Messages in this thread | | | Date | Mon, 2 May 2022 11:22:33 -0700 | From | Minchan Kim <> | Subject | Re: [PATCH] mm: fix is_pinnable_page against on cma page |
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On Mon, May 02, 2022 at 08:02:31PM +0200, David Hildenbrand wrote: > On 02.05.22 19:35, Minchan Kim wrote: > > Pages on CMA area could have MIGRATE_ISOLATE as well as MIGRATE_CMA > > so current is_pinnable_page could miss CMA pages which has MIGRATE_ > > ISOLATE. It ends up putting CMA pages longterm pinning possible on > > pin_user_pages APIs so CMA allocation fails. > > > > The CMA allocation path protects the migration type change race > > using zone->lock but what GUP path need to know is just whether the > > page is on CMA area or not rather than exact type. Thus, we don't > > need zone->lock but just checks the migratype in either of > > (MIGRATE_ISOLATE and MIGRATE_CMA). > > > > Signed-off-by: Minchan Kim <minchan@kernel.org> > > --- > > include/linux/mm.h | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 6acca5cecbc5..f59bbe3296e3 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -1625,8 +1625,10 @@ static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, > > #ifdef CONFIG_MIGRATION > > static inline bool is_pinnable_page(struct page *page) > > { > > - return !(is_zone_movable_page(page) || is_migrate_cma_page(page)) || > > - is_zero_pfn(page_to_pfn(page)); > > + int mt = get_pageblock_migratetype(page); > > + > > + return !(is_zone_movable_page(page) || mt == MIGRATE_CMA || > > + mt == MIGRATE_ISOLATE || is_zero_pfn(page_to_pfn(page))); > > } > > #else > > static inline bool is_pinnable_page(struct page *page) > > That implies that other memory ranges that are currently isolated > (memory offlining, alloc_contig_range()) cannot be pinned. That might > not be a bad thing, however, I think we could end up failing to pin > something that's temporarily unmovable (due to temporary references).
Sure.
> > However, I assume we have the same issue right now already with > ZONE_MOVABLE and MIGRATE_CMA when trying to pin a page residing on these
ZONE_MOVALBE is also changed dynamically?
> there are temporarily unmovable and we fail to migrate. But it would now > apply even without ZONE_MOVABLE or MIGRATE_CMA. Hm...
Didn't parse your last mention.
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