wic: if we can't get from ioctl, try from os.stat()

Under some conditions, ioctl FIGETBSZ can't return real value.
We can try to use fallback via os.stat() to get block size.

Source of patch:
https://github.com/intel/bmap-tools/commit/17365f4fe9089df7ee9800a2a0ced177ec4798a4

Signed-off-by: Dogukan Ergun <dogukan.ergun@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 77e32b9addbda4259eeec55127a05e200d4b776c..a72fa09ef5503a414dd6a366c268deda24f2cf0c 100644 (file)
--- a/scripts/lib/wic/filemap.py
+++ b/scripts/lib/wic/filemap.py
@@ -37,7 +37,15 @@ def get_block_size(file_obj):
     # Get the block size of the host file-system for the image file by calling
     # the FIGETBSZ ioctl (number 2).
     binary_data = fcntl.ioctl(file_obj, 2, struct.pack('I', 0))
-    return struct.unpack('I', binary_data)[0]
+    bsize = struct.unpack('I', binary_data)[0]
+    if not bsize:
+        import os
+        stat = os.fstat(file_obj.fileno())
+        if hasattr(stat, 'st_blksize'):
+            bsize = stat.st_blksize
+        else:
+            raise IOError("Unable to determine block size")
+    return bsize
 
 class ErrorNotSupp(Exception):
     """