On Wed, Mar 30, 2011 at 08:05:38AM +0200, Amir Goldstein wrote: > Just wanted to clarify there are 2 differences I notice between mmap > write to a hole > and mmap write to COWed file with ENOSPC: > > 1. A "good" application can avoid mmap write to a hole. > > 2. when initiating a hole, the mkwrite callback is in used (in ext4) to > reserve disk space for delayed allocation when a page becomes writable. > with COW a page may already be writable when the flush encounters COW > with ENOSPC. that flush can even happen after the application has exited, > so the data will be dropped on the floor silently (like in ext3). ocfs2 doesn't have delayed allocation yet, so we try and fail the allocation in write_begin() right under mkwrite(). Joel -- The Graham Corollary: The longer a socially-moderated news website exists, the probability of an old Paul Graham link appearing at the top approaches certainty. http://www.jlbec.org/ jlbec@xxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
