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BUG: KCSAN: data-race in __mark_inode_dirty / writeback_sb_inodes

read-write to 0xffff8881415ec890 of 8 bytes by task 1336 on cpu 1:
 redirty_tail_locked fs/fs-writeback.c:1190 [inline]
 redirty_tail fs/fs-writeback.c:1196 [inline]
 writeback_sb_inodes+0x37b/0x1020 fs/fs-writeback.c:1658
 wb_writeback+0x27d/0x660 fs/fs-writeback.c:1894
 wb_do_writeback+0x101/0x5d0 fs/fs-writeback.c:2039
 wb_workfn+0xb8/0x410 fs/fs-writeback.c:2080
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff8881415ec890 of 8 bytes by task 8466 on cpu 0:
 __mark_inode_dirty+0xb7/0x740 fs/fs-writeback.c:2274
 mark_buffer_dirty+0x143/0x230 fs/buffer.c:1141
 __ext4_handle_dirty_metadata+0x20a/0x590 fs/ext4/ext4_jbd2.c:362
 ext4_do_update_inode fs/ext4/inode.c:5134 [inline]
 ext4_mark_iloc_dirty+0x12ed/0x1650 fs/ext4/inode.c:5711
 __ext4_mark_inode_dirty+0x450/0x610 fs/ext4/inode.c:5905
 __ext4_unlink+0x730/0x7b0 fs/ext4/namei.c:3239
 ext4_unlink+0xc8/0x2a0 fs/ext4/namei.c:3281
 vfs_unlink+0x232/0x3b0 fs/namei.c:3833
 do_unlinkat+0x28a/0x4d0 fs/namei.c:3897
 __do_sys_unlink fs/namei.c:3943 [inline]
 __se_sys_unlink fs/namei.c:3941 [inline]
 __x64_sys_unlink+0x2c/0x30 fs/namei.c:3941
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8466 Comm: syz-executor.5 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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