bcachefs: Reduce the scope of gc_lock

gc_lock is now only for synchronization between check_alloc_info and
interior btree updates - nothing else
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_background.c

@@ -596,8 +596,6 @@ int bch2_alloc_read(struct bch_fs *c)
 	struct bch_dev *ca = NULL;
 	int ret;
 
-	down_read(&c->gc_lock);
-
 	if (c->sb.version_upgrade_complete >= bcachefs_metadata_version_bucket_gens) {
 		ret = for_each_btree_key(trans, iter, BTREE_ID_bucket_gens, POS_MIN,
 					 BTREE_ITER_prefetch, k, ({
@@ -646,7 +644,6 @@ int bch2_alloc_read(struct bch_fs *c)
 
 	bch2_dev_put(ca);
 	bch2_trans_put(trans);
-	up_read(&c->gc_lock);
 
 	bch_err_fn(c, ret);
 	return ret;

fs/bcachefs/bcachefs.h

@@ -538,8 +538,8 @@ struct bch_dev {
 	/*
 	 * Buckets:
 	 * Per-bucket arrays are protected by c->mark_lock, bucket_lock and
-	 * gc_lock, for device resize - holding any is sufficient for access:
-	 * Or rcu_read_lock(), but only for dev_ptr_stale():
+	 * gc_gens_lock, for device resize - holding any is sufficient for
+	 * access: Or rcu_read_lock(), but only for dev_ptr_stale():
 	 */
 	struct bucket_array __rcu *buckets_gc;
 	struct bucket_gens __rcu *bucket_gens;

fs/bcachefs/btree_gc.c

@@ -1240,7 +1240,7 @@ int bch2_gc_gens(struct bch_fs *c)
 	int ret;
 
 	/*
-	 * Ideally we would be using state_lock and not gc_lock here, but that
+	 * Ideally we would be using state_lock and not gc_gens_lock here, but that
 	 * introduces a deadlock in the RO path - we currently take the state
 	 * lock at the start of going RO, thus the gc thread may get stuck:
 	 */
@@ -1248,7 +1248,8 @@ int bch2_gc_gens(struct bch_fs *c)
 		return 0;
 
 	trace_and_count(c, gc_gens_start, c);
-	down_read(&c->gc_lock);
+
+	down_read(&c->state_lock);
 
 	for_each_member_device(c, ca) {
 		struct bucket_gens *gens = bucket_gens(ca);
@@ -1317,7 +1318,7 @@ int bch2_gc_gens(struct bch_fs *c)
 		ca->oldest_gen = NULL;
 	}
 
-	up_read(&c->gc_lock);
+	up_read(&c->state_lock);
 	mutex_unlock(&c->gc_gens_lock);
 	if (!bch2_err_matches(ret, EROFS))
 		bch_err_fn(c, ret);

fs/bcachefs/buckets.c

@@ -1217,7 +1217,6 @@ int bch2_dev_buckets_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 		bucket_gens->nbuckets - bucket_gens->first_bucket;
 
 	if (resize) {
-		down_write(&c->gc_lock);
 		down_write(&ca->bucket_lock);
 		percpu_down_write(&c->mark_lock);
 	}
@@ -1240,7 +1239,6 @@ int bch2_dev_buckets_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 	if (resize) {
 		percpu_up_write(&c->mark_lock);
 		up_write(&ca->bucket_lock);
-		up_write(&c->gc_lock);
 	}
 
 	ret = 0;

fs/bcachefs/buckets.h

@@ -85,7 +85,7 @@ static inline struct bucket_array *gc_bucket_array(struct bch_dev *ca)
 	return rcu_dereference_check(ca->buckets_gc,
 				     !ca->fs ||
 				     percpu_rwsem_is_held(&ca->fs->mark_lock) ||
-				     lockdep_is_held(&ca->fs->gc_lock) ||
+				     lockdep_is_held(&ca->fs->state_lock) ||
 				     lockdep_is_held(&ca->bucket_lock));
 }
 
@@ -103,7 +103,7 @@ static inline struct bucket_gens *bucket_gens(struct bch_dev *ca)
 	return rcu_dereference_check(ca->bucket_gens,
 				     !ca->fs ||
 				     percpu_rwsem_is_held(&ca->fs->mark_lock) ||
-				     lockdep_is_held(&ca->fs->gc_lock) ||
+				     lockdep_is_held(&ca->fs->state_lock) ||
 				     lockdep_is_held(&ca->bucket_lock));
 }
 

fs/bcachefs/recovery_passes.c

@@ -193,6 +193,8 @@ int bch2_run_online_recovery_passes(struct bch_fs *c)
 {
 	int ret = 0;
 
+	down_read(&c->state_lock);
+
 	for (unsigned i = 0; i < ARRAY_SIZE(recovery_pass_fns); i++) {
 		struct recovery_pass_fn *p = recovery_pass_fns + i;
 
@@ -208,6 +210,8 @@ int bch2_run_online_recovery_passes(struct bch_fs *c)
 			break;
 	}
 
+	up_read(&c->state_lock);
+
 	return ret;
 }