NFS: Fix double d_drop in nfs_instantiate() error path

If the LOOKUP or GETATTR in nfs_instantiate fail, nfs_instantiate will do a
d_drop before returning.  But some callers already do a d_drop in the case
of an error return.  Make certain we do only one d_drop in all error paths.

This issue was introduced because over time, the symlink proc API diverged
slightly from the create/mkdir/mknod proc API.  To prevent other coding
mistakes of this type, change the symlink proc API to be more like
create/mkdir/mknod and move the nfs_instantiate call into the symlink proc
routines so it is used in exactly the same way for create, mkdir, mknod,
and symlink.

Test plan:
Connectathon, all versions of NFS.

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

5 files changed, 59 insertions, 48 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 084e8cb41c84..affd3ae52e55 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1147,23 +1147,20 @@ int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
                 struct inode *dir = dentry->d_parent->d_inode;
                 error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr);
                 if (error)
-                        goto out_err;
+                        return error;
         }
         if (!(fattr->valid & NFS_ATTR_FATTR)) {
                 struct nfs_server *server = NFS_SB(dentry->d_sb);
                 error = server->nfs_client->rpc_ops->getattr(server, fhandle, fattr);
                 if (error < 0)
-                        goto out_err;
+                        return error;
         }
         inode = nfs_fhget(dentry->d_sb, fhandle, fattr);
         error = PTR_ERR(inode);
         if (IS_ERR(inode))
-                goto out_err;
+                return error;
         d_instantiate(dentry, inode);
         return 0;
-out_err:
-        d_drop(dentry);
-        return error;
 }
 
 /*
@@ -1448,8 +1445,6 @@ static int
 nfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
 {
         struct iattr attr;
-        struct nfs_fattr sym_attr;
-        struct nfs_fh sym_fh;
         struct qstr qsymname;
         int error;
 
@@ -1473,12 +1468,9 @@ dentry->d_parent->d_name.name, dentry->d_name.name);
 
         lock_kernel();
         nfs_begin_data_update(dir);
-        error = NFS_PROTO(dir)->symlink(dir, &dentry->d_name, &qsymname,
-                                          &attr, &sym_fh, &sym_attr);
+        error = NFS_PROTO(dir)->symlink(dir, dentry, &qsymname, &attr);
         nfs_end_data_update(dir);
         if (!error)
-                error = nfs_instantiate(dentry, &sym_fh, &sym_attr);
-        else
                 d_drop(dentry);
         unlock_kernel();
         return error;
diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
index 9e8258ece6fd..d85ac427c326 100644
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -544,23 +544,23 @@ nfs3_proc_link(struct inode *inode, struct inode *dir, struct qstr *name)
 }
 
 static int
-nfs3_proc_symlink(struct inode *dir, struct qstr *name, struct qstr *path,
-                  struct iattr *sattr, struct nfs_fh *fhandle,
-                  struct nfs_fattr *fattr)
+nfs3_proc_symlink(struct inode *dir, struct dentry *dentry, struct qstr *path,
+                  struct iattr *sattr)
 {
-        struct nfs_fattr        dir_attr;
+        struct nfs_fh fhandle;
+        struct nfs_fattr fattr, dir_attr;
         struct nfs3_symlinkargs arg = {
                 .fromfh         = NFS_FH(dir),
-                .fromname       = name->name,
-                .fromlen        = name->len,
+                .fromname       = dentry->d_name.name,
+                .fromlen        = dentry->d_name.len,
                 .topath         = path->name,
                 .tolen          = path->len,
                 .sattr          = sattr
         };
         struct nfs3_diropres    res = {
                 .dir_attr       = &dir_attr,
-                .fh             = fhandle,
-                .fattr          = fattr
+                .fh             = &fhandle,
+                .fattr          = &fattr
         };
         struct rpc_message msg = {
                 .rpc_proc       = &nfs3_procedures[NFS3PROC_SYMLINK],
@@ -571,11 +571,17 @@ nfs3_proc_symlink(struct inode *dir, struct qstr *name, struct qstr *path,
 
         if (path->len > NFS3_MAXPATHLEN)
                 return -ENAMETOOLONG;
-        dprintk("NFS call  symlink %s -> %s\n", name->name, path->name);
+
+        dprintk("NFS call  symlink %s -> %s\n", dentry->d_name.name,
+                        path->name);
         nfs_fattr_init(&dir_attr);
-        nfs_fattr_init(fattr);
+        nfs_fattr_init(&fattr);
         status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0);
         nfs_post_op_update_inode(dir, &dir_attr);
+        if (status != 0)
+                goto out;
+        status = nfs_instantiate(dentry, &fhandle, &fattr);
+out:
         dprintk("NFS reply symlink: %d\n", status);
         return status;
 }
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index a825547e8214..2d18eac6bee5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2084,24 +2084,24 @@ static int nfs4_proc_link(struct inode *inode, struct inode *dir, struct qstr *n
         return err;
 }
 
