NFSv4: Ensure asynchronous open() calls always pin the mountpoint

A number of race conditions may currently ensue if the user presses ^C
and then unmounts the partition while an asynchronous open() is in
progress.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 32 insertions, 18 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index c27258b5d3e1..4948ec1dd9bd 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1244,7 +1244,7 @@ static int nfs_create(struct inode *dir, struct dentry *dentry, int mode,
         attr.ia_mode = mode;
         attr.ia_valid = ATTR_MODE;
 
-        if (nd && (nd->flags & LOOKUP_CREATE))
+        if ((nd->flags & LOOKUP_CREATE) != 0)
                 open_flags = nd->intent.open.flags;
 
         lock_kernel();
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index c83db9def0fe..895e8e649c91 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -221,7 +221,7 @@ struct nfs4_opendata {
         struct nfs_open_confirmres c_res;
         struct nfs_fattr f_attr;
         struct nfs_fattr dir_attr;
-        struct dentry *dentry;
+        struct path path;
         struct dentry *dir;
         struct nfs4_state_owner *owner;
         struct iattr attrs;
@@ -230,11 +230,11 @@ struct nfs4_opendata {
         int cancelled;
 };
 
-static struct nfs4_opendata *nfs4_opendata_alloc(struct dentry *dentry,
+static struct nfs4_opendata *nfs4_opendata_alloc(struct path *path,
                 struct nfs4_state_owner *sp, int flags,
                 const struct iattr *attrs)
 {
-        struct dentry *parent = dget_parent(dentry);
+        struct dentry *parent = dget_parent(path->dentry);
         struct inode *dir = parent->d_inode;
         struct nfs_server *server = NFS_SERVER(dir);
         struct nfs4_opendata *p;
@@ -246,7 +246,8 @@ static struct nfs4_opendata *nfs4_opendata_alloc(struct dentry *dentry,
         if (p->o_arg.seqid == NULL)
                 goto err_free;
         atomic_set(&p->count, 1);
-        p->dentry = dget(dentry);
+        p->path.mnt = mntget(path->mnt);
+        p->path.dentry = dget(path->dentry);
         p->dir = parent;
         p->owner = sp;
         atomic_inc(&sp->so_count);
@@ -254,7 +255,7 @@ static struct nfs4_opendata *nfs4_opendata_alloc(struct dentry *dentry,
         p->o_arg.open_flags = flags,
         p->o_arg.clientid = server->nfs_client->cl_clientid;
         p->o_arg.id = sp->so_id;
-        p->o_arg.name = &dentry->d_name;
+        p->o_arg.name = &p->path.dentry->d_name;
         p->o_arg.server = server;
         p->o_arg.bitmask = server->attr_bitmask;
         p->o_arg.claim = NFS4_OPEN_CLAIM_NULL;
@@ -288,7 +289,8 @@ static void nfs4_opendata_free(struct nfs4_opendata *p)
                 nfs_free_seqid(p->o_arg.seqid);
                 nfs4_put_state_owner(p->owner);
                 dput(p->dir);
-                dput(p->dentry);
+                dput(p->path.dentry);
+                mntput(p->path.mnt);
                 kfree(p);
         }
 }
@@ -478,7 +480,7 @@ static int _nfs4_do_open_reclaim(struct nfs_open_context *ctx, struct nfs4_state
                 }
                 delegation_type = delegation->type;
         }
-        opendata = nfs4_opendata_alloc(ctx->path.dentry, state->owner, 0, NULL);
+        opendata = nfs4_opendata_alloc(&ctx->path, state->owner, 0, NULL);
         if (opendata == NULL)
                 return -ENOMEM;
         opendata->o_arg.claim = NFS4_OPEN_CLAIM_PREVIOUS;
@@ -525,7 +527,7 @@ static int _nfs4_open_delegation_recall(struct nfs_open_context *ctx, struct nfs
 
         if (!test_bit(NFS_DELEGATED_STATE, &state->flags))
                 return 0;
-        opendata = nfs4_opendata_alloc(ctx->path.dentry, sp, 0, NULL);
+        opendata = nfs4_opendata_alloc(&ctx->path, sp, 0, NULL);
         if (opendata == NULL)
                 return -ENOMEM;
         opendata->o_arg.claim = NFS4_OPEN_CLAIM_DELEGATE_CUR;
@@ -827,7 +829,7 @@ static int _nfs4_open_expired(struct nfs_open_context *ctx, struct nfs4_state *s
                 set_bit(NFS_DELEGATED_STATE, &state->flags);
                 return 0;
         }
-        opendata = nfs4_opendata_alloc(ctx->path.dentry, state->owner, openflags, NULL);
+        opendata = nfs4_opendata_alloc(&ctx->path, state->owner, openflags, NULL);
         if (opendata == NULL)
                 return -ENOMEM;
         ret = nfs4_open_recover(opendata, state);
@@ -955,7 +957,7 @@ static struct nfs4_state *nfs4_open_delegated(struct inode *inode, int flags, st
 /*
  * Returns a referenced nfs4_state
  */
-static int _nfs4_do_open(struct inode *dir, struct dentry *dentry, int flags, struct iattr *sattr, struct rpc_cred *cred, struct nfs4_state **res)
+static int _nfs4_do_open(struct inode *dir, struct path *path, int flags, struct iattr *sattr, struct rpc_cred *cred, struct nfs4_state **res)
 {
         struct nfs4_state_owner  *sp;
         struct nfs4_state     *state = NULL;
@@ -975,7 +977,7 @@ static int _nfs4_do_open(struct inode *dir, struct dentry *dentry, int flags, st
                 goto err_put_state_owner;
         down_read(&clp->cl_sem);
         status = -ENOMEM;
-        opendata = nfs4_opendata_alloc(dentry, sp, flags, sattr);
+        opendata = nfs4_opendata_alloc(path, sp, flags, sattr);
         if (opendata == NULL)
                 goto err_release_rwsem;
 
