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BUG: KCSAN: data-race in __mark_inode_dirty / __writeback_single_inode

write to 0xffff88821afab270 of 8 bytes by task 2569 on cpu 0:
 __writeback_single_inode+0x338/0x910 fs/fs-writeback.c:1486
 writeback_sb_inodes+0x4c8/0xa10 fs/fs-writeback.c:1716
 __writeback_inodes_wb+0xe9/0x1b0 fs/fs-writeback.c:1785
 wb_writeback+0x557/0x6a0 fs/fs-writeback.c:1894
 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 0xffff88821afab270 of 8 bytes by task 7700 on cpu 1:
 __mark_inode_dirty+0xb6/0x940 fs/fs-writeback.c:2272
 mark_buffer_dirty+0x28b/0x2b0 fs/buffer.c:1156
 __ext4_handle_dirty_metadata+0x2a8/0x400 fs/ext4/ext4_jbd2.c:338
 ext4_do_update_inode fs/ext4/inode.c:5027 [inline]
 ext4_mark_iloc_dirty+0xd60/0x1500 fs/ext4/inode.c:5578
 ext4_mark_inode_dirty+0xe6/0x420 fs/ext4/inode.c:5771
 ext4_unlink fs/ext4/namei.c:3225 [inline]
 ext4_unlink+0x71c/0x7d0 fs/ext4/namei.c:3166
 vfs_unlink+0x223/0x3e0 fs/namei.c:4073
 do_unlinkat+0x33f/0x550 fs/namei.c:4137
 __do_sys_unlink fs/namei.c:4184 [inline]
 __se_sys_unlink fs/namei.c:4182 [inline]
 __x64_sys_unlink+0x38/0x50 fs/namei.c:4182
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7700 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
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