From: Andrew Morton <akpm@zip.com.au> To: "Stephen C. Tweedie" <sct@redhat.com> Subject: Re: synchronous mounts Date: Thu, 15 Nov 2001 14:02:54 -0800 Cc: lkml <linux-kernel@vger.kernel.org>, Neil Brown <neilb@cse.unsw.edu.au> "Stephen C. Tweedie" wrote: > > Hi, > > On Thu, Nov 15, 2001 at 12:03:57AM -0800, Andrew Morton wrote: > > Linux is not syncing write() data for files on synchronously mounted > > filesystems, and it isn't syncing write() data for ext2/3 files which > > are operating under `chattr +S'. > > In the past, chattr +S and mount -o sync always resulted in sync > metadata with no guarantees about data. > > I'm not sure this makes much sense, but it's what has always happened. > For directories, the behaviour is fine, in particular as it gives us > the same directory sync consistency semantics as synchronous BSD UFS. > > It's not clear to me that chattr/mount sync options make _any_ sense > for regular file metadata. Rather than tightening up the semantics, > I'd actually prefer to restrict them so that they only apply to > directories. Users who set the sync bits are usually doing so for > applications like MTAs where it's directory syncing which is > what matters: the apps typically fsync the files themselves, anyway. > OK, that makes sense. Thanks. The `mount' and `chattr' manpages need updating... So shall we try to nail this down? Synchronous mounts and chattr +S provide synchronous semantics for directory contents, diretory metadata and directory inodes only. And fsync() will write out a file's data, metadata and inode? If this is correct then there are a few places where ext2 is syncing stuff unnecessarily - file indirect blocks, etc. Not very important at this stage I guess. - - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/