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BUG: KCSAN: data-race in __mark_inode_dirty / writeback_single_inode

write to 0xffff888106356590 of 8 bytes by task 20830 on cpu 1:
 writeback_single_inode+0x10e/0x4a0 fs/fs-writeback.c:1726
 sync_inode_metadata+0x56/0x80 fs/fs-writeback.c:2791
 __generic_file_fsync+0xf9/0x140 fs/libfs.c:1405
 fat_file_fsync+0x4c/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x111/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2584 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4094
 do_iter_write+0x4b4/0x7b0 fs/read_write.c:860
 vfs_iter_write+0x56/0x70 fs/read_write.c:901
 iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
 splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
 do_splice_direct+0x10d/0x190 fs/splice.c:1194
 do_sendfile+0x3b6/0x9a0 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1316 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888106356590 of 8 bytes by task 20835 on cpu 0:
 __mark_inode_dirty+0x58/0x7d0 fs/fs-writeback.c:2417
 fat_update_time+0x20b/0x220 fs/fat/misc.c:357
 inode_update_time fs/inode.c:1948 [inline]
 touch_atime+0x147/0x2d0 fs/inode.c:2020
 file_accessed include/linux/fs.h:2291 [inline]
 filemap_splice_read+0x76e/0x7f0 mm/filemap.c:2975
 vfs_splice_read fs/splice.c:993 [inline]
 splice_direct_to_actor+0x28c/0x690 fs/splice.c:1069
 do_splice_direct+0x10d/0x190 fs/splice.c:1194
 do_sendfile+0x3b6/0x9a0 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000007 -> 0x0000000000000080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20835 Comm: syz-executor.3 Not tainted 6.6.0-rc7-syzkaller-00018-gd88520ad73b7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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