raw-posix: Fix test for host CD-ROM

raw_pread_aligned() retries up to two times if the block device backs
a virtual CD-ROM (a drive with media=cdrom and if=ide, scsi, xen or
none).  This makes no sense.  Whether retrying reads can correct read
errors can only depend on what we're reading, not on how the result
gets used.  We need to check what whether we're reading from a
physical CD-ROM or floppy here.

I doubt retrying is useful even then.  Left for another day.

Impact:

* Virtual CD-ROM backed by host_cdrom behaves the same.

* Virtual CD-ROM backed by file or host_device no longer retries.

* A drive backed by host_cdrom now retries even if it's not a virtual
  CD-ROM.

* Any drive backed by host_floppy now retries.

While there, clean up gratuitous use of goto.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/raw-posix.c

@@ -242,15 +242,14 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset,
 
     ret = pread(s->fd, buf, count, offset);
     if (ret == count)
-        goto label__raw_read__success;
+        return ret;
 
     /* Allow reads beyond the end (needed for pwrite) */
     if ((ret == 0) && bs->growable) {
         int64_t size = raw_getlength(bs);
         if (offset >= size) {
             memset(buf, 0, count);
-            ret = count;
-            goto label__raw_read__success;
+            return count;
         }
     }
 
@@ -260,13 +259,13 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset,
                       bs->total_sectors, ret, errno, strerror(errno));
 
     /* Try harder for CDrom. */
-    if (bs->type == BDRV_TYPE_CDROM) {
+    if (s->type != FTYPE_FILE) {
         ret = pread(s->fd, buf, count, offset);
         if (ret == count)
-            goto label__raw_read__success;
+            return ret;
         ret = pread(s->fd, buf, count, offset);
         if (ret == count)
-            goto label__raw_read__success;
+            return ret;
 
         DEBUG_BLOCK_PRINT("raw_pread(%d:%s, %" PRId64 ", %p, %d) [%" PRId64
                           "] retry read failed %d : %d = %s\n",
@@ -274,8 +273,6 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset,
                           bs->total_sectors, ret, errno, strerror(errno));
     }
 
-label__raw_read__success:
-
     return  (ret < 0) ? -errno : ret;
 }
 
@@ -298,15 +295,13 @@ static int raw_pwrite_aligned(BlockDriverState *bs, int64_t offset,
 
     ret = pwrite(s->fd, buf, count, offset);
     if (ret == count)
-        goto label__raw_write__success;
+        return ret;
 
     DEBUG_BLOCK_PRINT("raw_pwrite(%d:%s, %" PRId64 ", %p, %d) [%" PRId64
                       "] write failed %d : %d = %s\n",
                       s->fd, bs->filename, offset, buf, count,
                       bs->total_sectors, ret, errno, strerror(errno));
 
-label__raw_write__success:
-
     return  (ret < 0) ? -errno : ret;
 }