[PATCH 02/13] mm/gup: Cache p4d in follow_p4d_mask()
From: peterx@redhat.com
Date: 2024-03-13 21:47:27
Also in:
linux-arm-kernel, lkml, sparclinux
Subsystem:
memory management, memory management - gup (get user pages), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
From: Peter Xu <peterx@redhat.com> Add a variable to cache p4d in follow_p4d_mask(). It's a good practise to make sure all the following checks will have a consistent view of the entry. Signed-off-by: Peter Xu <peterx@redhat.com> --- mm/gup.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index df83182ec72d..69a777f4fc5c 100644
--- a/mm/gup.c
+++ b/mm/gup.c@@ -772,16 +772,17 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma, unsigned int flags, struct follow_page_context *ctx) { - p4d_t *p4d; + p4d_t *p4dp, p4d; - p4d = p4d_offset(pgdp, address); - if (p4d_none(*p4d)) + p4dp = p4d_offset(pgdp, address); + p4d = READ_ONCE(*p4dp); + if (p4d_none(p4d)) return no_page_table(vma, flags); - BUILD_BUG_ON(p4d_huge(*p4d)); - if (unlikely(p4d_bad(*p4d))) + BUILD_BUG_ON(p4d_huge(p4d)); + if (unlikely(p4d_bad(p4d))) return no_page_table(vma, flags); - return follow_pud_mask(vma, address, p4d, flags, ctx); + return follow_pud_mask(vma, address, p4dp, flags, ctx); } /**
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2.44.0