NFSv4: Atomic open(). Fixes races w.r.t. opening files.

fs/nfs/dir.c

@@ -72,6 +72,26 @@ struct inode_operations nfs_dir_inode_operations = {
 	.setattr	= nfs_setattr,
 };
 
+#ifdef CONFIG_NFS_V4
+
+static struct dentry *nfs_atomic_lookup(struct inode *, struct dentry *, struct nameidata *);
+struct inode_operations nfs4_dir_inode_operations = {
+	.create		= nfs_create,
+	.lookup		= nfs_atomic_lookup,
+	.link		= nfs_link,
+	.unlink		= nfs_unlink,
+	.symlink	= nfs_symlink,
+	.mkdir		= nfs_mkdir,
+	.rmdir		= nfs_rmdir,
+	.mknod		= nfs_mknod,
+	.rename		= nfs_rename,
+	.permission	= nfs_permission,
+	.getattr	= nfs_getattr,
+	.setattr	= nfs_setattr,
+};
+
+#endif /* CONFIG_NFS_V4 */
+
 /*
  * Open file
  */
@@ -670,7 +690,7 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
 		goto out;
 
 	error = -ENOMEM;
-	dentry->d_op = &nfs_dentry_operations;
+	dentry->d_op = NFS_PROTO(dir)->dentry_ops;
 
 	lock_kernel();
 
@@ -702,6 +722,119 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
 	return ERR_PTR(error);
 }
 
+#ifdef CONFIG_NFS_V4
+static int nfs_open_revalidate(struct dentry *, struct nameidata *);
+
+struct dentry_operations nfs4_dentry_operations = {
+	.d_revalidate	= nfs_open_revalidate,
+	.d_delete	= nfs_dentry_delete,
+	.d_iput		= nfs_dentry_iput,
+};
+
+static int is_atomic_open(struct inode *dir, struct nameidata *nd)
+{
+	if (!nd)
+		return 0;
+	/* Check that we are indeed trying to open this file */
+	if ((nd->flags & LOOKUP_CONTINUE) || !(nd->flags & LOOKUP_OPEN))
+		return 0;
+	/* NFS does not (yet) have a stateful open for directories */
+	if (nd->flags & LOOKUP_DIRECTORY)
+		return 0;
+	/* Are we trying to write to a read only partition? */
+	if (IS_RDONLY(dir) && (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
+		return 0;
+	return 1;
+}
+
+static struct dentry *nfs_atomic_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
+{
+	struct inode *inode = NULL;
+	int error = 0;
+
+	/* Check that we are indeed trying to open this file */
+	if (!is_atomic_open(dir, nd))
+		goto no_open;
+
+	if (dentry->d_name.len > NFS_SERVER(dir)->namelen) {
+		error = -ENAMETOOLONG;
+		goto out;
+	}
+	dentry->d_op = NFS_PROTO(dir)->dentry_ops;
+
+	/* Let vfs_create() deal with O_EXCL */
+	if (nd->intent.open.flags & O_EXCL)
+		goto no_entry;
+
+	/* Open the file on the server */
+	lock_kernel();
+	inode = nfs4_atomic_open(dir, dentry, nd);
+	unlock_kernel();
+	if (IS_ERR(inode)) {
+		error = PTR_ERR(inode);
+		switch (error) {
+			/* Make a negative dentry */
+			case -ENOENT:
+				inode = NULL;
+				break;
+			/* This turned out not to be a regular file */
+			case -ELOOP:
+				if (!(nd->intent.open.flags & O_NOFOLLOW))
+					goto no_open;
+			/* case -EISDIR: */
+			/* case -EINVAL: */
+			default:
+				goto out;
+		}
+	}
+no_entry:
+	d_add(dentry, inode);
+	nfs_renew_times(dentry);
+out:
+	BUG_ON(error > 0);
+	return ERR_PTR(error);
+no_open:
+	return nfs_lookup(dir, dentry, nd);
+}
+
+static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)
+{
+	struct dentry *parent = NULL;
+	struct inode *inode = dentry->d_inode;
+	int openflags, ret = 0;
+
+	/* NFS only supports OPEN for regular files */
+	if (inode && !S_ISREG(inode->i_mode))
+		goto no_open;
+	parent = dget_parent(dentry);
+	if (!is_atomic_open(parent->d_inode, nd))
+		goto no_open;
+	openflags = nd->intent.open.flags;
+	if (openflags & O_CREAT) {
+		/* If this is a negative dentry, just drop it */
+		if (!inode)
+			goto out;
+		/* If this is exclusive open, just revalidate */
+		if (openflags & O_EXCL)
+			goto no_open;
+	}
+	/* We can't create new files, or truncate existing ones here */
+	openflags &= ~(O_CREAT|O_TRUNC);
+
+	lock_kernel();
+	ret = nfs4_open_revalidate(parent->d_inode, dentry, openflags);
+	unlock_kernel();
+out:
+	dput(parent);
+	if (!ret)
+		d_drop(dentry);
+	return ret;
+no_open:
+	dput(parent);
+	return nfs_lookup_revalidate(dentry, nd);
+}
+#endif /* CONFIG_NFSV4 */
+
 static inline
 int find_dirent_name(nfs_readdir_descriptor_t *desc, struct page *page, struct dentry *dentry)
 {
@@ -1306,6 +1439,9 @@ nfs_permission(struct inode *inode, int mask, struct nameidata *nd)
 		/* We only need to check permissions on file open() and access() */
 		if (!nd || !(nd->flags & (LOOKUP_OPEN|LOOKUP_ACCESS)))
 			return 0;
+		/* NFSv4 has atomic_open... */
+		if (NFS_PROTO(inode)->version > 3 && (nd->flags & LOOKUP_OPEN))
+			return 0;
 	}
 
