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[37.188.169.187]) by smtp.gmail.com with ESMTPSA id v24sm1347858eja.29.2020.07.15.01.24.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jul 2020 01:24:02 -0700 (PDT) Date: Wed, 15 Jul 2020 10:24:01 +0200 From: Michal Hocko To: js1304@gmail.com Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@lge.com, Vlastimil Babka , Christoph Hellwig , Roman Gushchin , Mike Kravetz , Naoya Horiguchi , "Aneesh Kumar K . V" , Joonsoo Kim Subject: Re: [PATCH 2/4] mm/gup: restrict CMA region by using allocation scope API Message-ID: <20200715082401.GC5451@dhcp22.suse.cz> References: <1594789529-6206-1-git-send-email-iamjoonsoo.kim@lge.com> <1594789529-6206-2-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1594789529-6206-2-git-send-email-iamjoonsoo.kim@lge.com> X-Rspamd-Queue-Id: 5ED7818038E60 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 15-07-20 14:05:27, Joonsoo Kim wrote: > From: Joonsoo Kim > > We have well defined scope API to exclude CMA region. > Use it rather than manipulating gfp_mask manually. With this change, > we can now use __GFP_MOVABLE for gfp_mask and the ZONE_MOVABLE is also > searched by page allocator. For hugetlb, gfp_mask is redefined since > it has a regular allocation mask filter for migration target. > > Note that this can be considered as a fix for the commit 9a4e9f3b2d73 > ("mm: update get_user_pages_longterm to migrate pages allocated from > CMA region"). However, "Fixes" tag isn't added here since it is just > suboptimal but it doesn't cause any problem. But it is breaking the contract that the longterm pins never end up in a cma managed memory. So I think Fixes tag is really due. I am not sure about stable backport. If the patch was the trivial move of memalloc_nocma_restore then it would be probably worth it because it is trivial to review and backport. I suspect that longterm pins in CMA regions would cause hard to debug issues where CMA memory will not be available. But I am not really sure this is a real problem considering how many long term pin users we have and I have also no idea whether those are usually used along with CMA users. Anyway I think it would really be much better to isolate the memalloc_nocma_restore and have it first in the series. The reword of the __GFP_MOVABLE functionality is orthogonal. Btw __GFP_NOWARN change is not documented. > Suggested-by: Michal Hocko > Signed-off-by: Joonsoo Kim > --- > include/linux/hugetlb.h | 2 ++ > mm/gup.c | 17 ++++++++--------- > 2 files changed, 10 insertions(+), 9 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 6b9508d..2660b04 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -708,6 +708,8 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask) > /* Some callers might want to enfoce node */ > modified_mask |= (gfp_mask & __GFP_THISNODE); > > + modified_mask |= (gfp_mask & __GFP_NOWARN); > + > return modified_mask; > } > > diff --git a/mm/gup.c b/mm/gup.c > index 5daadae..bbd36a1 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1619,10 +1619,12 @@ static struct page *new_non_cma_page(struct page *page, unsigned long private) > * Trying to allocate a page for migration. Ignore allocation > * failure warnings. We don't force __GFP_THISNODE here because > * this node here is the node where we have CMA reservation and > - * in some case these nodes will have really less non movable > + * in some case these nodes will have really less non CMA > * allocation memory. > + * > + * Note that CMA region is prohibited by allocation scope. > */ > - gfp_t gfp_mask = GFP_USER | __GFP_NOWARN; > + gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_NOWARN; > > if (PageHighMem(page)) > gfp_mask |= __GFP_HIGHMEM; > @@ -1630,6 +1632,8 @@ static struct page *new_non_cma_page(struct page *page, unsigned long private) > #ifdef CONFIG_HUGETLB_PAGE > if (PageHuge(page)) { > struct hstate *h = page_hstate(page); > + > + gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); > /* > * We don't want to dequeue from the pool because pool pages will > * mostly be from the CMA region. > @@ -1644,11 +1648,6 @@ static struct page *new_non_cma_page(struct page *page, unsigned long private) > */ > gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN; > > - /* > - * Remove the movable mask so that we don't allocate from > - * CMA area again. > - */ > - thp_gfpmask &= ~__GFP_MOVABLE; > thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER); > if (!thp) > return NULL; > @@ -1794,7 +1793,6 @@ static long __gup_longterm_locked(struct task_struct *tsk, > vmas_tmp, NULL, gup_flags); > > if (gup_flags & FOLL_LONGTERM) { > - memalloc_nocma_restore(flags); > if (rc < 0) > goto out; > > @@ -1807,9 +1805,10 @@ static long __gup_longterm_locked(struct task_struct *tsk, > > rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages, > vmas_tmp, gup_flags); > +out: > + memalloc_nocma_restore(flags); > } > > -out: > if (vmas_tmp != vmas) > kfree(vmas_tmp); > return rc; > -- > 2.7.4 -- Michal Hocko SUSE Labs