| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <e8dc674d-39c1-4ba4-99dd-9b0efc6ad466@nvidia.com>
Date: Tue, 5 Aug 2025 09:43:28 +1000
From: Balbir Singh <balbirs@...dia.com>
To: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org, Karol Herbst <kherbst@...hat.com>,
Lyude Paul <lyude@...hat.com>, Danilo Krummrich <dakr@...nel.org>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Jérôme Glisse <jglisse@...hat.com>,
Shuah Khan <shuah@...nel.org>, Barry Song <baohua@...nel.org>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Ryan Roberts <ryan.roberts@....com>, Matthew Wilcox <willy@...radead.org>,
Peter Xu <peterx@...hat.com>, Zi Yan <ziy@...dia.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>, Jane Chu <jane.chu@...cle.com>,
Alistair Popple <apopple@...dia.com>, Donet Tom <donettom@...ux.ibm.com>,
Ralph Campbell <rcampbell@...dia.com>, Mika Penttilä
<mpenttil@...hat.com>, Matthew Brost <matthew.brost@...el.com>,
Francois Dugast <francois.dugast@...el.com>
Subject: Re: [v2 01/11] mm/zone_device: support large zone device private
folios
On 7/30/25 19:50, David Hildenbrand wrote:
> On 30.07.25 11:21, Balbir Singh wrote:
>> Add routines to support allocation of large order zone device folios
>> and helper functions for zone device folios, to check if a folio is
>> device private and helpers for setting zone device data.
>>
>> When large folios are used, the existing page_free() callback in
>> pgmap is called when the folio is freed, this is true for both
>> PAGE_SIZE and higher order pages.
>>
>> Cc: Karol Herbst <kherbst@...hat.com>
>> Cc: Lyude Paul <lyude@...hat.com>
>> Cc: Danilo Krummrich <dakr@...nel.org>
>> Cc: David Airlie <airlied@...il.com>
>> Cc: Simona Vetter <simona@...ll.ch>
>> Cc: "Jérôme Glisse" <jglisse@...hat.com>
>> Cc: Shuah Khan <shuah@...nel.org>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Barry Song <baohua@...nel.org>
>> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> Cc: Ryan Roberts <ryan.roberts@....com>
>> Cc: Matthew Wilcox <willy@...radead.org>
>> Cc: Peter Xu <peterx@...hat.com>
>> Cc: Zi Yan <ziy@...dia.com>
>> Cc: Kefeng Wang <wangkefeng.wang@...wei.com>
>> Cc: Jane Chu <jane.chu@...cle.com>
>> Cc: Alistair Popple <apopple@...dia.com>
>> Cc: Donet Tom <donettom@...ux.ibm.com>
>> Cc: Ralph Campbell <rcampbell@...dia.com>
>> Cc: Mika Penttilä <mpenttil@...hat.com>
>> Cc: Matthew Brost <matthew.brost@...el.com>
>> Cc: Francois Dugast <francois.dugast@...el.com>
>>
>> Signed-off-by: Balbir Singh <balbirs@...dia.com>
>> ---
>> include/linux/memremap.h | 10 ++++++++-
>> mm/memremap.c | 48 +++++++++++++++++++++++++++++-----------
>> 2 files changed, 44 insertions(+), 14 deletions(-)
>>
>> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
>> index 4aa151914eab..a0723b35eeaa 100644
>> --- a/include/linux/memremap.h
>> +++ b/include/linux/memremap.h
>> @@ -199,7 +199,7 @@ static inline bool folio_is_fsdax(const struct folio *folio)
>> }
>> #ifdef CONFIG_ZONE_DEVICE
>> -void zone_device_page_init(struct page *page);
>> +void zone_device_folio_init(struct folio *folio, unsigned int order);
>> void *memremap_pages(struct dev_pagemap *pgmap, int nid);
>> void memunmap_pages(struct dev_pagemap *pgmap);
>> void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
>> @@ -209,6 +209,14 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
>> bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
>> unsigned long memremap_compat_align(void);
>> +
>> +static inline void zone_device_page_init(struct page *page)
>> +{
>> + struct folio *folio = page_folio(page);
>> +
>> + zone_device_folio_init(folio, 0);
>> +}
>> +
>> #else
>> static inline void *devm_memremap_pages(struct device *dev,
>> struct dev_pagemap *pgmap)
>> diff --git a/mm/memremap.c b/mm/memremap.c
>> index b0ce0d8254bd..3ca136e7455e 100644
>> --- a/mm/memremap.c
>> +++ b/mm/memremap.c
>> @@ -427,20 +427,19 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
>> void free_zone_device_folio(struct folio *folio)
>> {
>> struct dev_pagemap *pgmap = folio->pgmap;
>> + unsigned int nr = folio_nr_pages(folio);
>> + int i;
>
> "unsigned long" is to be future-proof.
