On Mon, Jan 30, 2017 at 05:17:00PM +1100, NeilBrown wrote:
>
> If you change the set of filesystems that are exported, then
> the contents of various directories in the NFSv4 pseudo-root
> is likely to change. However the change-id of those
> directories is currently tied to the underlying directory,
> so the clinet may not see the changes in a timely fashion.
Oh, good catch.
> This patch changes the change-id number to be derived from the
> "flush_time" of the export cache. Whenever any changes are
> made to the set of exported filesystems, this flush_time is
> updated. The result is that clients see changes to the set
> of exported filesystems much more quickly, often immediately.
And, a clever solution, as usual....
I wonder if it's completely right yet, though. Off the top of my head:
can't the client see the new flush time before it sees the new contents?
If so, a client that caches both during that window could cache the old
contents indefinitely.
--b.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> ---
> fs/nfsd/nfs4xdr.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 8fae53ce21d1..dbff0122b784 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -1966,9 +1966,13 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)
> DECODE_TAIL;
> }
>
> -static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode)
> +static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
> + struct svc_export *exp)
> {
> - if (IS_I_VERSION(inode)) {
> + if (exp->ex_flags & NFSEXP_V4ROOT) {
> + *p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
> + *p++ = 0;
> + } else if (IS_I_VERSION(inode)) {
> p = xdr_encode_hyper(p, inode->i_version);
> } else {
> *p++ = cpu_to_be32(stat->ctime.tv_sec);
> @@ -2490,7 +2494,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
> p = xdr_reserve_space(xdr, 8);
> if (!p)
> goto out_resource;
> - p = encode_change(p, &stat, d_inode(dentry));
> + p = encode_change(p, &stat, d_inode(dentry), exp);
> }
> if (bmval0 & FATTR4_WORD0_SIZE) {
> p = xdr_reserve_space(xdr, 8);
> --
> 2.11.0
>
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