bcachefs: for_each_online_member_rcu()

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

fs/bcachefs/alloc_foreground.c

@@ -1645,7 +1645,12 @@ static noinline void bch2_print_allocator_stuck(struct bch_fs *c)
 	printbuf_indent_sub(&buf, 2);
 	prt_newline(&buf);
 
-	for_each_online_member(c, ca) {
+	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);
@@ -1653,6 +1658,9 @@ static noinline void bch2_print_allocator_stuck(struct bch_fs *c)
 		prt_newline(&buf);
 	}
 
+	--buf.atomic;
+	rcu_read_unlock();
+
 	prt_printf(&buf, "Copygc debug:\n");
 	printbuf_indent_add(&buf, 2);
 	bch2_copygc_wait_to_text(&buf, c);

fs/bcachefs/bcachefs.h

@@ -891,6 +891,7 @@ struct bch_fs {
 	struct workqueue_struct *write_ref_wq;
 
 	/* ALLOCATION */
+	struct bch_devs_mask	online_devs;
 	struct bch_devs_mask	rw_devs[BCH_DATA_NR];
 	unsigned long		rw_devs_change_count;
 

fs/bcachefs/chardev.c

@@ -613,11 +613,13 @@ static long bch2_ioctl_disk_get_idx(struct bch_fs *c,
 	if (!dev)
 		return -EINVAL;
 
-	for_each_online_member(c, ca)
+	rcu_read_lock();
+	for_each_online_member_rcu(c, ca)
 		if (ca->dev == dev) {
-			percpu_ref_put(&ca->io_ref[READ]);
+			rcu_read_unlock();
 			return ca->dev_idx;
 		}
+	rcu_read_unlock();
 
 	return -BCH_ERR_ENOENT_dev_idx_not_found;
 }

fs/bcachefs/fs.c

@@ -2327,12 +2327,14 @@ static int bch2_show_devname(struct seq_file *seq, struct dentry *root)
 	struct bch_fs *c = root->d_sb->s_fs_info;
 	bool first = true;
 
-	for_each_online_member(c, ca) {
+	rcu_read_lock();
+	for_each_online_member_rcu(c, ca) {
 		if (!first)
 			seq_putc(seq, ':');
 		first = false;
 		seq_puts(seq, ca->disk_sb.sb_name);
 	}
+	rcu_read_unlock();
 
 	return 0;
 }
@@ -2529,15 +2531,16 @@ static int bch2_fs_get_tree(struct fs_context *fc)
 
 	sb->s_bdi->ra_pages		= VM_READAHEAD_PAGES;
 
-	for_each_online_member(c, ca) {
+	rcu_read_lock();
+	for_each_online_member_rcu(c, ca) {
 		struct block_device *bdev = ca->disk_sb.bdev;
 
 		/* XXX: create an anonymous device for multi device filesystems */
 		sb->s_bdev	= bdev;
 		sb->s_dev	= bdev->bd_dev;
-		percpu_ref_put(&ca->io_ref[READ]);
 		break;
 	}
+	rcu_read_unlock();
 
 	c->dev = sb->s_dev;
 

fs/bcachefs/sb-members.h

@@ -104,6 +104,9 @@ static inline struct bch_dev *__bch2_next_dev(struct bch_fs *c, struct bch_dev *
 	for (struct bch_dev *_ca = NULL;				\
 	     (_ca = __bch2_next_dev((_c), _ca, (_mask)));)
 
+#define for_each_online_member_rcu(_c, _ca)				\
+	for_each_member_device_rcu(_c, _ca, &(_c)->online_devs)
+
 static inline void bch2_dev_get(struct bch_dev *ca)
 {
 #ifdef CONFIG_BCACHEFS_DEBUG
@@ -307,17 +310,6 @@ static inline struct bch_dev *bch2_dev_get_ioref(struct bch_fs *c, unsigned dev,
 	return NULL;
 }
 
-/* XXX kill, move to struct bch_fs */
-static inline struct bch_devs_mask bch2_online_devs(struct bch_fs *c)
-{
-	struct bch_devs_mask devs;
-
-	memset(&devs, 0, sizeof(devs));
-	for_each_online_member(c, ca)
-		__set_bit(ca->dev_idx, devs.d);
-	return devs;
-}
-
 extern const struct bch_sb_field_ops bch_sb_field_ops_members_v1;
 extern const struct bch_sb_field_ops bch_sb_field_ops_members_v2;
 

fs/bcachefs/super.c

@@ -1105,7 +1105,7 @@ static bool bch2_fs_may_start(struct bch_fs *c)
 		break;
 	}
 
-	return bch2_have_enough_devs(c, bch2_online_devs(c), flags, true);
+	return bch2_have_enough_devs(c, c->online_devs, flags, true);
 }
 
 int bch2_fs_start(struct bch_fs *c)
@@ -1138,8 +1138,11 @@ int bch2_fs_start(struct bch_fs *c)
 		goto err;
 	}
 
-	for_each_online_member(c, ca)
-		bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx)->last_mount = cpu_to_le64(now);
+	rcu_read_lock();
+	for_each_online_member_rcu(c, ca)
+		bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx)->last_mount =
+		cpu_to_le64(now);
+	rcu_read_unlock();
 
 	/*
 	 * Dno't write superblock yet: recovery might have to downgrade
@@ -1294,6 +1297,9 @@ static int bch2_dev_in_fs(struct bch_sb_handle *fs,
 
 static void bch2_dev_io_ref_stop(struct bch_dev *ca, int rw)
 {
+	if (rw == READ)
+		clear_bit(ca->dev_idx, ca->fs->online_devs.d);
+
 	if (!percpu_ref_is_zero(&ca->io_ref[rw])) {
 		reinit_completion(&ca->io_ref_completion[rw]);
 		percpu_ref_kill(&ca->io_ref[rw]);
@@ -1577,6 +1583,8 @@ static int bch2_dev_attach_bdev(struct bch_fs *c, struct bch_sb_handle *sb)
 	if (ret)
 		return ret;
 
+	set_bit(ca->dev_idx, c->online_devs.d);
+
 	bch2_dev_sysfs_online(c, ca);
 
 	struct printbuf name = PRINTBUF;
@@ -1634,7 +1642,7 @@ bool bch2_dev_state_allowed(struct bch_fs *c, struct bch_dev *ca,
 			return true;
 
 		/* do we have enough devices to read from?  */
-		new_online_devs = bch2_online_devs(c);
+		new_online_devs = c->online_devs;
 		__clear_bit(ca->dev_idx, new_online_devs.d);
 
 		return bch2_have_enough_devs(c, new_online_devs, flags, false);