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authorChristoph Hellwig <hch@lst.de>2022-02-16 07:31:36 +0300
committerMatthew Wilcox (Oracle) <willy@infradead.org>2022-03-03 20:47:33 +0300
commit27674ef6c73f0c9096a9827dc5d6ba9fc7808422 (patch)
tree1f57be13e778f35d1ca21902eb4c355d5476b44c /mm/memcontrol.c
parentdc90f0846df4870b6cc8528c31e5c60f18fb68be (diff)
downloadlinux-27674ef6c73f0c9096a9827dc5d6ba9fc7808422.tar.xz
mm: remove the extra ZONE_DEVICE struct page refcount
ZONE_DEVICE struct pages have an extra reference count that complicates the code for put_page() and several places in the kernel that need to check the reference count to see that a page is not being used (gup, compaction, migration, etc.). Clean up the code so the reference count doesn't need to be treated specially for ZONE_DEVICE pages. Note that this excludes the special idle page wakeup for fsdax pages, which still happens at refcount 1. This is a separate issue and will be sorted out later. Given that only fsdax pages require the notifiacation when the refcount hits 1 now, the PAGEMAP_OPS Kconfig symbol can go away and be replaced with a FS_DAX check for this hook in the put_page fastpath. Based on an earlier patch from Ralph Campbell <rcampbell@nvidia.com>. Link: https://lkml.kernel.org/r/20220210072828.2930359-8-hch@lst.de Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Logan Gunthorpe <logang@deltatee.com> Reviewed-by: Ralph Campbell <rcampbell@nvidia.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> Tested-by: "Sierra Guiza, Alejandro (Alex)" <alex.sierra@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Chaitanya Kulkarni <kch@nvidia.com> Cc: Christian Knig <christian.koenig@amd.com> Cc: Karol Herbst <kherbst@redhat.com> Cc: Lyude Paul <lyude@redhat.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c11
1 files changed, 3 insertions, 8 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2c5032294c9f..8fef072dc1ce 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5503,17 +5503,12 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
return NULL;
/*
- * Handle MEMORY_DEVICE_PRIVATE which are ZONE_DEVICE page belonging to
- * a device and because they are not accessible by CPU they are store
- * as special swap entry in the CPU page table.
+ * Handle device private pages that are not accessible by the CPU, but
+ * stored as special swap entries in the page table.
*/
if (is_device_private_entry(ent)) {
page = pfn_swap_entry_to_page(ent);
- /*
- * MEMORY_DEVICE_PRIVATE means ZONE_DEVICE page and which have
- * a refcount of 1 when free (unlike normal page)
- */
- if (!page_ref_add_unless(page, 1, 1))
+ if (!get_page_unless_zero(page))
return NULL;
return page;
}