@@ -1006,14 +1008,14 @@ out_err:
 }
 
 
-static struct nfs4_state *nfs4_do_open(struct inode *dir, struct dentry *dentry, int flags, struct iattr *sattr, struct rpc_cred *cred)
+static struct nfs4_state *nfs4_do_open(struct inode *dir, struct path *path, int flags, struct iattr *sattr, struct rpc_cred *cred)
 {
         struct nfs4_exception exception = { };
         struct nfs4_state *res;
         int status;
 
         do {
-                status = _nfs4_do_open(dir, dentry, flags, sattr, cred, &res);
+                status = _nfs4_do_open(dir, path, flags, sattr, cred, &res);
                 if (status == 0)
                         break;
                 /* NOTE: BAD_SEQID means the server and client disagree about the
@@ -1259,6 +1261,10 @@ static int nfs4_intent_set_file(struct nameidata *nd, struct dentry *dentry, str
 struct dentry *
 nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
+        struct path path = {
+                .mnt = nd->mnt,
+                .dentry = dentry,
+        };
         struct iattr attr;
         struct rpc_cred *cred;
         struct nfs4_state *state;
@@ -1277,7 +1283,7 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
         cred = rpcauth_lookupcred(NFS_CLIENT(dir)->cl_auth, 0);
         if (IS_ERR(cred))
                 return (struct dentry *)cred;
-        state = nfs4_do_open(dir, dentry, nd->intent.open.flags, &attr, cred);
+        state = nfs4_do_open(dir, &path, nd->intent.open.flags, &attr, cred);
         put_rpccred(cred);
         if (IS_ERR(state)) {
                 if (PTR_ERR(state) == -ENOENT)
@@ -1294,6 +1300,10 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 int
 nfs4_open_revalidate(struct inode *dir, struct dentry *dentry, int openflags, struct nameidata *nd)
 {
+        struct path path = {
+                .mnt = nd->mnt,
+                .dentry = dentry,
+        };
         struct rpc_cred *cred;
         struct nfs4_state *state;
 
@@ -1302,7 +1312,7 @@ nfs4_open_revalidate(struct inode *dir, struct dentry *dentry, int openflags, st
                 return PTR_ERR(cred);
         state = nfs4_open_delegated(dentry->d_inode, openflags, cred);
         if (IS_ERR(state))
-                state = nfs4_do_open(dir, dentry, openflags, NULL, cred);
+                state = nfs4_do_open(dir, &path, openflags, NULL, cred);
         put_rpccred(cred);
         if (IS_ERR(state)) {
                 switch (PTR_ERR(state)) {
@@ -1752,6 +1762,10 @@ static int
 nfs4_proc_create(struct inode *dir, struct dentry *dentry, struct iattr *sattr,
                  int flags, struct nameidata *nd)
 {
+        struct path path = {
+                .mnt = nd->mnt,
+                .dentry = dentry,
+        };
         struct nfs4_state *state;
         struct rpc_cred *cred;
         int status = 0;
@@ -1761,7 +1775,7 @@ nfs4_proc_create(struct inode *dir, struct dentry *dentry, struct iattr *sattr,
                 status = PTR_ERR(cred);
                 goto out;
         }
-        state = nfs4_do_open(dir, dentry, flags, sattr, cred);
+        state = nfs4_do_open(dir, &path, flags, sattr, cred);
         put_rpccred(cred);
         if (IS_ERR(state)) {
                 status = PTR_ERR(state);
@@ -1774,7 +1788,7 @@ nfs4_proc_create(struct inode *dir, struct dentry *dentry, struct iattr *sattr,
                 if (status == 0)
                         nfs_setattr_update_inode(state->inode, sattr);
         }
-        if (status == 0 && nd != NULL && (nd->flags & LOOKUP_OPEN))
+        if (status == 0 && (nd->flags & LOOKUP_OPEN) != 0)
                 status = nfs4_intent_set_file(nd, dentry, state);
         else
                 nfs4_close_state(state, flags);