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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id t73sm15903831qke.71.2020.01.20.05.19.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Jan 2020 05:19:21 -0800 (PST) From: Qian Cai To: akpm@linux-foundation.org Cc: mhocko@kernel.org, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH -mm v2] mm/page_isolation: fix potential warning from user Date: Mon, 20 Jan 2020 08:19:09 -0500 Message-Id: <20200120131909.813-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122.2) MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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: It makes sense to call the WARN_ON_ONCE(zone_idx(zone) =3D=3D ZONE_MOVABL= E) from start_isolate_page_range(), but should avoid triggering it from userspace, i.e, from is_mem_section_removable() because it could be a DoS if warn_on_panic is set. While at it, simplify the code a bit by removing an unnecessary jump label and a local variable, so set_migratetype_isolate() could really return a bool. Suggested-by: Michal Hocko Signed-off-by: Qian Cai --- v2: Improve the commit log. Warn for all start_isolate_page_range() users not just offlining. mm/page_alloc.c | 11 ++++------- mm/page_isolation.c | 30 +++++++++++++++++------------- 2 files changed, 21 insertions(+), 20 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 621716a25639..3c4eb750a199 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -8231,7 +8231,7 @@ struct page *has_unmovable_pages(struct zone *zone,= struct page *page, if (is_migrate_cma(migratetype)) return NULL; =20 - goto unmovable; + return page; } =20 for (; iter < pageblock_nr_pages; iter++) { @@ -8241,7 +8241,7 @@ struct page *has_unmovable_pages(struct zone *zone,= struct page *page, page =3D pfn_to_page(pfn + iter); =20 if (PageReserved(page)) - goto unmovable; + return page; =20 /* * If the zone is movable and we have ruled out all reserved @@ -8261,7 +8261,7 @@ struct page *has_unmovable_pages(struct zone *zone,= struct page *page, unsigned int skip_pages; =20 if (!hugepage_migration_supported(page_hstate(head))) - goto unmovable; + return page; =20 skip_pages =3D compound_nr(head) - (page - head); iter +=3D skip_pages - 1; @@ -8303,12 +8303,9 @@ struct page *has_unmovable_pages(struct zone *zone= , struct page *page, * is set to both of a memory hole page and a _used_ kernel * page at boot. */ - goto unmovable; + return page; } return NULL; -unmovable: - WARN_ON_ONCE(zone_idx(zone) =3D=3D ZONE_MOVABLE); - return pfn_to_page(pfn + iter); } =20 #ifdef CONFIG_CONTIG_ALLOC diff --git a/mm/page_isolation.c b/mm/page_isolation.c index e70586523ca3..31f5516f5d54 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -15,12 +15,12 @@ #define CREATE_TRACE_POINTS #include =20 -static int set_migratetype_isolate(struct page *page, int migratetype, i= nt isol_flags) +static bool set_migratetype_isolate(struct page *page, int migratetype, + int isol_flags) { - struct page *unmovable =3D NULL; + struct page *unmovable =3D ERR_PTR(-EBUSY); struct zone *zone; unsigned long flags; - int ret =3D -EBUSY; =20 zone =3D page_zone(page); =20 @@ -49,21 +49,25 @@ static int set_migratetype_isolate(struct page *page,= int migratetype, int isol_ NULL); =20 __mod_zone_freepage_state(zone, -nr_pages, mt); - ret =3D 0; } =20 out: spin_unlock_irqrestore(&zone->lock, flags); - if (!ret) + + if (!unmovable) { drain_all_pages(zone); - else if ((isol_flags & REPORT_FAILURE) && unmovable) - /* - * printk() with zone->lock held will guarantee to trigger a - * lockdep splat, so defer it here. - */ - dump_page(unmovable, "unmovable page"); - - return ret; + } else { + WARN_ON_ONCE(zone_idx(zone) =3D=3D ZONE_MOVABLE); + + if ((isol_flags & REPORT_FAILURE) && !IS_ERR(unmovable)) + /* + * printk() with zone->lock held will likely trigger a + * lockdep splat, so defer it here. + */ + dump_page(unmovable, "unmovable page"); + } + + return !!unmovable; } =20 static void unset_migratetype_isolate(struct page *page, unsigned migrat= etype) --=20 2.21.0 (Apple Git-122.2)