loop4: detected capacity change from 0 to 8192
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BUG: KCSAN: data-race in mark_buffer_dirty_inode / sync_mapping_buffers

write to 0xffff8881479a4c88 of 8 bytes by task 32213 on cpu 0:
 __remove_assoc_queue fs/buffer.c:522 [inline]
 fsync_buffers_list fs/buffer.c:796 [inline]
 sync_mapping_buffers+0x165/0x7d0 fs/buffer.c:589
 fat_file_fsync+0xad/0x100 fs/fat/file.c:195
 vfs_fsync_range+0x111/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2493 [inline]
 generic_file_write_iter+0x191/0x1c0 mm/filemap.c:4048
 call_write_iter include/linux/fs.h:1871 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4ab/0x7d0 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 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 0xffff8881479a4c88 of 8 bytes by task 32212 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:692
 fat16_ent_put+0x4f/0x60 fs/fat/fatent.c:184
 fat_alloc_clusters+0x4b5/0xa60 fs/fat/fatent.c:503
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x25c/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x3c0/0xf30 fs/buffer.c:2128
 __block_write_begin fs/buffer.c:2178 [inline]
 block_write_begin+0x7c/0x180 fs/buffer.c:2239
 cont_write_begin+0x4c0/0x6f0 fs/buffer.c:2597
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1cf/0x410 mm/filemap.c:3923
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4018
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4044
 call_write_iter include/linux/fs.h:1871 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4ab/0x7d0 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 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: 0xffff88810638beb0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 32212 Comm: syz-executor.4 Not tainted 6.5.0-rc3-syzkaller-00044-g0a8db05b571a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
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