| Message ID | 20250306044239.3874247-8-balbirs@nvidia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | THP support for zone device pages | expand |
Hi, On 3/6/25 06:42, Balbir Singh wrote: > When a zone device page is split (via huge pmd folio split). The > driver callback for folio_split is invoked to let the device driver > know that the folio size has been split into a smaller order. > > The HMM test driver has been updated to handle the split, since the > test driver uses backing pages, it requires a mechanism of reorganizing > the backing pages (backing pages are used to create a mirror device) > again into the right sized order pages. This is supported by exporting > prep_compound_page(). > > Signed-off-by: Balbir Singh <balbirs@nvidia.com> > --- > include/linux/memremap.h | 7 +++++++ > include/linux/mm.h | 1 + > lib/test_hmm.c | 35 +++++++++++++++++++++++++++++++++++ > mm/huge_memory.c | 5 +++++ > mm/page_alloc.c | 1 + > 5 files changed, 49 insertions(+) > > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index 11d586dd8ef1..2091b754f1da 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -100,6 +100,13 @@ struct dev_pagemap_ops { > */ > int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn, > unsigned long nr_pages, int mf_flags); > + > + /* > + * Used for private (un-addressable) device memory only. > + * This callback is used when a folio is split into > + * a smaller folio > + */ > + void (*folio_split)(struct folio *head, struct folio *tail); > }; > > #define PGMAP_ALTMAP_VALID (1 << 0) > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 98a67488b5fe..3d0e91e0a923 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1415,6 +1415,7 @@ static inline struct folio *virt_to_folio(const void *x) > void __folio_put(struct folio *folio); > > void split_page(struct page *page, unsigned int order); > +void prep_compound_page(struct page *page, unsigned int order); > void folio_copy(struct folio *dst, struct folio *src); > int folio_mc_copy(struct folio *dst, struct folio *src); > > diff --git a/lib/test_hmm.c b/lib/test_hmm.c > index a81d2f8a0426..18b6a7b061d7 100644 > --- a/lib/test_hmm.c > +++ b/lib/test_hmm.c > @@ -1640,10 +1640,45 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf) > return ret; > } > > + > +static void dmirror_devmem_folio_split(struct folio *head, struct folio *tail) > +{ > + struct page *rpage = BACKING_PAGE(folio_page(head, 0)); > + struct folio *new_rfolio; > + struct folio *rfolio; > + unsigned long offset = 0; > + > + if (!rpage) { > + folio_page(tail, 0)->zone_device_data = NULL; > + return; > + } > + > + offset = folio_pfn(tail) - folio_pfn(head); > + rfolio = page_folio(rpage); > + new_rfolio = page_folio(folio_page(rfolio, offset)); > + > + folio_page(tail, 0)->zone_device_data = folio_page(new_rfolio, 0); > + > + if (folio_pfn(tail) - folio_pfn(head) == 1) { > + if (folio_order(head)) > + prep_compound_page(folio_page(rfolio, 0), > + folio_order(head)); > + folio_set_count(rfolio, 1); > + } I think this might need at least a comment. Also, isn't the folio_order(head) always 0, tail and head are splitted folios and if pfn difference == 1? If the intention is to adjust the backing folio's head page to the new order, shouldn't there be clear_compound_head() also for backing head page if split to zero order? > + clear_compound_head(folio_page(new_rfolio, 0)); > + if (folio_order(tail)) > + prep_compound_page(folio_page(new_rfolio, 0), > + folio_order(tail)); > + folio_set_count(new_rfolio, 1); > + folio_page(new_rfolio, 0)->mapping = folio_page(rfolio, 0)->mapping; > + tail->pgmap = head->pgmap; > +} > + > static const struct dev_pagemap_ops dmirror_devmem_ops = { > .page_free = dmirror_devmem_free, > .migrate_to_ram = dmirror_devmem_fault, > .page_free = dmirror_devmem_free, > + .folio_split = dmirror_devmem_folio_split, > }; > > static int dmirror_device_init(struct dmirror_device *mdevice, int id) > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 995ac8be5709..518a70d1b58a 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3655,6 +3655,11 @@ static int __split_unmapped_folio(struct folio *folio, int new_order, > MTHP_STAT_NR_ANON, 1); > } > > + if (folio_is_device_private(origin_folio) && > + origin_folio->pgmap->ops->folio_split) > + origin_folio->pgmap->ops->folio_split( > + origin_folio, release); > + > /* > * Unfreeze refcount first. Additional reference from > * page cache. > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 17ea8fb27cbf..563f7e39aa79 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -573,6 +573,7 @@ void prep_compound_page(struct page *page, unsigned int order) > > prep_compound_head(page, order); > } > +EXPORT_SYMBOL_GPL(prep_compound_page); > > static inline void set_buddy_order(struct page *page, unsigned int order) > { --Mika
diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 11d586dd8ef1..2091b754f1da 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -100,6 +100,13 @@ struct dev_pagemap_ops { */ int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn, unsigned long nr_pages, int mf_flags); + + /* + * Used for private (un-addressable) device memory only. + * This callback is used when a folio is split into + * a smaller folio + */ + void (*folio_split)(struct folio *head, struct folio *tail); }; #define PGMAP_ALTMAP_VALID (1 << 0) diff --git a/include/linux/mm.h b/include/linux/mm.h index 98a67488b5fe..3d0e91e0a923 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1415,6 +1415,7 @@ static inline struct folio *virt_to_folio(const void *x) void __folio_put(struct folio *folio); void split_page(struct page *page, unsigned int order); +void prep_compound_page(struct page *page, unsigned int order); void folio_copy(struct folio *dst, struct folio *src); int folio_mc_copy(struct folio *dst, struct folio *src); diff --git a/lib/test_hmm.c b/lib/test_hmm.c index a81d2f8a0426..18b6a7b061d7 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -1640,10 +1640,45 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf) return ret; } + +static void dmirror_devmem_folio_split(struct folio *head, struct folio *tail) +{ + struct page *rpage = BACKING_PAGE(folio_page(head, 0)); + struct folio *new_rfolio; + struct folio *rfolio; + unsigned long offset = 0; + + if (!rpage) { + folio_page(tail, 0)->zone_device_data = NULL; + return; + } + + offset = folio_pfn(tail) - folio_pfn(head); + rfolio = page_folio(rpage); + new_rfolio = page_folio(folio_page(rfolio, offset)); + + folio_page(tail, 0)->zone_device_data = folio_page(new_rfolio, 0); + + if (folio_pfn(tail) - folio_pfn(head) == 1) { + if (folio_order(head)) + prep_compound_page(folio_page(rfolio, 0), + folio_order(head)); + folio_set_count(rfolio, 1); + } + clear_compound_head(folio_page(new_rfolio, 0)); + if (folio_order(tail)) + prep_compound_page(folio_page(new_rfolio, 0), + folio_order(tail)); + folio_set_count(new_rfolio, 1); + folio_page(new_rfolio, 0)->mapping = folio_page(rfolio, 0)->mapping; + tail->pgmap = head->pgmap; +} + static const struct dev_pagemap_ops dmirror_devmem_ops = { .page_free = dmirror_devmem_free, .migrate_to_ram = dmirror_devmem_fault, .page_free = dmirror_devmem_free, + .folio_split = dmirror_devmem_folio_split, }; static int dmirror_device_init(struct dmirror_device *mdevice, int id) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 995ac8be5709..518a70d1b58a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3655,6 +3655,11 @@ static int __split_unmapped_folio(struct folio *folio, int new_order, MTHP_STAT_NR_ANON, 1); } + if (folio_is_device_private(origin_folio) && + origin_folio->pgmap->ops->folio_split) + origin_folio->pgmap->ops->folio_split( + origin_folio, release); + /* * Unfreeze refcount first. Additional reference from * page cache. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 17ea8fb27cbf..563f7e39aa79 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -573,6 +573,7 @@ void prep_compound_page(struct page *page, unsigned int order) prep_compound_head(page, order); } +EXPORT_SYMBOL_GPL(prep_compound_page); static inline void set_buddy_order(struct page *page, unsigned int order) {
When a zone device page is split (via huge pmd folio split). The driver callback for folio_split is invoked to let the device driver know that the folio size has been split into a smaller order. The HMM test driver has been updated to handle the split, since the test driver uses backing pages, it requires a mechanism of reorganizing the backing pages (backing pages are used to create a mirror device) again into the right sized order pages. This is supported by exporting prep_compound_page(). Signed-off-by: Balbir Singh <balbirs@nvidia.com> --- include/linux/memremap.h | 7 +++++++ include/linux/mm.h | 1 + lib/test_hmm.c | 35 +++++++++++++++++++++++++++++++++++ mm/huge_memory.c | 5 +++++ mm/page_alloc.c | 1 + 5 files changed, 49 insertions(+)