NFSv4: Ensure client submounts when following a referral

Set up mountpoint when hitting a referral on moved error by getting
fs_locations.

Signed-off-by: Manoj Naik <manoj@almaden.ibm.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 269 insertions, 3 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index ebdab885c475..0d8302e59d69 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -36,6 +36,8 @@
 #include <linux/mount.h>
 #include <linux/nfs_idmap.h>
 #include <linux/vfs.h>
+#include <linux/inet.h>
+#include <linux/nfs_xdr.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -1714,6 +1716,10 @@ struct nfs_clone_mount {
         const struct dentry *dentry;
         struct nfs_fh *fh;
         struct nfs_fattr *fattr;
+        char *hostname;
+        char *mnt_path;
+        struct sockaddr_in *addr;
+        rpc_authflavor_t authflavor;
 };
 
 static struct super_block *nfs_clone_generic_sb(struct nfs_clone_mount *data,
@@ -1724,17 +1730,19 @@ static struct super_block *nfs_clone_generic_sb(struct nfs_clone_mount *data,
         struct nfs_server *parent = NFS_SB(data->sb);
         struct super_block *sb = ERR_PTR(-EINVAL);
         void *err = ERR_PTR(-ENOMEM);
+        char *hostname;
         int len;
 
         server = kmalloc(sizeof(struct nfs_server), GFP_KERNEL);
         if (server == NULL)
                 goto out_err;
         memcpy(server, parent, sizeof(*server));
-        len = strlen(parent->hostname) + 1;
+        hostname = (data->hostname != NULL) ? data->hostname : parent->hostname;
+        len = strlen(hostname) + 1;
         server->hostname = kmalloc(len, GFP_KERNEL);
         if (server->hostname == NULL)
                 goto free_server;
-        memcpy(server->hostname, parent->hostname, len);
+        memcpy(server->hostname, hostname, len);
         if (rpciod_up() != 0)
                 goto free_hostname;
 
@@ -2458,7 +2466,8 @@ static inline void unregister_nfs4fs(void)
         nfs_unregister_sysctl();
 }
 #else
-#define nfs4_clone_client(a,b) ERR_PTR(-EINVAL)
+#define nfs4_fill_sb(a,b)       ERR_PTR(-EINVAL)
+#define nfs4_fill_super(a,b)    ERR_PTR(-EINVAL)
 #define nfs4_init_once(nfsi) \
         do { } while (0)
 #define register_nfs4fs() (0)
@@ -2521,6 +2530,261 @@ out:
         return mnt;
 }
 
