define NBD_FLAG_SEND_TRIM         (1 << 5) /* Send TRIM (discard) */

#define NBD_FLAG_SEND_WRITE_ZEROES (1 << 6) /* Send WRITE_ZEROES */

#define NBD_FLAG_SEND_DF           (1 << 7) /* Send DF (Do not Fragment) */

#define NBD_FLAG_SEND_CACHE        (1 << 8) /* Send CACHE (prefetch) */



/* New-style handshake (global) flags, sent from server to client, and

   control what will happen during handshake phase. */
@@ -195,7 +196,7 @@ enum { 
    NBD_CMD_DISC = 2,

    NBD_CMD_FLUSH = 3,

    NBD_CMD_TRIM = 4,

    /* 5 reserved for failed experiment NBD_CMD_CACHE */

    NBD_CMD_CACHE = 5,

    NBD_CMD_WRITE_ZEROES = 6,

    NBD_CMD_BLOCK_STATUS = 7,

};

nbd/common.c

+2 −0
Original line number Diff line number Diff line
@@ -148,6 +148,8 @@ const char *nbd_cmd_lookup(uint16_t cmd) 
        return "flush";

    case NBD_CMD_TRIM:

        return "trim";

    case NBD_CMD_CACHE:

        return "cache";

    case NBD_CMD_WRITE_ZEROES:

        return "write zeroes";

    case NBD_CMD_BLOCK_STATUS:

nbd/server.c

+7 −4
Original line number Diff line number Diff line
@@ -1252,7 +1252,7 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp) 
    int ret;

    const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |

                              NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA |

                              NBD_FLAG_SEND_WRITE_ZEROES);

                              NBD_FLAG_SEND_WRITE_ZEROES | NBD_FLAG_SEND_CACHE);

    bool oldStyle;



    /* Old style negotiation header, no room for options
@@ -2034,7 +2034,9 @@ static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request, 
        return -EIO;

    }



    if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE) {

    if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE ||

        request->type == NBD_CMD_CACHE)

    {

        if (request->len > NBD_MAX_BUFFER_SIZE) {

            error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",

                       request->len, NBD_MAX_BUFFER_SIZE);
@@ -2119,7 +2121,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request, 
    int ret;

    NBDExport *exp = client->exp;



    assert(request->type == NBD_CMD_READ);

    assert(request->type == NBD_CMD_READ || request->type == NBD_CMD_CACHE);



    /* XXX: NBD Protocol only documents use of FUA with WRITE */

    if (request->flags & NBD_CMD_FLAG_FUA) {
@@ -2138,7 +2140,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request, 


    ret = blk_pread(exp->blk, request->from + exp->dev_offset, data,

                    request->len);

    if (ret < 0) {

    if (ret < 0 || request->type == NBD_CMD_CACHE) {

        return nbd_send_generic_reply(client, request->handle, ret,

                                      "reading from file failed", errp);

    }
@@ -2171,6 +2173,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, 


    switch (request->type) {

    case NBD_CMD_READ:

    case NBD_CMD_CACHE:

        return nbd_do_cmd_read(client, request, data, errp);



    case NBD_CMD_WRITE: