target/linux/generic/backport-5.15/020-v6.1-15-mm-multi-gen-LRU-move-lru_gen_add_mm-out-of-IRQ-off-.patch

   1 From 255bb0ac393f1c2818cd75af45a9226300ab3daf Mon Sep 17 00:00:00 2001
   2 From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
   3 Date: Wed, 26 Oct 2022 15:48:30 +0200
   4 Subject: [PATCH 15/29] mm: multi-gen LRU: move lru_gen_add_mm() out of IRQ-off
   5  region
   6
   7 lru_gen_add_mm() has been added within an IRQ-off region in the commit
   8 mentioned below.  The other invocations of lru_gen_add_mm() are not within
   9 an IRQ-off region.
  10
  11 The invocation within IRQ-off region is problematic on PREEMPT_RT because
  12 the function is using a spin_lock_t which must not be used within
  13 IRQ-disabled regions.
  14
  15 The other invocations of lru_gen_add_mm() occur while
  16 task_struct::alloc_lock is acquired.  Move lru_gen_add_mm() after
  17 interrupts are enabled and before task_unlock().
  18
  19 Link: https://lkml.kernel.org/r/20221026134830.711887-1-bigeasy@linutronix.de
  20 Fixes: bd74fdaea1460 ("mm: multi-gen LRU: support page table walks")
  21 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  22 Acked-by: Yu Zhao <yuzhao@google.com>
  23 Cc: Al Viro <viro@zeniv.linux.org.uk>
  24 Cc: "Eric W . Biederman" <ebiederm@xmission.com>
  25 Cc: Kees Cook <keescook@chromium.org>
  26 Cc: Thomas Gleixner <tglx@linutronix.de>
  27 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  28 ---
  29  fs/exec.c | 2 +-
  30  1 file changed, 1 insertion(+), 1 deletion(-)
  31
  32 diff --git a/fs/exec.c b/fs/exec.c
  33 index 1afa15a07d26..718c58947be1 100644
  34 --- a/fs/exec.c
  35 +++ b/fs/exec.c
  36 @@ -1013,7 +1013,6 @@ static int exec_mmap(struct mm_struct *mm)
  37         active_mm = tsk->active_mm;
  38         tsk->active_mm = mm;
  39         tsk->mm = mm;
  40 -       lru_gen_add_mm(mm);
  41         /*
  42          * This prevents preemption while active_mm is being loaded and
  43          * it and mm are being updated, which could cause problems for
  44 @@ -1028,6 +1027,7 @@ static int exec_mmap(struct mm_struct *mm)
  45                 local_irq_enable();
  46         tsk->mm->vmacache_seqnum = 0;
  47         vmacache_flush(tsk);
  48 +       lru_gen_add_mm(mm);
  49         task_unlock(tsk);
  50         lru_gen_use_mm(mm);
  51         if (old_mm) {
  52 --
  53 2.40.0
  54