Re: [RFC] write_super is for syncing

[Andrew Morton]

Chris Mason wrote:
> 
> Hi everyone,
> 
> The fact that write_super gets called for both syncs and periodic
> commits causes problems for the journaled filesystems, since we
> need to trigger commits on write_super to have sync() behave
> properly.
> 
> So, this patch adds a new super operation called commit_super,
> and extends struct super.s_dirt a little so the filesystem
> can say: call me on sync() but don't call me from kupdate.
> 
> if (s_dirt & S_SUPER_DIRTY) call me from kupdate and on sync
> if (s_dirt & S_SUPER_DIRTY_COMMIT) call me on sync only.
> 

I'm not quite sure why these flags exist?  Would it not be
sufficient to just call ->write_super() inside kupdate,
and ->commit_super in fsync_dev()?  (With a ->write_super
fallback, of course).

Either way, this is good - ext3's write_super() can just
become a one-liner:  `sb->s_dirt = 0'.

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