Re: [PATCH 1/6] VFS: Ensure that writeback_single_inode() commits unstable writes

Wu Fengguang
2010-01-07T14:57:08Z

On Thu, Jan 07, 2010 at 12:38:02PM +0800, Myklebust, Trond wrote:

> > > diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> > > index d171696..910be28 100644
> > > --- a/fs/nfs/write.c
> > > +++ b/fs/nfs/write.c
> > > @@ -441,7 +441,7 @@ nfs_mark_request_commit(struct nfs_page *req)
> > > spin_unlock(&inode->i_lock);
> > > inc_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
> > > inc_bdi_stat(req->wb_page->mapping->backing_dev_info, BDI_RECLAIMABLE);
> > > - __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
> > > + mark_inode_unstable_pages(inode);
> >
> > Then we shall mark I_DIRTY_DATASYNC on other places that extend i_size.
>
> Why? The NFS client itself shouldn't ever set I_DIRTY_DATASYNC after
> this patch is applied. We won't ever need it.
>
> If the VM or VFS is doing it, then they ought to be fixed: there is no
> reason to assume that all filesystems need to sync their inodes on
> i_size changes.

Sorry, one more question.

It seems to me that you are replacing

I_DIRTY_DATASYNC => write_inode()
with
I_UNSTABLE_PAGES => commit_unstable_pages()

Is that change for the sake of clarity? Or to fix some problem?
(This patch does fix some problems, but do they inherently require
the above change?)

Thanks,
Fengguang