9 files changed, 247 insertions, 72 deletions

diff --git a/Documentation/filesystems/9p.txt b/Documentation/filesystems/9p.txt
index e694cd1b52cf..d6fd6c6e4244 100644
--- a/Documentation/filesystems/9p.txt
+++ b/Documentation/filesystems/9p.txt
@@ -88,6 +88,16 @@ OPTIONS
                 This can be used to share devices/named pipes/sockets between
                 hosts.  This functionality will be expanded in later versions.
 
+  access        there are three access modes.
+                        user  = if a user tries to access a file on v9fs
+                                filesystem for the first time, v9fs sends an
+                                attach command (Tattach) for that user.
+                                This is the default mode.
+                        <uid> = allows only user with uid=<uid> to access
+                                the files on the mounted filesystem
+                        any   = v9fs does single attach and performs all
+                                operations as one user
+
 RESOURCES
 =========
 
diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index 15e05a15b575..b364da70ff28 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -1,6 +1,7 @@
 /*
  * V9FS FID Management
  *
+ *  Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
  *  Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
  *
  *  This program is free software; you can redistribute it and/or modify
@@ -34,9 +35,9 @@
 #include "fid.h"
 
 /**
- * v9fs_fid_insert - add a fid to a dentry
+ * v9fs_fid_add - add a fid to a dentry
+ * @dentry: dentry that the fid is being added to
  * @fid: fid to add
- * @dentry: dentry that it is being added to
  *
  */
 
@@ -66,52 +67,144 @@ int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
 }
 
 /**
- * v9fs_fid_lookup - return a locked fid from a dentry
+ * v9fs_fid_find - retrieve a fid that belongs to the specified uid
  * @dentry: dentry to look for fid in
- *
- * find a fid in the dentry, obtain its semaphore and return a reference to it.
- * code calling lookup is responsible for releasing lock
- *
- * TODO: only match fids that have the same uid as current user
+ * @uid: return fid that belongs to the specified user
+ * @any: if non-zero, return any fid associated with the dentry
  *
  */
 
-struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
+static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any)
 {
         struct v9fs_dentry *dent;
-        struct p9_fid *fid;
-
-        P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
-        dent = dentry->d_fsdata;
-        if (dent)
-                fid = list_entry(dent->fidlist.next, struct p9_fid, dlist);
-        else
-                fid = ERR_PTR(-EBADF);
+        struct p9_fid *fid, *ret;
+
+        P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
+                dentry->d_iname, dentry, uid, any);
+        dent = (struct v9fs_dentry *) dentry->d_fsdata;
+        ret = NULL;
+        if (dent) {
+                spin_lock(&dent->lock);
+                list_for_each_entry(fid, &dent->fidlist, dlist) {
+                        if (any || fid->uid == uid) {
+                                ret = fid;
+                                break;
+                        }
+                }
+                spin_unlock(&dent->lock);
+        }
 
-        P9_DPRINTK(P9_DEBUG_VFS, " fid: %p\n", fid);
-        return fid;
+        return ret;
 }
 
 /**
- * v9fs_fid_clone - lookup the fid for a dentry, clone a private copy and
- *      release it
+ * v9fs_fid_lookup - lookup for a fid, try to walk if not found
  * @dentry: dentry to look for fid in
  *
- * find a fid in the dentry and then clone to a new private fid
- *
- * TODO: only match fids that have the same uid as current user
- *
+ * Look for a fid in the specified dentry for the current user.
+ * If no fid is found, try to create one walking from a fid from the parent
+ * dentry (if it has one), or the root dentry. If the user haven't accessed
+ * the fs yet, attach now and walk from the root.
  */
 
-struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
+struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 {
-        struct p9_fid *ofid, *fid;
+        int i, n, l, clone, any, access;
+        u32 uid;
+        struct p9_fid *fid;
+        struct dentry *d, *ds;
+        struct v9fs_session_info *v9ses;
+        char **wnames, *uname;
+
+        v9ses = v9fs_inode2v9ses(dentry->d_inode);
+        access = v9ses->flags & V9FS_ACCESS_MASK;
+        switch (access) {
+        case V9FS_ACCESS_SINGLE:
+        case V9FS_ACCESS_USER:
+                uid = current->fsuid;
+                any = 0;
+                break;
+
+        case V9FS_ACCESS_ANY:
+                uid = v9ses->uid;
+                any = 1;
+                break;
+
+        default:
+                uid = ~0;
+                any = 0;
+                break;
+        }
 
-        P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
-        ofid = v9fs_fid_lookup(dentry);
-        if (IS_ERR(ofid))
-                return ofid;
+        fid = v9fs_fid_find(dentry, uid, any);
+        if (fid)
+                return fid;
+
+        ds = dentry->d_parent;
+        fid = v9fs_fid_find(ds, uid, any);
+        if (!fid) { /* walk from the root */
+                n = 0;
+                for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
+                        n++;
+
+                fid = v9fs_fid_find(ds, uid, any);
+                if (!fid) { /* the user is not attached to the fs yet */
+                        if (access == V9FS_ACCESS_SINGLE)
+                                return ERR_PTR(-EPERM);
+
+                        if (v9fs_extended(v9ses))
+                                uname = NULL;
+                        else
+                                uname = v9ses->uname;
+
+                        fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
+                                v9ses->aname);
+
+                        if (IS_ERR(fid))
+                                return fid;
+
+                        v9fs_fid_add(ds, fid);
+                }
+        } else /* walk from the parent */
+                n = 1;
+
+        if (ds == dentry)
+                return fid;
+
+        wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
+        if (!wnames)
+                return ERR_PTR(-ENOMEM);
+
+        for (d = dentry, i = n; i >= 0; i--, d = d->d_parent)
+                wnames[i] = (char *) d->d_name.name;
+
+        clone = 1;
+        i = 0;
+        while (i < n) {
+                l = min(n - i, P9_MAXWELEM);
+                fid = p9_client_walk(fid, l, &wnames[i], clone);
+                if (!fid) {
+                        kfree(wnames);
+                        return fid;
+                }
+
+                i += l;
+                clone = 0;
+        }
 
-        fid = p9_client_walk(ofid, 0, NULL, 1);
+        kfree(wnames);
+        v9fs_fid_add(dentry, fid);
         return fid;
 }
+
+struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
+{
+        struct p9_fid *fid, *ret;
+
+        fid = v9fs_fid_lookup(dentry);
+        if (IS_ERR(fid))
+                return fid;
+
+        ret = p9_client_walk(fid, 0, NULL, 1);
+        return ret;
+}
diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index 68f82be3bf37..89ee0bace41d 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -91,6 +91,8 @@ enum {
         Opt_legacy, Opt_nodevmap,
         /* Cache options */
         Opt_cache_loose,
+        /* Access options */
+        Opt_access,
         /* Error token */
         Opt_err
 };
@@ -108,6 +110,7 @@ static match_table_t tokens = {
         {Opt_nodevmap, "nodevmap"},
         {Opt_cache_loose, "cache=loose"},
         {Opt_cache_loose, "loose"},
+        {Opt_access, "access=%s"},
         {Opt_err, NULL}
 };
 
@@ -125,10 +128,10 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses)
         char *p;
         int option;
         int ret;
+        char *s, *e;
 