Will change this for v3
>
> (folio_nr_pages() returns long and probably soon unsigned long)
>
> [ I'd probably all it "nr_pages" ]
Ack
>
>> if (WARN_ON_ONCE(!pgmap))
>> return;
>> mem_cgroup_uncharge(folio);
>> - /*
>> - * Note: we don't expect anonymous compound pages yet. Once supported
>> - * and we could PTE-map them similar to THP, we'd have to clear
>> - * PG_anon_exclusive on all tail pages.
>> - */
>> if (folio_test_anon(folio)) {
>> - VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
>> - __ClearPageAnonExclusive(folio_page(folio, 0));
>> + for (i = 0; i < nr; i++)
>> + __ClearPageAnonExclusive(folio_page(folio, i));
>> + } else {
>> + VM_WARN_ON_ONCE(folio_test_large(folio));
>> }
>> /*
>> @@ -464,11 +463,20 @@ void free_zone_device_folio(struct folio *folio)
>> switch (pgmap->type) {
>> case MEMORY_DEVICE_PRIVATE:
>> + if (folio_test_large(folio)) {
>
> Could do "nr > 1" if we already have that value around.
>
Ack
>> + folio_unqueue_deferred_split(folio);
>
> I think I asked that already but maybe missed the reply: Should these folios ever be added to the deferred split queue and is there any value in splitting them under memory pressure in the shrinker?
>
> My gut feeling is "No", because the buddy cannot make use of these folios, but maybe there is an interesting case where we want that behavior?
>
>> +
>> + percpu_ref_put_many(&folio->pgmap->ref, nr - 1);
>> + }
>> + pgmap->ops->page_free(&folio->page);
>> + percpu_ref_put(&folio->pgmap->ref);
>
> Coold you simply do a
>
> percpu_ref_put_many(&folio->pgmap->ref, nr);
>
> here, or would that be problematic?
>
I can definitely try that
>> + folio->page.mapping = NULL;
>> + break;
>> case MEMORY_DEVICE_COHERENT:
>> if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->page_free))
>> break;
>> - pgmap->ops->page_free(folio_page(folio, 0));
>> - put_dev_pagemap(pgmap);
>> + pgmap->ops->page_free(&folio->page);
>> + percpu_ref_put(&folio->pgmap->ref);
>> break;
>> case MEMORY_DEVICE_GENERIC:
>> @@ -491,14 +499,28 @@ void free_zone_device_folio(struct folio *folio)
>> }
>> }
>> -void zone_device_page_init(struct page *page)
>> +void zone_device_folio_init(struct folio *folio, unsigned int order)
>> {
>> + struct page *page = folio_page(folio, 0);
>> +
>> + VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES);
>> +
>> + /*
>> + * Only PMD level migration is supported for THP migration
>> + */
>
> Talking about something that does not exist yet (and is very specific) sounds a bit weird.
>
> Should this go into a different patch, or could we rephrase the comment to be a bit more generic?
>
> In this patch here, nothing would really object to "order" being intermediate.
>
> (also, this is a device_private limitation? shouldn't that check go somehwere where we can perform this device-private limitation check?)
>
I can remove the limitation and keep it generic
>> + WARN_ON_ONCE(order && order != HPAGE_PMD_ORDER);
>> +
>> /*
>> * Drivers shouldn't be allocating pages after calling
>> * memunmap_pages().
>> */
>> - WARN_ON_ONCE(!percpu_ref_tryget_live(&page_pgmap(page)->ref));
>> - set_page_count(page, 1);
>> + WARN_ON_ONCE(!percpu_ref_tryget_many(&page_pgmap(page)->ref, 1 << order));
>> + folio_set_count(folio, 1);
>> lock_page(page);
>> +
>> + if (order > 1) {
>> + prep_compound_page(page, order);
>> + folio_set_large_rmappable(folio);
>> + }
>> }
>> -EXPORT_SYMBOL_GPL(zone_device_page_init);
>> +EXPORT_SYMBOL_GPL(zone_device_folio_init);
>
>
Thanks,
Balbir
Powered by blists - more mailing lists