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BUG: KCSAN: data-race in __remove_assoc_queue / mark_buffer_dirty_inode

write to 0xffff8881251670c0 of 8 bytes by task 25662 on cpu 1:
 __remove_assoc_queue+0xa0/0x130 fs/buffer.c:496
 fsync_buffers_list fs/buffer.c:728 [inline]
 sync_mapping_buffers+0x169/0x720 fs/buffer.c:563
 fat_file_fsync+0xc8/0x120 fs/fat/file.c:194
 vfs_fsync_range+0x7c/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2867 [inline]
 generic_file_write_iter+0x31c/0x38e mm/filemap.c:3452
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x4a7/0x5d0 fs/read_write.c:693
 do_iter_write fs/read_write.c:998 [inline]
 do_iter_write+0x137/0x3a0 fs/read_write.c:979
 vfs_iter_write+0x56/0x80 fs/read_write.c:1039
 iter_file_splice_write+0x530/0x830 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881251670c0 of 8 bytes by task 25557 on cpu 0:
 mark_buffer_dirty_inode+0x9e/0x240 fs/buffer.c:596
 fat16_ent_put+0x7b/0x90 fs/fat/fatent.c:182
 fat_ent_write+0x69/0xf0 fs/fat/fatent.c:415
 fat_chain_add+0x356/0x410 fs/fat/misc.c:130
 fat_add_cluster+0x91/0xd0 fs/fat/inode.c:113
 fat_fallocate+0x13b/0x1d0 fs/fat/file.c:291
 vfs_fallocate+0x3b1/0x650 fs/open.c:309
 ksys_fallocate+0x5b/0xa0 fs/open.c:332
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x59/0x70 fs/open.c:338
 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: 0 PID: 25557 Comm: syz-executor.0 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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