mm: oom_kill: add trace logs in process_mrelease() system call

The process_mrelease() system call is used to release the memory of a
dying process from the context of the caller, which is similar to and uses
the functions of the oom reaper logic.  There exist trace logs for a
process when reaped by the oom reaper.  Just extend the same to when done
by the process_mrelease() system call.

This patch provides information on how much memory is freed from a process
which is being reaped.  Adding trace events in the process_mrelease() path
when process is being reaped would enable more holistic debug as it
happens in oom_reap_task_mm() currently.

This extends the debug functionality for the events as described in [1] to
the process_mrelease() system call.  Now the coverage of trace events is
complete.

[1] https://lore.kernel.org/all/20170530185231.GA13412@castle/T/#u

Link: https://lkml.kernel.org/r/20220816060017.17996-1-pbrahma@qti.qualcomm.com
Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Signed-off-by: Pratyush Brahma <quic_pbrahma@quicinc.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 3c6cf9e3cd66ea67cfe317dbe0f91c54d2e4faa8..51ad5f0b612e6be4ddaafed8bb31d3a2dedef964 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -995,7 +995,6 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
        mmdrop(mm);
        put_task_struct(victim);
 }
-#undef K
 
 /*
  * Kill provided task unless it's secured by setting
@@ -1241,17 +1240,33 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
                goto drop_mm;
 
        if (mmap_read_lock_killable(mm)) {
+               trace_skip_task_reaping(task->pid);
                ret = -EINTR;
-               goto drop_mm;
+               goto read_unlock;
        }
        /*
         * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
         * possible change in exit_mmap is seen
         */
-       if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
+       if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
+               trace_skip_task_reaping(task->pid);
+               goto read_unlock;
+       }
+
+       trace_start_task_reaping(task->pid);
+
+       if (!__oom_reap_task_mm(mm))
                ret = -EAGAIN;
-       mmap_read_unlock(mm);
 
+       pr_debug("process_mrelease: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
+                                               task_pid_nr(task), task->comm,
+                                               K(get_mm_counter(mm, MM_ANONPAGES)),
+                                               K(get_mm_counter(mm, MM_FILEPAGES)),
+                                               K(get_mm_counter(mm, MM_SHMEMPAGES)));
+       trace_finish_task_reaping(task->pid);
+
+read_unlock:
+       mmap_read_unlock(mm);
 drop_mm:
        mmdrop(mm);
 put_task:
@@ -1261,3 +1276,4 @@ put_task:
        return -ENOSYS;
 #endif /* CONFIG_MMU */
 }
+#undef K