On Mon, Apr 27, 2015 at 02:50:13PM +0200, Christoph Hellwig wrote:
> Commit df52699e4fcef ("NFSv4.1: Don't cache deviceids that have no
> notifications") causes the Linux NFS client stop caching deviceid
> unless a server pretends to support deviceid notifications. While
> this behavior is stupid and the language around this area in rfc5661
> is a mess carified by an errata that I submittted, Trond insists
> on this behavior. Not caching deviceids degrades block layout
> performance massively as a GETDEVICEINFO is fairly expensive.
>
> So add this hack to make the Linux client happy again.
OK, thanks.--b.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/nfsd/blocklayout.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
> index 03d647b..cdefaa3 100644
> --- a/fs/nfsd/blocklayout.c
> +++ b/fs/nfsd/blocklayout.c
> @@ -181,6 +181,17 @@ nfsd4_block_proc_layoutcommit(struct inode *inode,
> }
>
> const struct nfsd4_layout_ops bl_layout_ops = {
> + /*
> + * Pretend that we send notification to the client. This is a blatant
> + * lie to force recent Linux clients to cache our device IDs.
> + * We rarely ever change the device ID, so the harm of leaking deviceids
> + * for a while isn't too bad. Unfortunately RFC5661 is a complete mess
> + * in this regard, but I filed errata 4119 for this a while ago, and
> + * hopefully the Linux client will eventually start caching deviceids
> + * without this again.
> + */
> + .notify_types =
> + NOTIFY_DEVICEID4_DELETE | NOTIFY_DEVICEID4_CHANGE,
> .proc_getdeviceinfo = nfsd4_block_proc_getdeviceinfo,
> .encode_getdeviceinfo = nfsd4_block_encode_getdeviceinfo,
> .proc_layoutget = nfsd4_block_proc_layoutget,
> --
> 1.9.1
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