From 3ebafb7b468ba6595d9f1a2b899c8555374779aa Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Mon, 24 Jul 2023 19:54:10 +0100 Subject: [PATCH] BACKPORT: FROMGIT: mm: handle faults that merely update the accessed bit under the VMA lock Move FAULT_FLAG_VMA_LOCK check out of handle_pte_fault(). This should have a significant performance improvement for mmaped files. Write faults (on read-only shared pages) still take the mmap lock as we do not want to audit all the implementations of ->pfn_mkwrite() and ->page_mkwrite(). However write-faults on private mappings are handled under the VMA lock. Link: https://lkml.kernel.org/r/20230724185410.1124082-11-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Cc: Arjun Roy Cc: Eric Dumazet Cc: Punit Agrawal Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton (cherry picked from commit 88e2667632d43928d3ed50d0163ecd73aaa2d455 https: //git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable) [surenb: replaced folio_put() with put_page() in wp_page_shared()] Bug: 293665307 Change-Id: I27ac40bb0f7347083f641e0cfc8ab33e182c4c5b Signed-off-by: Suren Baghdasaryan --- mm/memory.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 7586f5f0f414..0f780a8dfaef 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3314,6 +3314,11 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf) vm_fault_t ret; pte_unmap_unlock(vmf->pte, vmf->ptl); + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + vma_end_read(vmf->vma); + return VM_FAULT_RETRY; + } + vmf->flags |= FAULT_FLAG_MKWRITE; ret = vma->vm_ops->pfn_mkwrite(vmf); if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) @@ -3336,6 +3341,12 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf) vm_fault_t tmp; pte_unmap_unlock(vmf->pte, vmf->ptl); + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + put_page(vmf->page); + vma_end_read(vmf->vma); + return VM_FAULT_RETRY; + } + tmp = do_page_mkwrite(vmf); if (unlikely(!tmp || (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { @@ -5046,12 +5057,6 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma)) return do_numa_page(vmf); - if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vmf->vma)) { - pte_unmap(vmf->pte); - vma_end_read(vmf->vma); - return VM_FAULT_RETRY; - } - vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); spin_lock(vmf->ptl); entry = vmf->orig_pte;