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[79.242.62.87]) by smtp.gmail.com with ESMTPSA id k37sm2365944wms.21.2021.12.07.03.23.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Dec 2021 03:23:51 -0800 (PST) Message-ID: <0a9bc228-21ba-abe3-d9c8-b9d52b936366@redhat.com> Date: Tue, 7 Dec 2021 12:23:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH RESEND v2 3/5] mm_zone: add function to check if managed dma zone exists To: Baoquan He , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, robin.murphy@arm.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, m.szyprowski@samsung.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org References: <20211207030750.30824-1-bhe@redhat.com> <20211207030750.30824-4-bhe@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20211207030750.30824-4-bhe@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D10DB100002 X-Stat-Signature: mmdcj1ngtqunag3pnkfzfshgcawq9wps Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bEPoquO8; spf=none (imf05.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1638876235-775188 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 07.12.21 04:07, Baoquan He wrote: > In some places of the current kernel, it assumes that dma zone must have > managed pages if CONFIG_ZONE_DMA is enabled. While this is not always true. > E.g in kdump kernel of x86_64, only low 1M is presented and locked down > at very early stage of boot, so that there's no managed pages at all in > DMA zone. This exception will always cause page allocation failure if page > is requested from DMA zone. > > Here add function has_managed_dma() and the relevant helper functions to > check if there's DMA zone with managed pages. It will be used in later > patches. > > Signed-off-by: Baoquan He > --- > include/linux/mmzone.h | 21 +++++++++++++++++++++ > mm/page_alloc.c | 11 +++++++++++ > 2 files changed, 32 insertions(+) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 58e744b78c2c..82d23e13e0e5 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -998,6 +998,18 @@ static inline bool zone_is_zone_device(struct zone *zone) > } > #endif > > +#ifdef CONFIG_ZONE_DMA > +static inline bool zone_is_dma(struct zone *zone) > +{ > + return zone_idx(zone) == ZONE_DMA; > +} > +#else > +static inline bool zone_is_dma(struct zone *zone) > +{ > + return false; > +} > +#endif > + > /* > * Returns true if a zone has pages managed by the buddy allocator. > * All the reclaim decisions have to use this function rather than > @@ -1046,6 +1058,7 @@ static inline int is_highmem_idx(enum zone_type idx) > #endif > } > > +bool has_managed_dma(void); > /** > * is_highmem - helper function to quickly check if a struct zone is a > * highmem zone or not. This is an attempt to keep references > @@ -1131,6 +1144,14 @@ extern struct zone *next_zone(struct zone *zone); > ; /* do nothing */ \ > else > > +#define for_each_managed_zone(zone) \ > + for (zone = (first_online_pgdat())->node_zones; \ > + zone; \ > + zone = next_zone(zone)) \ > + if (!managed_zone(zone)) \ > + ; /* do nothing */ \ > + else > + > static inline struct zone *zonelist_zone(struct zoneref *zoneref) > { > return zoneref->zone; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c5952749ad40..ac0ea42a4e5f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -9459,4 +9459,15 @@ bool take_page_off_buddy(struct page *page) > spin_unlock_irqrestore(&zone->lock, flags); > return ret; > } > + > +bool has_managed_dma(void) > +{ > + struct zone *zone; > + > + for_each_managed_zone(zone) { > + if (zone_is_dma(zone)) > + return true; > + } > + return false; > +} Wouldn't it be "easier/faster" to just iterate online nodes and directly obtain the ZONE_DMA, checking if there are managed pages? -- Thanks, David / dhildenb