[Xen-changelog] [xen-unstable] libxenlight: implement blktap2 support

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1259578460 0
# Node ID 5b724b482f37c89a8020e347127b0fa657aea05e
# Parent  093cd0e7d537860df31cb85da5400b437fe7cb7e
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@xxxxxxxxxxxxx>
---
 tools/libxl/libxl.c        |   91 +++++++++++++++++++++++++++++++++++++++++++--
 tools/libxl/libxl_device.c |    3 -
 2 files changed, 89 insertions(+), 5 deletions(-)

diff -r 093cd0e7d537 -r 5b724b482f37 tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Mon Nov 30 10:53:39 2009 +0000
+++ b/tools/libxl/libxl.c       Mon Nov 30 10:54:20 2009 +0000
@@ -901,6 +901,44 @@ int libxl_confirm_device_model_startup(s
 
 
 
/******************************************************************************/
+
+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_c
     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_c
     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_c
             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 -r 093cd0e7d537 -r 5b724b482f37 tools/libxl/libxl_device.c
--- a/tools/libxl/libxl_device.c        Mon Nov 30 10:53:39 2009 +0000
+++ b/tools/libxl/libxl_device.c        Mon Nov 30 10:54:20 2009 +0000
@@ -119,7 +119,8 @@ char *device_disk_backend_type_of_physty
         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;
     }

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