sorry for not processing for a long time. I met it again.
patch v1 https://lkml.org/lkml/2019/9/20/656
do_machine_check()
do_memory_failure()
memory_failure()
hw_poison_user_mappings()
try_to_unmap()
pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
...and now we have a swap entry that indicates that the page entry
refers to a bad (and poisoned) page of memory, but gup_fast() at this
level of the page table was ignoring swap entries, and incorrectly
assuming that "!pxd_none() == valid and present".
And this was not just a poisoned page problem, but a generaly swap entry
problem. So, any swap entry type (device memory migration, numa migration,
or just regular swapping) could lead to the same problem.
Fix this by checking for pxd_present(), instead of pxd_none().
Signed-off-by: Qiujun Huang <[email protected]>
---
mm/gup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c
index 7646bf9..9c41670 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2237,7 +2237,7 @@ static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
pud_t pud = READ_ONCE(*pudp);
next = pud_addr_end(addr, end);
- if (pud_none(pud))
+ if (unlikely(!pud_present(pud)))
return 0;
if (unlikely(pud_huge(pud))) {
if (!gup_huge_pud(pud, pudp, addr, next, flags,
--
1.8.3.1