From: Johannes Thumshirn johannes.thumshirn@wdc.com
commit 0b9e66762aa0cda2a9c2d5542d64e04dac528fa6 upstream.
btrfs_can_activate_zone() can be called with the device_list_mutex already held, which will lead to a deadlock:
insert_dev_extents() // Takes device_list_mutex `-> insert_dev_extent() `-> btrfs_insert_empty_item() `-> btrfs_insert_empty_items() `-> btrfs_search_slot() `-> btrfs_cow_block() `-> __btrfs_cow_block() `-> btrfs_alloc_tree_block() `-> btrfs_reserve_extent() `-> find_free_extent() `-> find_free_extent_update_loop() `-> can_allocate_chunk() `-> btrfs_can_activate_zone() // Takes device_list_mutex again
Instead of using the RCU on fs_devices->device_list we can use fs_devices->alloc_list, protected by the chunk_mutex to traverse the list of active devices.
We are in the chunk allocation thread. The newer chunk allocation happens from the devices in the fs_device->alloc_list protected by the chunk_mutex.
btrfs_create_chunk() lockdep_assert_held(&info->chunk_mutex); gather_device_info list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list)
Also, a device that reappears after the mount won't join the alloc_list yet and, it will be in the dev_list, which we don't want to consider in the context of the chunk alloc.
[15.166572] WARNING: possible recursive locking detected [15.167117] 5.17.0-rc6-dennis #79 Not tainted [15.167487] -------------------------------------------- [15.167733] kworker/u8:3/146 is trying to acquire lock: [15.167733] ffff888102962ee0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: find_free_extent+0x15a/0x14f0 [btrfs] [15.167733] [15.167733] but task is already holding lock: [15.167733] ffff888102962ee0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_create_pending_block_groups+0x20a/0x560 [btrfs] [15.167733] [15.167733] other info that might help us debug this: [15.167733] Possible unsafe locking scenario: [15.167733] [15.171834] CPU0 [15.171834] ---- [15.171834] lock(&fs_devs->device_list_mutex); [15.171834] lock(&fs_devs->device_list_mutex); [15.171834] [15.171834] *** DEADLOCK *** [15.171834] [15.171834] May be due to missing lock nesting notation [15.171834] [15.171834] 5 locks held by kworker/u8:3/146: [15.171834] #0: ffff888100050938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1c3/0x5a0 [15.171834] #1: ffffc9000067be80 ((work_completion)(&fs_info->async_data_reclaim_work)){+.+.}-{0:0}, at: process_one_work+0x1c3/0x5a0 [15.176244] #2: ffff88810521e620 (sb_internal){.+.+}-{0:0}, at: flush_space+0x335/0x600 [btrfs] [15.176244] #3: ffff888102962ee0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_create_pending_block_groups+0x20a/0x560 [btrfs] [15.176244] #4: ffff8881152e4b78 (btrfs-dev-00){++++}-{3:3}, at: __btrfs_tree_lock+0x27/0x130 [btrfs] [15.179641] [15.179641] stack backtrace: [15.179641] CPU: 1 PID: 146 Comm: kworker/u8:3 Not tainted 5.17.0-rc6-dennis #79 [15.179641] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35 04/01/2014 [15.179641] Workqueue: events_unbound btrfs_async_reclaim_data_space [btrfs] [15.179641] Call Trace: [15.179641] <TASK> [15.179641] dump_stack_lvl+0x45/0x59 [15.179641] __lock_acquire.cold+0x217/0x2b2 [15.179641] lock_acquire+0xbf/0x2b0 [15.183838] ? find_free_extent+0x15a/0x14f0 [btrfs] [15.183838] __mutex_lock+0x8e/0x970 [15.183838] ? find_free_extent+0x15a/0x14f0 [btrfs] [15.183838] ? find_free_extent+0x15a/0x14f0 [btrfs] [15.183838] ? lock_is_held_type+0xd7/0x130 [15.183838] ? find_free_extent+0x15a/0x14f0 [btrfs] [15.183838] find_free_extent+0x15a/0x14f0 [btrfs] [15.183838] ? _raw_spin_unlock+0x24/0x40 [15.183838] ? btrfs_get_alloc_profile+0x106/0x230 [btrfs] [15.187601] btrfs_reserve_extent+0x131/0x260 [btrfs] [15.187601] btrfs_alloc_tree_block+0xb5/0x3b0 [btrfs] [15.187601] __btrfs_cow_block+0x138/0x600 [btrfs] [15.187601] btrfs_cow_block+0x10f/0x230 [btrfs] [15.187601] btrfs_search_slot+0x55f/0xbc0 [btrfs] [15.187601] ? lock_is_held_type+0xd7/0x130 [15.187601] btrfs_insert_empty_items+0x2d/0x60 [btrfs] [15.187601] btrfs_create_pending_block_groups+0x2b3/0x560 [btrfs] [15.187601] __btrfs_end_transaction+0x36/0x2a0 [btrfs] [15.192037] flush_space+0x374/0x600 [btrfs] [15.192037] ? find_held_lock+0x2b/0x80 [15.192037] ? btrfs_async_reclaim_data_space+0x49/0x180 [btrfs] [15.192037] ? lock_release+0x131/0x2b0 [15.192037] btrfs_async_reclaim_data_space+0x70/0x180 [btrfs] [15.192037] process_one_work+0x24c/0x5a0 [15.192037] worker_thread+0x4a/0x3d0
Fixes: a85f05e59bc1 ("btrfs: zoned: avoid chunk allocation if active block group has enough space") CC: stable@vger.kernel.org # 5.16+ Reviewed-by: Anand Jain anand.jain@oracle.com Signed-off-by: Johannes Thumshirn johannes.thumshirn@wdc.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/zoned.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
--- a/fs/btrfs/zoned.c +++ b/fs/btrfs/zoned.c @@ -1936,18 +1936,19 @@ int btrfs_zone_finish(struct btrfs_block
bool btrfs_can_activate_zone(struct btrfs_fs_devices *fs_devices, u64 flags) { + struct btrfs_fs_info *fs_info = fs_devices->fs_info; struct btrfs_device *device; bool ret = false;
- if (!btrfs_is_zoned(fs_devices->fs_info)) + if (!btrfs_is_zoned(fs_info)) return true;
/* Non-single profiles are not supported yet */ ASSERT((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0);
/* Check if there is a device with active zones left */ - mutex_lock(&fs_devices->device_list_mutex); - list_for_each_entry(device, &fs_devices->devices, dev_list) { + mutex_lock(&fs_info->chunk_mutex); + list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) { struct btrfs_zoned_device_info *zinfo = device->zone_info;
if (!device->bdev) @@ -1959,7 +1960,7 @@ bool btrfs_can_activate_zone(struct btrf break; } } - mutex_unlock(&fs_devices->device_list_mutex); + mutex_unlock(&fs_info->chunk_mutex);
return ret; }