NFSD: Cleanup for nfsd4_path()

The current code is sort of hackish in that it assumes a referral is always
matched to an export. When we add support for junctions that may not be the
case.
We can replace nfsd4_path() with a function that encodes the components
directly from the dentries. Since nfsd4_path is currently the only user of
the 'ex_pathname' field in struct svc_export, this has the added benefit
of allowing us to get rid of that.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 80 insertions, 30 deletions

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index d491421cd708..99229b0c153e 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1009,7 +1009,7 @@ rqst_exp_parent(struct svc_rqst *rqstp, struct path *path)
         return exp;
 }
 
-static struct svc_export *find_fsidzero_export(struct svc_rqst *rqstp)
+struct svc_export *rqst_find_fsidzero_export(struct svc_rqst *rqstp)
 {
         u32 fsidv[2];
 
@@ -1029,7 +1029,7 @@ exp_pseudoroot(struct svc_rqst *rqstp, struct svc_fh *fhp)
         struct svc_export *exp;
         __be32 rv;
 
-        exp = find_fsidzero_export(rqstp);
+        exp = rqst_find_fsidzero_export(rqstp);
         if (IS_ERR(exp))
                 return nfserrno(PTR_ERR(exp));
         rv = fh_compose(fhp, exp, exp->ex_path.dentry, NULL);
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 182570bed472..5252d6681960 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1696,36 +1696,89 @@ static __be32 nfsd4_encode_fs_location4(struct nfsd4_fs_location *location,
 }
 
 /*
- * Return the path to an export point in the pseudo filesystem namespace
- * Returned string is safe to use as long as the caller holds a reference
- * to @exp.
+ * Encode a path in RFC3530 'pathname4' format
  */
-static char *nfsd4_path(struct svc_rqst *rqstp, struct svc_export *exp, __be32 *stat)
+static __be32 nfsd4_encode_path(const struct path *root,
+                const struct path *path, __be32 **pp, int *buflen)
 {
-        struct svc_fh tmp_fh;
-        char *path = NULL, *rootpath;
-        size_t rootlen;
+        struct path cur = {
+                .mnt = path->mnt,
+                .dentry = path->dentry,
+        };
+        __be32 *p = *pp;
+        struct dentry **components = NULL;
+        unsigned int ncomponents = 0;
+        __be32 err = nfserr_jukebox;
 
-        fh_init(&tmp_fh, NFS4_FHSIZE);
-        *stat = exp_pseudoroot(rqstp, &tmp_fh);
-        if (*stat)
-                return NULL;
-        rootpath = tmp_fh.fh_export->ex_pathname;
+        dprintk("nfsd4_encode_components(");
 
-        path = exp->ex_pathname;
+        path_get(&cur);
+        /* First walk the path up to the nfsd root, and store the
+         * dentries/path components in an array.
+         */
+        for (;;) {
+                if (cur.dentry == root->dentry && cur.mnt == root->mnt)
+                        break;
+                if (cur.dentry == cur.mnt->mnt_root) {
+                        if (follow_up(&cur))
+                                continue;
+                        goto out_free;
+                }
+                if ((ncomponents & 15) == 0) {
+                        struct dentry **new;
+                        new = krealloc(components,
+                                        sizeof(*new) * (ncomponents + 16),
+                                        GFP_KERNEL);
+                        if (!new)
+                                goto out_free;
+                        components = new;
+                }
+                components[ncomponents++] = cur.dentry;
+                cur.dentry = dget_parent(cur.dentry);
+        }
 
-        rootlen = strlen(rootpath);
-        if (strncmp(path, rootpath, rootlen)) {
-                dprintk("nfsd: fs_locations failed;"
-                        "%s is not contained in %s\n", path, rootpath);
-                *stat = nfserr_notsupp;
-                path = NULL;
-                goto out;
+        *buflen -= 4;
+        if (*buflen < 0)
+                goto out_free;
+        WRITE32(ncomponents);
+
+        while (ncomponents) {
+                struct dentry *dentry = components[ncomponents - 1];
+                unsigned int len = dentry->d_name.len;
+
+                *buflen -= 4 + (XDR_QUADLEN(len) << 2);
+                if (*buflen < 0)
+                        goto out_free;
+                WRITE32(len);
+                WRITEMEM(dentry->d_name.name, len);
+                dprintk("/%s", dentry->d_name.name);
+                dput(dentry);
+                ncomponents--;
         }
-        path += rootlen;
-out:
-        fh_put(&tmp_fh);
-        return path;
+
+        *pp = p;
+        err = 0;
+out_free:
+        dprintk(")\n");
+        while (ncomponents)
+                dput(components[--ncomponents]);
+        kfree(components);
+        path_put(&cur);
+        return err;
+}
+
+static __be32 nfsd4_encode_fsloc_fsroot(struct svc_rqst *rqstp,
+                const struct path *path, __be32 **pp, int *buflen)
+{
+        struct svc_export *exp_ps;
+        __be32 res;
+
+        exp_ps = rqst_find_fsidzero_export(rqstp);
+        if (IS_ERR(exp_ps))
+                return nfserrno(PTR_ERR(exp_ps));
+        res = nfsd4_encode_path(&exp_ps->ex_path, path, pp, buflen);
+        exp_put(exp_ps);
+        return res;
 }
 
 /*
@@ -1739,11 +1792,8 @@ static __be32 nfsd4_encode_fs_locations(struct svc_rqst *rqstp,
         int i;
         __be32 *p = *pp;
         struct nfsd4_fs_locations *fslocs = &exp->ex_fslocs;
-        char *root = nfsd4_path(rqstp, exp, &status);
 
-        if (status)
-                return status;
-        status = nfsd4_encode_components('/', root, &p, buflen);
+        status = nfsd4_encode_fsloc_fsroot(rqstp, &exp->ex_path, &p, buflen);
         if (status)
                 return status;
         if ((*buflen -= 4) < 0)