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From:   "Chengguang Xu" <cgxu519@gmx.com>
To:     =?UTF-8?Q?=E7=8E=8B=E5=85=83=E8=89=AF?= 
        <yuanliang.wyl@alibaba-inc.com>
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        linux-kernel@vger.kernel.org,
        =?UTF-8?Q?=E7=8E=8B=E5=85=83=E8=89=AF?= 
        <yuanliang.wyl@alibaba-inc.com>
Subject: Re: [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file
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Date:   Tue, 20 Mar 2018 07:44:30 +0100
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Hi Yuanliang,

Can you explain how to reproduce it? and what filesystem do you use as underlying fs?


> Sent: Tuesday, March 20, 2018 at 2:03 PM
> From: 王元良 <yuanliang.wyl@alibaba-inc.com>
> To: miklos@szeredi.hu
> Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, 王元良 <yuanliang.wyl@alibaba-inc.com>
> Subject: [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file status
>
> When the dentry cache is not destroyed, statfs will
> take unknown status '?'
> Undestroyed cache dentry also caused new file creating fails
> 
> Drop it using d_delete may be a choice
> 
> [root@host /]
> Loaded plugins: bestyumcache, branch, fastestmirror, langpacks
> Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache
> fast
> Cleaning repos: xxx.base.x86_64 ops.x.noarch ops.x.x86_64
> Cleaning up everything
> Cleaning up list of best yumcache
> Cleaning up list of fastest mirrors
> 
> [root@host /]
> Loaded plugins: bestyumcache, branch, fastestmirror, langpacks
> Cleaning repos: xxx.base.x86_64 ops.x.noarch ops.x.x86_64
> Cleaning up everything
> Cleaning up list of best yumcache
> Traceback (most recent call last):
>     File "/usr/bin/yum", line 29, in <module>
>     yummain.user_main(sys.argv[1:], exit_code=True)
>     File "/usr/share/yum-cli/yummain.py", line 365, in user_main
>     errcode = main(args)
>     File "/usr/share/yum-cli/yummain.py", line 174, in main
>     result, resultmsgs = base.doCommands()
>     File "/usr/share/yum-cli/cli.py", line 573, in doCommands
>     return self.yum_cli_commands[self.basecmd].doCommand(self,
> 	    self.basecmd, self.extcmds)
> 	   File "/usr/share/yum-cli/yumcommands.py", line
>     1475, in doCommand
>     return base.cleanCli(extcmds)
>     File "/usr/share/yum-cli/cli.py", line 1666, in
>     cleanCli
>     self.plugins.run('clean')
>     File
>     "/usr/lib/python2.7/site-packages/yum/plugins.py", line 188, in run
>     func(conduitcls(self, self.base, conf, **kwargs))
>     File "/usr/lib/yum-plugins/branch.py", line 65, in clean_hook
>     os.remove(os.path.join(root,filespath))
>     OSError: [Errno 2] No such file or directory:
> 	      '/var/cache/yum/x86_64/x/xxxx.noarch.stable/
> 	     b49e49b87d17818d799363091c7a01dde83b421d-primary.sqlite.bz2'
> 
> [root@host /]
>     ls: cannot access
>     /var/cache/yum/x86_64/x/xxxx.noarch.stable/
>     b49e49b87d17818d799363091c7a01dde83b421d-primary.sqlite.bz2:
>     No such file or directory
>     ls: cannot access
>     /var/cache/yum/x86_64/x/xxxx.noarch.stable/cachecookie:
>     No such file or directory
>     ls: cannot access
>     /var/cache/yum/x86_64/x/xxxx.noarch.stable/repomd.xml:
>     No such file or directory
>     total 0
>     ?????????? ? ?    ?     ?            ?
>     b49e49b87d17818d799363091c7a01dde83b421d-primary.sqlite.bz2
>     ?????????? ? ?    ?     ?            ?
>     cachecookie
>     drwxr-xr-x 1 root root 30 Mar 15 16:12 gen
>     drwxr-xr-x 2 root root  6 Jan 31 13:13
>     packages
>     ?????????? ? ?    ?     ?            ?
>     repomd.xml
> 
> Signed-off-by: Yuanliang Wang <yuanliang.wyl@alibaba-inc.com>
> ---
>  fs/overlayfs/super.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index e7c8ac4..f9343d3 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -380,9 +380,15 @@ static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
>  	return ret;
>  }
>  
> +static int ovl_dentry_delete(const struct dentry *dentry)
> +{
> +	return 1;
> +}
> +
>  static const struct dentry_operations ovl_dentry_operations = {
>  	.d_release = ovl_dentry_release,
>  	.d_real = ovl_d_real,
> +	.d_delete = ovl_dentry_delete,
>  };
>  
>  static const struct dentry_operations ovl_reval_dentry_operations = {
> -- 
> 1.8.3.1
> 
> --
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