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SubjectRe: [syzbot] [hfs?] possible deadlock in hfs_find_init (2)
From
syzbot has found a reproducer for the following issue on:

HEAD commit: edb2f0dc90f2 Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=12506805480000
kernel config: https://syzkaller.appspot.com/x/.config?x=a1c301efa2b11613
dashboard link: https://syzkaller.appspot.com/bug?extid=e390d66dda462b51fde1
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13d841fe480000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=134aa8fa480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ca1677dc6969/disk-edb2f0dc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/22527595a2dd/vmlinux-edb2f0dc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/45308e5f6962/Image-edb2f0dc.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/7b6fdf809f4c/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e390d66dda462b51fde1@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
6.2.0-rc4-syzkaller-16807-gedb2f0dc90f2 #0 Not tainted
--------------------------------------------
kworker/u4:3/103 is trying to acquire lock:
ffff0000c7f8c0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0xac/0xcc

but task is already holding lock:
ffff0000c7f8c0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0xac/0xcc

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&tree->tree_lock/1);
lock(&tree->tree_lock/1);

*** DEADLOCK ***

May be due to missing lock nesting notation

4 locks held by kworker/u4:3/103:
#0: ffff0000c0250138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x270/0x504 kernel/workqueue.c:2262
#1: ffff80000f90bd80 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x29c/0x504 kernel/workqueue.c:2264
#2: ffff0000c7f8c0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0xac/0xcc
#3: ffff0000cc2500f8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0x54/0x740 fs/hfs/extent.c:397

stack backtrace:
CPU: 1 PID: 103 Comm: kworker/u4:3 Not tainted 6.2.0-rc4-syzkaller-16807-gedb2f0dc90f2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: writeback wb_workfn (flush-7:0)
Call trace:
dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:163
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106
dump_stack+0x1c/0x58 lib/dump_stack.c:113
__lock_acquire+0x808/0x3084
lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
hfs_find_init+0xac/0xcc
hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
hfs_extend_file+0x120/0x740 fs/hfs/extent.c:401
hfs_bmap_reserve+0x44/0xe8 fs/hfs/btree.c:234
__hfs_ext_write_extent+0xb8/0x138 fs/hfs/extent.c:121
hfs_ext_write_extent+0x9c/0xd8 fs/hfs/extent.c:144
hfs_write_inode+0x68/0x478 fs/hfs/inode.c:431
write_inode fs/fs-writeback.c:1451 [inline]
__writeback_single_inode+0x240/0x2e4 fs/fs-writeback.c:1663
writeback_sb_inodes+0x308/0x678 fs/fs-writeback.c:1889
wb_writeback+0x198/0x328 fs/fs-writeback.c:2063
wb_do_writeback+0xc8/0x384 fs/fs-writeback.c:2206
wb_workfn+0x70/0x15c fs/fs-writeback.c:2246
process_one_work+0x2d8/0x504 kernel/workqueue.c:2289
worker_thread+0x340/0x610 kernel/workqueue.c:2436
kthread+0x12c/0x158 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:863

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