syzbot

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BUG: KCSAN: data-race in __bforget / __remove_assoc_queue

write to 0xffff8880bb920e28 of 8 bytes by task 5569 on cpu 0:
 __remove_assoc_queue+0xa0/0x130 fs/buffer.c:490
 fsync_buffers_list fs/buffer.c:722 [inline]
 sync_mapping_buffers+0x169/0x720 fs/buffer.c:557
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x400/0x8b0 fs/ext4/fsync.c:172
 vfs_fsync_range+0x7c/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2872 [inline]
 ext4_buffered_write_iter+0x211/0x280 fs/ext4/file.c:277
 ext4_file_write_iter+0xf4/0xd30 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1907 [inline]
 do_iter_readv_writev+0x4a7/0x5d0 fs/read_write.c:694
 do_iter_write fs/read_write.c:999 [inline]
 do_iter_write+0x137/0x3a0 fs/read_write.c:980
 vfs_iter_write+0x56/0x80 fs/read_write.c:1040
 iter_file_splice_write+0x530/0x830 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x380/0x800 fs/read_write.c:1521
 __do_sys_sendfile64 fs/read_write.c:1576 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xb8/0x140 fs/read_write.c:1568
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bb920e28 of 8 bytes by task 11415 on cpu 1:
 __bforget+0x41/0x180 fs/buffer.c:1190
 bforget include/linux/buffer_head.h:301 [inline]
 __ext4_forget+0x247/0x300 fs/ext4/ext4_jbd2.c:244
 ext4_free_blocks+0x1142/0x1590 fs/ext4/mballoc.c:4816
 ext4_ext_try_to_merge_up fs/ext4/extents.c:1820 [inline]
 ext4_ext_try_to_merge+0x30b/0x360 fs/ext4/extents.c:1847
 ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3710 [inline]
 ext4_ext_handle_unwritten_extents+0x291/0x18c0 fs/ext4/extents.c:3837
 ext4_ext_map_blocks+0xa7e/0x1fb0 fs/ext4/extents.c:4098
 ext4_map_blocks+0x230/0xcf0 fs/ext4/inode.c:621
 ext4_convert_unwritten_extents+0x18b/0x3b0 fs/ext4/extents.c:4729
 ext4_convert_unwritten_io_end_vec+0xe0/0x1b0 fs/ext4/extents.c:4764
 ext4_end_io_end fs/ext4/page-io.c:187 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:260 [inline]
 ext4_end_io_rsv_work+0x2c2/0x400 fs/ext4/page-io.c:274
 process_one_work+0x424/0x930 kernel/workqueue.c:2268
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2414
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 11415 Comm: kworker/u4:9 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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