[05/86] mm/memory.c: replace is_zero_pfn with is_huge_zero_pmd for thp

Commit Message

Andrew Morton Dec. 5, 2019, 12:49 a.m. UTC

From: Yu Zhao <[e-mail]>
Subject: mm/memory.c: replace is_zero_pfn with is_huge_zero_pmd for thp

For hugely mapped thp, we use is_huge_zero_pmd() to check if it's zero
page or not.

We do fill ptes with my_zero_pfn() when we split zero thp pmd, but this is
not what we have in vm_normal_page_pmd() -- pmd_trans_huge_lock() makes
sure of it.

This is a trivial fix for /proc/pid/numa_maps, and AFAIK nobody complains
about it.

Gerald Schaefer asked:
: Maybe the description could also mention the symptom of this bug?
: I would assume that it affects anon/dirty accounting in gather_pte_stats(),
: for huge mappings, if zero page mappings are not correctly recognized.

I came across this while I was looking at the code, so I'm not aware of
any symptom.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Yu Zhao <[e-mail]>
Acked-by: Andrew Morton <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Ralph Campbell <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: "Aneesh Kumar K . V" <[e-mail]>
Cc: Dave Airlie <[e-mail]>
Cc: Thomas Hellstrom <[e-mail]>
Cc: Souptick Joarder <[e-mail]>
Cc: Gerald Schaefer <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memory.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- a/mm/memory.c~mm-replace-is_zero_pfn-with-is_huge_zero_pmd-for-thp
+++ a/mm/memory.c
@@ -672,7 +672,7 @@  struct page *vm_normal_page_pmd(struct v
 
 	if (pmd_devmap(pmd))
 		return NULL;
-	if (is_zero_pfn(pfn))
+	if (is_huge_zero_pmd(pmd))
 		return NULL;
 	if (unlikely(pfn > highest_memmap_pfn))
 		return NULL;