linux-next test error: BUG: using smp_processor_id() in preemptible [ADDR] code: systemd-rfkill/6726

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    0e21d462 Add linux-next specific files for 20200602
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13a7ffe2100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ecc1aef35f550ee3
dashboard link: https://syzkaller.appspot.com/bug?extid=94f7894cc5600cc07094
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+94f7894cc5600cc07094@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: using smp_processor_id() in preemptible [00000000] code: systemd-rfkill/6726
caller is ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711
CPU: 0 PID: 6726 Comm: systemd-rfkill Not tainted 5.7.0-next-20200602-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 check_preemption_disabled+0x20d/0x220 lib/smp_processor_id.c:48
 ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711
 ext4_ext_map_blocks+0x201b/0x33e0 fs/ext4/extents.c:4244
 ext4_map_blocks+0x4cb/0x1640 fs/ext4/inode.c:626
 ext4_getblk+0xad/0x520 fs/ext4/inode.c:833
 ext4_bread+0x7c/0x380 fs/ext4/inode.c:883
 ext4_append+0x153/0x360 fs/ext4/namei.c:67
 ext4_init_new_dir fs/ext4/namei.c:2757 [inline]
 ext4_mkdir+0x5e0/0xdf0 fs/ext4/namei.c:2802
 vfs_mkdir+0x419/0x690 fs/namei.c:3632
 do_mkdirat+0x21e/0x280 fs/namei.c:3655
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fa49b78d687
Code: Bad RIP value.
RSP: 002b:00007ffde44382d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00005647ba692985 RCX: 00007fa49b78d687
RDX: 00007ffde44381a0 RSI: 00000000000001ed RDI: 00005647ba692985
RBP: 00007fa49b78d680 R08: 0000000000000100 R09: 0000000000000000
R10: 00005647ba692980 R11: 0000000000000246 R12: 00000000000001ed
R13: 00007ffde4438460 R14: 0000000000000000 R15: 0000000000000000


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