From 80bad981f884d1b08b8ec038511ddffdb060d60c Mon Sep 17 00:00:00 2001
From: Roger Pau Monne <roger.pau@citrix.com>
Date: Fri, 26 Feb 2016 10:53:21 +0100
Subject: [PATCH 5/8] libxl: properly use vdev vs local device
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The current code in libxl assumed that vdev is equal to local device, but
this is only true for Linux systems. In other OSes the local device can use
a nomenclature completely different from the virtual device one.

Move the current libxl__devid_to_localdev Linux implementation out of the
OS-specific file and rename it to libxl__devid_to_vdev, and then make sure
local_device_attach_cb return the local device in the diskpath field.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
---
 tools/libxl/libxl.c          | 12 ++++------
 tools/libxl/libxl_device.c   | 57 ++++++++++++++++++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h |  1 +
 tools/libxl/libxl_linux.c    | 49 +------------------------------------
 4 files changed, 64 insertions(+), 55 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 069d5bd..cbe1608 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -3024,7 +3024,7 @@ static char * libxl__alloc_vdev(libxl__gc *gc, void *get_vdev_user,
                     libxl__sprintf(gc, "%s/device/vbd/%d/backend",
                         dompath, devid)) == NULL) {
             if (errno == ENOENT)
-                return libxl__devid_to_localdev(gc, devid);
+                return libxl__devid_to_vdev(gc, devid);
             else
                 return NULL;
         }
@@ -3125,7 +3125,7 @@ static void local_device_attach_cb(libxl__egc *egc, libxl__ao_device *aodev)
 {
     STATE_AO_GC(aodev->ao);
     libxl__disk_local_state *dls = CONTAINER_OF(aodev, *dls, aodev);
-    char *dev = NULL, *be_path = NULL;
+    char *be_path = NULL;
     int rc;
     libxl__device device;
     libxl_device_disk *disk = &dls->disk;
@@ -3139,9 +3139,6 @@ static void local_device_attach_cb(libxl__egc *egc, libxl__ao_device *aodev)
         goto out;
     }
 
-    dev = GCSPRINTF("/dev/%s", disk->vdev);
-    LOG(DEBUG, "locally attaching qdisk %s", dev);
-
     rc = libxl__device_from_disk(gc, LIBXL_TOOLSTACK_DOMID, disk, &device);
     if (rc < 0)
         goto out;
@@ -3150,8 +3147,9 @@ static void local_device_attach_cb(libxl__egc *egc, libxl__ao_device *aodev)
     if (rc < 0)
         goto out;
 
-    if (dev != NULL)
-        dls->diskpath = libxl__strdup(gc, dev);
+    dls->diskpath = GCSPRINTF("/dev/%s",
+                              libxl__devid_to_localdev(gc, device.devid));
+    LOG(DEBUG, "locally attached disk %s", dls->diskpath);
 
     dls->callback(egc, dls, 0);
     return;
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 4b51ded..82e86c0 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -434,6 +434,63 @@ int libxl__device_disk_dev_number(const char *virtpath, int *pdisk,
     return -1;
 }
 
