[Qemu-devel] [PATCH 0/2] qemu-nbd: add --cache and --aio options

[Qemu-devel] [PATCH 0/2] qemu-nbd: add --cache and --aio options

[Paolo Bonzini]

Two simple patches that let qemu-nbd use native AIO and --cache=unsafe
mode.

Paolo Bonzini (2):
  qemu-nbd: reorganize help message
  qemu-nbd: add --cache and --aio options

 qemu-nbd.c |   75 +++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 62 insertions(+), 13 deletions(-)

-- 
1.7.10.4

[Qemu-devel] [PATCH 1/2] qemu-nbd: reorganize help message

[Paolo Bonzini]

This patch separates qemu-nbd's options in logical groups, thus making
the help message easier to read.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-nbd.c |   33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 5a0300e..1c32290 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -46,28 +46,39 @@ static int nb_fds;
 
 static void usage(const char *name)
 {
-    printf(
+    (printf) (
 "Usage: %s [OPTIONS] FILE\n"
 "QEMU Disk Network Block Device Server\n"
 "\n"
+"  -h, --help           display this help and exit\n"
+"  -V, --version        output version information and exit\n"
+"\n"
+"Connection properties:\n"
 "  -p, --port=PORT      port to listen on (default `%d')\n"
-"  -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"
-"  -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"
-"  -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"
 "  -v, --verbose        display extra debugging information\n"
-"  -h, --help           display this help and exit\n"
-"  -V, --version        output version information and exit\n"
 "\n"
-"Report bugs to <anthony@codemonkey.ws>\n"
+"Exposing part of the image:\n"
+"  -o, --offset=OFFSET  offset into the image\n"
+"  -P, --partition=NUM  only expose partition NUM\n"
+"\n"
+#ifdef __linux__
+"Kernel NBD client support:\n"
+"  -c, --connect=DEV    connect FILE to the local NBD device DEV\n"
+"  -d, --disconnect     disconnect the specified device\n"
+"\n"
+#endif
+"\n"
+"Block device options:\n"
+"  -r, --read-only      export read-only\n"
+"  -s, --snapshot       use snapshot file\n"
+"  -n, --nocache        disable host cache\n"
+"\n"
+"Report bugs to <qemu-devel@nongnu.org>\n"
     , name, NBD_DEFAULT_PORT, "DEVICE");
 }
 
-- 
1.7.10.4

[Qemu-devel] [PATCH 2/2] qemu-nbd: add --cache and --aio options

[Paolo Bonzini]

Add two options to tune the I/O implementation of qemu-nbd, matching
the possibilities given by the QEMU -drive option.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-nbd.c |   42 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 1c32290..1c1cf6a 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -33,7 +33,9 @@
 #include <libgen.h>
 #include <pthread.h>
 
-#define SOCKET_PATH    "/var/lock/qemu-nbd-%s"
+#define SOCKET_PATH         "/var/lock/qemu-nbd-%s"
+#define QEMU_NBD_OPT_CACHE  1
+#define QEMU_NBD_OPT_AIO    2
 
 static NBDExport *exp;
 static int verbose;
@@ -77,6 +79,10 @@ static void usage(const char *name)
 "  -r, --read-only      export read-only\n"
 "  -s, --snapshot       use snapshot file\n"
 "  -n, --nocache        disable host cache\n"
+"      --cache=MODE     set cache mode (none, writeback, ...)\n"
+#ifdef CONFIG_LINUX_AIO
+"      --aio=MODE       set AIO mode (native or threads)\n"
+#endif
 "\n"
 "Report bugs to <qemu-devel@nongnu.org>\n"
     , name, NBD_DEFAULT_PORT, "DEVICE");
@@ -306,6 +312,10 @@ int main(int argc, char **argv)
         { "disconnect", 0, NULL, 'd' },
         { "snapshot", 0, NULL, 's' },
         { "nocache", 0, NULL, 'n' },
+        { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
+#ifdef CONFIG_LINUX_AIO
+        { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
+#endif
         { "shared", 1, NULL, 'e' },
         { "persistent", 0, NULL, 't' },
         { "verbose", 0, NULL, 'v' },
@@ -320,6 +330,10 @@ int main(int argc, char **argv)
     int ret;
     int fd;
     int persistent = 0;
+    bool seen_cache = false;
+#ifdef CONFIG_LINUX_AIO
+    bool seen_aio = false;
+#endif
     pthread_t client_thread;
 
     /* The client thread uses SIGTERM to interrupt the server.  A signal
@@ -336,8 +350,32 @@ int main(int argc, char **argv)
             flags |= BDRV_O_SNAPSHOT;
             break;
         case 'n':
-            flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB;
+            optarg = (char *) "none";
+            /* fallthrough */
+        case QEMU_NBD_OPT_CACHE:
+            if (seen_cache) {
+                errx(EXIT_FAILURE, "-n and --cache can only be specified once");
+            }
+            seen_cache = true;
+            if (bdrv_parse_cache_flags(optarg, &flags) == -1) {
+                errx(EXIT_FAILURE, "Invalid cache mode `%s'", optarg);
+            }
             break;
+#ifdef CONFIG_LINUX_AIO
+        case QEMU_NBD_OPT_AIO:
+            if (seen_aio) {
+                errx(EXIT_FAILURE, "--aio can only be specified once");
+            }
+            seen_aio = true;
+            if (!strcmp(optarg, "native")) {
+                flags |= BDRV_O_NATIVE_AIO;
+            } else if (!strcmp(optarg, "threads")) {
+                /* this is the default */
+            } else {
+               errx(EXIT_FAILURE, "invalid aio mode `%s'", optarg);
+            }
+            break;
+#endif
         case 'b':
             bindto = optarg;
             break;
-- 
1.7.10.4