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BUG: KCSAN: data-race in ext4_alloc_da_blocks / ext4_da_reserve_space

write to 0xffff88814b870858 of 4 bytes by task 13088 on cpu 0:
 ext4_da_reserve_space+0x147/0x200 fs/ext4/inode.c:1491
 ext4_insert_delayed_block fs/ext4/inode.c:1656 [inline]
 ext4_da_map_blocks fs/ext4/inode.c:1770 [inline]
 ext4_da_get_block_prep+0x512/0x9b0 fs/ext4/inode.c:1834
 __block_write_begin_int+0x4a2/0x1060 fs/buffer.c:2006
 __block_write_begin+0x2b/0x40 fs/buffer.c:2056
 ext4_da_write_begin+0x4c8/0x820 fs/ext4/inode.c:3018
 generic_perform_write+0x196/0x3c0 mm/filemap.c:3656
 ext4_buffered_write_iter+0x2f2/0x3f0 fs/ext4/file.c:269
 ext4_file_write_iter+0x2e7/0x11d0 fs/ext4/file.c:519
 call_write_iter include/linux/fs.h:2114 [inline]
 aio_write+0x287/0x360 fs/aio.c:1578
 __io_submit_one fs/aio.c:1837 [inline]
 io_submit_one+0x82f/0x1350 fs/aio.c:1880
 __do_sys_io_submit fs/aio.c:1939 [inline]
 __se_sys_io_submit+0xf5/0x260 fs/aio.c:1909
 __x64_sys_io_submit+0x3f/0x50 fs/aio.c:1909
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88814b870858 of 4 bytes by task 13083 on cpu 1:
 ext4_alloc_da_blocks+0x1a/0xd0 fs/ext4/inode.c:3130
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:141
 __fput+0x25b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13083 Comm: syz-executor.5 Tainted: G        W         5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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