linux-kernel - Question about how to trigger BUG_ON() in sm_disk_new

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Message-ID: <3475f910-68fd-76da-c7f9-4fcc32d878e7@huawei.com>
Date:   Fri, 13 Jan 2023 16:07:31 +0800
From:   "lilingfeng (A)" <lilingfeng3@...wei.com>
To:     <linux-kernel@...r.kernel.org>, Joe Thornber <ejt@...hat.com>
CC:     <snitzer@...hat.com>, <yi.zhang@...wei.com>,
        <yangerkun@...wei.com>, <chengzhihao1@...wei.com>,
        <zhangxiaoxu5@...wei.com>
Subject: Question about how to trigger BUG_ON() in sm_disk_new_block()

Hello,

I notice the patch 4feaef830de7ffdd8352e1fe14ad3bf13c9688f8 (dm space 
map common: fix to ensure new block isn't already in use) can explain 
the BUG_ON() in sm_disk_new_block().
However, I'm still confused since I can't find the code path in which 
'begin' field was not being updated (as you say "increment of a data 
block reference count due to breaking sharing of a neighbour block in 
the same btree leaf").

What I found are as below:
break_sharing
  alloc_data_block
   dm_pool_alloc_data_block
    dm_sm_new_block
     sm_disk_new_block
      sm_ll_find_free_block
      smd->begin = *b + 1

May I bother you to list the path?

Thanks