==================================================================
BUG: KCSAN: data-race in __mark_inode_dirty / writeback_sb_inodes

write to 0xffff8881256076f8 of 8 bytes by task 30873 on cpu 0:
 writeback_sb_inodes+0x3bd/0xa10 fs/fs-writeback.c:1705
 wb_writeback+0x1f9/0x6a0 fs/fs-writeback.c:1892
 wb_do_writeback fs/fs-writeback.c:2037 [inline]
 wb_workfn+0x215/0x970 fs/fs-writeback.c:2078
 process_one_work+0x424/0x930 kernel/workqueue.c:2264
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2410
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8881256076f8 of 8 bytes by task 15538 on cpu 1:
 __mark_inode_dirty+0xb6/0x940 fs/fs-writeback.c:2272
 mark_buffer_dirty+0x28b/0x2b0 fs/buffer.c:1156
 __block_commit_write.isra.0+0x11d/0x170 fs/buffer.c:2081
 block_commit_write fs/buffer.c:2473 [inline]
 block_page_mkwrite+0x21d/0x230 fs/buffer.c:2522
 ext4_page_mkwrite+0x4e8/0x800 fs/ext4/inode.c:5933
 do_page_mkwrite+0xfa/0x210 mm/memory.c:2364
 wp_page_shared mm/memory.c:2691 [inline]
 do_wp_page+0xaa3/0xcc0 mm/memory.c:2803
 handle_pte_fault mm/memory.c:4049 [inline]
 __handle_mm_fault+0x1c5e/0x2cf0 mm/memory.c:4163
 handle_mm_fault+0x21c/0x540 mm/memory.c:4200
 do_user_addr_fault arch/x86/mm/fault.c:1442 [inline]
 do_page_fault+0x4a4/0xa52 arch/x86/mm/fault.c:1517
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1203

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15538 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================