Re: [PATCH v10 22/33] mm/filemap: Add __folio_lock_or_retry

[Matthew Wilcox]

On Tue, May 18, 2021 at 12:38:46PM +0200, Vlastimil Babka wrote:
> > -int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
> > +int __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
> >  			 unsigned int flags)
> >  {
> > -	struct folio *folio = page_folio(page);
> > -
> >  	if (fault_flag_allow_retry_first(flags)) {
> >  		/*
> >  		 * CAUTION! In this case, mmap_lock is not released
> 
> A bit later in this branch, 'page' is accessed, but it no longer exists. And
> thus as expected, it doesn't compile. Assuming it's fixed later, but
> bisectability etc...

Oops.  Thanks for catching that; I've reordered this patch and the
folio_wait_locked() patch, which makes the entire problem go away.