syzbot

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BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff8881376e22c8 of 8 bytes by task 5729 on cpu 1:
 mark_buffer_dirty_inode+0x18c/0x1b0 fs/buffer.c:585
 fat_mirror_bhs+0x1f6/0x300 fs/fat/fatent.c:398
 fat_alloc_clusters+0x983/0xa80 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+0x263/0x600 fs/fat/inode.c:190
 __block_write_begin_int+0x30d/0xbc0 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x73/0x170 fs/buffer.c:2117
 cont_write_begin+0x3f1/0x520 fs/buffer.c:2471
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3738
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3866
 generic_file_write_iter+0x79/0x1c0 mm/filemap.c:3898
 do_iter_write+0x494/0x750 fs/read_write.c:855
 vfs_iter_write+0x4c/0x70 fs/read_write.c:896
 iter_file_splice_write+0x44a/0x7c0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:931
 splice_direct_to_actor+0x305/0x620 fs/splice.c:886
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1303 [inline]
 __x64_sys_sendfile64+0xb9/0x150 fs/read_write.c:1303
 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+0x63/0xcd

read to 0xffff8881376e22c8 of 8 bytes by task 5747 on cpu 0:
 mark_buffer_dirty_inode+0x92/0x1b0 fs/buffer.c:581
 fat_mirror_bhs+0x1f6/0x300 fs/fat/fatent.c:398
 fat_alloc_clusters+0x983/0xa80 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+0x263/0x600 fs/fat/inode.c:190
 __block_write_begin_int+0x30d/0xbc0 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x73/0x170 fs/buffer.c:2117
 cont_write_begin+0x3f1/0x520 fs/buffer.c:2471
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3738
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3866
 generic_file_write_iter+0x79/0x1c0 mm/filemap.c:3898
 call_write_iter include/linux/fs.h:2192 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:578
 ksys_write+0xe8/0x1a0 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 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+0x63/0xcd

value changed: 0x0000000000000000 -> 0xffff888137594e50

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5747 Comm: syz-executor.4 Not tainted 5.19.0-syzkaller-13930-g7ebfc85e2cd7-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
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