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 <vsement...@virtuozzo.com>
---
include/block/nbd.h | 3 ++-
nbd/server.c | 10 ++++++----
2 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/include/block/nbd.h b/include/block/nbd.h
index fcdcd54502..b4793d0a29 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -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,
};
diff --git a/nbd/server.c b/nbd/server.c
index 9e1f227178..30d7d3f444 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1134,7 +1134,7 @@ 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
@@ -1826,7 +1826,9 @@ 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);
@@ -1911,7 +1913,7 @@ 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) {
@@ -1930,7 +1932,7 @@ 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);
}
--
2.11.1