 	lock_kernel();

fs/nfs/inode.c

@@ -303,7 +303,6 @@ nfs_sb_init(struct super_block *sb, rpc_authflavor_t authflavor)
 	server = NFS_SB(sb);
 
 	sb->s_magic      = NFS_SUPER_MAGIC;
-	sb->s_op         = &nfs_sops;
 
 	/* Did getting the root inode fail? */
 	if (nfs_get_root(&root_inode, authflavor, sb, &server->fh) < 0)
@@ -312,7 +311,7 @@ nfs_sb_init(struct super_block *sb, rpc_authflavor_t authflavor)
 	if (!sb->s_root)
 		goto out_no_root;
 
-	sb->s_root->d_op = &nfs_dentry_operations;
+	sb->s_root->d_op = server->rpc_ops->dentry_ops;
 
 	/* Get some general file system info */
         if (server->rpc_ops->fsinfo(server, &server->fh, &fsinfo) < 0) {
@@ -513,6 +512,7 @@ nfs_fill_super(struct super_block *sb, struct nfs_mount_data *data, int silent)
 		goto out_shutdown;
 	}
 
+	sb->s_op = &nfs_sops;
 	err = nfs_sb_init(sb, authflavor);
 	if (err != 0)
 		goto out_noinit;
@@ -745,7 +745,7 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
 			inode->i_data.a_ops = &nfs_file_aops;
 			inode->i_data.backing_dev_info = &NFS_SB(sb)->backing_dev_info;
 		} else if (S_ISDIR(inode->i_mode)) {
-			inode->i_op = &nfs_dir_inode_operations;
+			inode->i_op = NFS_SB(sb)->rpc_ops->dir_inode_ops;
 			inode->i_fop = &nfs_dir_operations;
 			if (nfs_server_capable(inode, NFS_CAP_READDIRPLUS)
 			    && fattr->size <= NFS_LIMIT_READDIRPLUS)
@@ -837,7 +837,12 @@ printk("nfs_setattr: revalidate failed, error=%d\n", error);
 		filemap_fdatawait(inode->i_mapping);
 		if (error)
 			goto out;
+		/* Optimize away unnecessary truncates */
+		if ((attr->ia_valid & ATTR_SIZE) && i_size_read(inode) == attr->ia_size)
+			attr->ia_valid &= ~ATTR_SIZE;
 	}
+	if (!attr->ia_valid)
+		goto out;
 
 	error = NFS_PROTO(inode)->setattr(dentry, &fattr, attr);
 	if (error)
@@ -1357,6 +1362,48 @@ static struct file_system_type nfs_fs_type = {
 