         /* setup defaults */
         v9ses->maxdata = 8192;
-        v9ses->flags = V9FS_EXTENDED;
         v9ses->afid = ~0;
         v9ses->debug = 0;
         v9ses->cache = 0;
@@ -172,10 +175,10 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses)
                         v9ses->trans = v9fs_match_trans(&args[0]);
                         break;
                 case Opt_uname:
-                        match_strcpy(v9ses->name, &args[0]);
+                        match_strcpy(v9ses->uname, &args[0]);
                         break;
                 case Opt_remotename:
-                        match_strcpy(v9ses->remotename, &args[0]);
+                        match_strcpy(v9ses->aname, &args[0]);
                         break;
                 case Opt_legacy:
                         v9ses->flags &= ~V9FS_EXTENDED;
@@ -186,6 +189,22 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses)
                 case Opt_cache_loose:
                         v9ses->cache = CACHE_LOOSE;
                         break;
+
+                case Opt_access:
+                        s = match_strdup(&args[0]);
+                        v9ses->flags &= ~V9FS_ACCESS_MASK;
+                        if (strcmp(s, "user") == 0)
+                                v9ses->flags |= V9FS_ACCESS_USER;
+                        else if (strcmp(s, "any") == 0)
+                                v9ses->flags |= V9FS_ACCESS_ANY;
+                        else {
+                                v9ses->flags |= V9FS_ACCESS_SINGLE;
+                                v9ses->uid = simple_strtol(s, &e, 10);
+                                if (*e != '\0')
+                                        v9ses->uid = ~0;
+                        }
+                        break;
+
                 default:
                         continue;
                 }
@@ -207,21 +226,22 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
         struct p9_trans *trans = NULL;
         struct p9_fid *fid;
 
-        v9ses->name = __getname();
-        if (!v9ses->name)
+        v9ses->uname = __getname();
+        if (!v9ses->uname)
                 return ERR_PTR(-ENOMEM);
 
-        v9ses->remotename = __getname();
-        if (!v9ses->remotename) {
-                __putname(v9ses->name);
+        v9ses->aname = __getname();
+        if (!v9ses->aname) {
+                __putname(v9ses->uname);
                 return ERR_PTR(-ENOMEM);
         }
 
-        strcpy(v9ses->name, V9FS_DEFUSER);
-        strcpy(v9ses->remotename, V9FS_DEFANAME);
+        v9ses->flags = V9FS_EXTENDED | V9FS_ACCESS_USER;
+        strcpy(v9ses->uname, V9FS_DEFUSER);
+        strcpy(v9ses->aname, V9FS_DEFANAME);
+        v9ses->uid = ~0;
         v9ses->dfltuid = V9FS_DEFUID;
         v9ses->dfltgid = V9FS_DEFGID;
-
         v9ses->options = kstrdup(data, GFP_KERNEL);
         v9fs_parse_options(v9ses);
 
@@ -255,8 +275,20 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
                 goto error;
         }
 
-        fid = p9_client_attach(v9ses->clnt, NULL, v9ses->name,
-                                                        v9ses->remotename);
+        if (!v9ses->clnt->dotu)
+                v9ses->flags &= ~V9FS_EXTENDED;
+
+        /* for legacy mode, fall back to V9FS_ACCESS_ANY */
+        if (!v9fs_extended(v9ses) &&
+                ((v9ses->flags&V9FS_ACCESS_MASK) == V9FS_ACCESS_USER)) {
+
+                v9ses->flags &= ~V9FS_ACCESS_MASK;
+                v9ses->flags |= V9FS_ACCESS_ANY;
+                v9ses->uid = ~0;
+        }
+
+        fid = p9_client_attach(v9ses->clnt, NULL, v9ses->uname, ~0,
+                                                        v9ses->aname);
         if (IS_ERR(fid)) {
                 retval = PTR_ERR(fid);
                 fid = NULL;
@@ -264,6 +296,11 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
                 goto error;
         }
 
+        if ((v9ses->flags & V9FS_ACCESS_MASK) == V9FS_ACCESS_SINGLE)
+                fid->uid = v9ses->uid;
+        else
+                fid->uid = ~0;
+
         return fid;
 
 error:
@@ -284,8 +321,8 @@ void v9fs_session_close(struct v9fs_session_info *v9ses)
                 v9ses->clnt = NULL;
         }
 
