repo writes: call posix_fadvise between fsync and close

less calls to posix_fadvise (which seem to force a write-cache sync-to-disk and
wait for that to complete) - if we call it after we synced anyway, we don't lose time.

also: fixed a bug in the os.fsync call, it needs the fileno.

attic/repository.py

@@ -555,10 +555,6 @@ class LoggedIO(object):
         header = self.header_no_crc_fmt.pack(size, TAG_PUT)
         crc = self.crc_fmt.pack(crc32(data, crc32(id, crc32(header))) & 0xffffffff)
         fd.write(b''.join((crc, header, id, data)))
-        if hasattr(os, 'posix_fadvise'):  # python >= 3.3, only on UNIX
-            # tell the OS that it does not need to cache what we just wrote,
-            # avoids spoiling the cache for the OS and other processes.
-            os.posix_fadvise(fd.fileno(), 0, 0, os.POSIX_FADV_DONTNEED)
         self.offset += size
         return self.segment, offset
 
@@ -581,6 +577,10 @@ class LoggedIO(object):
         if self._write_fd:
             self.segment += 1
             self.offset = 0
-            os.fsync(self._write_fd)
+            os.fsync(self._write_fd.fileno())
+            if hasattr(os, 'posix_fadvise'):  # python >= 3.3, only on UNIX
+                # tell the OS that it does not need to cache what we just wrote,
+                # avoids spoiling the cache for the OS and other processes.
+                os.posix_fadvise(self._write_fd.fileno(), 0, 0, os.POSIX_FADV_DONTNEED)
             self._write_fd.close()
             self._write_fd = None