On Fri, 12 Oct 2007 16:39:27 -0400 Chris Mason <chris.mason@xxxxxxxxxx> wrote: > Hello everyone, > > The test below creates a sparse file and then fills a hole with > O_DIRECT. As far as I can tell from reading generic_osync_inode, the > filesystem metadata is only forced to disk if i_size changes during the > file write. I've tested ext3, xfs and reiserfs and they all skip the > commit when filling holes. > > I would argue that filling holes via O_DIRECT is supposed to commit the > metadata required to find those file blocks later. At least on ext3, > O_SYNC does force a commit on fill holes (haven't tested others). > > So, is the current behavior a bug or a feature? I don't think it's a bug. Sure, O_DIRECT is synchronous, but that's because it is, err, direct. Not because it provides extra data-integrity guarantees. If you want those guarantees, use O_SYNC as well. > dd if=/dev/zero of=foo bs=1M seek=1 count=1 oflag=direct > > hexdump foo | head -n 2 > 0000000 62b1 ea2d 73e8 c64f f5ef 1af5 dd09 8ccd > 0000010 75ec 9581 e0ea ae9b e28f b76d a700 4d5b > > dd if=/dev/urandom of=foo bs=4k count=1 conv=notrunc oflag=direct > reboot -nf > > (after reboot) > > hexdump foo > 0000000 0000 0000 0000 0000 0000 0000 0000 0000 > * > 0200000 > > -chris > - 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
