On Thu, Mar 18, 2021 at 11:25 AM <fdman...@kernel.org> wrote:
>
> From: Filipe Manana <fdman...@suse.com>
>
> While removing a qgroup's sysfs entry we end up taking the kernfs_mutex,
> through kobject_del(), while holding the fs_info->qgroup_lock spinlock,
> producing the following trace:
>
> [ 821.843637] BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:281
> [ 821.843641] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 28214,
> name: podman
> [ 821.843644] CPU: 3 PID: 28214 Comm: podman Tainted: G W
> 5.11.6 #15
> [ 821.843646] Hardware name: Dell Inc. PowerEdge R330/084XW4, BIOS 2.11.0
> 12/08/2020
> [ 821.843647] Call Trace:
> [ 821.843650] dump_stack+0xa1/0xfb
> [ 821.843656] ___might_sleep+0x144/0x160
> [ 821.843659] mutex_lock+0x17/0x40
> [ 821.843662] kernfs_remove_by_name_ns+0x1f/0x80
> [ 821.843666] sysfs_remove_group+0x7d/0xe0
> [ 821.843668] sysfs_remove_groups+0x28/0x40
> [ 821.843670] kobject_del+0x2a/0x80
> [ 821.843672] btrfs_sysfs_del_one_qgroup+0x2b/0x40 [btrfs]
> [ 821.843685] __del_qgroup_rb+0x12/0x150 [btrfs]
> [ 821.843696] btrfs_remove_qgroup+0x288/0x2a0 [btrfs]
> [ 821.843707] btrfs_ioctl+0x3129/0x36a0 [btrfs]
> [ 821.843717] ? __mod_lruvec_page_state+0x5e/0xb0
> [ 821.843719] ? page_add_new_anon_rmap+0xbc/0x150
> [ 821.843723] ? kfree+0x1b4/0x300
> [ 821.843725] ? mntput_no_expire+0x55/0x330
> [ 821.843728] __x64_sys_ioctl+0x5a/0xa0
> [ 821.843731] do_syscall_64+0x33/0x70
> [ 821.843733] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 821.843736] RIP: 0033:0x4cd3fb
> [ 821.843739] Code: fa ff eb bd e8 86 8b fa ff e9 61 ff ff ff cc e8 fb 55 fa
> ff 48 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 48 8b 44 24 08 0f 05 <48> 3d
> 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30
> [ 821.843741] RSP: 002b:000000c000906b20 EFLAGS: 00000206 ORIG_RAX:
> 0000000000000010
> [ 821.843744] RAX: ffffffffffffffda RBX: 000000c000050000 RCX:
> 00000000004cd3fb
> [ 821.843745] RDX: 000000c000906b98 RSI: 000000004010942a RDI:
> 000000000000000f
> [ 821.843747] RBP: 000000c000907cd0 R08: 000000c000622901 R09:
> 0000000000000000
> [ 821.843748] R10: 000000c000d992c0 R11: 0000000000000206 R12:
> 000000000000012d
> [ 821.843749] R13: 000000000000012c R14: 0000000000000200 R15:
> 0000000000000049
>
> Fix this by removing the qgroup sysfs entry while not holding the spinlock,
> since the spinlock is only meant for protection of the qgroup rbtree.
>
> Reported-by: Stuart Shelton <srcshel...@gmail.com>
> Link:
> https://lore.kernel.org/linux-btrfs/7a5485bb-0628-419d-a4d3-27b1af47e...@gmail.com/
> Signed-off-by: Filipe Manana <fdman...@suse.com>
Missed:
Fixes: 49e5fb46211de0 ("btrfs: qgroup: export qgroups in sysfs")
> ---
> fs/btrfs/qgroup.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index 9d8d1ac86962..2319c923c9e6 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -227,7 +227,6 @@ static void __del_qgroup_rb(struct btrfs_fs_info *fs_info,
> {
> struct btrfs_qgroup_list *list;
>
> - btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
> list_del(&qgroup->dirty);
> while (!list_empty(&qgroup->groups)) {
> list = list_first_entry(&qgroup->groups,
> @@ -244,7 +243,6 @@ static void __del_qgroup_rb(struct btrfs_fs_info *fs_info,
> list_del(&list->next_member);
> kfree(list);
> }
> - kfree(qgroup);
> }
>
> /* must be called with qgroup_lock held */
> @@ -570,6 +568,8 @@ void btrfs_free_qgroup_config(struct btrfs_fs_info
> *fs_info)
> qgroup = rb_entry(n, struct btrfs_qgroup, node);
> rb_erase(n, &fs_info->qgroup_tree);
> __del_qgroup_rb(fs_info, qgroup);
> + btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
> + kfree(qgroup);
> }
> /*
> * We call btrfs_free_qgroup_config() when unmounting
> @@ -1579,6 +1579,14 @@ int btrfs_remove_qgroup(struct btrfs_trans_handle
> *trans, u64 qgroupid)
> spin_lock(&fs_info->qgroup_lock);
> del_qgroup_rb(fs_info, qgroupid);
> spin_unlock(&fs_info->qgroup_lock);
> +
> + /*
> + * Remove the qgroup from sysfs now without holding the qgroup_lock
> + * spinlock, since the sysfs_remove_group() function needs to take
> + * the mutex kernfs_mutex through kernfs_remove_by_name_ns().
> + */
> + btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
> + kfree(qgroup);
> out:
> mutex_unlock(&fs_info->qgroup_ioctl_lock);
> return ret;
> --
> 2.28.0
>