-        __putname(v9ses->name);
-        __putname(v9ses->remotename);
+        __putname(v9ses->uname);
+        __putname(v9ses->aname);
         kfree(v9ses->options);
 }
 
diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index 8e0999b3d0cc..db4b4193f2e2 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -36,10 +36,11 @@ struct v9fs_session_info {
         unsigned int cache;     /* cache mode */
 
         char *options;          /* copy of mount options */
-        char *name;             /* user name to mount as */
-        char *remotename;       /* name of remote hierarchy being mounted */
+        char *uname;            /* user name to mount as */
+        char *aname;            /* name of remote hierarchy being mounted */
         unsigned int dfltuid;   /* default uid/muid for legacy support */
         unsigned int dfltgid;   /* default gid for legacy support */
+        u32 uid;                /* if ACCESS_SINGLE, the uid that has access */
         struct p9_trans_module *trans; /* 9p transport */
         struct p9_client *clnt; /* 9p client */
         struct dentry *debugfs_dir;
@@ -47,7 +48,11 @@ struct v9fs_session_info {
 
 /* session flags */
 enum {
-        V9FS_EXTENDED,
+        V9FS_EXTENDED           = 0x01, /* 9P2000.u */
+        V9FS_ACCESS_MASK        = 0x06, /* access mask */
+        V9FS_ACCESS_SINGLE      = 0x02, /* only one user can access the files */
+        V9FS_ACCESS_USER        = 0x04, /* attache per user */
+        V9FS_ACCESS_ANY         = 0x06, /* use the same attach for all users */
 };
 
 /* possible values of ->cache */
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index f08a35d2973a..175b4d9bf3f8 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -364,7 +364,7 @@ static int v9fs_remove(struct inode *dir, struct dentry *file, int rmdir)
         file_inode = file->d_inode;
         v9ses = v9fs_inode2v9ses(file_inode);
         v9fid = v9fs_fid_clone(file);
-        if(IS_ERR(v9fid))
+        if (IS_ERR(v9fid))
                 return PTR_ERR(v9fid);
 
         return p9_client_remove(v9fid);
@@ -398,7 +398,7 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
         fid = NULL;
         name = (char *) dentry->d_name.name;
         dfid = v9fs_fid_clone(dentry->d_parent);
-        if(IS_ERR(dfid)) {
+        if (IS_ERR(dfid)) {
                 err = PTR_ERR(dfid);
                 dfid = NULL;
                 goto error;
@@ -432,7 +432,7 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
                 goto error;
         }
 
-        if(v9ses->cache)
+        if (v9ses->cache)
                 dentry->d_op = &v9fs_cached_dentry_operations;
         else
                 dentry->d_op = &v9fs_dentry_operations;
@@ -593,7 +593,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
         if (result < 0)
                 goto error;
 
-        if((fid->qid.version)&&(v9ses->cache))
+        if ((fid->qid.version) && (v9ses->cache))
                 dentry->d_op = &v9fs_cached_dentry_operations;
         else
                 dentry->d_op = &v9fs_dentry_operations;
@@ -658,17 +658,17 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
         old_inode = old_dentry->d_inode;
         v9ses = v9fs_inode2v9ses(old_inode);
         oldfid = v9fs_fid_lookup(old_dentry);
-        if(IS_ERR(oldfid))
+        if (IS_ERR(oldfid))
                 return PTR_ERR(oldfid);
 
         olddirfid = v9fs_fid_clone(old_dentry->d_parent);
-        if(IS_ERR(olddirfid)) {
+        if (IS_ERR(olddirfid)) {
                 retval = PTR_ERR(olddirfid);
                 goto done;
         }
 
         newdirfid = v9fs_fid_clone(new_dentry->d_parent);
-        if(IS_ERR(newdirfid)) {
+        if (IS_ERR(newdirfid)) {
                 retval = PTR_ERR(newdirfid);
                 goto clunk_olddir;
         }
@@ -682,7 +682,7 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
         }
 
         v9fs_blank_wstat(&wstat);
-        wstat.muid = v9ses->name;
+        wstat.muid = v9ses->uname;
         wstat.name = (char *) new_dentry->d_name.name;
         retval = p9_client_wstat(oldfid, &wstat);
 
