Re: [bug report] mm: convert ksm_might_need_to_copy() to work on folios

[Matthew Wilcox <willy@infradead.org>]

On Wed, Dec 13, 2023 at 10:01:46AM +0300, Dan Carpenter wrote:
> Hello Matthew Wilcox (Oracle),
> 
> The patch 6faef19bdfcc: "mm: convert ksm_might_need_to_copy() to work
> on folios" from Dec 11, 2023 (linux-next), leads to the following
> Smatch static checker warning:
> 
> 	mm/memory.c:4118 do_swap_page()
> 	error: 'folio' dereferencing possible ERR_PTR()

Right!  Andrew, please squash in:

diff --git a/mm/memory.c b/mm/memory.c
index 318f923134e4..1270d70dcb80 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3945,9 +3945,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		folio = ksm_might_need_to_copy(folio, vma, vmf->address);
 		if (unlikely(!folio)) {
 			ret = VM_FAULT_OOM;
+			folio = swapcache;
 			goto out_page;
 		} else if (unlikely(folio == ERR_PTR(-EHWPOISON))) {
 			ret = VM_FAULT_HWPOISON;
+			folio = swapcache;
 			goto out_page;
 		}
 		page = folio_page(folio, 0);