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authorAlistair Popple <apopple@nvidia.com>2022-09-28 22:01:16 +1000
committerAndrew Morton <akpm@linux-foundation.org>2022-10-12 18:51:49 -0700
commitef233450898f8893dafa193a9f3211fa077a3d05 (patch)
tree7629c2f144fc4a3d43d4e5d3db459f98e2f3fed5 /mm/memremap.c
parent16ce101db85db694a91380aa4c89b25530871d33 (diff)
downloadlwn-ef233450898f8893dafa193a9f3211fa077a3d05.tar.gz
lwn-ef233450898f8893dafa193a9f3211fa077a3d05.zip
mm: free device private pages have zero refcount
Since 27674ef6c73f ("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: Alistair Popple <apopple@nvidia.com> Acked-by: Felix 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: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/memremap.c')
-rw-r--r--mm/memremap.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/mm/memremap.c b/mm/memremap.c
index 25029a474d30..1c2c038f3410 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -505,8 +505,17 @@ void free_zone_device_page(struct page *page)
/*
* Reset the page count to 1 to prepare for handing out the page again.
*/
+ if (page->pgmap->type != MEMORY_DEVICE_PRIVATE &&
+ page->pgmap->type != MEMORY_DEVICE_COHERENT)
+ set_page_count(page, 1);
+}
+
+void zone_device_page_init(struct page *page)
+{
set_page_count(page, 1);
+ lock_page(page);
}
+EXPORT_SYMBOL_GPL(zone_device_page_init);
#ifdef CONFIG_FS_DAX
bool __put_devmap_managed_page_refs(struct page *page, int refs)