syzbot

==================================================================
BUG: KCSAN: data-race in p9_client_rpc / p9_write_work

write to 0xffff8880a082be10 of 4 bytes by task 19866 on cpu 1:
 p9_write_work+0x32a/0x6d0 net/9p/trans_fd.c:460
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880a082be10 of 4 bytes by task 15444 on cpu 0:
 p9_client_rpc+0x27e/0xae0 net/9p/client.c:757
 p9_client_open+0xc2/0x2b0 net/9p/client.c:1259
 v9fs_file_open+0x241/0x4a0 fs/9p/vfs_file.c:66
 do_dentry_open+0x301/0x970 fs/open.c:797
 vfs_open+0x62/0x80 fs/open.c:914
 do_last fs/namei.c:3408 [inline]
 path_openat+0xf73/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15444 Comm: syz-executor.4 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================