linux-kernel - Re: [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file status

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Date:   Tue, 20 Mar 2018 08:07:34 +0100
From:   "Chengguang Xu" <cgxu519@....com>
To:     "Chengguang Xu" <cgxu519@....com>
Cc:     王元良 
        <yuanliang.wyl@...baba-inc.com>, miklos@...redi.hu,
        linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file
 status

Hi Yuanliang,

Can you try ext4 or xfs(with ftype=1) as underlying fs? 
It seems the phenomenon that I met on xfs(with ftype=0) as underlying fs.
Thanks,
Chengguang.


> Sent: Tuesday, March 20, 2018 at 2:44 PM
> From: "Chengguang Xu" <cgxu519@....com>
> To: 王元良 <yuanliang.wyl@...baba-inc.com>
> Cc: miklos@...redi.hu, linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org, 王元良 <yuanliang.wyl@...baba-inc.com>
> Subject: Re: [PATCH] fs/overlayfs: Drop dentry cache to prevent unknown file status
>
> 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@...baba-inc.com>
> > To: miklos@...redi.hu
> > Cc: linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org, 王元良 <yuanliang.wyl@...baba-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@...t /]
> > 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@...t /]
> > 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@...t /]
> >     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@...baba-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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