+/* Check if fs_root is valid */
+static inline char *nfs4_pathname_string(struct nfs4_pathname *pathname, char *buffer, ssize_t buflen)
+{
+        char *end = buffer + buflen;
+        int n;
+
+        *--end = '\0';
+        buflen--;
+
+        n = pathname->ncomponents;
+        while (--n >= 0) {
+                struct nfs4_string *component = &pathname->components[n];
+                buflen -= component->len + 1;
+                if (buflen < 0)
+                        goto Elong;
+                end -= component->len;
+                memcpy(end, component->data, component->len);
+                *--end = '/';
+        }
+        return end;
+Elong:
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+/* Check if the string represents a "valid" IPv4 address */
+static inline int valid_ipaddr4(const char *buf)
+{
+        int rc, count, in[4];
+
+        rc = sscanf(buf, "%d.%d.%d.%d", &in[0], &in[1], &in[2], &in[3]);
+        if (rc != 4)
+                return -EINVAL;
+        for (count = 0; count < 4; count++) {
+                if (in[count] > 255)
+                        return -EINVAL;
+        }
+        return 0;
+}
+
+static struct super_block *nfs4_referral_sb(struct nfs_server *server, struct nfs_clone_mount *data)
+{
+        struct super_block *sb = ERR_PTR(-ENOMEM);
+        int len;
+
+        len = strlen(data->mnt_path) + 1;
+        server->mnt_path = kmalloc(len, GFP_KERNEL);
+        if (server->mnt_path == NULL)
+                goto err;
+        memcpy(server->mnt_path, data->mnt_path, len);
+        memcpy(&server->addr, data->addr, sizeof(struct sockaddr_in));
+
+        sb = sget(&nfs4_fs_type, nfs4_compare_super, nfs_set_super, server);
+        if (IS_ERR(sb) || sb->s_root)
+                goto free_path;
+        return sb;
+free_path:
+        kfree(server->mnt_path);
+err:
+        server->mnt_path = NULL;
+        return sb;
+}
+
+static struct nfs_server *nfs4_referral_server(struct super_block *sb, struct nfs_clone_mount *data)
+{
+        struct nfs_server *server = NFS_SB(sb);
+        struct rpc_timeout timeparms;
+        int proto, timeo, retrans;
+        void *err;
+
+        proto = IPPROTO_TCP;
+        /* Since we are following a referral and there may be alternatives,
+           set the timeouts and retries to low values */
+        timeo = 2;
+        retrans = 1;
+        nfs_init_timeout_values(&timeparms, proto, timeo, retrans);
+
+        server->client = nfs4_create_client(server, &timeparms, proto, data->authflavor);
+        if (IS_ERR((err = server->client)))
+                goto out_err;
+
+        sb->s_time_gran = 1;
+        sb->s_op = &nfs4_sops;
+        err = ERR_PTR(nfs_sb_init(sb, data->authflavor));
+        if (!IS_ERR(err))
+                return server;
+out_err:
+        return (struct nfs_server *)err;
+}
+
+static struct super_block *nfs_referral_nfs4_sb(struct file_system_type *fs_type,
+                int flags, const char *dev_name, void *raw_data)
+{
+        struct nfs_clone_mount *data = raw_data;
+        return nfs_clone_generic_sb(data, nfs4_referral_sb, nfs4_referral_server);
+}
+
+static struct file_system_type nfs_referral_nfs4_fs_type = {
+        .owner          = THIS_MODULE,
+        .name           = "nfs4",
+        .get_sb         = nfs_referral_nfs4_sb,
+        .kill_sb        = nfs4_kill_super,
+        .fs_flags       = FS_ODD_RENAME|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+};
+
+/**
+ * nfs_follow_referral - set up mountpoint when hitting a referral on moved error
+ * @mnt_parent - mountpoint of parent directory
+ * @dentry - parent directory
+ * @fspath - fs path returned in fs_locations
+ * @mntpath - mount path to new server
+ * @hostname - hostname of new server
+ * @addr - host addr of new server
+ *
+ */
+struct vfsmount *nfs_follow_referral(const struct vfsmount *mnt_parent,
+             const struct dentry *dentry, struct nfs4_fs_locations *locations)
+{
+        struct vfsmount *mnt = ERR_PTR(-ENOENT);
+        struct nfs_clone_mount mountdata = {
+                .sb = mnt_parent->mnt_sb,
+                .dentry = dentry,
+                .authflavor = NFS_SB(mnt_parent->mnt_sb)->client->cl_auth->au_flavor,
+        };
+        char *page, *page2;
+        char *path, *fs_path;
+        char *devname;
+        int loc, s;
+
+        if (locations == NULL || locations->nlocations <= 0)
+                goto out;
+
+        dprintk("%s: referral at %s/%s\n", __FUNCTION__,
+                dentry->d_parent->d_name.name, dentry->d_name.name);
+
+        /* Ensure fs path is a prefix of current dentry path */
+        page = (char *) __get_free_page(GFP_USER);
+        if (page == NULL)
+                goto out;
