bcachefs: fix odebug warn and lockdep splat due to on-stack rhashtable

Guenter Roeck reports a lockdep splat and DEBUG_OBJECTS_WORK related
warning when bch2_copygc_thread() initializes its rhashtable. The
lockdep splat relates to a warning print caused by the fact that the
rhashtable exists on the stack but is not annotated as so. This is
something that could be addressed by INIT_WORK_ONSTACK(), but
rhashtable doesn't expose that control and probably isnt worth the
churn for just one user. Instead, dynamically allocate the
buckets_in_flight structure and avoid the splat that way.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/movinggc.c b/fs/bcachefs/movinggc.c
index 4d955f3..0a05763 100644 (file)
--- a/fs/bcachefs/movinggc.c
+++ b/fs/bcachefs/movinggc.c
@@ -305,14 +305,16 @@ static int bch2_copygc_thread(void *arg)
        struct moving_context ctxt;
        struct bch_move_stats move_stats;
        struct io_clock *clock = &c->io_clock[WRITE];
-       struct buckets_in_flight buckets;
+       struct buckets_in_flight *buckets;
        u64 last, wait;
        int ret = 0;
 
-       memset(&buckets, 0, sizeof(buckets));
-
-       ret = rhashtable_init(&buckets.table, &bch_move_bucket_params);
+       buckets = kzalloc(sizeof(struct buckets_in_flight), GFP_KERNEL);
+       if (!buckets)
+               return -ENOMEM;
+       ret = rhashtable_init(&buckets->table, &bch_move_bucket_params);
        if (ret) {
+               kfree(buckets);
                bch_err_msg(c, ret, "allocating copygc buckets in flight");
                return ret;
        }
@@ -331,12 +333,12 @@ static int bch2_copygc_thread(void *arg)
                cond_resched();
 
                if (!c->copy_gc_enabled) {
-                       move_buckets_wait(&ctxt, &buckets, true);
+                       move_buckets_wait(&ctxt, buckets, true);
                        kthread_wait_freezable(c->copy_gc_enabled);
                }
 
                if (unlikely(freezing(current))) {
-                       move_buckets_wait(&ctxt, &buckets, true);
+                       move_buckets_wait(&ctxt, buckets, true);
                        __refrigerator(false);
                        continue;
                }
@@ -347,7 +349,7 @@ static int bch2_copygc_thread(void *arg)
                if (wait > clock->max_slop) {
                        c->copygc_wait_at = last;
                        c->copygc_wait = last + wait;
-                       move_buckets_wait(&ctxt, &buckets, true);
+                       move_buckets_wait(&ctxt, buckets, true);
                        trace_and_count(c, copygc_wait, c, wait, last + wait);
                        bch2_kthread_io_clock_wait(clock, last + wait,
                                        MAX_SCHEDULE_TIMEOUT);
@@ -357,7 +359,7 @@ static int bch2_copygc_thread(void *arg)
                c->copygc_wait = 0;
 
                c->copygc_running = true;
-               ret = bch2_copygc(&ctxt, &buckets, &did_work);
+               ret = bch2_copygc(&ctxt, buckets, &did_work);
                c->copygc_running = false;
 
                wake_up(&c->copygc_running_wq);
@@ -374,8 +376,10 @@ static int bch2_copygc_thread(void *arg)
                }
        }
 
-       move_buckets_wait(&ctxt, &buckets, true);
-       rhashtable_destroy(&buckets.table);
+       move_buckets_wait(&ctxt, buckets, true);
+
+       rhashtable_destroy(&buckets->table);
+       kfree(buckets);
        bch2_moving_ctxt_exit(&ctxt);
        bch2_move_stats_exit(&move_stats, c);