syzbot


BUG: spinlock bad magic in release_metapage

Status: upstream: reported C repro on 2024/09/10 08:16
Subsystems: jfs
[Documentation on labels]
Reported-by: syzbot+e380443eaa59bfb75a84@syzkaller.appspotmail.com
First crash: 72d, last: 1d02h
Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: general protection fault in release_metapage (log)
Repro: C syz .config
  
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [jfs?] BUG: spinlock bad magic in release_metapage 0 (1) 2024/09/10 08:16
Similar bugs (7)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 BUG: spinlock bad magic in release_metapage origin:upstream C 32 24d 66d 0/3 upstream: reported C repro on 2024/09/15 11:43
upstream BUG: unable to handle kernel paging request in take_dentry_name_snapshot reiserfs overlayfs C error done 30 228d 720d 0/28 closed as dup on 2023/10/04 08:35
linux-6.1 BUG: spinlock bad magic in release_metapage 25 28d 48d 0/3 upstream: reported on 2024/10/04 04:01
upstream BUG: spinlock bad magic in lock_sock_nested (2) bluetooth 1 1038d 1038d 0/28 auto-closed as invalid on 2022/04/18 01:34
upstream BUG: spinlock bad magic in lock_sock_nested bluetooth 26 1179d 1534d 0/28 auto-closed as invalid on 2021/12/27 15:41
upstream BUG: spinlock bad magic in btrfs_stop_all_workers btrfs 5 155d 155d 26/28 fixed on 2024/07/31 03:12
upstream BUG: spinlock bad magic in skb_queue_tail afs net 1 702d 698d 0/28 auto-obsoleted due to no activity on 2023/03/19 17:50

Sample crash report:
BUG: spinlock bad magic on CPU#1, jfsCommit/113
==================================================================
BUG: KASAN: slab-out-of-bounds in string_nocheck lib/vsprintf.c:646 [inline]
BUG: KASAN: slab-out-of-bounds in string+0x218/0x2b0 lib/vsprintf.c:728
Read of size 1 at addr ffff88807658c9f0 by task jfsCommit/113

CPU: 1 UID: 0 PID: 113 Comm: jfsCommit Not tainted 6.12.0-rc6-syzkaller-00110-gff7afaeca1a1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 string_nocheck lib/vsprintf.c:646 [inline]
 string+0x218/0x2b0 lib/vsprintf.c:728
 vsnprintf+0x1101/0x1da0 lib/vsprintf.c:2803
 vprintk_store+0x480/0x1160 kernel/printk/printk.c:2260
 vprintk_emit+0x271/0xa10 kernel/printk/printk.c:2383
 _printk+0xd5/0x120 kernel/printk/printk.c:2432
 spin_dump kernel/locking/spinlock_debug.c:64 [inline]
 spin_bug+0x13b/0x1d0 kernel/locking/spinlock_debug.c:78
 debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]
 do_raw_spin_lock+0x209/0x370 kernel/locking/spinlock_debug.c:115
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
 _raw_spin_lock_irqsave+0xe1/0x120 kernel/locking/spinlock.c:162
 __wake_up_common_lock+0x25/0x1e0 kernel/sched/wait.c:105
 unlock_metapage fs/jfs/jfs_metapage.c:39 [inline]
 release_metapage+0xb2/0x960 fs/jfs/jfs_metapage.c:763
 xtTruncate+0x1006/0x3270
 jfs_free_zero_link+0x46e/0x6e0 fs/jfs/namei.c:759
 jfs_evict_inode+0x35f/0x440 fs/jfs/inode.c:153
 evict+0x4e8/0x9b0 fs/inode.c:725
 txUpdateMap+0x931/0xb10 fs/jfs/jfs_txnmgr.c:2367
 txLazyCommit fs/jfs/jfs_txnmgr.c:2664 [inline]
 jfs_lazycommit+0x49a/0xb80 fs/jfs/jfs_txnmgr.c:2733
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

