releases/3.4.96/mm-memory-failure.c-don-t-let-collect_procs-skip-over-processes-for-mf_action_required.patch

   1 From 74614de17db6fb472370c426d4f934d8d616edf2 Mon Sep 17 00:00:00 2001
   2 From: Tony Luck <tony.luck@intel.com>
   3 Date: Wed, 4 Jun 2014 16:11:01 -0700
   4 Subject: mm/memory-failure.c: don't let collect_procs() skip over processes for MF_ACTION_REQUIRED
   5
   6 From: Tony Luck <tony.luck@intel.com>
   7
   8 commit 74614de17db6fb472370c426d4f934d8d616edf2 upstream.
   9
  10 When Linux sees an "action optional" machine check (where h/w has reported
  11 an error that is not in the current execution path) we generally do not
  12 want to signal a process, since most processes do not have a SIGBUS
  13 handler - we'd just prematurely terminate the process for a problem that
  14 they might never actually see.
  15
  16 task_early_kill() decides whether to consider a process - and it checks
  17 whether this specific process has been marked for early signals with
  18 "prctl", or if the system administrator has requested early signals for
  19 all processes using /proc/sys/vm/memory_failure_early_kill.
  20
  21 But for MF_ACTION_REQUIRED case we must not defer.  The error is in the
  22 execution path of the current thread so we must send the SIGBUS
  23 immediatley.
  24
  25 Fix by passing a flag argument through collect_procs*() to
  26 task_early_kill() so it knows whether we can defer or must take action.
  27
  28 Signed-off-by: Tony Luck <tony.luck@intel.com>
  29 Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
  30 Cc: Andi Kleen <andi@firstfloor.org>
  31 Cc: Borislav Petkov <bp@suse.de>
  32 Cc: Chen Gong <gong.chen@linux.jf.intel.com>
  33 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  34 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  35 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  36
  37 ---
  38  mm/memory-failure.c |   21 ++++++++++++---------
  39  1 file changed, 12 insertions(+), 9 deletions(-)
  40
  41 --- a/mm/memory-failure.c
  42 +++ b/mm/memory-failure.c
  43 @@ -382,10 +382,12 @@ static void kill_procs(struct list_head
  44         }
  45  }
  46
  47 -static int task_early_kill(struct task_struct *tsk)
  48 +static int task_early_kill(struct task_struct *tsk, int force_early)
  49  {
  50         if (!tsk->mm)
  51                 return 0;
  52 +       if (force_early)
  53 +               return 1;
  54         if (tsk->flags & PF_MCE_PROCESS)
  55                 return !!(tsk->flags & PF_MCE_EARLY);
  56         return sysctl_memory_failure_early_kill;
  57 @@ -395,7 +397,7 @@ static int task_early_kill(struct task_s
  58   * Collect processes when the error hit an anonymous page.
  59   */
  60  static void collect_procs_anon(struct page *page, struct list_head *to_kill,
  61 -                             struct to_kill **tkc)
  62 +                             struct to_kill **tkc, int force_early)
  63  {
  64         struct vm_area_struct *vma;
  65         struct task_struct *tsk;
  66 @@ -409,7 +411,7 @@ static void collect_procs_anon(struct pa
  67         for_each_process (tsk) {
  68                 struct anon_vma_chain *vmac;
  69
  70 -               if (!task_early_kill(tsk))
  71 +               if (!task_early_kill(tsk, force_early))
  72                         continue;
  73                 list_for_each_entry(vmac, &av->head, same_anon_vma) {
  74                         vma = vmac->vma;
  75 @@ -427,7 +429,7 @@ static void collect_procs_anon(struct pa
  76   * Collect processes when the error hit a file mapped page.
  77   */
  78  static void collect_procs_file(struct page *page, struct list_head *to_kill,
  79 -                             struct to_kill **tkc)
  80 +                             struct to_kill **tkc, int force_early)
  81  {
  82         struct vm_area_struct *vma;
  83         struct task_struct *tsk;
  84 @@ -439,7 +441,7 @@ static void collect_procs_file(struct pa
  85         for_each_process(tsk) {
  86                 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
  87
  88 -               if (!task_early_kill(tsk))
  89 +               if (!task_early_kill(tsk, force_early))
  90                         continue;
  91
  92                 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
  93 @@ -465,7 +467,8 @@ static void collect_procs_file(struct pa
  94   * First preallocate one tokill structure outside the spin locks,
  95   * so that we can kill at least one process reasonably reliable.
  96   */
  97 -static void collect_procs(struct page *page, struct list_head *tokill)
  98 +static void collect_procs(struct page *page, struct list_head *tokill,
  99 +                               int force_early)
 100  {
 101         struct to_kill *tk;
 102
 103 @@ -476,9 +479,9 @@ static void collect_procs(struct page *p
 104         if (!tk)
 105                 return;
 106         if (PageAnon(page))
 107 -               collect_procs_anon(page, tokill, &tk);
 108 +               collect_procs_anon(page, tokill, &tk, force_early);
 109         else
 110 -               collect_procs_file(page, tokill, &tk);
 111 +               collect_procs_file(page, tokill, &tk, force_early);
 112         kfree(tk);
 113  }
 114
 115 @@ -948,7 +951,7 @@ static int hwpoison_user_mappings(struct
 116          * there's nothing that can be done.
 117          */
 118         if (kill)
 119 -               collect_procs(ppage, &tokill);
 120 +               collect_procs(ppage, &tokill, flags & MF_ACTION_REQUIRED);
 121
 122         if (hpage != ppage)
 123                 lock_page(ppage);