From 6606f4c3c48c7a75b13816266d3ea562eeec0b44 Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Thu, 9 Feb 2023 10:29:53 -0700 Subject: PCI/P2PDMA: Annotate RCU dereference A dereference of the __rcu pointer was noticed by sparse: drivers/pci/p2pdma.c:199:44: sparse: sparse: dereference of noderef expression Dereference the __rcu pointer using rcu_dereference_protected() instead of accessing it directly. It's safe to use rcu_dereference_protected() because a reference is held on the pgmap's percpu reference counter and thus it cannot disappear. Link: https://lore.kernel.org/r/20230209172953.4597-1-logang@deltatee.com Reported-by: kernel test robot Signed-off-by: Logan Gunthorpe Signed-off-by: Bjorn Helgaas Reviewed-by: Chaitanya Kulkarni --- drivers/pci/p2pdma.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers/pci') diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 86812d2073ea..9e8205572830 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -194,11 +194,13 @@ static const struct attribute_group p2pmem_group = { static void p2pdma_page_free(struct page *page) { struct pci_p2pdma_pagemap *pgmap = to_p2p_pgmap(page->pgmap); + /* safe to dereference while a reference is held to the percpu ref */ + struct pci_p2pdma *p2pdma = + rcu_dereference_protected(pgmap->provider->p2pdma, 1); struct percpu_ref *ref; - gen_pool_free_owner(pgmap->provider->p2pdma->pool, - (uintptr_t)page_to_virt(page), PAGE_SIZE, - (void **)&ref); + gen_pool_free_owner(p2pdma->pool, (uintptr_t)page_to_virt(page), + PAGE_SIZE, (void **)&ref); percpu_ref_put(ref); } -- cgit v1.2.3-58-ga151