raw-posix: improve detection of scsi-generic devices

Allow symbolic links which point to /dev/sgX devices.
Signed-off-by: NBernhard Kohl <bernhard.kohl@nsn.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/raw-posix.c

@@ -48,6 +48,7 @@
 #endif
 #ifdef __linux__
 #include <sys/ioctl.h>
+#include <sys/param.h>
 #include <linux/cdrom.h>
 #include <linux/fd.h>
 #endif
@@ -868,8 +869,13 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
 
     s->type = FTYPE_FILE;
 #if defined(__linux__)
-    if (strstart(filename, "/dev/sg", NULL)) {
-        bs->sg = 1;
+    {
+        char resolved_path[ MAXPATHLEN ], *temp;
+
+        temp = realpath(filename, resolved_path);
+        if (temp && strstart(temp, "/dev/sg", NULL)) {
+            bs->sg = 1;
+        }
     }
 #endif