From: Hou Tao Commit b7e282378773 has already changed the initial page refcount of p2pdma page from one to zero, however, in p2pmem_alloc_mmap() it uses "VM_WARN_ON_ONCE_PAGE(!page_ref_count(page))" to assert the initial page refcount should not be zero and the following will be reported when CONFIG_DEBUG_VM is enabled: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x380400000 flags: 0x20000000002000(reserved|node=0|zone=4) raw: 0020000000002000 ff1100015e3ab440 0000000000000000 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: VM_WARN_ON_ONCE_PAGE(!page_ref_count(page)) ------------[ cut here ]------------ WARNING: CPU: 5 PID: 449 at drivers/pci/p2pdma.c:240 p2pmem_alloc_mmap+0x83a/0xa60 Fix by using "page_ref_count(page)" as the assertion condition. Fixes: b7e282378773 ("mm/mm_init: move p2pdma page refcount initialisation to p2pdma") Signed-off-by: Hou Tao --- drivers/pci/p2pdma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 218c1f5252b6..dd64ec830fdd 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -147,7 +147,7 @@ static int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj, * we have just allocated the page no one else should be * using it. */ - VM_WARN_ON_ONCE_PAGE(!page_ref_count(page), page); + VM_WARN_ON_ONCE_PAGE(page_ref_count(page), page); set_page_count(page, 1); ret = vm_insert_page(vma, vaddr, page); if (ret) { -- 2.29.2