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To:     <viro@zeniv.linux.org.uk>
CC:     <linux-fsdevel@vger.kernel.org>, <yi.zhang@huawei.com>,
        <houtao1@huawei.com>, <miaoxie@huawei.com>
From:   yangerkun <yangerkun@huawei.com>
Subject: system panic while dentry reference count overflow
Message-ID: <af9a8dec-98a2-896f-448b-04ded0af95f0@huawei.com>
Date:   Mon, 6 May 2019 11:36:10 +0800
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Hi,

Run process parallel which each code show as below(2T memory), reference 
count of root dentry will overflow since allocation of negative dentry 
should do count++ for root dentry. Then, another dput of root dentry 
will free it, which cause crash of system. I wondered is there anyone 
has found this problem?

#include<stdlib.h> 

#include<stdio.h> 

#include<string.h> 

#include<time.h> 

 

int main() 

{ 

     const char *forname="_dOeSnotExist_.db"; 

     int i; 

     char filename[100]=""; 

     struct timespec time1 = {0, 0}; 

     for(;;) 

     { 

         clock_gettime(CLOCK_REALTIME, &time1); 

         for(i=0; i < 10000; i++) { 

 
sprintf(filename,"/%d%d%d%s",time1.tv_sec,time1.tv_nsec,i,forname); 

             access(filename,0); 

             memset(filename,'\0',100); 

         } 

     } 

     return 0; 

 

} 

~ 

Thanks,
Kun.