-static int _nfs4_proc_symlink(struct inode *dir, struct qstr *name,
-                struct qstr *path, struct iattr *sattr, struct nfs_fh *fhandle,
-                struct nfs_fattr *fattr)
+static int _nfs4_proc_symlink(struct inode *dir, struct dentry *dentry,
+                struct qstr *path, struct iattr *sattr)
 {
         struct nfs_server *server = NFS_SERVER(dir);
-        struct nfs_fattr dir_fattr;
+        struct nfs_fh fhandle;
+        struct nfs_fattr fattr, dir_fattr;
         struct nfs4_create_arg arg = {
                 .dir_fh = NFS_FH(dir),
                 .server = server,
-                .name = name,
+                .name = &dentry->d_name,
                 .attrs = sattr,
                 .ftype = NF4LNK,
                 .bitmask = server->attr_bitmask,
         };
         struct nfs4_create_res res = {
                 .server = server,
-                .fh = fhandle,
-                .fattr = fattr,
+                .fh = &fhandle,
+                .fattr = &fattr,
                 .dir_fattr = &dir_fattr,
         };
         struct rpc_message msg = {
@@ -2113,27 +2113,28 @@ static int _nfs4_proc_symlink(struct inode *dir, struct qstr *name,
 
         if (path->len > NFS4_MAXPATHLEN)
                 return -ENAMETOOLONG;
+
         arg.u.symlink = path;
-        nfs_fattr_init(fattr);
+        nfs_fattr_init(&fattr);
         nfs_fattr_init(&dir_fattr);
         
         status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0);
-        if (!status)
+        if (!status) {
                 update_changeattr(dir, &res.dir_cinfo);
-        nfs_post_op_update_inode(dir, res.dir_fattr);
+                nfs_post_op_update_inode(dir, res.dir_fattr);
+                status = nfs_instantiate(dentry, &fhandle, &fattr);
+        }
         return status;
 }
 
-static int nfs4_proc_symlink(struct inode *dir, struct qstr *name,
-                struct qstr *path, struct iattr *sattr, struct nfs_fh *fhandle,
-                struct nfs_fattr *fattr)
+static int nfs4_proc_symlink(struct inode *dir, struct dentry *dentry,
+                struct qstr *path, struct iattr *sattr)
 {
         struct nfs4_exception exception = { };
         int err;
         do {
                 err = nfs4_handle_exception(NFS_SERVER(dir),
-                                _nfs4_proc_symlink(dir, name, path, sattr,
-                                        fhandle, fattr),
+                                _nfs4_proc_symlink(dir, dentry, path, sattr),
                                 &exception);
         } while (exception.retry);
         return err;
diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index 5a8b9407ee9a..0b507bf0f330 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -425,14 +425,15 @@ nfs_proc_link(struct inode *inode, struct inode *dir, struct qstr *name)
 }
 
 static int
-nfs_proc_symlink(struct inode *dir, struct qstr *name, struct qstr *path,
-                 struct iattr *sattr, struct nfs_fh *fhandle,
-                 struct nfs_fattr *fattr)
+nfs_proc_symlink(struct inode *dir, struct dentry *dentry, struct qstr *path,
+                 struct iattr *sattr)
 {
+        struct nfs_fh fhandle;
+        struct nfs_fattr fattr;
         struct nfs_symlinkargs  arg = {
                 .fromfh         = NFS_FH(dir),
-                .fromname       = name->name,
-                .fromlen        = name->len,
+                .fromname       = dentry->d_name.name,
+                .fromlen        = dentry->d_name.len,
                 .topath         = path->name,
                 .tolen          = path->len,
                 .sattr          = sattr
@@ -445,11 +446,23 @@ nfs_proc_symlink(struct inode *dir, struct qstr *name, struct qstr *path,
 
         if (path->len > NFS2_MAXPATHLEN)
                 return -ENAMETOOLONG;
-        dprintk("NFS call  symlink %s -> %s\n", name->name, path->name);
-        nfs_fattr_init(fattr);
-        fhandle->size = 0;
+
+        dprintk("NFS call  symlink %s -> %s\n", dentry->d_name.name,
+                        path->name);
         status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0);
         nfs_mark_for_revalidate(dir);
+
+        /*
+         * V2 SYMLINK requests don't return any attributes.  Setting the
+         * filehandle size to zero indicates to nfs_instantiate that it
+         * should fill in the data with a LOOKUP call on the wire.
+         */
+        if (status == 0) {
+                nfs_fattr_init(&fattr);
+                fhandle.size = 0;
+                status = nfs_instantiate(dentry, &fhandle, &fattr);
+        }
+
         dprintk("NFS reply symlink: %d\n", status);
         return status;
 }
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 0f33e621892f..ddf5d75e97a2 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -793,9 +793,8 @@ struct nfs_rpc_ops {
         int     (*rename)  (struct inode *, struct qstr *,
                             struct inode *, struct qstr *);
         int     (*link)    (struct inode *, struct inode *, struct qstr *);
-        int     (*symlink) (struct inode *, struct qstr *, struct qstr *,
-                            struct iattr *, struct nfs_fh *,
-                            struct nfs_fattr *);
+        int     (*symlink) (struct inode *, struct dentry *, struct qstr *,
+                            struct iattr *);
         int     (*mkdir)   (struct inode *, struct dentry *, struct iattr *);
         int     (*rmdir)   (struct inode *, struct qstr *);
         int     (*readdir) (struct dentry *, struct rpc_cred *,