bcachefs: Replace rcu_read_lock() with guards

The new guard(), scoped_guard() allow for more natural code.

Some of the uses with creative flow control have been left.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/alloc_background.c

@@ -1000,14 +1000,11 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		}
 
 		if (new_a->gen != old_a->gen) {
-			rcu_read_lock();
+			guard(rcu)();
 			u8 *gen = bucket_gen(ca, new.k->p.offset);
-			if (unlikely(!gen)) {
-				rcu_read_unlock();
+			if (unlikely(!gen))
 				goto invalid_bucket;
-			}
 			*gen = new_a->gen;
-			rcu_read_unlock();
 		}
 
 #define eval_state(_a, expr)		({ const struct bch_alloc_v4 *a = _a; expr; })
@@ -1033,15 +1030,12 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 	}
 
 	if ((flags & BTREE_TRIGGER_gc) && (flags & BTREE_TRIGGER_insert)) {
-		rcu_read_lock();
+		guard(rcu)();
 		struct bucket *g = gc_bucket(ca, new.k->p.offset);
-		if (unlikely(!g)) {
-			rcu_read_unlock();
+		if (unlikely(!g))
 			goto invalid_bucket;
-		}
 		g->gen_valid	= 1;
 		g->gen		= new_a->gen;
-		rcu_read_unlock();
 	}
 err:
 fsck_err:
@@ -1117,13 +1111,12 @@ static bool next_bucket(struct bch_fs *c, struct bch_dev **ca, struct bpos *buck
 		bucket->offset = 0;
 	}
 
-	rcu_read_lock();
+	guard(rcu)();
 	*ca = __bch2_next_dev_idx(c, bucket->inode, NULL);
 	if (*ca) {
 		*bucket = POS((*ca)->dev_idx, (*ca)->mi.first_bucket);
 		bch2_dev_get(*ca);
 	}
-	rcu_read_unlock();
 
 	return *ca != NULL;
 }
@@ -2514,7 +2507,7 @@ void bch2_recalc_capacity(struct bch_fs *c)
 
 	lockdep_assert_held(&c->state_lock);
 
-	rcu_read_lock();
+	guard(rcu)();
 	for_each_member_device_rcu(c, ca, NULL) {
 		struct block_device *bdev = READ_ONCE(ca->disk_sb.bdev);
 		if (bdev)
@@ -2559,7 +2552,6 @@ void bch2_recalc_capacity(struct bch_fs *c)
 		bucket_size_max = max_t(unsigned, bucket_size_max,
 					ca->mi.bucket_size);
 	}
-	rcu_read_unlock();
 
 	bch2_set_ra_pages(c, ra_pages);
 
@@ -2584,10 +2576,9 @@ u64 bch2_min_rw_member_capacity(struct bch_fs *c)
 {
 	u64 ret = U64_MAX;
 
-	rcu_read_lock();
+	guard(rcu)();
 	for_each_rw_member_rcu(c, ca)
 		ret = min(ret, ca->mi.nbuckets * ca->mi.bucket_size);
-	rcu_read_unlock();
 	return ret;
 }
 

fs/bcachefs/alloc_background.h

@@ -13,11 +13,9 @@
 
 static inline bool bch2_dev_bucket_exists(struct bch_fs *c, struct bpos pos)
 {
-	rcu_read_lock();
+	guard(rcu)();
 	struct bch_dev *ca = bch2_dev_rcu_noerror(c, pos.inode);
-	bool ret = ca && bucket_valid(ca, pos.offset);
-	rcu_read_unlock();
-	return ret;
+	return ca && bucket_valid(ca, pos.offset);
 }
 
 static inline u64 bucket_to_u64(struct bpos bucket)

fs/bcachefs/alloc_foreground.c

@@ -69,10 +69,9 @@ const char * const bch2_watermarks[] = {
 
 void bch2_reset_alloc_cursors(struct bch_fs *c)
 {
-	rcu_read_lock();
+	guard(rcu)();
 	for_each_member_device_rcu(c, ca, NULL)
 		memset(ca->alloc_cursor, 0, sizeof(ca->alloc_cursor));
-	rcu_read_unlock();
 }
 