@@ -887,7 +887,7 @@ static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
         retval = -EPERM;
         v9ses = v9fs_inode2v9ses(dentry->d_inode);
         fid = v9fs_fid_lookup(dentry);
-        if(IS_ERR(fid))
+        if (IS_ERR(fid))
                 return PTR_ERR(fid);
 
         if (!v9fs_extended(v9ses))
@@ -1070,7 +1070,7 @@ v9fs_vfs_link(struct dentry *old_dentry, struct inode *dir,
                 old_dentry->d_name.name);
 
         oldfid = v9fs_fid_clone(old_dentry);
-        if(IS_ERR(oldfid))
+        if (IS_ERR(oldfid))
                 return PTR_ERR(oldfid);
 
         name = __getname();
diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 7726ff41c3e6..7a448a30e39b 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -216,6 +216,7 @@ struct p9_tauth {
         u32 afid;
         struct p9_str uname;
         struct p9_str aname;
+        u32 n_uname;            /* 9P2000.u extensions */
 };
 
 struct p9_rauth {
@@ -239,6 +240,7 @@ struct p9_tattach {
         u32 afid;
         struct p9_str uname;
         struct p9_str aname;
+        u32 n_uname;            /* 9P2000.u extensions */
 };
 
 struct p9_rattach {
@@ -382,8 +384,9 @@ int p9_deserialize_fcall(void *buf, u32 buflen, struct p9_fcall *fc, int dotu);
 void p9_set_tag(struct p9_fcall *fc, u16 tag);
 struct p9_fcall *p9_create_tversion(u32 msize, char *version);
 struct p9_fcall *p9_create_tattach(u32 fid, u32 afid, char *uname,
-        char *aname);
-struct p9_fcall *p9_create_tauth(u32 afid, char *uname, char *aname);
+        char *aname, u32 n_uname, int dotu);
+struct p9_fcall *p9_create_tauth(u32 afid, char *uname, char *aname,
+        u32 n_uname, int dotu);
 struct p9_fcall *p9_create_tflush(u16 oldtag);
 struct p9_fcall *p9_create_twalk(u32 fid, u32 newfid, u16 nwname,
         char **wnames);
diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index 0adafdb273f0..9b9221a21392 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -57,8 +57,9 @@ struct p9_client *p9_client_create(struct p9_trans *trans, int msize,
 void p9_client_destroy(struct p9_client *clnt);
 void p9_client_disconnect(struct p9_client *clnt);
 struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
-                                                     char *uname, char *aname);
-struct p9_fid *p9_client_auth(struct p9_client *clnt, char *uname, char *aname);
+                                        char *uname, u32 n_uname, char *aname);
+struct p9_fid *p9_client_auth(struct p9_client *clnt, char *uname,
+                                                u32 n_uname, char *aname);
 struct p9_fid *p9_client_walk(struct p9_fid *oldfid, int nwname, char **wnames,
                                                                 int clone);
 int p9_client_open(struct p9_fid *fid, int mode);
diff --git a/net/9p/client.c b/net/9p/client.c
index e1610125a882..d83cc1247f1e 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -146,7 +146,7 @@ void p9_client_disconnect(struct p9_client *clnt)
 EXPORT_SYMBOL(p9_client_disconnect);
 
 struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
-        char *uname, char *aname)
+        char *uname, u32 n_uname, char *aname)
 {
         int err;
         struct p9_fcall *tc, *rc;
@@ -165,7 +165,8 @@ struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
                 goto error;
         }
 
-        tc = p9_create_tattach(fid->fid, afid?afid->fid:P9_NOFID, uname, aname);
+        tc = p9_create_tattach(fid->fid, afid?afid->fid:P9_NOFID, uname, aname,
+                n_uname, clnt->dotu);
         if (IS_ERR(tc)) {
                 err = PTR_ERR(tc);
                 tc = NULL;
@@ -190,7 +191,8 @@ error:
 }
 EXPORT_SYMBOL(p9_client_attach);
 