 #ifdef CONFIG_NFS_V4
 
+static void nfs4_clear_inode(struct inode *);
+
+static struct super_operations nfs4_sops = { 
+	.alloc_inode	= nfs_alloc_inode,
+	.destroy_inode	= nfs_destroy_inode,
+	.write_inode	= nfs_write_inode,
+	.delete_inode	= nfs_delete_inode,
+	.put_super	= nfs_put_super,
+	.statfs		= nfs_statfs,
+	.clear_inode	= nfs4_clear_inode,
+	.umount_begin	= nfs_umount_begin,
+	.show_options	= nfs_show_options,
+};
+
+/*
+ * Clean out any remaining NFSv4 state that might be left over due
+ * to open() calls that passed nfs_atomic_lookup, but failed to call
+ * nfs_open().
+ */
+static void nfs4_clear_inode(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	while (!list_empty(&nfsi->open_states)) {
+		struct nfs4_state *state;
+		
+		state = list_entry(nfsi->open_states.next,
+				struct nfs4_state,
+				inode_states);
+		dprintk("%s(%s/%Ld): found unclaimed NFSv4 state %p\n",
+				__FUNCTION__,
+				inode->i_sb->s_id,
+				(long long)NFS_FILEID(inode),
+				state);
+		list_del(&state->inode_states);
+		nfs4_put_open_state(state);
+	}
+	/* Now call standard NFS clear_inode() code */
+	nfs_clear_inode(inode);
+}
+
+
 static int nfs4_fill_super(struct super_block *sb, struct nfs4_mount_data *data, int silent)
 {
 	struct nfs_server *server;
@@ -1481,6 +1528,7 @@ static int nfs4_fill_super(struct super_block *sb, struct nfs4_mount_data *data,
 	if ((server->idmap = nfs_idmap_new(server)) == NULL)
 		printk(KERN_WARNING "NFS: couldn't start IDmap\n");
 
+	sb->s_op = &nfs4_sops;
 	err = nfs_sb_init(sb, authflavour);
 	if (err == 0)
 		return 0;

fs/nfs/nfs3proc.c

@@ -898,6 +898,8 @@ nfs3_request_compatible(struct nfs_page *req, struct file *filp, struct page *pa
 
 struct nfs_rpc_ops	nfs_v3_clientops = {
 	.version	= 3,			/* protocol version */
+	.dentry_ops	= &nfs_dentry_operations,
+	.dir_inode_ops	= &nfs_dir_inode_operations,
 	.getroot	= nfs3_proc_get_root,
 	.getattr	= nfs3_proc_getattr,
 	.setattr	= nfs3_proc_setattr,

fs/nfs/nfs4proc.c

@@ -45,6 +45,7 @@
 #include <linux/nfs_fs.h>
 #include <linux/nfs_page.h>
 #include <linux/smp_lock.h>
+#include <linux/namei.h>
 
 #define NFSDBG_FACILITY		NFSDBG_PROC
 
@@ -509,6 +510,9 @@ nfs4_open_reclaim(struct nfs4_state_owner *sp, struct nfs4_state *state)
 	return status;
 }
 