 static void bch2_open_bucket_hash_add(struct bch_fs *c, struct open_bucket *ob)
@@ -166,9 +165,8 @@ static void open_bucket_free_unused(struct bch_fs *c, struct open_bucket *ob)
 	       ARRAY_SIZE(c->open_buckets_partial));
 
 	spin_lock(&c->freelist_lock);
-	rcu_read_lock();
-	bch2_dev_rcu(c, ob->dev)->nr_partial_buckets++;
-	rcu_read_unlock();
+	scoped_guard(rcu)
+		bch2_dev_rcu(c, ob->dev)->nr_partial_buckets++;
 
 	ob->on_partial_list = true;
 	c->open_buckets_partial[c->open_buckets_partial_nr++] =
@@ -873,9 +871,8 @@ static int bucket_alloc_set_partial(struct bch_fs *c,
 					  i);
 			ob->on_partial_list = false;
 
-			rcu_read_lock();
-			bch2_dev_rcu(c, ob->dev)->nr_partial_buckets--;
-			rcu_read_unlock();
+			scoped_guard(rcu)
+				bch2_dev_rcu(c, ob->dev)->nr_partial_buckets--;
 
 			ret = add_new_bucket(c, req, ob);
 			if (ret)
@@ -1057,9 +1054,8 @@ void bch2_open_buckets_stop(struct bch_fs *c, struct bch_dev *ca,
 
 			ob->on_partial_list = false;
 
-			rcu_read_lock();
-			bch2_dev_rcu(c, ob->dev)->nr_partial_buckets--;
-			rcu_read_unlock();
+			scoped_guard(rcu)
+				bch2_dev_rcu(c, ob->dev)->nr_partial_buckets--;
 
 			spin_unlock(&c->freelist_lock);
 			bch2_open_bucket_put(c, ob);
@@ -1087,14 +1083,11 @@ static struct write_point *__writepoint_find(struct hlist_head *head,
 {
 	struct write_point *wp;
 
-	rcu_read_lock();
+	guard(rcu)();
 	hlist_for_each_entry_rcu(wp, head, node)
 		if (wp->write_point == write_point)
-			goto out;
-	wp = NULL;
-out:
-	rcu_read_unlock();
-	return wp;
+			return wp;
+	return NULL;
 }
 
 static inline bool too_many_writepoints(struct bch_fs *c, unsigned factor)
@@ -1638,19 +1631,16 @@ static noinline void bch2_print_allocator_stuck(struct bch_fs *c)
 
 	bch2_printbuf_make_room(&buf, 4096);
 
-	rcu_read_lock();
 	buf.atomic++;
-
-	for_each_online_member_rcu(c, ca) {
-		prt_printf(&buf, "Dev %u:\n", ca->dev_idx);
-		printbuf_indent_add(&buf, 2);
-		bch2_dev_alloc_debug_to_text(&buf, ca);
-		printbuf_indent_sub(&buf, 2);
-		prt_newline(&buf);
-	}
-
+	scoped_guard(rcu)
+		for_each_online_member_rcu(c, ca) {
+			prt_printf(&buf, "Dev %u:\n", ca->dev_idx);
+			printbuf_indent_add(&buf, 2);
+			bch2_dev_alloc_debug_to_text(&buf, ca);
+			printbuf_indent_sub(&buf, 2);
+			prt_newline(&buf);
+		}
 	--buf.atomic;
-	rcu_read_unlock();
 
 	prt_printf(&buf, "Copygc debug:\n");
 	printbuf_indent_add(&buf, 2);

fs/bcachefs/backpointers.c

@@ -48,17 +48,19 @@ void bch2_backpointer_to_text(struct printbuf *out, struct bch_fs *c, struct bke
 {
 	struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(k);
 
