lockdep/mm: Fix might_fault() lockdep check of current->mm->mmap_lock

commit a1b65f3
Author: Peter Zijlstra <[email protected]>
Date:   Mon Nov 4 14:39:10 2024 +0100

    lockdep/mm: Fix might_fault() lockdep check of current->mm->mmap_lock

    Turns out that this commit, about 10 years ago:

      9ec2353 ("sched/preempt, mm/fault: Trigger might_sleep() in might_fault() with disabled pagefaults")

    ... accidentally (and unnessecarily) put the lockdep part of
    __might_fault() under CONFIG_DEBUG_ATOMIC_SLEEP=y.

    This is potentially notable because large distributions such as
    Ubuntu are running with !CONFIG_DEBUG_ATOMIC_SLEEP.

    Restore the debug check.

    [ mingo: Update changelog. ]

    Fixes: 9ec2353 ("sched/preempt, mm/fault: Trigger might_sleep() in might_fault() with disabled pagefaults")
    Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
    Signed-off-by: Ingo Molnar <[email protected]>
    Cc: Linus Torvalds <[email protected]>
    Cc: Andrew Morton <[email protected]>
    Link: https://lore.kernel.org/r/[email protected]

JIRA: https://issues.redhat.com/browse/RHEL-77742
Signed-off-by: Nico Pache <[email protected]>

Author: PacheNico

mm/memory.c

@@ -6747,10 +6747,8 @@ void __might_fault(const char *file, int line)
 	if (pagefault_disabled())
 		return;
 	__might_sleep(file, line);
-#if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
 	if (current->mm)
 		might_lock_read(&current->mm->mmap_lock);
-#endif
 }
 EXPORT_SYMBOL(__might_fault);
 #endif