The buggy address belongs to the object at ffff88807658c9c0
 which belongs to the cache jfs_ip of size 2232
The buggy address is located 48 bytes inside of
 allocated 2232-byte region [ffff88807658c9c0, ffff88807658d278)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x76588
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801db27780 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800d000d 00000001f5000000 0000000000000000
head: 00fff00000000040 ffff88801db27780 dead000000000122 0000000000000000
head: 0000000000000000 00000000800d000d 00000001f5000000 0000000000000000
head: 00fff00000000003 ffffea0001d96201 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0xd2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE), pid 5833, tgid 5833 (syz-executor280), ts 78527233732, free_ts 25457634676
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1537
 prep_new_page mm/page_alloc.c:1545 [inline]
 get_page_from_freelist+0x3033/0x3180 mm/page_alloc.c:3457
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4733
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 alloc_slab_page+0x6a/0x140 mm/slub.c:2412
 allocate_slab+0x5a/0x2f0 mm/slub.c:2578
 new_slab mm/slub.c:2631 [inline]
 ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3818
 __slab_alloc+0x58/0xa0 mm/slub.c:3908
 __slab_alloc_node mm/slub.c:3961 [inline]
 slab_alloc_node mm/slub.c:4122 [inline]
 kmem_cache_alloc_lru_noprof+0x1c5/0x2b0 mm/slub.c:4153
 jfs_alloc_inode+0x28/0x70 fs/jfs/super.c:105
 alloc_inode+0x65/0x1a0 fs/inode.c:265
 new_inode_pseudo fs/inode.c:1104 [inline]
 new_inode+0x22/0x1d0 fs/inode.c:1123
 jfs_fill_super+0x408/0xc50 fs/jfs/super.c:544
 mount_bdev+0x20a/0x2d0 fs/super.c:1693
 legacy_get_tree+0xee/0x190 fs/fs_context.c:662
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1108 [inline]
 free_unref_page+0xcd0/0xf00 mm/page_alloc.c:2638
 free_contig_range+0x152/0x550 mm/page_alloc.c:6748
 destroy_args+0x92/0x910 mm/debug_vm_pgtable.c:1017
 debug_vm_pgtable+0x4be/0x550 mm/debug_vm_pgtable.c:1397
 do_one_initcall+0x248/0x880 init/main.c:1269
 do_initcall_level+0x157/0x210 init/main.c:1331
 do_initcalls+0x3f/0x80 init/main.c:1347
 kernel_init_freeable+0x435/0x5d0 init/main.c:1580
 kernel_init+0x1d/0x2b0 init/main.c:1469
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffff88807658c880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807658c900: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff88807658c980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                             ^
 ffff88807658ca00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807658ca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (197):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/11/07 18:11 upstream ff7afaeca1a1 867e44df .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/30 15:38 upstream c1e939a21eb1 fb888278 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/10 14:17 upstream d3d1556696c1 0278d004 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/03 23:52 upstream 7ec462100ef9 d7906eff .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/01 22:04 upstream e32cde8d2bd7 ea2b66a6 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/09/19 16:40 upstream 839c4f596f89 c673ca06 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/09/18 13:59 upstream bdf56c7580d2 c673ca06 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/23 11:40 upstream c2ee9f594da8 15fa2979 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/10/02 04:45 upstream e32cde8d2bd7 ea2b66a6 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/09/21 21:02 upstream 1ec6d097897a 6f888b75 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/09/20 16:23 upstream baeb9a7d8b60 6f888b75 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/09/19 13:36 upstream 932d2d1fcb2b 6f888b75 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/09/19 13:06 upstream 932d2d1fcb2b 6f888b75 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/09/19 12:31 upstream 932d2d1fcb2b 6f888b75 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/09/09 19:28 upstream da3ea35007d0 8f722c94 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/11/20 04:30 upstream 158f238aa69d 7d02db5a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/19 10:10 upstream 23acd177540d 571351cb .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/19 04:38 upstream 23acd177540d 571351cb .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/18 21:24 upstream 23acd177540d e7bb5d6e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/18 16:03 upstream adc218676eef e7bb5d6e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/17 18:59 upstream 4a5df3796467 cfe3a04a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/16 14:46 upstream e8bdb3c8be08 cfe3a04a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/16 13:23 upstream e8bdb3c8be08 cfe3a04a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/16 07:49 upstream f868cd251776 cfe3a04a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/14 13:33 upstream 0a9b9d17f3a7 a8c99394 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/14 09:07 upstream 0a9b9d17f3a7 a8c99394 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/13 14:26 upstream f1b785f4c787 bb3f8425 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/11 21:25 upstream 2d5404caa8c7 0c4b1325 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/11 03:49 upstream a9cda7c0ffed 6b856513 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/10 15:40 upstream de2f378f2b77 6b856513 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root BUG: spinlock bad magic in release_metapage