+        page2 = (char *) __get_free_page(GFP_USER);
+        if (page2 == NULL)
+                goto out;
+
+        path = nfs4_path(dentry, page, PAGE_SIZE);
+        if (IS_ERR(path))
+                goto out_free;
+
+        fs_path = nfs4_pathname_string(&locations->fs_path, page2, PAGE_SIZE);
+        if (IS_ERR(fs_path))
+                goto out_free;
+
+        if (strncmp(path, fs_path, strlen(fs_path)) != 0) {
+                dprintk("%s: path %s does not begin with fsroot %s\n", __FUNCTION__, path, fs_path);
+                goto out_free;
+        }
+
+        devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
+        if (IS_ERR(devname)) {
+                mnt = (struct vfsmount *)devname;
+                goto out_free;
+        }
+
+        loc = 0;
+        while (loc < locations->nlocations && IS_ERR(mnt)) {
+                struct nfs4_fs_location *location = &locations->locations[loc];
+                char *mnt_path;
+
+                if (location == NULL || location->nservers <= 0 ||
+                    location->rootpath.ncomponents == 0) {
+                        loc++;
+                        continue;
+                }
+
+                mnt_path = nfs4_pathname_string(&location->rootpath, page2, PAGE_SIZE);
+                if (IS_ERR(mnt_path)) {
+                        loc++;
+                        continue;
+                }
+                mountdata.mnt_path = mnt_path;
+
+                s = 0;
+                while (s < location->nservers) {
+                        struct sockaddr_in addr = {};
+
+                        if (location->servers[s].len <= 0 ||
+                            valid_ipaddr4(location->servers[s].data) < 0) {
+                                s++;
+                                continue;
+                        }
+
+                        mountdata.hostname = location->servers[s].data;
+                        addr.sin_addr.s_addr = in_aton(mountdata.hostname);
+                        addr.sin_family = AF_INET;
+                        addr.sin_port = htons(NFS_PORT);
+                        mountdata.addr = &addr;
+
+                        mnt = vfs_kern_mount(&nfs_referral_nfs4_fs_type, 0, devname, &mountdata);
+                        if (!IS_ERR(mnt)) {
+                                break;
+                        }
+                        s++;
+                }
+                loc++;
+        }
+
+out_free:
+        free_page((unsigned long)page);
+        free_page((unsigned long)page2);
+out:
+        dprintk("%s: done\n", __FUNCTION__);
+        return mnt;
+}
+
+/*
+ * nfs_do_refmount - handle crossing a referral on server
+ * @dentry - dentry of referral
+ * @nd - nameidata info
+ *
+ */
+struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent, struct dentry *dentry)
+{
+        struct vfsmount *mnt = ERR_PTR(-ENOENT);
+        struct dentry *parent;
+        struct nfs4_fs_locations *fs_locations = NULL;
+        struct page *page;
+        int err;
+
+        /* BUG_ON(IS_ROOT(dentry)); */
+        dprintk("%s: enter\n", __FUNCTION__);
+
+        page = alloc_page(GFP_KERNEL);
+        if (page == NULL)
+                goto out;
+
+        fs_locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
+        if (fs_locations == NULL)
+                goto out_free;
+
+        /* Get locations */
+        parent = dget_parent(dentry);
+        dprintk("%s: getting locations for %s/%s\n", __FUNCTION__, parent->d_name.name, dentry->d_name.name);
+        err = nfs4_proc_fs_locations(parent->d_inode, dentry, fs_locations, page);
+        dput(parent);
+        if (err != 0 || fs_locations->nlocations <= 0 ||
+            fs_locations->fs_path.ncomponents <= 0)
+                goto out_free;
+
+        mnt = nfs_follow_referral(mnt_parent, dentry, fs_locations);
+out_free:
+        __free_page(page);
+        kfree(fs_locations);
+out:
+        dprintk("%s: done\n", __FUNCTION__);
+        return mnt;
+}
+
 extern int nfs_init_nfspagecache(void);
 extern void nfs_destroy_nfspagecache(void);
 extern int nfs_init_readpagecache(void);
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index a34b3ee443f1..09271b10f9a8 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -317,6 +317,8 @@ extern struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
                                         const struct dentry *dentry,
                                         struct nfs_fh *fh,
                                         struct nfs_fattr *fattr);
+extern struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent,
+                                        struct dentry *dentry);
 
 /* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
 extern u32 root_nfs_parse_addr(char *name); /*__init*/