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BUG: KCSAN: data-race in ext4_mb_find_by_goal / mb_free_blocks

write to 0xffff88812b8b75b4 of 4 bytes by task 23970 on cpu 0:
 mb_free_blocks+0x141/0xf90 fs/ext4/mballoc.c:1495
 ext4_free_blocks+0xfda/0x1610 fs/ext4/mballoc.c:5092
 ext4_remove_blocks+0x592/0xa20 fs/ext4/extents.c:2503
 ext4_ext_rm_leaf+0x563/0xe70 fs/ext4/extents.c:2669
 ext4_ext_remove_space+0x8c9/0x1470 fs/ext4/extents.c:2917
 ext4_ext_truncate+0xf9/0x160 fs/ext4/extents.c:4377
 ext4_truncate+0x7a5/0xb40 fs/ext4/inode.c:4217
 ext4_setattr+0xba0/0xeb0 fs/ext4/inode.c:5409
 notify_change+0x7d4/0xa20 fs/attr.c:336
 do_truncate+0xe0/0x120 fs/open.c:64
 handle_truncate fs/namei.c:2901 [inline]
 do_open fs/namei.c:3247 [inline]
 path_openat+0x1a4c/0x20e0 fs/namei.c:3360
 do_filp_open+0xbd/0x1d0 fs/namei.c:3387
 do_sys_openat2+0x33c/0x4a0 fs/open.c:1179
 do_sys_open fs/open.c:1195 [inline]
 __do_sys_openat fs/open.c:1209 [inline]
 __se_sys_openat fs/open.c:1204 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1204
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812b8b75b4 of 4 bytes by task 23963 on cpu 1:
 ext4_mb_find_by_goal+0x12b/0x640 fs/ext4/mballoc.c:1900
 ext4_mb_regular_allocator+0xe0/0xf90 fs/ext4/mballoc.c:2232
 ext4_mb_new_blocks+0x304/0xcf0 fs/ext4/mballoc.c:4721
 ext4_ext_map_blocks+0x164e/0x20c0 fs/ext4/extents.c:4244
 ext4_map_blocks+0x6a6/0xf60 fs/ext4/inode.c:626
 ext4_alloc_file_blocks+0x24e/0x6d0 fs/ext4/extents.c:4433
 ext4_zero_range+0x24e/0xa10 fs/ext4/extents.c:4544
 ext4_fallocate+0x22a/0x550 fs/ext4/extents.c:4672
 vfs_fallocate+0x431/0x580 fs/open.c:309
 file_ioctl fs/ioctl.c:494 [inline]
 do_vfs_ioctl+0xde0/0xec0 fs/ioctl.c:732
 ksys_ioctl fs/ioctl.c:751 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0x81/0x130 fs/ioctl.c:760
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23963 Comm: syz-executor.0 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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