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BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff888105766878 of 8 bytes by task 25197 on cpu 0:
 mark_buffer_dirty_inode+0x18d/0x1c0 fs/buffer.c:684
 fat_mirror_bhs+0x241/0x330 fs/fat/fatent.c:398
 fat_alloc_clusters+0x994/0xa80 fs/fat/fatent.c:543
 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+0x417/0xfa0 fs/buffer.c:2128
 __block_write_begin fs/buffer.c:2177 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2236
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2590
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1d5/0x410 mm/filemap.c:4015
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4110
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4136
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x78f/0x900 fs/read_write.c:590
 ksys_write+0xeb/0x1b0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:652
 x64_sys_call+0x27ef/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105766878 of 8 bytes by task 25214 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:680
 fat_mirror_bhs+0x241/0x330 fs/fat/fatent.c:398
 fat_alloc_clusters+0x994/0xa80 fs/fat/fatent.c:543
 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+0x417/0xfa0 fs/buffer.c:2128
 __block_write_begin fs/buffer.c:2177 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2236
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2590
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1d5/0x410 mm/filemap.c:4015
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4110
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4136
 iter_file_splice_write+0x5e6/0x970 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x16c/0x2c0 fs/splice.c:1164
 splice_direct_to_actor+0x305/0x670 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3ab/0x950 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
 x64_sys_call+0x2c9f/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff888106774820

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25214 Comm: syz.3.6575 Not tainted 6.10.0-rc6-syzkaller-00041-g9903efbddba0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
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