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Re: [Qemu-devel] [PATCH][resend] Add -f option to qemu-nbd
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PATCH][resend] Add -f option to qemu-nbd |
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Date: |
Wed, 18 Jan 2012 11:51:31 +0100 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111222 Thunderbird/9.0 |
On 01/18/2012 09:48 AM, Chunyan Liu wrote:
Stefan, could you help commit it if it's OK? Thanks.
Same as in thread:
http://lists.gnu.org/archive/html/qemu-devel/2011-12/msg01083.html
but rebase it to latest code.
Add -f option to qemu-nbd to find a free nbd device for user and connect
disk image to that device.
Hi Chunyan,
I'm now the NBD maintainer so I can take care of the patch. There are
still a couple of nits.
The main problem is that the device name is never printed, which
requires some imagination on part of the user. :)
This pretty much requires that you set "verbose = 1" together with -f.
This disables daemonization, unfortunately, but there isn't really any
better way to do so. I'm inclined towards removing daemonization
altogether from 1.1; other opinions are welcome.
Anyhow, please set "verbose = 1" and change the help text for -c/-v from
" -c, --connect=DEV connect FILE to the local NBD device DEV\n"
" -v, --verbose display extra debugging information\n"
to
" -c, --connect=DEV connect FILE to the local NBD device DEV\n"
" and run in the background\n"
" -v, --verbose with -c, display extra information and\n"
" do not run in the background\n"
Since a respin is required, there are a couple of other comments inline.
syntax: qemu-nbd -f disk.img
---
qemu-nbd.c | 76 ++++++++++++++++++++++++++++++++++++++++++-----------------
1 files changed, 54 insertions(+), 22 deletions(-)
diff --git a/qemu-nbd.c b/qemu-nbd.c
index eb61c33..f4c1437 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -33,7 +33,7 @@
#include<libgen.h>
#include<pthread.h>
-#define SOCKET_PATH "/var/lock/qemu-nbd-%s"
+#define SOCKET_PATH "/var/lock/qemu-nbd-%d"
static NBDExport *exp;
static int verbose;
@@ -55,12 +55,13 @@ static void usage(const char *name)
" -o, --offset=OFFSET offset into the image\n"
" -b, --bind=IFACE interface to bind to (default `0.0.0.0')\n"
" -k, --socket=PATH path to the unix socket\n"
-" (default '"SOCKET_PATH"')\n"
+" (default /var/lock/qemu-nbd-PID)\n"
" -r, --read-only export read-only\n"
" -P, --partition=NUM only expose partition NUM\n"
" -s, --snapshot use snapshot file\n"
" -n, --nocache disable host cache\n"
" -c, --connect=DEV connect FILE to the local NBD device DEV\n"
+" -f, --find find a free NBD device and connect FILE to it\n"
" -d, --disconnect disconnect the specified device\n"
" -e, --shared=NUM device can be shared by NUM clients (default '1')\n"
" -t, --persistent don't exit on the last connection\n"
@@ -69,7 +70,7 @@ static void usage(const char *name)
" -V, --version output version information and exit\n"
"\n"
"Report bugs to<address@hidden>\n"
- , name, NBD_DEFAULT_PORT, "DEVICE");
+ , name, NBD_DEFAULT_PORT);
}
static void version(const char *name)
@@ -194,7 +195,8 @@ static void *show_parts(void *arg)
static void *nbd_client_thread(void *arg)
{
- int fd = *(int *)arg;
+ int fd = -1;
+ int find = *(int *)arg;
off_t size;
size_t blocksize;
uint32_t nbdflags;
@@ -213,9 +215,42 @@ static void *nbd_client_thread(void *arg)
goto out;
}
- ret = nbd_init(fd, sock, nbdflags, size, blocksize);
- if (ret == -1) {
- goto out;
+ if (!find) {
+ fd = open(device, O_RDWR);
+ if (fd == -1) {
+ fprintf(stderr, "Failed to open %s\n", device);
+ goto out;
+ }
+
+ ret = nbd_init(fd, sock, nbdflags, size, blocksize);
+ if (ret == -1) {
+ goto out;
+ }
+ } else {
+ int i = 0;
+ int max_nbd = 16;
+ device = g_malloc(64);
+
+ for (i = 0; i< max_nbd; i++) {
+ snprintf(device, 64, "/dev/nbd%d", i);
+ fd = open(device, O_RDWR);
+ if (fd == -1) {
+ continue;
+ }
+
+ if (nbd_init(fd, sock, nbdflags, size, blocksize) == -1) {
+ close(fd);
+ continue;
+ }
+
+ break;
+ }
+
+ if (i>= max_nbd) {
+ fprintf(stderr, "Fail to find a free nbd device\n");
+ g_free(device);
+ goto out;
Just use errx(EXIT_FAILURE, "Could not find a free NBD device.") here.