+/*
+ * Returns an nfs4_state + an referenced inode
+ */
 struct nfs4_state *
 nfs4_do_open(struct inode *dir, struct qstr *name, int flags, struct iattr *sattr, struct rpc_cred *cred)
 {
@@ -617,19 +621,23 @@ nfs4_do_open(struct inode *dir, struct qstr *name, int flags, struct iattr *satt
 
 	up(&sp->so_sema);
 	nfs4_put_state_owner(sp);
-	iput(inode);
 	return state;
 
 out_up:
 	up(&sp->so_sema);
 	nfs4_put_state_owner(sp);
-	if (state)
+	if (state) {
 		nfs4_put_open_state(state);
-	if (inode)
+		state = NULL;
+	}
+	if (inode) {
 		iput(inode);
+		inode = NULL;
+	}
 	status = nfs4_handle_error(server, status);
 	if (!status)
 		goto retry;
+	BUG_ON(status < -1000 || status > 0);
 out:
 	return ERR_PTR(status);
 }
@@ -718,6 +726,56 @@ nfs4_do_close(struct inode *inode, struct nfs4_state *state)
 	return status;
 }
 
+struct inode *
+nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
+{
+	struct iattr attr;
+	struct rpc_cred *cred;
+	struct nfs4_state *state;
+
+	if (nd->flags & LOOKUP_CREATE) {
+		attr.ia_mode = nd->intent.open.create_mode;
+		attr.ia_valid = ATTR_MODE;
+		if (!IS_POSIXACL(dir))
+			attr.ia_mode &= ~current->fs->umask;
+	} else {
+		attr.ia_valid = 0;
+		BUG_ON(nd->intent.open.flags & O_CREAT);
+	}
+
+	cred = rpcauth_lookupcred(NFS_SERVER(dir)->client->cl_auth, 0);
+	state = nfs4_do_open(dir, &dentry->d_name, nd->intent.open.flags, &attr, cred);
+	put_rpccred(cred);
+	if (IS_ERR(state))
+		return (struct inode *)state;
+	return state->inode;
+}
+
+int
+nfs4_open_revalidate(struct inode *dir, struct dentry *dentry, int openflags)
+{
+	struct rpc_cred *cred;
+	struct nfs4_state *state;
+	struct inode *inode;
+
+	cred = rpcauth_lookupcred(NFS_SERVER(dir)->client->cl_auth, 0);
+	state = nfs4_do_open(dir, &dentry->d_name, openflags, NULL, cred);
+	put_rpccred(cred);
+	if (state == ERR_PTR(-ENOENT) && dentry->d_inode == 0)
+		return 1;
+	if (IS_ERR(state))
+		return 0;
+	inode = state->inode;
+	if (inode == dentry->d_inode) {
+		iput(inode);
+		return 1;
+	}
+	d_drop(dentry);
+	nfs4_put_open_state(state);
+	iput(inode);
+	return 0;
+}
+
 static int
 nfs4_proc_get_root(struct nfs_server *server, struct nfs_fh *fhandle,
 		   struct nfs_fattr *fattr)
@@ -808,28 +866,39 @@ nfs4_proc_setattr(struct dentry *dentry, struct nfs_fattr *fattr,
 	struct inode *		inode = dentry->d_inode;
 	int			size_change = sattr->ia_valid & ATTR_SIZE;
 	struct nfs4_state	*state = NULL;
-	int			status;
+	int need_iput = 0;
+	int status;
 
 	fattr->valid = 0;
 	
 	if (size_change) {
-		struct rpc_cred *cred = rpcauth_lookupcred(NFS_SERVER(inode)->client->cl_auth, 0);
-		state = nfs4_do_open(dentry->d_parent->d_inode, 
+		state = nfs4_find_state_bypid(inode, current->pid);
+
+		if (!state) {
+			struct rpc_cred *cred = rpcauth_lookupcred(NFS_SERVER(inode)->client->cl_auth, 0);
+			state = nfs4_do_open(dentry->d_parent->d_inode, 
 				&dentry->d_name, FMODE_WRITE, NULL, cred);
-		put_rpccred(cred);
+			put_rpccred(cred);
+			need_iput = 1;
+		}
 		if (IS_ERR(state))
 			return PTR_ERR(state);
 
