linux-next test error: BUG: using smp_processor_id() in preemptible [ADDR] code: syz-fuzzer/6927

[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=1597f2fe100000
kernel config: https://syzkaller.appspot.com/x/.config?x=ecc1aef35f550ee3
dashboard link: https://syzkaller.appspot.com/bug?extid=cd8a20b91d68ef113b45
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+cd8a20...@syzkaller.appspotmail.com

BUG: using smp_processor_id() in preemptible [00000000] code: syz-fuzzer/6927
caller is ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711
CPU: 1 PID: 6927 Comm: syz-fuzzer 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: 0033:0x4b02a0
Code: Bad RIP value.
RSP: 002b:000000c0000cf4b8 EFLAGS: 00000212 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 000000c00002c000 RCX: 00000000004b02a0
RDX: 00000000000001c0 RSI: 000000c000116be0 RDI: ffffffffffffff9c
RBP: 000000c0000cf510 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: ffffffffffffffff
R13: 0000000000000060 R14: 000000000000005f R15: 0000000000000100


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[Eric Biggers]

#syz dup: linux-next test error: BUG: using smp_processor_id() in preemptible [ADDR] code: syz-fuzzer/6792