Is remount racy?
find_entry called with index = 0
find_entry called with index = 0
find_entry called with index = 0
find_entry called with index = 0
Oops: general protection fault, probably for non-canonical address 0xdffffc00000000c7: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000638-0x000000000000063f]
CPU: 1 UID: 0 PID: 7386 Comm: syz.2.322 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:txEnd+0xb4/0x530
Code: 49 8d 5e 20 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 cc 18 dd fe 41 bf 38 06 00 00 4c 03 3b 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 ad 18 dd fe 49 8b 1f 48 83 c3 30
RSP: 0018:ffffc90004fe7b00 EFLAGS: 00010202
RAX: 00000000000000c7 RBX: ffffc90002a59020 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff8d779815 RDI: 00000000ffffffff
RBP: ffffc90004fe7d90 R08: ffffffff8f7d5a77 R09: 1ffffffff1efab4e
R10: dffffc0000000000 R11: fffffbfff1efab4f R12: ffff888117730758
R13: dffffc0000000000 R14: ffffc90002a59000 R15: 0000000000000638
FS:  00007fe3482326c0(0000) GS:ffff8882a9eeb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000562db829a000 CR3: 00000001133bc000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 jfs_mkdir+0x344/0xa70
 vfs_mkdir+0x306/0x510
 do_mkdirat+0x247/0x590
 __x64_sys_mkdirat+0x87/0xa0
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe34738efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe348232038 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fe3475e5fa0 RCX: 00007fe34738efc9
RDX: 0000000000000000 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007fe347411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe3475e6038 R14: 00007fe3475e5fa0 R15: 00007ffc6ea9e548
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:txEnd+0xb4/0x530
Code: 49 8d 5e 20 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 cc 18 dd fe 41 bf 38 06 00 00 4c 03 3b 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 ad 18 dd fe 49 8b 1f 48 83 c3 30
RSP: 0018:ffffc90004fe7b00 EFLAGS: 00010202
RAX: 00000000000000c7 RBX: ffffc90002a59020 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff8d779815 RDI: 00000000ffffffff
RBP: ffffc90004fe7d90 R08: ffffffff8f7d5a77 R09: 1ffffffff1efab4e
R10: dffffc0000000000 R11: fffffbfff1efab4f R12: ffff888117730758
R13: dffffc0000000000 R14: ffffc90002a59000 R15: 0000000000000638
FS:  00007fe3482326c0(0000) GS:ffff8882a9eeb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000562db829a000 CR3: 00000001133bc000 CR4: 00000000000006f0
