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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>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2018-04-13 17:31:56 +03:00 committed by Eric Blake
parent 3229a835a3
commit bc37b06a5c
3 changed files with 11 additions and 5 deletions
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3
include/block/nbd.h
View File

@ -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,
};

2
nbd/common.c
View File

@ -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:

11
nbd/server.c
View File

@ -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: