The patch titled
Subject: userfaultfd: don't retake mmap_sem to emulate NOPAGE
has been added to the -mm tree. Its filename is
userfaultfd-dont-retake-mmap_sem-to-emulate-nopage.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-dont-retake-mmap_sem-to-emulate-nopage.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-dont-retake-mmap_sem-to-emulate-nopage.patch
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The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: userfaultfd: don't retake mmap_sem to emulate NOPAGE
This patch removes the risk path in handle_userfault() then we will be
sure that the callers of handle_mm_fault() will know that the VMAs might
have changed. Meanwhile with previous patch we don't lose responsiveness
as well since the core mm code now can handle the nonfatal userspace
signals even if we return VM_FAULT_RETRY.
Link: http://lkml.kernel.org/r/20200220160234.9646-1-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Suggested-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Bobby Powers <bobbypowers@xxxxxxxxx>
Cc: Brian Geffon <bgeffon@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx>
Cc: "Dr . David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Martin Cracauer <cracauer@xxxxxxxx>
Cc: Marty McFadden <mcfadden8@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Maya Gokhale <gokhale2@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 24 ------------------------
1 file changed, 24 deletions(-)
--- a/fs/userfaultfd.c~userfaultfd-dont-retake-mmap_sem-to-emulate-nopage
+++ a/fs/userfaultfd.c
@@ -524,30 +524,6 @@ vm_fault_t handle_userfault(struct vm_fa
__set_current_state(TASK_RUNNING);
- if (return_to_userland) {
- if (signal_pending(current) &&
- !fatal_signal_pending(current)) {
- /*
- * If we got a SIGSTOP or SIGCONT and this is
- * a normal userland page fault, just let
- * userland return so the signal will be
- * handled and gdb debugging works. The page
- * fault code immediately after we return from
- * this function is going to release the
- * mmap_sem and it's not depending on it
- * (unlike gup would if we were not to return
- * VM_FAULT_RETRY).
- *
- * If a fatal signal is pending we still take
- * the streamlined VM_FAULT_RETRY failure path
- * and there's no need to retake the mmap_sem
- * in such case.
- */
- down_read(&mm->mmap_sem);
- ret = VM_FAULT_NOPAGE;
- }
- }
-
/*
* Here we race with the list_del; list_add in
* userfaultfd_ctx_read(), however because we don't ever run
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-gup-rename-nonblocking-to-locked-where-proper.patch
mm-gup-fix-__get_user_pages-on-fault-retry-of-hugetlb.patch
mm-introduce-fault_signal_pending.patch
x86-mm-use-helper-fault_signal_pending.patch
arc-mm-use-helper-fault_signal_pending.patch
arm64-mm-use-helper-fault_signal_pending.patch
powerpc-mm-use-helper-fault_signal_pending.patch
sh-mm-use-helper-fault_signal_pending.patch
mm-return-faster-for-non-fatal-signals-in-user-mode-faults.patch
userfaultfd-dont-retake-mmap_sem-to-emulate-nopage.patch
mm-introduce-fault_flag_default.patch
mm-introduce-fault_flag_interruptible.patch
mm-allow-vm_fault_retry-for-multiple-times.patch
mm-gup-allow-vm_fault_retry-for-multiple-times.patch
mm-gup-allow-to-react-to-fatal-signals.patch
mm-userfaultfd-honor-fault_flag_killable-in-fault-path.patch
mm-merge-parameters-for-change_protection.patch
userfaultfd-wp-apply-_page_uffd_wp-bit.patch
userfaultfd-wp-drop-_page_uffd_wp-properly-when-fork.patch
userfaultfd-wp-add-pmd_swp_uffd_wp-helpers.patch
userfaultfd-wp-support-swap-and-page-migration.patch
khugepaged-skip-collapse-if-uffd-wp-detected.patch
userfaultfd-wp-dont-wake-up-when-doing-write-protect.patch
userfaultfd-wp-declare-_uffdio_writeprotect-conditionally.patch
userfaultfd-selftests-refactor-statistics.patch
userfaultfd-selftests-add-write-protect-test.patch
