Le 19/04/2019 à 00:04, Jerome Glisse a écrit :
On Tue, Apr 16, 2019 at 03:44:56PM +0200, Laurent Dufour wrote:
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
When speculating faults (without holding mmap_sem) we need to validate
that the vma against which we loaded pages is still valid when we're
ready to install the new PTE.
Therefore, replace the pte_offset_map_lock() calls that (re)take the
PTL with pte_map_lock() which can fail in case we find the VMA changed
since we started the fault.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
[Port to 4.12 kernel]
[Remove the comment about the fault_env structure which has been
implemented as the vm_fault structure in the kernel]
[move pte_map_lock()'s definition upper in the file]
[move the define of FAULT_FLAG_SPECULATIVE later in the series]
[review error path in do_swap_page(), do_anonymous_page() and
wp_page_copy()]
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
---
mm/memory.c | 87 +++++++++++++++++++++++++++++++++++------------------
1 file changed, 58 insertions(+), 29 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index c6ddadd9d2b7..fc3698d13cb5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2073,6 +2073,13 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
}
EXPORT_SYMBOL_GPL(apply_to_page_range);
+static inline bool pte_map_lock(struct vm_fault *vmf)
I am not fan of the name maybe pte_offset_map_lock_if_valid() ? But
that just a taste thing. So feel free to ignore this comment.
I agree with you that adding _if_valid or something equivalent to
highlight the conditional of this function would be a good idea.
I'll think further about that name but yours looks good ;)
+{
+ vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd,
+ vmf->address, &vmf->ptl);
+ return true;
+}
+
/*
* handle_pte_fault chooses page fault handler according to an entry which was
* read non-atomically. Before making any commitment, on those architectures