+static char *encode_disk_name(char *ptr, unsigned int n)
+{
+    if (n >= 26)
+        ptr = encode_disk_name(ptr, n / 26 - 1);
+    *ptr = 'a' + n % 26;
+    return ptr + 1;
+}
+
+char *libxl__devid_to_vdev(libxl__gc *gc, int devid)
+{
+    unsigned int minor;
+    int offset;
+    int nr_parts;
+    char *ptr = NULL;
+/* Same as in Linux.
+ * encode_disk_name might end up using up to 29 bytes (BUFFER_SIZE - 3)
+ * including the trailing \0.
+ *
+ * The code is safe because 26 raised to the power of 28 (that is the
+ * maximum offset that can be stored in the allocated buffer as a
+ * string) is far greater than UINT_MAX on 64 bits so offset cannot be
+ * big enough to exhaust the available bytes in ret. */
+#define BUFFER_SIZE 32
+    char *ret = libxl__zalloc(gc, BUFFER_SIZE);
+
+#define EXT_SHIFT 28
+#define EXTENDED (1<<EXT_SHIFT)
+#define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
+#define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
+/* the size of the buffer to store the device name is 32 bytes to match the
+ * equivalent buffer in the Linux kernel code */
+
+    if (!VDEV_IS_EXTENDED(devid)) {
+        minor = devid & 0xff;
+        nr_parts = 16;
+    } else {
+        minor = BLKIF_MINOR_EXT(devid);
+        nr_parts = 256;
+    }
+    offset = minor / nr_parts;
+
+    strcpy(ret, "xvd");
+    ptr = encode_disk_name(ret + 3, offset);
+    if (minor % nr_parts == 0)
+        *ptr = 0;
+    else
+        /* overflow cannot happen, thanks to the upper bound */
+        snprintf(ptr, ret + 32 - ptr,
+                "%d", minor & (nr_parts - 1));
+    return ret;
+#undef BUFFER_SIZE
+#undef EXT_SHIFT
+#undef EXTENDED
+#undef VDEV_IS_EXTENDED
+#undef BLKIF_MINOR_EXT
+}
+
 /* Device AO operations */
 
 void libxl__prepare_ao_device(libxl__ao *ao, libxl__ao_device *aodev)
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 17e6139..d35d49f 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1048,6 +1048,7 @@ _hidden int libxl__device_disk_set_backend(libxl__gc*, libxl_device_disk*);
 _hidden int libxl__device_physdisk_major_minor(const char *physpath, int *major, int *minor);
 _hidden int libxl__device_disk_dev_number(const char *virtpath,
                                           int *pdisk, int *ppartition);
+_hidden char *libxl__devid_to_vdev(libxl__gc *gc, int devid);
 
 _hidden int libxl__device_console_add(libxl__gc *gc, uint32_t domid,
                                       libxl__device_console *console,
diff --git a/tools/libxl/libxl_linux.c b/tools/libxl/libxl_linux.c
index 02046fe..bd1d040 100644
--- a/tools/libxl/libxl_linux.c
+++ b/tools/libxl/libxl_linux.c
@@ -26,56 +26,9 @@ int libxl__try_phy_backend(mode_t st_mode)
     return 1;
 }
 
-#define EXT_SHIFT 28
-#define EXTENDED (1<<EXT_SHIFT)
-#define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
-#define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
-/* the size of the buffer to store the device name is 32 bytes to match the
- * equivalent buffer in the Linux kernel code */
-#define BUFFER_SIZE 32
-
-/* Same as in Linux.
- * encode_disk_name might end up using up to 29 bytes (BUFFER_SIZE - 3)
- * including the trailing \0.
- *
- * The code is safe because 26 raised to the power of 28 (that is the
- * maximum offset that can be stored in the allocated buffer as a
- * string) is far greater than UINT_MAX on 64 bits so offset cannot be
- * big enough to exhaust the available bytes in ret. */
-static char *encode_disk_name(char *ptr, unsigned int n)
-{
-    if (n >= 26)
-        ptr = encode_disk_name(ptr, n / 26 - 1);
-    *ptr = 'a' + n % 26;
-    return ptr + 1;
-}
-
 char *libxl__devid_to_localdev(libxl__gc *gc, int devid)
 {
-    unsigned int minor;
-    int offset;
-    int nr_parts;
-    char *ptr = NULL;
-    char *ret = libxl__zalloc(gc, BUFFER_SIZE);
-
-    if (!VDEV_IS_EXTENDED(devid)) {
-        minor = devid & 0xff;
-        nr_parts = 16;
-    } else {
-        minor = BLKIF_MINOR_EXT(devid);
-        nr_parts = 256;
-    }
-    offset = minor / nr_parts;
-
-    strcpy(ret, "xvd");
-    ptr = encode_disk_name(ret + 3, offset);
-    if (minor % nr_parts == 0)
-        *ptr = 0;
-    else
-        /* overflow cannot happen, thanks to the upper bound */
-        snprintf(ptr, ret + 32 - ptr,
-                "%d", minor & (nr_parts - 1));
-    return ret;
+    return libxl__devid_to_vdev(gc, devid);
 }
 
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