Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote:
> > > @@ -432,7 +432,12 @@ static int nfs_release_page(struct page *page, gfp_t gfp)
> > > /* If PagePrivate() is set, then the page is not freeable */
> > > if (PagePrivate(page))
> > > return 0;
> > > - return nfs_fscache_release_page(page, gfp);
> > > + if (PageFsCache(page)) {
> > > + if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS))
> > > + return false;
> > > + wait_on_page_fscache(page);
> > > + }
> > > + return true;
> > > }
>
> I've found this generally not to be safe. The VM calls ->release_page()
> from a variety of contexts, and often fails to report it correctly in
> the gfp flags. That's particularly true of the stuff in mm/vmscan.c.
> This is why we have the check above that vetos page removal upon
> PagePrivate() being set.
[Adding Willy and the mm crew to the cc list]
I wonder if that matters in this case. In the worst case, we'll wait for the
page to cease being DMA'd - but we won't return true if it is.
But if vmscan is generating the wrong VM flags, we should look at fixing that.
David
