On Mon, 26 May 2008 06:07:51 -0400 Theodore Tso <tytso@xxxxxxx> wrote: > On Mon, May 26, 2008 at 12:05:06AM -0700, Andrew Morton wrote: > > It's purportedly showing that fdatasync() on ext3 is syncing the whole > > world in fsync()-fashion even with an application which does not grow > > the file size. > > > > But fdatasync() shouldn't do that. Even if the inode is dirty from > > atime or mtime updates, that shouldn't cause fdatasync() to run an > > ext3 commit? > > Well, ideally it shouldn't, although POSIX allows fdatasync() to be > implemented in terms of fsync(). It is at the moment. :-/ Well.. > The problem is we don't currently have a way of distinguishing between > a "smudged" inode (only the mtime/atime has changed) and a "dirty" > inode (even if the number of blocks hasn't changed, if i_size has > changed, or i_mode, or anything else, including extended attributes > inline in the inode). Who do you mena by "we"? ext3 or the kernel as a whole? > We're not tracking that difference. If we only > allow mtime/atime changes through setattr (see Cristoph's patches), > and don't set the VFS dirty bit, but our own "smudged" bit, we could > do it --- but at the moment, we're not. But the VFS _does_ track these things, via the eternally incomprehensible I_DIRTY_SYNC and I_DIRTY_DATASYNC. We have: if (datasync && !(inode->i_state & I_DIRTY_DATASYNC)) goto out; which _should_ cause the fs to skip the commit during fdatasync() if only mtime and ctime have changed? -- 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
