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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: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20180413143156.11409-1-vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> [eblake: fix two missing case labels in switch statements] Signed-off-by: Eric Blake <eblake@redhat.com>
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@ -135,6 +135,7 @@ typedef struct NBDExtent {
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#define NBD_FLAG_SEND_TRIM (1 << 5) /* Send TRIM (discard) */
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#define NBD_FLAG_SEND_WRITE_ZEROES (1 << 6) /* Send WRITE_ZEROES */
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#define NBD_FLAG_SEND_DF (1 << 7) /* Send DF (Do not Fragment) */
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#define NBD_FLAG_SEND_CACHE (1 << 8) /* Send CACHE (prefetch) */
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/* New-style handshake (global) flags, sent from server to client, and
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control what will happen during handshake phase. */
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@ -195,7 +196,7 @@ enum {
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NBD_CMD_DISC = 2,
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NBD_CMD_FLUSH = 3,
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NBD_CMD_TRIM = 4,
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/* 5 reserved for failed experiment NBD_CMD_CACHE */
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NBD_CMD_CACHE = 5,
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NBD_CMD_WRITE_ZEROES = 6,
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NBD_CMD_BLOCK_STATUS = 7,
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};
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@ -148,6 +148,8 @@ const char *nbd_cmd_lookup(uint16_t cmd)
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return "flush";
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case NBD_CMD_TRIM:
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return "trim";
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case NBD_CMD_CACHE:
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return "cache";
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case NBD_CMD_WRITE_ZEROES:
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return "write zeroes";
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case NBD_CMD_BLOCK_STATUS:
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11
nbd/server.c
11
nbd/server.c
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@ -1252,7 +1252,7 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
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int ret;
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const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
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NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA |
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NBD_FLAG_SEND_WRITE_ZEROES);
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NBD_FLAG_SEND_WRITE_ZEROES | NBD_FLAG_SEND_CACHE);
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bool oldStyle;
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/* Old style negotiation header, no room for options
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@ -2034,7 +2034,9 @@ static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request,
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return -EIO;
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}
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if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE) {
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if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE ||
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request->type == NBD_CMD_CACHE)
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{
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if (request->len > NBD_MAX_BUFFER_SIZE) {
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error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",
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request->len, NBD_MAX_BUFFER_SIZE);
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@ -2119,7 +2121,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
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int ret;
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NBDExport *exp = client->exp;
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assert(request->type == NBD_CMD_READ);
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assert(request->type == NBD_CMD_READ || request->type == NBD_CMD_CACHE);
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/* XXX: NBD Protocol only documents use of FUA with WRITE */
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if (request->flags & NBD_CMD_FLAG_FUA) {
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@ -2138,7 +2140,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
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ret = blk_pread(exp->blk, request->from + exp->dev_offset, data,
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request->len);
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if (ret < 0) {
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if (ret < 0 || request->type == NBD_CMD_CACHE) {
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return nbd_send_generic_reply(client, request->handle, ret,
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"reading from file failed", errp);
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}
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@ -2171,6 +2173,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
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switch (request->type) {
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case NBD_CMD_READ:
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case NBD_CMD_CACHE:
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return nbd_do_cmd_read(client, request, data, errp);
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case NBD_CMD_WRITE:
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