To:     <linux-nfs@vger.kernel.org>
From:   =?UTF-8?B?Q3VpLCBZdWUv5bSUIOaCpg==?= <cuiyue-fnst@cn.fujitsu.com>
Subject: open_by_handle_at() cannot open file after drop_caches
Message-ID: <e703a3e1-64b9-c225-0087-f29d4d2915de@cn.fujitsu.com>
Date:   Wed, 20 Feb 2019 17:38:53 +0800
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Hi,

When I tested xfstest/generic/426 with NFSv4.0, it failed..

The test steps are as follows:

1. Use name_to_handle_at() to change the filename to filehandle.

2. Execute "echo 3 > /proc/sys/vm/drop_caches".

3. Use open_by_handle_at() to open files with the filehandle created 
bystep 1.

Step 3 calls nfs_fh_to_dentry() to convert the filehandle to dentry.

But because the inode and dentry cache information was deleted in step 
2, a new inode is generated using the nfs_fhget().

And then a new dentry is generated using the d_obtain_alias().

However, during the call to the d_obtain_alias() function, the d_iname 
of the dentry is assigned the slash_name"/".

Nfsd will check the dentry's d_iname, when open claim type is 
NFS4_OPEN_CLAIM_NULL.

So when dentry's d_inameis "/", it fails with the error "nfserr_badname"

So I want to know why the newly created dentry is named "/",

and when using open_by_handle_at() to open a file, is it possible to set 
the claim type to NFS4_OPEN_CLAIM_PREVIOUS ?


Thanks,

cuiyue