2024/11/10 04:36 upstream de2f378f2b77 6b856513 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/03 02:35 upstream 11066801dd4b f00eed24 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/02 00:19 upstream 6c52d4da1c74 f00eed24 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/01 14:17 upstream 6c52d4da1c74 96eb609f .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/29 13:29 upstream e42b1a9a2557 66aeb999 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/28 19:24 upstream 819837584309 9efb3cc7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root BUG: spinlock bad magic in release_metapage
2024/10/28 12:21 upstream 819837584309 65e8686b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root BUG: spinlock bad magic in release_metapage
2024/10/28 04:50 upstream 284a2f899676 65e8686b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root BUG: spinlock bad magic in release_metapage
2024/10/28 00:10 upstream 284a2f899676 65e8686b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root BUG: spinlock bad magic in release_metapage
2024/10/27 09:04 upstream 850925a8133c 65e8686b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root BUG: spinlock bad magic in release_metapage
2024/10/25 16:10 upstream ae90f6a6170d 045e728d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/25 12:50 upstream ae90f6a6170d 045e728d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/25 10:52 upstream 4e46774408d9 c79b8ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/25 09:31 upstream 4e46774408d9 c79b8ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/25 08:32 upstream 4e46774408d9 c79b8ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/25 06:19 upstream 4e46774408d9 c79b8ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/25 04:11 upstream 4e46774408d9 c79b8ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 23:26 upstream 4e46774408d9 c79b8ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 22:08 upstream 4e46774408d9 0d144d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 16:24 upstream c2ee9f594da8 0d144d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 14:41 upstream c2ee9f594da8 0d144d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 13:34 upstream c2ee9f594da8 0d144d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 10:20 upstream c2ee9f594da8 0d144d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 04:00 upstream c2ee9f594da8 15fa2979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 02:52 upstream c2ee9f594da8 15fa2979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/24 01:45 upstream c2ee9f594da8 15fa2979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/23 21:19 upstream c2ee9f594da8 15fa2979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/10/23 18:28 upstream c2ee9f594da8 15fa2979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: spinlock bad magic in release_metapage
2024/11/12 14:51 upstream 2d5404caa8c7 c819f227 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root BUG: spinlock bad magic in release_metapage
2024/10/02 22:55 linux-next fe2173353674 a4c7fd36 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root BUG: spinlock bad magic in release_metapage
2024/11/18 09:09 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 887407160d72 cfe3a04a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/11/15 01:11 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 887407160d72 77f3eeb7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/11/11 05:31 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 563047e691f2 6b856513 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/11/08 20:05 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci eb17c12d043d 179b040e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/11/02 11:17 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 5283dc78f4da f00eed24 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/11/01 20:07 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 1bf329c696cf f00eed24 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/10/29 05:35 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 1bf329c696cf 9efb3cc7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: spinlock bad magic in release_metapage
2024/11/14 06:48 upstream f1b785f4c787 a8c99394 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root BUG: spinlock bad magic in btrfs_stop_all_workers
* Struck through repros no longer work on HEAD.