On Wed, Jun 27, 2007 at 09:18:04AM +1000, David Chinner wrote: > 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. Since XFS also does not free preallocated space on error and this behavior is inline with dd, posix_fallocate() and the current ext4 implementation, do we still need FA_FL_FREE_ENOSPC flag ? > > 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. Will the FA_MKSWAP mode still be required with your suggested change of teaching do_mpage_readpage() about unwritten extents being in place ? Or, will you still like to have FA_MKSWAP mode ? -- Regards, Amit Arora - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
