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BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff888122f6ec88 of 8 bytes by task 15980 on cpu 1:
 mark_buffer_dirty_inode+0x18c/0x1b0 fs/buffer.c:585
 fat_mirror_bhs+0x22a/0x330 fs/fat/fatent.c:397
 fat_alloc_clusters+0x983/0xa80 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+0x263/0x600 fs/fat/inode.c:190
 __block_write_begin_int+0x33d/0xc90 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x77/0x170 fs/buffer.c:2117
 cont_write_begin+0x3cf/0x500 fs/buffer.c:2463
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x1d6/0x3f0 mm/filemap.c:3787
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3915
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3947
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:852
 vfs_iter_write+0x4c/0x70 fs/read_write.c:893
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1305 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0xb9/0x150 fs/read_write.c:1297
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888122f6ec88 of 8 bytes by task 15991 on cpu 0:
 mark_buffer_dirty_inode+0x92/0x1b0 fs/buffer.c:581
 fat_mirror_bhs+0x22a/0x330 fs/fat/fatent.c:397
 fat_alloc_clusters+0x983/0xa80 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+0x263/0x600 fs/fat/inode.c:190
 __block_write_begin_int+0x33d/0xc90 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x77/0x170 fs/buffer.c:2117
 cont_write_begin+0x3cf/0x500 fs/buffer.c:2463
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x1d6/0x3f0 mm/filemap.c:3787
 __generic_file_write_iter+0x172/0x280 mm/filemap.c:3883
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3947
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:852
 vfs_iter_write+0x4c/0x70 fs/read_write.c:893
 iter_file_splice_write+0x44a/0x7c0 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+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1297
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000000000 -> 0xffff888122f71e80

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15991 Comm: syz-executor.4 Tainted: G        W         5.18.0-rc3-syzkaller-00218-g13bc32bad705-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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