| Message ID | 20230927052505.2855872-5-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Handle more faults under the VMA lock | expand |
On Tue, Sep 26, 2023 at 10:25 PM Matthew Wilcox (Oracle) <willy@infradead.org> wrote: > > 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. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > mm/memory.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 0f3da4889230..02231a9394ed 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_maybe_unlock_vma(vmf); > + if (!ret) > + ret = vmf_anon_prepare(vmf); Same comment as in [PATCH 2/6]. If we reach here with FAULT_FLAG_VMA_LOCK then vma->anon_vma will not be NULL unless we change lock_vma_under_rcu(). > + if (ret) > + return ret; > > vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); > if (!vmf->cow_page) > -- > 2.40.1 >
diff --git a/mm/memory.c b/mm/memory.c index 0f3da4889230..02231a9394ed 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_maybe_unlock_vma(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)
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. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- mm/memory.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)