libxenlight: implement blktap2 support

This patch implements blktap2 support in libxenlight; blktap2 is only
enabled if it is actually supported by the host, otherwise we fall
back to the previous code. Also for the moment we pretend that disk
type file is actually tap:aio.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 3e7711cbca3d02a28f332a8703fa5c2abc419b61..904b93f9f08ae8dc85c38c50e0315d07290506b8 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -901,6 +901,44 @@ int libxl_confirm_device_model_startup(struct libxl_ctx *ctx,
 
 
 /******************************************************************************/
+
+static int is_blktap2_supported(void)
+{
+    char buf[1024];
+    FILE *f = fopen("/proc/devices", "r");
+
+    
+    while (fgets(buf, sizeof(buf), f) != NULL) {
+        if (strstr(buf, "blktap2")) {
+            fclose(f);
+            return 1;
+        }
+    }
+    fclose(f);
+    return 0;
+}
+
+static char *get_blktap2_device(struct libxl_ctx *ctx, char *name, char *type)
+{
+    char buf[1024];
+    char *p;
+    int devnum;
+    FILE *f = fopen("/sys/class/blktap2/devices", "r");
+
+    
+    while (!feof(f)) {
+        fscanf(f, "%d %s", &devnum, buf);
+        p = strchr(buf, ':');
+        p++;
+        if (!strcmp(p, name) && !strncmp(buf, type, 3)) {
+            fclose(f);
+            return libxl_sprintf(ctx, "/dev/xen/blktap-2/tapdev%d", devnum);
+        }
+    }
+    fclose(f);
+    return NULL;
+}
+
 int libxl_device_disk_add(struct libxl_ctx *ctx, uint32_t domid, libxl_device_disk *disk)
 {
     flexarray_t *front;
@@ -910,6 +948,7 @@ int libxl_device_disk_add(struct libxl_ctx *ctx, uint32_t domid, libxl_device_di
     unsigned int foffset = 0;
     int devid;
     libxl_device device;
+    int major, minor;
 
     front = flexarray_make(16, 1);
     if (!front)
@@ -928,11 +967,7 @@ int libxl_device_disk_add(struct libxl_ctx *ctx, uint32_t domid, libxl_device_di
     device.kind = DEVICE_VBD;
 
     switch (disk->phystype) {
-        case PHYSTYPE_FILE:
-            return ERROR_NI; /* FIXME */
-            break;
         case PHYSTYPE_PHY: {
-            int major, minor;
 
             device_physdisk_major_minor(disk->physpath, &major, &minor);
             flexarray_set(back, boffset++, "physical-device");
@@ -944,7 +979,55 @@ int libxl_device_disk_add(struct libxl_ctx *ctx, uint32_t domid, libxl_device_di
             device.backend_kind = DEVICE_VBD;
             break;
         }
+        case PHYSTYPE_FILE:
+            /* let's pretend is tap:aio for the moment */
+            disk->phystype = PHYSTYPE_AIO;
         case PHYSTYPE_AIO: case PHYSTYPE_QCOW: case PHYSTYPE_QCOW2: case PHYSTYPE_VHD:
+            if (is_blktap2_supported()) {
+                int rc, c, p[2], tot;
+                char buf[1024], *dev;
+                if ((dev = get_blktap2_device(ctx, disk->physpath, device_disk_string_of_phystype(disk->phystype))) == NULL) {
+                    if (pipe(p) < 0) {
+                        XL_LOG(ctx, XL_LOG_ERROR, "Failed to create a pipe");
+                        return -1;
+                    }
+                    rc = fork();
+                    if (rc < 0) {
+                        XL_LOG(ctx, XL_LOG_ERROR, "Failed to fork a new process");
+                        return -1;
+                    } else if (!rc) { /* child */
+                        int null_r, null_w;
+                        char *args[4];
+                        args[0] = "tapdisk2";
+                        args[1] = "-n";
+                        args[2] = libxl_sprintf(ctx, "%s:%s", device_disk_string_of_phystype(disk->phystype), disk->physpath);
+                        args[3] = NULL;
+
+                        null_r = open("/dev/null", O_RDONLY);
+                        null_w = open("/dev/null", O_WRONLY);
+                        libxl_exec(ctx, null_r, p[1], null_w, "/usr/sbin/tapdisk2", args);
+                        XL_LOG(ctx, XL_LOG_ERROR, "Error execing tapdisk2");
+                    }
+                    close(p[1]);
+                    tot = 0;
+                    while ((c = read(p[0], buf + tot, sizeof(buf) - tot)) > 0)
+                        tot = tot + c;
+                    close(p[0]);
+                    buf[tot - 1] = '\0';
+                    dev = buf;
+                }
+                flexarray_set(back, boffset++, "tapdisk-params");
+                flexarray_set(back, boffset++, libxl_sprintf(ctx, "%s:%s", device_disk_string_of_phystype(disk->phystype), disk->physpath));
+                flexarray_set(back, boffset++, "params");
+                flexarray_set(back, boffset++, libxl_sprintf(ctx, "%s", dev));
+                backend_type = "phy";
+                device_physdisk_major_minor(dev, &major, &minor);
+                flexarray_set(back, boffset++, "physical-device");
+                flexarray_set(back, boffset++, libxl_sprintf(ctx, "%x:%x", major, minor));
+                device.backend_kind = DEVICE_VBD;
+
+                break;
+            }
             flexarray_set(back, boffset++, "params");
             flexarray_set(back, boffset++, libxl_sprintf(ctx, "%s:%s",
                           device_disk_string_of_phystype(disk->phystype), disk->physpath));

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 076694decc33fc36be152a475a176b91cd988399..13ef9bde48b01c8f30d8cd80b961f23d89726b5d 100644 (file)
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -119,7 +119,8 @@ char *device_disk_backend_type_of_phystype(libxl_disk_phystype phystype)
         case PHYSTYPE_QCOW: return "tap";
         case PHYSTYPE_VHD: return "tap";
         case PHYSTYPE_AIO: return "tap";
-        case PHYSTYPE_FILE: return "file";
+        /* let's pretend file is tap:aio */
+        case PHYSTYPE_FILE: return "tap";
         case PHYSTYPE_PHY: return "phy";
         default: return NULL;
     }