-	rcu_read_lock();
-	struct bch_dev *ca = bch2_dev_rcu_noerror(c, bp.k->p.inode);
-	if (ca) {
-		u32 bucket_offset;
-		struct bpos bucket = bp_pos_to_bucket_and_offset(ca, bp.k->p, &bucket_offset);
-		rcu_read_unlock();
+	struct bch_dev *ca;
+	u32 bucket_offset;
+	struct bpos bucket;
+	scoped_guard(rcu) {
+		ca = bch2_dev_rcu_noerror(c, bp.k->p.inode);
+		if (ca)
+			bucket = bp_pos_to_bucket_and_offset(ca, bp.k->p, &bucket_offset);
+	}
+
+	if (ca)
 		prt_printf(out, "bucket=%llu:%llu:%u ", bucket.inode, bucket.offset, bucket_offset);
-	} else {
-		rcu_read_unlock();
+	else
 		prt_printf(out, "sector=%llu:%llu ", bp.k->p.inode, bp.k->p.offset >> MAX_EXTENT_COMPRESS_RATIO_SHIFT);
-	}
 
 	bch2_btree_id_level_to_text(out, bp.v->btree_id, bp.v->level);
 	prt_str(out, " data_type=");
@@ -591,6 +593,7 @@ static int check_bp_exists(struct btree_trans *trans,
 		bkey_for_each_ptr(other_extent_ptrs, ptr)
 			if (ptr->dev == bp->k.p.inode &&
 			    dev_ptr_stale_rcu(ca, ptr)) {
+				rcu_read_unlock();
 				ret = drop_dev_and_update(trans, other_bp.v->btree_id,
 							  other_extent, bp->k.p.inode);
 				if (ret)
@@ -679,26 +682,23 @@ static int check_extent_to_backpointers(struct btree_trans *trans,
 		if (p.ptr.dev == BCH_SB_MEMBER_INVALID)
 			continue;
 
-		rcu_read_lock();
-		struct bch_dev *ca = bch2_dev_rcu_noerror(c, p.ptr.dev);
-		if (!ca) {
-			rcu_read_unlock();
-			continue;
-		}
+		bool empty;
+		{
+			/* scoped_guard() is a loop, so it breaks continue */
+			guard(rcu)();
+			struct bch_dev *ca = bch2_dev_rcu_noerror(c, p.ptr.dev);
+			if (!ca)
+				continue;
 
-		if (p.ptr.cached && dev_ptr_stale_rcu(ca, &p.ptr)) {
-			rcu_read_unlock();
-			continue;
-		}
+			if (p.ptr.cached && dev_ptr_stale_rcu(ca, &p.ptr))
+				continue;
 
-		u64 b = PTR_BUCKET_NR(ca, &p.ptr);
-		if (!bch2_bucket_bitmap_test(&ca->bucket_backpointer_mismatch, b)) {
-			rcu_read_unlock();
-			continue;
-		}
+			u64 b = PTR_BUCKET_NR(ca, &p.ptr);
+			if (!bch2_bucket_bitmap_test(&ca->bucket_backpointer_mismatch, b))
+				continue;
 
-		bool empty = bch2_bucket_bitmap_test(&ca->bucket_backpointer_empty, b);
-		rcu_read_unlock();
+			empty = bch2_bucket_bitmap_test(&ca->bucket_backpointer_empty, b);
+		}
 
 		struct bkey_i_backpointer bp;
 		bch2_extent_ptr_to_bp(c, btree, level, k, p, entry, &bp);
@@ -981,7 +981,7 @@ static bool backpointer_node_has_missing(struct bch_fs *c, struct bkey_s_c k)
 	case KEY_TYPE_btree_ptr_v2: {
 		bool ret = false;
 
-		rcu_read_lock();
+		guard(rcu)();
 		struct bpos pos = bkey_s_c_to_btree_ptr_v2(k).v->min_key;
 		while (pos.inode <= k.k->p.inode) {
 			if (pos.inode >= c->sb.nr_devices)
@@ -1009,7 +1009,6 @@ static bool backpointer_node_has_missing(struct bch_fs *c, struct bkey_s_c k)
 next:
 			pos = SPOS(pos.inode + 1, 0, 0);
 		}
-		rcu_read_unlock();
 
 		return ret;
 	}

fs/bcachefs/backpointers.h

@@ -53,11 +53,10 @@ static inline struct bpos bp_pos_to_bucket_and_offset(const struct bch_dev *ca,
 
