Commit ef233450 authored by Alistair Popple's avatar Alistair Popple Committed by Andrew Morton
Browse files

mm: free device private pages have zero refcount 

Since 27674ef6 ("mm: remove the extra ZONE_DEVICE struct page
refcount") device private pages have no longer had an extra reference
count when the page is in use.  However before handing them back to the
owning device driver we add an extra reference count such that free pages
have a reference count of one.

This makes it difficult to tell if a page is free or not because both free
and in use pages will have a non-zero refcount.  Instead we should return
pages to the drivers page allocator with a zero reference count.  Kernel
code can then safely use kernel functions such as get_page_unless_zero().

Link: https://lkml.kernel.org/r/cf70cf6f8c0bdb8aaebdbfb0d790aea4c683c3c6.1664366292.git-series.apopple@nvidia.com


Signed-off-by: default avatarAlistair Popple <apopple@nvidia.com>
Acked-by: default avatarFelix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 16ce101d

arch/powerpc/kvm/book3s_hv_uvmem.c

+1 −1
Original line number Diff line number Diff line
@@ -718,7 +718,7 @@ static struct page *kvmppc_uvmem_get_page(unsigned long gpa, struct kvm *kvm) 


	dpage = pfn_to_page(uvmem_pfn);

	dpage->zone_device_data = pvt;

	lock_page(dpage);

	zone_device_page_init(dpage);

	return dpage;

out_clear:

	spin_lock(&kvmppc_uvmem_bitmap_lock);

drivers/gpu/drm/amd/amdkfd/kfd_migrate.c

+1 −1
Original line number Diff line number Diff line
@@ -223,7 +223,7 @@ svm_migrate_get_vram_page(struct svm_range *prange, unsigned long pfn) 
	page = pfn_to_page(pfn);

	svm_range_bo_ref(prange->svm_bo);

	page->zone_device_data = prange->svm_bo;

	lock_page(page);

	zone_device_page_init(page);

}



static void

drivers/gpu/drm/nouveau/nouveau_dmem.c

+1 −1
Original line number Diff line number Diff line
@@ -326,7 +326,7 @@ nouveau_dmem_page_alloc_locked(struct nouveau_drm *drm) 
			return NULL;

	}



	lock_page(page);

	zone_device_page_init(page);

	return page;

}

include/linux/memremap.h

+1 −0
Original line number Diff line number Diff line
@@ -187,6 +187,7 @@ static inline bool folio_is_device_coherent(const struct folio *folio) 
}



#ifdef CONFIG_ZONE_DEVICE

void zone_device_page_init(struct page *page);

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);

lib/test_hmm.c

+1 −1
Original line number Diff line number Diff line
@@ -627,8 +627,8 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice) 
			goto error;

	}



	zone_device_page_init(dpage);

	dpage->zone_device_data = rpage;

	lock_page(dpage);

	return dpage;



error: