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BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff88813e874ae8 of 8 bytes by task 21441 on cpu 1:
 mark_buffer_dirty_inode+0x18c/0x1b0 fs/buffer.c:585
 fat_mirror_bhs+0x205/0x330 fs/fat/fatent.c:397
 fat_ent_write+0xc2/0xd0 fs/fat/fatent.c:422
 fat_chain_add+0x15b/0x410 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+0x48d/0x610 fs/fat/inode.c:190
 __block_write_begin_int+0x47c/0xf90 fs/buffer.c:2010
 __block_write_begin fs/buffer.c:2060 [inline]
 block_write_begin fs/buffer.c:2121 [inline]
 cont_write_begin+0x4fb/0x7e0 fs/buffer.c:2470
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x1c8/0x400 mm/filemap.c:3765
 __generic_file_write_iter+0x195/0x2b0 mm/filemap.c:3860
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3924
 call_write_iter include/linux/fs.h:2074 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:725
 do_iter_write+0x192/0x5c0 fs/read_write.c:851
 vfs_iter_write+0x4c/0x70 fs/read_write.c:892
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x675/0xc40 fs/read_write.c:1245
 __do_sys_sendfile64 fs/read_write.c:1310 [inline]
 __se_sys_sendfile64 fs/read_write.c:1296 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1296
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813e874ae8 of 8 bytes by task 21433 on cpu 0:
 mark_buffer_dirty_inode+0x92/0x1b0 fs/buffer.c:581
 fat_mirror_bhs+0x205/0x330 fs/fat/fatent.c:397
 fat_alloc_clusters+0x9ad/0xab0 fs/fat/fatent.c:542
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x267/0x610 fs/fat/inode.c:190
 __block_write_begin_int+0x47c/0xf90 fs/buffer.c:2010
 __block_write_begin fs/buffer.c:2060 [inline]
 block_write_begin fs/buffer.c:2121 [inline]
 cont_write_begin+0x4fb/0x7e0 fs/buffer.c:2470
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x1c8/0x400 mm/filemap.c:3765
 __generic_file_write_iter+0xf7/0x2b0 mm/filemap.c:3892
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3924
 call_write_iter include/linux/fs.h:2074 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:725
 do_iter_write+0x192/0x5c0 fs/read_write.c:851
 vfs_iter_write+0x4c/0x70 fs/read_write.c:892
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x675/0xc40 fs/read_write.c:1245
 __do_sys_sendfile64 fs/read_write.c:1310 [inline]
 __se_sys_sendfile64 fs/read_write.c:1296 [inline]
 __x64_sys_sendfile64+0x102/0x140 fs/read_write.c:1296
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000000000 -> 0xffff8881347777f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21433 Comm: syz-executor.4 Not tainted 5.17.0-rc7-syzkaller-00235-gaad611a868d1-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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