On 10/13/2017 02:07 PM, Michal Hocko wrote: > On Fri 13-10-17 14:04:08, Vlastimil Babka wrote: >> On 10/13/2017 02:00 PM, Michal Hocko wrote: >>> From: Michal Hocko <mho...@suse.com> >>> >>> Reserved pages should be completely ignored by the core mm because they >>> have a special meaning for their owners. has_unmovable_pages doesn't >>> check those so we rely on other tests (reference count, or PageLRU) to >>> fail on such pages. Althought this happens to work it is safer to simply >>> check for those explicitly and do not rely on the owner of the page >>> to abuse those fields for special purposes. >>> >>> Please note that this is more of a further fortification of the code >>> rahter than a fix of an existing issue. >>> >>> Signed-off-by: Michal Hocko <mho...@suse.com> >>> --- >>> mm/page_alloc.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index ad0294ab3e4f..a8800b0a5619 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct >>> page *page, int count, >>> >>> page = pfn_to_page(check); >>> >>> + if (PageReferenced(page)) >> >> "Referenced" != "Reserved" > > Dohh, you are right of course. I blame auto-completion ;) but I am lame > in fact... > --- > From 44b20bdb03846bc5fd79c883d16b8f3aa436878f Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mho...@suse.com> > Date: Fri, 13 Oct 2017 13:55:21 +0200 > Subject: [PATCH] mm, page_alloc: fail has_unmovable_pages when seeing reserved > pages > > Reserved pages should be completely ignored by the core mm because they > have a special meaning for their owners. has_unmovable_pages doesn't > check those so we rely on other tests (reference count, or PageLRU) to > fail on such pages. Althought this happens to work it is safer to simply > check for those explicitly and do not rely on the owner of the page > to abuse those fields for special purposes. > > Please note that this is more of a further fortification of the code > rahter than a fix of an existing issue. > > Signed-off-by: Michal Hocko <mho...@suse.com>
Acked-by: Vlastimil Babka <vba...@suse.cz> > --- > mm/page_alloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ad0294ab3e4f..5b4d85ae445c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page > *page, int count, > > page = pfn_to_page(check); > > + if (PageReserved(page)) > + return true; > + > /* > * Hugepages are not in LRU lists, but they're movable. > * We need not scan over tail pages bacause we don't >
