[PATCH v2 06/14] mm: handle_pte_fault() use pte_offset_map_rw_nolock()
From: Qi Zheng <hidden>
Date: 2024-08-22 07:14:23
Also in:
linux-arm-kernel, linux-mm, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
In handle_pte_fault(), we may modify the vmf->pte after acquiring the vmf->ptl, so convert it to using pte_offset_map_rw_nolock(). But since we will do the pte_same() check, so there is no need to get pmdval to do pmd_same() check, just pass a dummy variable to it. Signed-off-by: Qi Zheng <redacted> --- mm/memory.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 93c0c25433d02..7b6071a0e21e2 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -5499,14 +5499,22 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) vmf->pte = NULL; vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID; } else { + pmd_t dummy_pmdval; + /* * A regular pmd is established and it can't morph into a huge * pmd by anon khugepaged, since that takes mmap_lock in write * mode; but shmem or file collapse to THP could still morph * it into a huge pmd: just retry later if so. + * + * Use the maywrite version to indicate that vmf->pte will be + * modified, but since we will use pte_same() to detect the + * change of the pte entry, there is no need to get pmdval, so + * just pass a dummy variable to it. */ - vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); + vmf->pte = pte_offset_map_rw_nolock(vmf->vma->vm_mm, vmf->pmd, + vmf->address, &dummy_pmdval, + &vmf->ptl); if (unlikely(!vmf->pte)) return 0; vmf->orig_pte = ptep_get_lockless(vmf->pte);
--
2.20.1