+ }
}
/* update partition table */
@@ -275,7 +310,7 @@ int main(int argc, char **argv)
const char *bindto = "0.0.0.0";
int port = NBD_DEFAULT_PORT;
off_t fd_size;
- const char *sopt = "hVb:o:p:rsnP:c:dvk:e:t";
+ const char *sopt = "hVb:o:p:rsnP:c:dvk:e:tf";
struct option lopt[] = {
{ "help", 0, NULL, 'h' },
{ "version", 0, NULL, 'V' },
@@ -292,6 +327,7 @@ int main(int argc, char **argv)
{ "shared", 1, NULL, 'e' },
{ "persistent", 0, NULL, 't' },
{ "verbose", 0, NULL, 'v' },
+ { "find", 0, NULL, 'f'},
{ NULL, 0, NULL, 0 }
};
int ch;
@@ -303,6 +339,7 @@ int main(int argc, char **argv)
int ret;
int fd;
int persistent = 0;
+ int find = 0;
pthread_t client_thread;
/* The client thread uses SIGTERM to interrupt the server. A signal
@@ -380,6 +417,9 @@ int main(int argc, char **argv)
case 'v':
verbose = 1;
break;
+ case 'f':
+ find = 1;
+ break;
case 'V':
version(argv[0]);
exit(0);
@@ -414,7 +454,7 @@ int main(int argc, char **argv)
return 0;
}
Please give an error here if "device && find" ("The -f option is
incompatible with -c").
- if (device&& !verbose) {
+ if ((device || find)&& !verbose) {
int stderr_fd[2];
pid_t pid;
int ret;
@@ -466,18 +506,10 @@ int main(int argc, char **argv)
}
}
- if (device) {
- /* Open before spawning new threads. In the future, we may
- * drop privileges after opening.
- */
- fd = open(device, O_RDWR);
- if (fd == -1) {
- err(EXIT_FAILURE, "Failed to open %s", device);
- }
-
+ if (device || find) {
if (sockpath == NULL) {
sockpath = g_malloc(128);
- snprintf(sockpath, 128, SOCKET_PATH, basename(device));
+ snprintf(sockpath, 128, SOCKET_PATH, getpid());
}
}
@@ -510,10 +542,10 @@ int main(int argc, char **argv)
return 1;
}
- if (device) {
+ if (device || find) {
int ret;
- ret = pthread_create(&client_thread, NULL, nbd_client_thread,&fd);
+ ret = pthread_create(&client_thread, NULL, nbd_client_thread,&find);
Just pass NULL here and test "device != NULL" in the nbd_client_thread.
if (ret != 0) {
errx(EXIT_FAILURE, "Failed to create client thread: %s",
strerror(ret));
@@ -536,7 +568,7 @@ int main(int argc, char **argv)
unlink(sockpath);
}
- if (device) {
+ if (device || find) {
void *ret;
pthread_join(client_thread,&ret);
exit(ret != NULL);
Thanks,
Paolo