 static inline bool bp_pos_to_bucket_nodev_noerror(struct bch_fs *c, struct bpos bp_pos, struct bpos *bucket)
 {
-	rcu_read_lock();
+	guard(rcu)();
 	struct bch_dev *ca = bch2_dev_rcu_noerror(c, bp_pos.inode);
 	if (ca)
 		*bucket = bp_pos_to_bucket(ca, bp_pos);
-	rcu_read_unlock();
 	return ca != NULL;
 }
 

fs/bcachefs/btree_gc.c

@@ -1093,42 +1093,41 @@ static int gc_btree_gens_key(struct btree_trans *trans,
 {
 	struct bch_fs *c = trans->c;
 	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
-	struct bkey_i *u;
-	int ret;
 
 	if (unlikely(test_bit(BCH_FS_going_ro, &c->flags)))
 		return -EROFS;
 
-	rcu_read_lock();
-	bkey_for_each_ptr(ptrs, ptr) {
-		struct bch_dev *ca = bch2_dev_rcu(c, ptr->dev);
-		if (!ca)
-			continue;
+	bool too_stale = false;
+	scoped_guard(rcu) {
+		bkey_for_each_ptr(ptrs, ptr) {
+			struct bch_dev *ca = bch2_dev_rcu(c, ptr->dev);
+			if (!ca)
+				continue;
 
-		if (dev_ptr_stale(ca, ptr) > 16) {
-			rcu_read_unlock();
-			goto update;
+			too_stale |= dev_ptr_stale(ca, ptr) > 16;
 		}
+
+		if (!too_stale)
+			bkey_for_each_ptr(ptrs, ptr) {
+				struct bch_dev *ca = bch2_dev_rcu(c, ptr->dev);
+				if (!ca)
+					continue;
+
+				u8 *gen = &ca->oldest_gen[PTR_BUCKET_NR(ca, ptr)];
+				if (gen_after(*gen, ptr->gen))
+					*gen = ptr->gen;
+			}
 	}
 
-	bkey_for_each_ptr(ptrs, ptr) {
-		struct bch_dev *ca = bch2_dev_rcu(c, ptr->dev);
-		if (!ca)
-			continue;
+	if (too_stale) {
+		struct bkey_i *u = bch2_bkey_make_mut(trans, iter, &k, 0);
+		int ret = PTR_ERR_OR_ZERO(u);
+		if (ret)
+			return ret;
 
-		u8 *gen = &ca->oldest_gen[PTR_BUCKET_NR(ca, ptr)];
-		if (gen_after(*gen, ptr->gen))
-			*gen = ptr->gen;
+		bch2_extent_normalize(c, bkey_i_to_s(u));
 	}
-	rcu_read_unlock();
-	return 0;
-update:
-	u = bch2_bkey_make_mut(trans, iter, &k, 0);
-	ret = PTR_ERR_OR_ZERO(u);
-	if (ret)
-		return ret;
 
-	bch2_extent_normalize(c, bkey_i_to_s(u));
 	return 0;
 }
 

fs/bcachefs/btree_io.c

@@ -1325,14 +1325,13 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
 
 	btree_node_reset_sib_u64s(b);
 
-	rcu_read_lock();
-	bkey_for_each_ptr(bch2_bkey_ptrs(bkey_i_to_s(&b->key)), ptr) {
-		struct bch_dev *ca2 = bch2_dev_rcu(c, ptr->dev);
+	scoped_guard(rcu)
+		bkey_for_each_ptr(bch2_bkey_ptrs(bkey_i_to_s(&b->key)), ptr) {
+			struct bch_dev *ca2 = bch2_dev_rcu(c, ptr->dev);
 
-		if (!ca2 || ca2->mi.state != BCH_MEMBER_STATE_rw)
-			set_btree_node_need_rewrite(b);
-	}
-	rcu_read_unlock();
+			if (!ca2 || ca2->mi.state != BCH_MEMBER_STATE_rw)
+				set_btree_node_need_rewrite(b);
+		}
 
 	if (!ptr_written)
 		set_btree_node_need_rewrite(b);