From 4de8c93a4751e10737b6af65db42c743228c67a6 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Fri, 6 Oct 2023 20:53:16 +0100 Subject: [PATCH] mm: handle COW faults under the VMA lock If the page is not currently present in the page tables, we need to call the page fault handler to find out which page we're supposed to COW, so we need to both check that there is already an anon_vma and that the fault handler doesn't need the mmap_lock. Link: https://lkml.kernel.org/r/20231006195318.4087158-5-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Suren Baghdasaryan Signed-off-by: Andrew Morton --- mm/memory.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 7b240a67f207..be9469a29413 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4639,13 +4639,11 @@ static vm_fault_t do_cow_fault(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; vm_fault_t ret; - if (vmf->flags & FAULT_FLAG_VMA_LOCK) { - vma_end_read(vma); - return VM_FAULT_RETRY; - } - - if (unlikely(anon_vma_prepare(vma))) - return VM_FAULT_OOM; + ret = vmf_can_call_fault(vmf); + if (!ret) + ret = vmf_anon_prepare(vmf); + if (ret) + return ret; vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); if (!vmf->cow_page)