NFS: Add ability to send MOUNTPROC_UMNT to the kernel's mountd client

After certain failure modes of an NFS mount, an NFS client should send
a MOUNTPROC_UMNT request to remove the just-added mount entry from the
server's mount table.  While no-one should rely on the accuracy of the
server's mount table, sending a UMNT is simply being a good internet
neighbor.

Since NFS mount processing is handled in the kernel now, we will need
a function in the kernel's mountd client that can post a MOUNTRPC_UMNT
request, in order to handle these failure modes.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 7dd90a6..8d2b71d 100644 (file)
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -102,6 +102,7 @@ struct nfs_mount_request {
 };
 
 extern int nfs_mount(struct nfs_mount_request *info);
+extern void nfs_umount(const struct nfs_mount_request *info);
 
 /* client.c */
 extern struct rpc_program nfs_program;

diff --git a/fs/nfs/mount_clnt.c b/fs/nfs/mount_clnt.c
index 38ef9ea..72dd8b6 100644 (file)
--- a/fs/nfs/mount_clnt.c
+++ b/fs/nfs/mount_clnt.c
@@ -209,6 +209,71 @@ out_mnt_err:
        goto out;
 }
 
+/**
+ * nfs_umount - Notify a server that we have unmounted this export
+ * @info: pointer to umount request arguments
+ *
+ * MOUNTPROC_UMNT is advisory, so we set a short timeout, and always
+ * use UDP.
+ */
+void nfs_umount(const struct nfs_mount_request *info)
+{
+       static const struct rpc_timeout nfs_umnt_timeout = {
+               .to_initval = 1 * HZ,
+               .to_maxval = 3 * HZ,
+               .to_retries = 2,
+       };
+       struct rpc_create_args args = {
+               .protocol       = IPPROTO_UDP,
+               .address        = info->sap,
+               .addrsize       = info->salen,
+               .timeout        = &nfs_umnt_timeout,
+               .servername     = info->hostname,
+               .program        = &mnt_program,
+               .version        = info->version,
+               .authflavor     = RPC_AUTH_UNIX,
+               .flags          = RPC_CLNT_CREATE_NOPING,
+       };
+       struct mountres result;
+       struct rpc_message msg  = {
+               .rpc_argp       = info->dirpath,
+               .rpc_resp       = &result,
+       };
+       struct rpc_clnt *clnt;
+       int status;
+
+       if (info->noresvport)
+               args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
+
+       clnt = rpc_create(&args);
+       if (unlikely(IS_ERR(clnt)))
+               goto out_clnt_err;
+
+       dprintk("NFS: sending UMNT request for %s:%s\n",
+               (info->hostname ? info->hostname : "server"), info->dirpath);
+
+       if (info->version == NFS_MNT3_VERSION)
+               msg.rpc_proc = &clnt->cl_procinfo[MOUNTPROC3_UMNT];
+       else
+               msg.rpc_proc = &clnt->cl_procinfo[MOUNTPROC_UMNT];
+
+       status = rpc_call_sync(clnt, &msg, 0);
+       rpc_shutdown_client(clnt);
+
+       if (unlikely(status < 0))
+               goto out_call_err;
+
+       return;
+
+out_clnt_err:
+       dprintk("NFS: failed to create UMNT RPC client, status=%ld\n",
+                       PTR_ERR(clnt));
+       return;
+
+out_call_err:
+       dprintk("NFS: UMNT request failed, status=%d\n", status);
+}
+
 /*
  * XDR encode/decode functions for MOUNT
  */
@@ -407,6 +472,13 @@ static struct rpc_procinfo mnt_procedures[] = {
                .p_statidx      = MOUNTPROC_MNT,
                .p_name         = "MOUNT",
        },
+       [MOUNTPROC_UMNT] = {
+               .p_proc         = MOUNTPROC_UMNT,
+               .p_encode       = (kxdrproc_t)mnt_enc_dirpath,
+               .p_arglen       = MNT_enc_dirpath_sz,
+               .p_statidx      = MOUNTPROC_UMNT,
+               .p_name         = "UMOUNT",
+       },
 };
 
 static struct rpc_procinfo mnt3_procedures[] = {
@@ -419,6 +491,13 @@ static struct rpc_procinfo mnt3_procedures[] = {
                .p_statidx      = MOUNTPROC3_MNT,
                .p_name         = "MOUNT",
        },
+       [MOUNTPROC3_UMNT] = {
+               .p_proc         = MOUNTPROC3_UMNT,
+               .p_encode       = (kxdrproc_t)mnt_enc_dirpath,
+               .p_arglen       = MNT_enc_dirpath_sz,
+               .p_statidx      = MOUNTPROC3_UMNT,
+               .p_name         = "UMOUNT",
+       },
 };