Re: [PATCH] cramfs corruption after BLKFLSBUF on loop device

Olaf Hering
2006-06-01T21:42:03Z

On Thu, Jun 01, Andrew Morton wrote:

> Olaf Hering <olh@suse.de> wrote:
> >
> >
> >
> > +/* return a page in PageUptodate state, BLKFLSBUF may have flushed the page */
> > +static struct page *cramfs_read_cache_page(struct address_space *m, unsigned int n)
> > +{
> > + struct page *page;
> > + int readagain = 5;
> > +retry:
> > + page = read_cache_page(m, n, (filler_t *)m->a_ops->readpage, NULL);
> > + if (IS_ERR(page))
> > + return NULL;
> > + lock_page(page);
> > + if (PageUptodate(page))
> > + return page;
> > + unlock_page(page);
> > + page_cache_release(page);
> > + if (readagain--)
> > + goto retry;
> > + return NULL;
> > +}
>
> Better, but it's still awful, isn't it? The things you were discussing
> with Chris look more promising. PG_Dirty would be a bit of a hack, but at
> least it'd be a 100% reliable hack, whereas the above is a
> whatever-the-previous-failure-rate-was-to-the-fifth hack.

Do you want it like that?

lock_page(page);
if (PageUptodate(page)) {
SetPageDirty(page);
mb();
return page;
}

and perhaps a ClearPageDirty() after memcpy.