block: allow resizing of images residing on host devices

Allow to resize images that reside on host devices up to the available
space.  This allows to grow images after resizing the device manually or
vice versa.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/raw-posix.c

@@ -649,10 +649,24 @@ static void raw_close(BlockDriverState *bs)
 static int raw_truncate(BlockDriverState *bs, int64_t offset)
 {
     BDRVRawState *s = bs->opaque;
-    if (s->type != FTYPE_FILE)
-        return -ENOTSUP;
-    if (ftruncate(s->fd, offset) < 0)
+    struct stat st;
+
+    if (fstat(s->fd, &st)) {
         return -errno;
+    }
+
+    if (S_ISREG(st.st_mode)) {
+        if (ftruncate(s->fd, offset) < 0) {
+            return -errno;
+        }
+    } else if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode)) {
+       if (offset > raw_getlength(bs)) {
+           return -EINVAL;
+       }
+    } else {
+        return -ENOTSUP;
+    }
+
     return 0;
 }
 
@@ -1178,6 +1192,7 @@ static BlockDriver bdrv_host_device = {
 
     .bdrv_read          = raw_read,
     .bdrv_write         = raw_write,
+    .bdrv_truncate      = raw_truncate,
     .bdrv_getlength	= raw_getlength,
     .bdrv_get_allocated_file_size
                         = raw_get_allocated_file_size,
@@ -1299,6 +1314,7 @@ static BlockDriver bdrv_host_floppy = {
 
     .bdrv_read          = raw_read,
     .bdrv_write         = raw_write,
+    .bdrv_truncate      = raw_truncate,
     .bdrv_getlength	= raw_getlength,
     .bdrv_get_allocated_file_size
                         = raw_get_allocated_file_size,
@@ -1400,6 +1416,7 @@ static BlockDriver bdrv_host_cdrom = {
 
     .bdrv_read          = raw_read,
     .bdrv_write         = raw_write,
+    .bdrv_truncate      = raw_truncate,
     .bdrv_getlength     = raw_getlength,
     .bdrv_get_allocated_file_size
                         = raw_get_allocated_file_size,
@@ -1521,6 +1538,7 @@ static BlockDriver bdrv_host_cdrom = {
 
     .bdrv_read          = raw_read,
     .bdrv_write         = raw_write,
+    .bdrv_truncate      = raw_truncate,
     .bdrv_getlength     = raw_getlength,
     .bdrv_get_allocated_file_size
                         = raw_get_allocated_file_size,