Re: [PATCH 3/3] ext4: Use separate super_operations structure for no_journal filesystems

[Theodore Tso <tytso@mit.edu>]

On Fri, May 01, 2009 at 03:04:22AM -0400, Christoph Hellwig wrote:
> On Fri, May 01, 2009 at 12:37:17AM -0400, Theodore Ts'o wrote:
> > By using a separate super_operations structure for filesystems that
> > have and don't have journals, we can simply ext4_write_super() ---
> > which is only needed when no journal is present --- and ext4_freeze(),
> > ext4_unfreeze(), and ext4_sync_fs(), which are only needed when the
> > journal is present.
> 
> FYI: I will make ->sync_fs mandatory pretty soon.  At that point
> ->write_super will only be left for d_dirt-induced periodic writeback.
> (Still have to figure out what to do about file_fsync, but that won't
> affect ext4)

So I'm guessing your plans are to have sys_sync() no longer call
write_super(), but to only call sync_fs()?  If that's the case, I
think all we need to do is set ext4_nojournal_sops.sync_fs to be
ext4_commit_super.

I assume the idea is so that the filesystem can distinguish between
periodic s_dirt writeback versus a request to write the superblock
caused by an explicit fsync or sync system call?

						- Ted