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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) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-10-06 20:53:16 +01:00 committed by Andrew Morton
parent 4ed4379881
commit 4de8c93a47
1 changed files with 5 additions and 7 deletions
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12
mm/memory.c
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@ -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)