syzbot

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BUG: KCSAN: data-race in __mark_inode_dirty / iput

write to 0xffff88812b403830 of 8 bytes by task 12620 on cpu 0:
 __mark_inode_dirty+0x1ce/0x940 fs/fs-writeback.c:2286
 mark_buffer_dirty+0x29c/0x2c0 fs/buffer.c:1116
 __ext4_handle_dirty_metadata+0x284/0x350 fs/ext4/ext4_jbd2.c:298
 ext4_do_update_inode fs/ext4/inode.c:5334 [inline]
 ext4_mark_iloc_dirty+0xdb3/0x1580 fs/ext4/inode.c:5876
 ext4_mark_inode_dirty+0xe9/0x420 fs/ext4/inode.c:6055
 ext4_dirty_inode+0x86/0xb0 fs/ext4/inode.c:6086
 __mark_inode_dirty+0x5d4/0x940 fs/fs-writeback.c:2255
 generic_update_time+0x184/0x270 fs/inode.c:1667
 update_time fs/inode.c:1683 [inline]
 file_update_time+0x237/0x300 fs/inode.c:1898
 ext4_page_mkwrite+0xf9/0xce0 fs/ext4/inode.c:6204
 do_page_mkwrite+0x100/0x210 mm/memory.c:2208
 wp_page_shared mm/memory.c:2507 [inline]
 do_wp_page+0xd65/0x11f0 mm/memory.c:2619
 handle_pte_fault mm/memory.c:3865 [inline]
 __handle_mm_fault+0x1ab1/0x2c70 mm/memory.c:3973
 handle_mm_fault+0x21b/0x530 mm/memory.c:4010
 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
 __do_page_fault+0x3fb/0x9e0 arch/x86/mm/fault.c:1506
 do_page_fault+0x54/0x233 arch/x86/mm/fault.c:1530
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1202

read to 0xffff88812b403830 of 8 bytes by task 12641 on cpu 1:
 iput+0x53/0x4e0 fs/inode.c:1579
 iterate_bdevs+0x219/0x22d fs/block_dev.c:2247
 ksys_sync+0x8c/0xf0 fs/sync.c:116
 __ia32_sys_sync+0x17/0x20 fs/sync.c:124
 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: 1 PID: 12641 Comm: syz-executor.1 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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