[blktap] Fix block device getsize bug in qcow when backing_filename is a block device.

diff --git a/tools/blktap/drivers/block-qcow.c b/tools/blktap/drivers/block-qcow.c
index d89cbcfc02bce2a0731b665e566adc8e064f55f6..d1c8777a2ce3a48d4cad3519b70badc61df74797 100644 (file)
--- a/tools/blktap/drivers/block-qcow.c
+++ b/tools/blktap/drivers/block-qcow.c
@@ -237,6 +237,25 @@ static uint32_t gen_cksum(char *ptr, int len)
        return ret;
 }
 
+static int get_filesize(char *filename, uint64_t *size, struct stat *st)
+{
+       int blockfd;
+
+       /*Set to the backing file size*/
+       if(S_ISBLK(st->st_mode)) {
+               blockfd = open(filename, O_RDONLY);
+               if (blockfd < 0)
+                       return -1;
+               if (ioctl(blockfd,BLKGETSIZE,size)!=0) {
+                       printf("Unable to get Block device size\n");
+                       close(blockfd);
+                       return -1;
+               }
+               close(blockfd);
+       } else *size = (st->st_size >> SECTOR_SHIFT);   
+       return 0;
+}
+
 static int qcow_set_key(struct td_state *bs, const char *key)
 {
        struct tdqcow_state *s = (struct tdqcow_state *)bs->private;
@@ -1204,12 +1223,14 @@ int qcow_create(const char *filename, uint64_t total_size,
                        header_size += backing_filename_len;
                        
                        /*Set to the backing file size*/
-                       size = (st.st_size >> SECTOR_SHIFT);
+                       if(get_filesize(backing_filename, &size, &st)) {
+                               return -1;
+                       }
                        DPRINTF("Backing file size detected: %lld sectors" 
                                "(total %lld [%lld MB])\n", 
-                               (long long)total_size, 
-                               (long long)(total_size << SECTOR_SHIFT), 
-                               (long long)(total_size >> 11));
+                               (long long)size, 
+                               (long long)(size << SECTOR_SHIFT), 
+                               (long long)(size >> 11));
                } else {
                        backing_file = NULL;
                        DPRINTF("Setting file size: %lld (total %lld)\n",