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nbd: support large NBD requests 

The Linux nbd driver recently increased the maximum supported request
size up to 32 MB:

  commit 078be02b80359a541928c899c2631f39628f56df
  Author: Michal Belczyk <belczyk@bsd.krakow.pl>
  Date:   Tue Apr 30 15:28:28 2013 -0700

      nbd: increase default and max request sizes

      Raise the default max request size for nbd to 128KB (from 127KB) to get it
      4KB aligned.  This patch also allows the max request size to be increased
      (via /sys/block/nbd<x>/queue/max_sectors_kb) to 32MB.

QEMU's 1 MB buffers are too small to handle these requests.

This patch allocates data buffers dynamically and allows up to 32 MB per
request.

Reported-by: Nick Thomas <nick@bytemark.co.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-05-02 14:23:08 +02:00
parent e1adb27a83
commit 2d82148859
2 changed files with 13 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/block/nbd.h
View File

@ -58,7 +58,8 @@ enum {
#define NBD_DEFAULT_PORT 10809
#define NBD_BUFFER_SIZE (1024*1024)
/* Maximum size of a single READ/WRITE data buffer */
#define NBD_MAX_BUFFER_SIZE (32 * 1024 * 1024)
ssize_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read);
int tcp_socket_incoming(const char *address, uint16_t port);

17
nbd.c
View File

@ -844,13 +844,11 @@ void nbd_client_close(NBDClient *client)
static NBDRequest *nbd_request_get(NBDClient *client)
{
NBDRequest *req;
NBDExport *exp = client->exp;
assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
client->nb_requests++;
req = g_slice_new0(NBDRequest);
req->data = qemu_blockalign(exp->bs, NBD_BUFFER_SIZE);
nbd_client_get(client);
req->client = client;
return req;
@ -860,7 +858,9 @@ static void nbd_request_put(NBDRequest *req)
{
NBDClient *client = req->client;
qemu_vfree(req->data);
if (req->data) {
qemu_vfree(req->data);
}
g_slice_free(NBDRequest, req);
if (client->nb_requests-- == MAX_NBD_REQUESTS) {
@ -1007,6 +1007,7 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
{
NBDClient *client = req->client;
int csock = client->sock;
uint32_t command;
ssize_t rc;
client->recv_coroutine = qemu_coroutine_self();
@ -1018,9 +1019,9 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
goto out;
}
if (request->len > NBD_BUFFER_SIZE) {
if (request->len > NBD_MAX_BUFFER_SIZE) {
LOG("len (%u) is larger than max len (%u)",
request->len, NBD_BUFFER_SIZE);
request->len, NBD_MAX_BUFFER_SIZE);
rc = -EINVAL;
goto out;
}
@ -1034,7 +1035,11 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
TRACE("Decoding type");
if ((request->type & NBD_CMD_MASK_COMMAND) == NBD_CMD_WRITE) {
command = request->type & NBD_CMD_MASK_COMMAND;
if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
req->data = qemu_blockalign(client->exp->bs, request->len);
}
if (command == NBD_CMD_WRITE) {
TRACE("Reading %u byte(s)", request->len);
if (qemu_co_recv(csock, req->data, request->len) != request->len) {