btrfs: call __btrfs_remove_free_space_cache_locked on cache load failure

In the Linux kernel, the following vulnerability has been resolved:

btrfs: call __btrfs_remove_free_space_cache_locked on cache load failure

Now that lockdep is staying enabled through our entire CI runs I started

seeing the following stack in generic/475

------------[ cut here ]------------

WARNING: CPU: 1 PID: 2171864 at fs/btrfs/discard.c:604 btrfs_discard_update_discardable+0x98/0xb0

CPU: 1 PID: 2171864 Comm: kworker/u4:0 Not tainted 5.19.0-rc8+ #789

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014

Workqueue: btrfs-cache btrfs_work_helper

RIP: 0010:btrfs_discard_update_discardable+0x98/0xb0

RSP: 0018:ffffb857c2f7bad0 EFLAGS: 00010246

RAX: 0000000000000000 RBX: ffff8c85c605c200 RCX: 0000000000000001

RDX: 0000000000000000 RSI: ffffffff86807c5b RDI: ffffffff868a831e

RBP: ffff8c85c4c54000 R08: 0000000000000000 R09: 0000000000000000

R10: ffff8c85c66932f0 R11: 0000000000000001 R12: ffff8c85c3899010

R13: ffff8c85d5be4f40 R14: ffff8c85c4c54000 R15: ffff8c86114bfa80

FS: 0000000000000000(0000) GS:ffff8c863bd00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f2e7f168160 CR3: 000000010289a004 CR4: 0000000000370ee0

Call Trace:

__btrfs_remove_free_space_cache+0x27/0x30

load_free_space_cache+0xad2/0xaf0

caching_thread+0x40b/0x650

? lock_release+0x137/0x2d0

btrfs_work_helper+0xf2/0x3e0

? lock_is_held_type+0xe2/0x140

process_one_work+0x271/0x590

? process_one_work+0x590/0x590

worker_thread+0x52/0x3b0

? process_one_work+0x590/0x590

kthread+0xf0/0x120

? kthread_complete_and_exit+0x20/0x20

ret_from_fork+0x1f/0x30

This is the code

ctl = block_group->free_space_ctl;

discard_ctl = &block_group->fs_info->discard_ctl;

lockdep_assert_held(&ctl->tree_lock);

We have a temporary free space ctl for loading the free space cache in

order to avoid having allocations happening while we're loading the

cache. When we hit an error we free it all up, however this also calls

btrfs_discard_update_discardable, which requires

block_group->free_space_ctl->tree_lock to be held. However this is our

temporary ctl so this lock isn't held. Fix this by calling

__btrfs_remove_free_space_cache_locked instead so that we only clean up

the entries and do not mess with the discardable stats.