On Wed, Jun 23, 2021 at 01:43:30PM +0200, Christoph Hellwig wrote:
> On Tue, Jun 22, 2021 at 01:15:51PM +0100, Matthew Wilcox (Oracle) wrote:
> > Allow filemap_get_folio() to wait for writeback to complete (if the
> > filesystem wants that behaviour). This is the folio equivalent of
> > grab_cache_page_write_begin(), which is moved into the folio-compat
> > file as a reminder to migrate all the code using it. This paves the
> > way for getting rid of AOP_FLAG_NOFS once grab_cache_page_write_begin()
> > is removed.
>
> We actually should kill FGP_NOFS as well by switching everything over
> to memalloc_nofs_{save, restore} eventually, given how error prone
> all these manual flags settings are.
Well, yes, but it's been four years and we still have over 1100 uses of
GFP_NOFS. Until someone takes on that Augean Stables, we're going to need
FGP_NOFS. I added that context to the readahead path in f2c817bed58d,
but of course that doesn't let me remove any uses of GFP_NOFS.
> > diff --git a/mm/folio-compat.c b/mm/folio-compat.c
> > index 78365eaee7d3..206bedd621d0 100644
> > --- a/mm/folio-compat.c
> > +++ b/mm/folio-compat.c
> > @@ -115,6 +115,7 @@ void lru_cache_add(struct page *page)
> > }
> > EXPORT_SYMBOL(lru_cache_add);
> >
> > +noinline
> > struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> > int fgp_flags, gfp_t gfp)
>
> How did that sneak in here?
Without it, pagecache_get_page() gets inlined by
grab_cache_page_write_begin() which is just too much code.
