Messages in this thread | | | Date | Mon, 6 Dec 2021 21:53:49 -0600 | Subject | Re: [PATCH RESEND v2 3/5] mm_zone: add function to check if managed dma zone exists | From | John Donnelly <> |
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On 12/6/21 9:07 PM, 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 <bhe@redhat.com> Reviewed-by: John Donnelly <john.p.donnelly@oracle.com> Tested-by: John Donnelly <john.p.donnelly@oracle.com> > --- > 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; > +} > #endif >
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