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| author | Kent Overstreet <kent.overstreet@linux.dev> | 2024-10-12 14:36:38 -0400 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2024-10-14 05:43:01 -0400 |
| commit | 5e3b72324d32629fa013f86657308f3dbc1115e1 (patch) | |
| tree | 66d1d167a942aef22a89cfa0df092d1a593f663d /fs | |
| parent | cb6055e66faa0d4c15587ef67be18bc199aef085 (diff) | |
| download | lwn-5e3b72324d32629fa013f86657308f3dbc1115e1.tar.gz lwn-5e3b72324d32629fa013f86657308f3dbc1115e1.zip | |
bcachefs: Fix sysfs warning in fstests generic/730,731
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 <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/bcachefs/super.c | 34 |
1 files changed, 24 insertions, 10 deletions
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c index 873e4be7e1dc..77d811a539af 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); @@ -1187,9 +1186,7 @@ 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); @@ -1226,10 +1223,7 @@ 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); @@ -1251,6 +1245,26 @@ 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_remove_link(b, "bcachefs"); + sysfs_remove_link(&ca->kobj, "block"); + } +} + static int bch2_dev_sysfs_online(struct bch_fs *c, struct bch_dev *ca) { int ret; |