On Tue, Jun 26, 2007 at 11:34:13AM -0400, Andreas Dilger wrote: > On Jun 26, 2007 16:02 +0530, Amit K. Arora wrote: > > On Mon, Jun 25, 2007 at 03:46:26PM -0600, Andreas Dilger wrote: > > > Can you clarify - what is the current behaviour when ENOSPC (or some other > > > error) is hit? Does it keep the current fallocate() or does it free it? > > > > Currently it is left on the file system implementation. In ext4, we do > > not undo preallocation if some error (say, ENOSPC) is hit. Hence it may > > end up with partial (pre)allocation. This is inline with dd and > > posix_fallocate, which also do not free the partially allocated space. > > Since I believe the XFS allocation ioctls do it the opposite way (free > preallocated space on error) this should be encoded into the flags. > Having it "filesystem dependent" just means that nobody will be happy. No, XFs does not free preallocated space on error. it is up to the application to clean up. > What I mean is that any data read from the file should have the "appearance" > of being zeroed (whether zeroes are actually written to disk or not). What > I _think_ David is proposing is to allow fallocate() to return without > marking the blocks even "uninitialized" and subsequent reads would return > the old data from the disk. Correct, but for swap files that's not an issue - no user should be able too read them, and FA_MKSWAP would really need root privileges to execute. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - 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
