sysfs warns if we're removing a symlink from a directory that's no longer in sysfs; this is triggered by fstests generic/730, which simulates hot removal of a block device.
This patch is however not a correct fix, since checking kobj->state_in_sysfs on a kobj owned by another subsystem is racy. A better fix would be to add the appropriate check to sysfs_remove_link() - and sysfs_create_link() as well. But kobject_add_internal()/kobject_del() do not as of today have locking that would support that. Note that the block/holder.c code appears to be subject to this race as well. Cc: Greg Kroah-Hartman <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Cc: Christoph Hellwig <[email protected]> Signed-off-by: Kent Overstreet <[email protected]> --- fs/bcachefs/super.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c index 843431e58cf5..f96355ecb296 100644 --- a/fs/bcachefs/super.c +++ b/fs/bcachefs/super.c @@ -184,6 +184,7 @@ static DEFINE_MUTEX(bch_fs_list_lock); DECLARE_WAIT_QUEUE_HEAD(bch2_read_only_wait); +static void bch2_dev_unlink(struct bch_dev *); static void bch2_dev_free(struct bch_dev *); static int bch2_dev_alloc(struct bch_fs *, unsigned); static int bch2_dev_sysfs_online(struct bch_fs *, struct bch_dev *); @@ -620,9 +621,7 @@ void __bch2_fs_stop(struct bch_fs *c) up_write(&c->state_lock); for_each_member_device(c, ca) - if (ca->kobj.state_in_sysfs && - ca->disk_sb.bdev) - sysfs_remove_link(bdev_kobj(ca->disk_sb.bdev), "bcachefs"); + bch2_dev_unlink(ca); if (c->kobj.state_in_sysfs) kobject_del(&c->kobj); @@ -1188,9 +1187,7 @@ static void bch2_dev_free(struct bch_dev *ca) { cancel_work_sync(&ca->io_error_work); - if (ca->kobj.state_in_sysfs && - ca->disk_sb.bdev) - sysfs_remove_link(bdev_kobj(ca->disk_sb.bdev), "bcachefs"); + bch2_dev_unlink(ca); if (ca->kobj.state_in_sysfs) kobject_del(&ca->kobj); @@ -1227,10 +1224,7 @@ static void __bch2_dev_offline(struct bch_fs *c, struct bch_dev *ca) percpu_ref_kill(&ca->io_ref); wait_for_completion(&ca->io_ref_completion); - if (ca->kobj.state_in_sysfs) { - sysfs_remove_link(bdev_kobj(ca->disk_sb.bdev), "bcachefs"); - sysfs_remove_link(&ca->kobj, "block"); - } + bch2_dev_unlink(ca); bch2_free_super(&ca->disk_sb); bch2_dev_journal_exit(ca); @@ -1252,6 +1246,26 @@ static void bch2_dev_io_ref_complete(struct percpu_ref *ref) complete(&ca->io_ref_completion); } +static void bch2_dev_unlink(struct bch_dev *ca) +{ + struct kobject *b; + + /* + * This is racy w.r.t. the underlying block device being hot-removed, + * which removes it from sysfs. + * + * It'd be lovely if we had a way to handle this race, but the sysfs + * code doesn't appear to provide a good method and block/holder.c is + * susceptible as well: + */ + if (ca->kobj.state_in_sysfs && + ca->disk_sb.bdev && + (b = bdev_kobj(ca->disk_sb.bdev))->state_in_sysfs) { + sysfs_delete_link(b, &ca->kobj, "bcachefs"); + sysfs_delete_link(&ca->kobj, b, "block"); + } +} + static int bch2_dev_sysfs_online(struct bch_fs *c, struct bch_dev *ca) { int ret; -- 2.45.2
