[RFC PATCH v9 6/7] mm: Update alloc_set_pte() for zero page
From: Yu-cheng Yu <hidden>
Date: 2020-02-05 18:23:46
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Update alloc_set_pte() for the zero-page case. A special mapping can also use a zero page for read. One use case is the Indirect Branch Tracking legacy code page (introduced next). Signed-off-by: Yu-cheng Yu <redacted> --- mm/memory.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c
index 6daa28614327..58c1e4b60991 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -3447,6 +3447,12 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, flush_icache_page(vma, page); entry = mk_pte(page, vma->vm_page_prot); + + if (is_zero_pfn(pte_pfn(entry))) { + entry = pte_mkspecial(entry); + goto alloc_set_pte_out; + } + if (write) entry = maybe_mkwrite(pte_mkdirty(entry), vma); /* copy-on-write page */
@@ -3459,6 +3465,8 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page)); page_add_file_rmap(page, false); } + +alloc_set_pte_out: set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); /* no need to invalidate: a not-present page won't be cached */
--
2.21.0