 		if (state->inode != inode) {
-			printk(KERN_WARNING "nfs: raced in setattr, returning -EIO\n");
-			nfs4_put_open_state(state);
-			return -EIO;
+			printk(KERN_WARNING "nfs: raced in setattr (%p != %p), returning -EIO\n", inode, state->inode);
+			status = -EIO;
+			goto out;
 		}
 	}
 	status = nfs4_do_setattr(NFS_SERVER(inode), fattr,
 			NFS_FH(inode), sattr, state);
-	if (state)
+out:
+	if (state) {
+		inode = state->inode;
 		nfs4_put_open_state(state);
+		if (need_iput)
+			iput(inode);
+	}
 	return status;
 }
 
@@ -1085,18 +1154,18 @@ nfs4_proc_create(struct inode *dir, struct qstr *name, struct iattr *sattr,
 	state = nfs4_do_open(dir, name, flags, sattr, cred);
 	put_rpccred(cred);
 	if (!IS_ERR(state)) {
-		inode = igrab(state->inode);
+		inode = state->inode;
 		if (flags & O_EXCL) {
 			struct nfs_fattr fattr;
 			int status;
 			status = nfs4_do_setattr(NFS_SERVER(dir), &fattr,
 			                     NFS_FH(inode), sattr, state);
 			if (status != 0) {
+				nfs4_put_open_state(state);
 				iput(inode);
 				inode = ERR_PTR(status);
 			}
 		}
-		nfs4_put_open_state(state);
 	} else
 		inode = (struct inode *)state;
 	return inode;
@@ -1672,43 +1741,28 @@ static int
 nfs4_proc_file_open(struct inode *inode, struct file *filp)
 {
 	struct dentry *dentry = filp->f_dentry;
-	struct inode *dir = dentry->d_parent->d_inode;
-	struct rpc_cred *cred;
 	struct nfs4_state *state;
-	int flags = filp->f_flags;
-	int status = 0;
 
 	dprintk("nfs4_proc_file_open: starting on (%.*s/%.*s)\n",
 	                       (int)dentry->d_parent->d_name.len,
 	                       dentry->d_parent->d_name.name,
 	                       (int)dentry->d_name.len, dentry->d_name.name);
 
-	if ((flags + 1) & O_ACCMODE)
-		flags++;
-
-	lock_kernel();
 
-/*
-* We have already opened the file "O_EXCL" in nfs4_proc_create!!
-* This ugliness will go away with lookup-intent...
-*/
-	cred = rpcauth_lookupcred(NFS_SERVER(inode)->client->cl_auth, 0);
-	state = nfs4_do_open(dir, &dentry->d_name, flags, NULL, cred);
-	if (IS_ERR(state)) {
-		status = PTR_ERR(state);
-		state = NULL;
-	} else if (filp->f_mode & FMODE_WRITE)
-		nfs_set_mmcred(inode, cred);
-	if (inode != filp->f_dentry->d_inode) {
+	/* Find our open stateid */
+	state = nfs4_find_state_bypid(inode, current->pid);
+	if (state == NULL) {
 		printk(KERN_WARNING "NFS: v4 raced in function %s\n", __FUNCTION__);
-		status = -EIO; /* ERACE actually */
-		nfs4_put_open_state(state);
-		state = NULL;
+		return -EIO; /* ERACE actually */
+	}
+	nfs4_put_open_state(state);
+	if (filp->f_mode & FMODE_WRITE) {
+		lock_kernel();
+		nfs_set_mmcred(inode, state->owner->so_cred);
+		unlock_kernel();
 	}
 	filp->private_data = state;
-	put_rpccred(cred);
-	unlock_kernel();
-	return status;
+	return 0;
 }
 
