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V" , Mel Gorman , kernel-team@lge.com, Joonsoo Kim Subject: Re: [PATCH v2 for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs Message-ID: <20200929080814.GB22035@dhcp22.suse.cz> References: <1601283046-15329-1-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1601283046-15329-1-git-send-email-iamjoonsoo.kim@lge.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 28-09-20 17:50:46, Joonsoo Kim wrote: > From: Joonsoo Kim > > memalloc_nocma_{save/restore} APIs can be used to skip page allocation > on CMA area, but, there is a missing case and the page on CMA area could > be allocated even if APIs are used. This patch handles this case to fix > the potential issue. > > Missing case is an allocation from the pcplist. MIGRATE_MOVABLE pcplist > could have the pages on CMA area so we need to skip it if ALLOC_CMA isn't > specified. > > Fixes: 8510e69c8efe (mm/page_alloc: fix memalloc_nocma_{save/restore} APIs) > Signed-off-by: Joonsoo Kim > --- > mm/page_alloc.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fab5e97..104d2e1 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3367,9 +3367,16 @@ struct page *rmqueue(struct zone *preferred_zone, > struct page *page; > > if (likely(order == 0)) { > - page = rmqueue_pcplist(preferred_zone, zone, gfp_flags, > + /* > + * MIGRATE_MOVABLE pcplist could have the pages on CMA area and > + * we need to skip it when CMA area isn't allowed. > + */ > + if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA || > + migratetype != MIGRATE_MOVABLE) { > + page = rmqueue_pcplist(preferred_zone, zone, gfp_flags, > migratetype, alloc_flags); > - goto out; > + goto out; > + } > } This approach looks definitely better than the previous version. > > /* > @@ -3381,7 +3388,7 @@ struct page *rmqueue(struct zone *preferred_zone, > > do { > page = NULL; > - if (alloc_flags & ALLOC_HARDER) { > + if (order > 0 && alloc_flags & ALLOC_HARDER) { > page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > if (page) > trace_mm_page_alloc_zone_locked(page, order, migratetype); But this condition is not clear to me. __rmqueue_smallest doesn't access pcp lists. Maybe I have missed the point in the original discussion but this deserves a comment at least. > -- > 2.7.4 -- Michal Hocko SUSE Labs