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BUG: KCSAN: data-race in __ext4_update_other_inode_time / writeback_single_inode

write to 0xffff888120322200 of 8 bytes by task 30476 on cpu 0:
 inode_sync_complete fs/fs-writeback.c:1197 [inline]
 writeback_single_inode+0x4a4/0x530 fs/fs-writeback.c:1578
 sync_inode fs/fs-writeback.c:2602 [inline]
 sync_inode_metadata+0x52/0x70 fs/fs-writeback.c:2622
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x335/0x6e0 fs/ext4/fsync.c:170
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2882 [inline]
 ext4_buffered_write_iter+0x369/0x3b0 fs/ext4/file.c:277
 ext4_file_write_iter+0x76f/0x1010 include/linux/fs.h:805
 call_write_iter include/linux/fs.h:1908 [inline]
 do_iter_readv_writev+0x321/0x3c0 fs/read_write.c:713
 do_iter_write+0x10e/0x470 fs/read_write.c:1018
 vfs_iter_write+0x4c/0x70 fs/read_write.c:1059
 iter_file_splice_write+0x41a/0x770 fs/splice.c:750
 do_splice_from fs/splice.c:846 [inline]
 direct_splice_actor+0x95/0x160 fs/splice.c:1016
 splice_direct_to_actor+0x365/0x660 fs/splice.c:971
 do_splice_direct+0xf2/0x170 fs/splice.c:1059
 do_sendfile+0x562/0xb10 fs/read_write.c:1540
 __do_sys_sendfile64 fs/read_write.c:1595 [inline]
 __se_sys_sendfile64 fs/read_write.c:1587 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1587
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888120322200 of 8 bytes by task 30481 on cpu 1:
 __ext4_update_other_inode_time+0x45/0x570 fs/ext4/inode.c:4893
 ext4_update_other_inodes_time fs/ext4/inode.c:4940 [inline]
 ext4_do_update_inode fs/ext4/inode.c:5068 [inline]
 ext4_mark_iloc_dirty+0x1296/0x1660 fs/ext4/inode.c:5624
 __ext4_mark_inode_dirty+0x448/0x630 fs/ext4/inode.c:5818
 ext4_dirty_inode+0xa6/0xc0 fs/ext4/inode.c:5854
 __mark_inode_dirty+0x72/0x7e0 fs/fs-writeback.c:2258
 mark_inode_dirty_sync include/linux/fs.h:2197 [inline]
 dquot_claim_block include/linux/quotaops.h:367 [inline]
 ext4_da_update_reserve_space+0x160/0x310 fs/ext4/inode.c:369
 ext4_map_blocks+0x746/0xf60 fs/ext4/inode.c:647
 mpage_map_one_extent+0x10d/0x3c0 fs/ext4/inode.c:2377
 mpage_map_and_submit_extent fs/ext4/inode.c:2430 [inline]
 ext4_writepages+0xa4c/0x1ef0 fs/ext4/inode.c:2782
 do_writepages+0x7b/0x150 mm/page-writeback.c:2354
 __filemap_fdatawrite_range+0x19b/0x1d0 mm/filemap.c:421
 filemap_write_and_wait_range+0x8b/0x2a0 mm/filemap.c:654
 ext4_punch_hole+0x143/0xa20 fs/ext4/inode.c:3976
 ext4_fallocate+0xe5/0x560 fs/ext4/extents.c:4659
 vfs_fallocate+0x431/0x580 fs/open.c:309
 ksys_fallocate fs/open.c:332 [inline]
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x75/0xc0 fs/open.c:338
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30481 Comm: syz-executor.1 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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