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BUG: KCSAN: data-race in mark_buffer_dirty_inode / sync_mapping_buffers

write to 0xffff888136588d58 of 8 bytes by task 10584 on cpu 1:
 __remove_assoc_queue fs/buffer.c:481 [inline]
 fsync_buffers_list fs/buffer.c:688 [inline]
 sync_mapping_buffers+0x155/0x8b0 fs/buffer.c:548
 fat_file_fsync+0xa9/0x100 fs/fat/file.c:194
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2987 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3819
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888136588d58 of 8 bytes by task 10570 on cpu 0:
 mark_buffer_dirty_inode+0x92/0x1d0 fs/buffer.c:581
 fat_mirror_bhs+0x205/0x330 fs/fat/fatent.c:396
 fat_ent_write+0xc2/0xd0 fs/fat/fatent.c:421
 fat_chain_add+0x149/0x400 fs/fat/misc.c:130
 fat_add_cluster fs/fat/inode.c:113 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x429/0x5a0 fs/fat/inode.c:190
 __block_write_begin_int+0x4a2/0x1060 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin fs/buffer.c:2116 [inline]
 cont_write_begin+0x522/0x850 fs/buffer.c:2465
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x196/0x3c0 mm/filemap.c:3656
 __generic_file_write_iter+0x161/0x300 mm/filemap.c:3783
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3815
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff888136444e50 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10570 Comm: syz-executor.4 Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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