linux-kernel - Re: [PATCH] allow file system to configure for no leases

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Date:	Tue, 05 Jun 2007 15:50:43 -0400
From:	Peter Staubach <staubach@...hat.com>
To:	Trond Myklebust <trond.myklebust@....uio.no>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] allow file system to configure for no leases

Trond Myklebust wrote:
> On Tue, 2007-06-05 at 15:10 -0400, Peter Staubach wrote:
>   
>> Hi.
>>
>> Attached is a small patch to allow file systems to inform the file
>> system independent layers that they don't support file leases.
>>
>> The problem is that some file system such as NFSv2 and NFSv3 do
>> not have sufficient support to be able to support leases correctly.
>> In particular for these two file systems, there is no over the wire
>> protocol support.
>>
>> Currently, these two file systems fail the fcntl(F_SETLEASE) call
>> accidently, due to a reference counting difference.  These file systems
>> should fail more consciously, with a proper error to indicate that
>> the call is invalid for them.
>>
>>     Thanx...
>>
>>        ps
>> plain text document attachment (devel.tototoday)
>> --- linux-2.6.21.i686/fs/nfs/super.c.org
>> +++ linux-2.6.21.i686/fs/nfs/super.c
>> @@ -522,6 +522,9 @@ static inline void nfs_initialise_sb(str
>>  
>>  	sb->s_magic = NFS_SUPER_MAGIC;
>>  
>> +	if (server->nfs_client->cl_nfsversion < 4)
>> +		sb->s_flags |= MS_NO_LEASES;
>> +
>>     
>
> This should be unconditional since we have no support for "lease locks"
> under NFSv4 either. The NFSv4 concept of leases and delegations is very
> different, since it is really tied to the ability to cache data.

No problem.  I wasn't sure, what with the changes that Bruce Fields
is constructing.

Attached is the simplified version.

    Thanx...

       ps

View attachment "leases.devel" of type "text/plain" (1536 bytes)