On Fri, May 13, 2022 at 10:29:52AM -0400, Jeff Layton wrote: > We've seen some instances where we call __filemap_get_folio and get back > one with a ->private value that is non-NULL. Let's have the allocator > bug if that happens. Oh, I meant for this to be a debugging aid for your case, rather than be something we put into upstream. If we do find out that the page allocator is returning pages with page->private non-NULL, we should discuss what the guarantee is that the page allocator provides -- does it guarantee that page->private is NULL, or is that something the page cache should zero out itself. If we do end up changing filemap_alloc_folio(), we need to remember to change the one in pagemap.h too. > URL: https://tracker.ceph.com/issues/55421 > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Cc: Xiubo Li <xiubli@xxxxxxxxxx> > Cc: Luís Henriques <lhenriques@xxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > mm/filemap.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > It might not hurt to merge this into mainline. If it pops then we know > something is very wrong. > > diff --git a/mm/filemap.c b/mm/filemap.c > index 9a1eef6c5d35..74c3fb062ef7 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -990,10 +990,12 @@ struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order) > n = cpuset_mem_spread_node(); > folio = __folio_alloc_node(gfp, order, n); > } while (!folio && read_mems_allowed_retry(cpuset_mems_cookie)); > - > - return folio; > + } else { > + folio = folio_alloc(gfp, order); > } > - return folio_alloc(gfp, order); > + if (folio) > + VM_BUG_ON_FOLIO(folio->private, folio); > + return folio; > } > EXPORT_SYMBOL(filemap_alloc_folio); > #endif > -- > 2.36.1 >
