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UPSTREAM: mm: handle COW faults under the VMA lock

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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>
(cherry picked from commit 4de8c93a4751e10737b6af65db42c743228c67a6)

Bug: 293665307
Change-Id: If749a6f8fcf69d83bbf872c1d45865d1b1b77ea0
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-10-06 20:53:16 +01:00 committed by Suren Baghdasaryan
parent c7fa581a79
commit 6541fffd92
1 changed files with 5 additions and 7 deletions
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12
mm/memory.c
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@ -4672,13 +4672,11 @@ 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)