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BUG: KCSAN: data-race in ext4_mb_regular_allocator / mb_free_blocks

write to 0xffff8881010c8a94 of 4 bytes by task 371 on cpu 1:
 mb_free_blocks+0x156/0xb40 fs/ext4/mballoc.c:1802
 ext4_free_blocks+0x14ea/0x1c20 fs/ext4/mballoc.c:6061
 ext4_remove_blocks+0x61a/0x800 fs/ext4/extents.c:2506
 ext4_ext_rm_leaf+0x684/0xd40 fs/ext4/extents.c:2672
 ext4_ext_remove_space+0x8f6/0x12b0 fs/ext4/extents.c:2920
 ext4_ext_truncate+0xfe/0x170 fs/ext4/extents.c:4382
 ext4_truncate+0x76e/0xa80 fs/ext4/inode.c:4204
 ext4_setattr+0xb00/0xef0 fs/ext4/inode.c:5463
 notify_change+0x8a3/0xac0 fs/attr.c:410
 do_truncate+0xf7/0x140 fs/open.c:64
 handle_truncate fs/namei.c:3084 [inline]
 do_open fs/namei.c:3432 [inline]
 path_openat+0x1925/0x1ec0 fs/namei.c:3561
 do_filp_open+0x105/0x220 fs/namei.c:3588
 do_sys_openat2+0xb5/0x2b0 fs/open.c:1200
 do_sys_open fs/open.c:1216 [inline]
 __do_sys_openat fs/open.c:1232 [inline]
 __se_sys_openat fs/open.c:1227 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1227
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881010c8a94 of 4 bytes by task 8850 on cpu 0:
 ext4_mb_good_group_nolock fs/ext4/mballoc.c:2504 [inline]
 ext4_mb_regular_allocator+0xaf9/0x2530 fs/ext4/mballoc.c:2747
 ext4_mb_new_blocks+0x792/0x1fc0 fs/ext4/mballoc.c:5586
 ext4_ext_map_blocks+0x15ed/0x1ff0 fs/ext4/extents.c:4250
 ext4_map_blocks+0x71e/0xf00 fs/ext4/inode.c:637
 mpage_map_one_extent+0x10d/0x360 fs/ext4/inode.c:2393
 mpage_map_and_submit_extent fs/ext4/inode.c:2446 [inline]
 ext4_writepages+0xc5a/0x1d70 fs/ext4/inode.c:2798
 do_writepages+0x26b/0x3c0 mm/page-writeback.c:2364
 __writeback_single_inode+0x80/0x440 fs/fs-writeback.c:1616
 writeback_sb_inodes+0x563/0xd30 fs/fs-writeback.c:1881
 wb_writeback+0x27d/0x6d0 fs/fs-writeback.c:2053
 wb_do_writeback+0x101/0x530 fs/fs-writeback.c:2196
 wb_workfn+0xc8/0x540 fs/fs-writeback.c:2237
 process_one_work+0x402/0x910 kernel/workqueue.c:2297
 worker_thread+0x636/0xae0 kernel/workqueue.c:2444
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30

value changed: 0x00000071 -> 0x00000072

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8850 Comm: kworker/u4:10 Not tainted 5.15.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-8:0)
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