-struct p9_fid *p9_client_auth(struct p9_client *clnt, char *uname, char *aname)
+struct p9_fid *p9_client_auth(struct p9_client *clnt, char *uname,
+        u32 n_uname, char *aname)
 {
         int err;
         struct p9_fcall *tc, *rc;
@@ -209,7 +211,7 @@ struct p9_fid *p9_client_auth(struct p9_client *clnt, char *uname, char *aname)
                 goto error;
         }
 
-        tc = p9_create_tauth(fid->fid, uname, aname);
+        tc = p9_create_tauth(fid->fid, uname, aname, n_uname, clnt->dotu);
         if (IS_ERR(tc)) {
                 err = PTR_ERR(tc);
                 tc = NULL;
diff --git a/net/9p/conv.c b/net/9p/conv.c
index d979d958ea19..aa2aa9884f95 100644
--- a/net/9p/conv.c
+++ b/net/9p/conv.c
@@ -547,7 +547,8 @@ error:
 }
 EXPORT_SYMBOL(p9_create_tversion);
 
-struct p9_fcall *p9_create_tauth(u32 afid, char *uname, char *aname)
+struct p9_fcall *p9_create_tauth(u32 afid, char *uname, char *aname,
+        u32 n_uname, int dotu)
 {
         int size;
         struct p9_fcall *fc;
@@ -555,7 +556,16 @@ struct p9_fcall *p9_create_tauth(u32 afid, char *uname, char *aname)
         struct cbuf *bufp = &buffer;
 
         /* afid[4] uname[s] aname[s] */
-        size = 4 + 2 + strlen(uname) + 2 + strlen(aname);
+        size = 4 + 2 + 2;
+        if (uname)
+                size += strlen(uname);
+
+        if (aname)
+                size += strlen(aname);
+
+        if (dotu)
+                size += 4;      /* n_uname */
+
         fc = p9_create_common(bufp, size, P9_TAUTH);
         if (IS_ERR(fc))
                 goto error;
@@ -563,6 +573,8 @@ struct p9_fcall *p9_create_tauth(u32 afid, char *uname, char *aname)
         p9_put_int32(bufp, afid, &fc->params.tauth.afid);
         p9_put_str(bufp, uname, &fc->params.tauth.uname);
         p9_put_str(bufp, aname, &fc->params.tauth.aname);
+        if (dotu)
+                p9_put_int32(bufp, n_uname, &fc->params.tauth.n_uname);
 
         if (buf_check_overflow(bufp)) {
                 kfree(fc);
@@ -574,7 +586,8 @@ error:
 EXPORT_SYMBOL(p9_create_tauth);
 
 struct p9_fcall *
-p9_create_tattach(u32 fid, u32 afid, char *uname, char *aname)
+p9_create_tattach(u32 fid, u32 afid, char *uname, char *aname,
+        u32 n_uname, int dotu)
 {
         int size;
         struct p9_fcall *fc;
@@ -582,7 +595,16 @@ p9_create_tattach(u32 fid, u32 afid, char *uname, char *aname)
         struct cbuf *bufp = &buffer;
 
         /* fid[4] afid[4] uname[s] aname[s] */
-        size = 4 + 4 + 2 + strlen(uname) + 2 + strlen(aname);
+        size = 4 + 4 + 2 + 2;
+        if (uname)
+                size += strlen(uname);
+
+        if (aname)
+                size += strlen(aname);
+
+        if (dotu)
+                size += 4;      /* n_uname */
+
         fc = p9_create_common(bufp, size, P9_TATTACH);
         if (IS_ERR(fc))
                 goto error;
@@ -591,6 +613,8 @@ p9_create_tattach(u32 fid, u32 afid, char *uname, char *aname)
         p9_put_int32(bufp, afid, &fc->params.tattach.afid);
         p9_put_str(bufp, uname, &fc->params.tattach.uname);
         p9_put_str(bufp, aname, &fc->params.tattach.aname);
+        if (dotu)
+                p9_put_int32(bufp, n_uname, &fc->params.tattach.n_uname);
 
 error:
         return fc;