 /*
@@ -1922,6 +1976,8 @@ nfs4_proc_setclientid_confirm(struct nfs4_client *clp)
 
 struct nfs_rpc_ops	nfs_v4_clientops = {
 	.version	= 4,			/* protocol version */
+	.dentry_ops	= &nfs4_dentry_operations,
+	.dir_inode_ops	= &nfs4_dir_inode_operations,
 	.getroot	= nfs4_proc_get_root,
 	.getattr	= nfs4_proc_getattr,
 	.setattr	= nfs4_proc_setattr,

fs/nfs/nfs4state.c

@@ -349,7 +349,6 @@ nfs4_get_open_state(struct inode *inode, struct nfs4_state_owner *owner)
 		atomic_inc(&owner->so_count);
 		list_add(&state->inode_states, &nfsi->open_states);
 		state->inode = inode;
-		atomic_inc(&inode->i_count);
 		spin_unlock(&inode->i_lock);
 	} else {
 		spin_unlock(&inode->i_lock);
@@ -384,7 +383,6 @@ nfs4_put_open_state(struct nfs4_state *state)
 		} while (!status);
 	}
 	up(&owner->so_sema);
-	iput(inode);
 	nfs4_free_open_state(state);
 	nfs4_put_state_owner(owner);
 }

fs/nfs/proc.c

@@ -656,6 +656,8 @@ nfs_request_compatible(struct nfs_page *req, struct file *filp, struct page *pag
 
 struct nfs_rpc_ops	nfs_v2_clientops = {
 	.version	= 2,		       /* protocol version */
+	.dentry_ops	= &nfs_dentry_operations,
+	.dir_inode_ops	= &nfs_dir_inode_operations,
 	.getroot	= nfs_proc_get_root,
 	.getattr	= nfs_proc_getattr,
 	.setattr	= nfs_proc_setattr,

include/linux/nfs_fs.h

@@ -558,6 +558,9 @@ struct nfs4_state {
 };
 
 
+extern struct dentry_operations nfs4_dentry_operations;
+extern struct inode_operations nfs4_dir_inode_operations;
+
 /* nfs4proc.c */
 extern int nfs4_proc_setclientid(struct nfs4_client *, u32, unsigned short);
 extern int nfs4_proc_setclientid_confirm(struct nfs4_client *);
@@ -566,6 +569,8 @@ extern int nfs4_proc_async_renew(struct nfs4_client *);
 extern int nfs4_proc_renew(struct nfs4_client *);
 extern int nfs4_do_close(struct inode *, struct nfs4_state *);
 extern int nfs4_wait_clnt_recover(struct rpc_clnt *, struct nfs4_client *);
+extern struct inode *nfs4_atomic_open(struct inode *, struct dentry *, struct nameidata *);
+extern int nfs4_open_revalidate(struct inode *, struct dentry *, int);
 
 /* nfs4renewd.c */
 extern void nfs4_schedule_state_renewal(struct nfs4_client *);
@@ -581,6 +586,7 @@ extern struct nfs4_state_owner * nfs4_get_state_owner(struct nfs_server *, struc
 extern void nfs4_put_state_owner(struct nfs4_state_owner *);
 extern struct nfs4_state * nfs4_get_open_state(struct inode *, struct nfs4_state_owner *);
 extern void nfs4_put_open_state(struct nfs4_state *);
+extern struct nfs4_state *nfs4_find_state_bypid(struct inode *, pid_t);
 extern void nfs4_increment_seqid(int status, struct nfs4_state_owner *sp);
 extern int nfs4_handle_error(struct nfs_server *, int);
 extern void nfs4_schedule_state_recovery(struct nfs4_client *);

include/linux/nfs_xdr.h

@@ -637,6 +637,8 @@ struct nfs_page;
  */
 struct nfs_rpc_ops {
 	int	version;		/* Protocol version */
+	struct dentry_operations *dentry_ops;
+	struct inode_operations *dir_inode_ops;
 
 	int	(*getroot) (struct nfs_server *, struct nfs_fh *,
 			    struct nfs_fattr *);