aboutsummaryrefslogtreecommitdiff
path: root/nbd
diff options
context:
space:
mode:
authorVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>2019-07-25 13:05:50 +0300
committerEric Blake <eblake@redhat.com>2019-08-15 13:22:13 -0500
commit7fa5c5657f11096101f5be18fe1f7395776be5a6 (patch)
tree3526092b0bcea6fe6897eb6699d61acb65b51fd5 /nbd
parent99136607b1edb0129d1ebb6ecac21738ad3d9c36 (diff)
downloadqemu-7fa5c5657f11096101f5be18fe1f7395776be5a6.zip
qemu-7fa5c5657f11096101f5be18fe1f7395776be5a6.tar.gz
qemu-7fa5c5657f11096101f5be18fe1f7395776be5a6.tar.bz2
nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
This helps to avoid extra io, allocations and memory copying. We assume here that CMD_CACHE is always used with copy-on-read, as otherwise it's a noop. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20190725100550.33801-4-vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>
Diffstat (limited to 'nbd')
-rw-r--r--nbd/server.c43
1 files changed, 35 insertions, 8 deletions
diff --git a/nbd/server.c b/nbd/server.c
index 10faedc..a2cf085 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -2104,12 +2104,15 @@ static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request,
return -EINVAL;
}
- req->data = blk_try_blockalign(client->exp->blk, request->len);
- if (req->data == NULL) {
- error_setg(errp, "No memory");
- return -ENOMEM;
+ if (request->type != NBD_CMD_CACHE) {
+ req->data = blk_try_blockalign(client->exp->blk, request->len);
+ if (req->data == NULL) {
+ error_setg(errp, "No memory");
+ return -ENOMEM;
+ }
}
}
+
if (request->type == NBD_CMD_WRITE) {
if (nbd_read(client->ioc, req->data, request->len, "CMD_WRITE data",
errp) < 0)
@@ -2194,7 +2197,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
int ret;
NBDExport *exp = client->exp;
- assert(request->type == NBD_CMD_READ || request->type == NBD_CMD_CACHE);
+ assert(request->type == NBD_CMD_READ);
/* XXX: NBD Protocol only documents use of FUA with WRITE */
if (request->flags & NBD_CMD_FLAG_FUA) {
@@ -2206,7 +2209,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
}
if (client->structured_reply && !(request->flags & NBD_CMD_FLAG_DF) &&
- request->len && request->type != NBD_CMD_CACHE)
+ request->len)
{
return nbd_co_send_sparse_read(client, request->handle, request->from,
data, request->len, errp);
@@ -2214,7 +2217,7 @@ 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 || request->type == NBD_CMD_CACHE) {
+ if (ret < 0) {
return nbd_send_generic_reply(client, request->handle, ret,
"reading from file failed", errp);
}
@@ -2233,6 +2236,28 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
}
}
+/*
+ * nbd_do_cmd_cache
+ *
+ * Handle NBD_CMD_CACHE request.
+ * Return -errno if sending fails. Other errors are reported directly to the
+ * client as an error reply.
+ */
+static coroutine_fn int nbd_do_cmd_cache(NBDClient *client, NBDRequest *request,
+ Error **errp)
+{
+ int ret;
+ NBDExport *exp = client->exp;
+
+ assert(request->type == NBD_CMD_CACHE);
+
+ ret = blk_co_preadv(exp->blk, request->from + exp->dev_offset, request->len,
+ NULL, BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
+
+ return nbd_send_generic_reply(client, request->handle, ret,
+ "caching data failed", errp);
+}
+
/* Handle NBD request.
* Return -errno if sending fails. Other errors are reported directly to the
* client as an error reply. */
@@ -2246,8 +2271,10 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
char *msg;
switch (request->type) {
- case NBD_CMD_READ:
case NBD_CMD_CACHE:
+ return nbd_do_cmd_cache(client, request, errp);
+
+ case NBD_CMD_READ:
return nbd_do_cmd_read(client, request, data, errp);
case NBD_CMD_WRITE: