Re: [PATCH] NFS: Revert default r/wsize behavior

[James Pearson <james-p-5Ol4pYTxKWu0ML75eksnrtBPR1lH4CV8@public.gmane.org>]

Chuck Lever wrote:
> When the "rsize=" or "wsize=" mount options are not specified,
> text-based mounts have slightly different behavior than legacy binary
> mounts.  Text-based mounts use the smaller of the server's maximum
> and the client's maximum, but binary mounts use the smaller of the
> server's _preferred_ size and the client's maximum.
> 
> This difference is actually pretty subtle.  Most servers advertise
> the same value as their largest and their preferred transfer size, so
> the end result is the same in most cases.
> 
> The reason for this difference is that for text-based mounts, if
> r/wsize are not specified, they are set to the largest value supported
> by the client.  For binary mounts, the values are set to zero if these
> options are not specified.
> 
> nfs_server_set_fsinfo() can negotiate the defaults correctly in any
> case.  There's no need to specify any particular value as default in
> the text-based option parsing logic.
> 
> Thanks to James Pearson <james-p-5Ol4pYTxKWu0ML75eksnrtBPR1lH4CV8@public.gmane.org> for reporting and
> diagnosing the problem.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> 
> James-
> 
> Is this what you want?
> 
>  fs/nfs/super.c |    4 ----
>  1 files changed, 0 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index bde444b..cf0d754 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -1635,8 +1635,6 @@ static int nfs_validate_mount_data(void *options,
>  		goto out_no_data;
>  
>  	args->flags		= (NFS_MOUNT_VER3 | NFS_MOUNT_TCP);
> -	args->rsize		= NFS_MAX_FILE_IO_SIZE;
> -	args->wsize		= NFS_MAX_FILE_IO_SIZE;
>  	args->acregmin		= NFS_DEF_ACREGMIN;
>  	args->acregmax		= NFS_DEF_ACREGMAX;
>  	args->acdirmin		= NFS_DEF_ACDIRMIN;
> @@ -2351,8 +2349,6 @@ static int nfs4_validate_mount_data(void *options,
>  	if (data == NULL)
>  		goto out_no_data;
>  
> -	args->rsize		= NFS_MAX_FILE_IO_SIZE;
> -	args->wsize		= NFS_MAX_FILE_IO_SIZE;
>  	args->acregmin		= NFS_DEF_ACREGMIN;
>  	args->acregmax		= NFS_DEF_ACREGMAX;
>  	args->acdirmin		= NFS_DEF_ACDIRMIN;

That is what I've already done myself for the NFSv3 case - personally I 
would implicitly set args->[rw]size to zero (although args would have 
been initialled with kzalloc()), just to make it clear that the defaults 
are zero.

Thanks

James Pearson