[patch 01/10] vfs: add path_create() and path_mknod()

[Miklos Szeredi <miklos@szeredi.hu>]

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From: Miklos Szeredi <mszeredi@suse.cz>

R/o bind mounts require operations which modify the filesystem to be
wrapped in mnt_want_write()/mnt_drop_write().  Create helpers which do
this, so callers won't need to bother, and more importantly, cannot
forget!  Call these path_*, analogous to vfs_*.  Where there are no
callers of vfs_* left, make them static.

This series is a cleanup, as well as fixing several places (mostly in
nfsd) where mnt_{want,drop}_write() were missing.

It will also help with merging You Know What(*) security module, which
needs to know the path within the namespace, and not just within the
filesystem.  These helpers will allow the security hooks to be in a
common place, and need not be repeated in all callers.

(*) AppArmor is a swear word in VFS circles, for some reason or other.

This patch:

Introduce path_create() and path_mknod().  Make vfs_create() and
vfs_mknod() static.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
 fs/ecryptfs/inode.c |   21 +++++++-------
 fs/namei.c          |   75 +++++++++++++++++++++++++++-------------------------
 fs/nfsd/vfs.c       |   19 ++++++-------
 include/linux/fs.h  |    4 +-
 ipc/mqueue.c        |    6 +++-
 net/unix/af_unix.c  |    6 ----
 6 files changed, 68 insertions(+), 63 deletions(-)

Index: vfs-2.6/fs/namei.c
===================================================================
--- vfs-2.6.orig/fs/namei.c	2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/fs/namei.c	2008-04-02 21:10:17.000000000 +0200
@@ -1574,7 +1574,7 @@ void unlock_rename(struct dentry *p1, st
 	}
 }
 
-int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
+static int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
 		struct nameidata *nd)
 {
 	int error = may_create(dir, dentry, nd);
@@ -1596,6 +1596,20 @@ int vfs_create(struct inode *dir, struct
 	return error;
 }
 
+int path_create(struct path *dir_path, struct dentry *dentry, int mode,
+		struct nameidata *nd)
+{
+	int error = mnt_want_write(dir_path->mnt);
+
+	if (!error) {
+		error = vfs_create(dir_path->dentry->d_inode, dentry, mode, nd);
+		mnt_drop_write(dir_path->mnt);
+	}
+
+	return error;
+}
+EXPORT_SYMBOL(path_create);
+
 int may_open(struct nameidata *nd, int acc_mode, int flag)
 {
 	struct dentry *dentry = nd->path.dentry;
@@ -2015,7 +2029,7 @@ fail:
 }
 EXPORT_SYMBOL_GPL(lookup_create);
 
-int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
+static int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 {
 	int error = may_create(dir, dentry, NULL);
 
@@ -2039,22 +2053,19 @@ int vfs_mknod(struct inode *dir, struct 
 	return error;
 }
 
-static int may_mknod(mode_t mode)
+int path_mknod(struct path *dir_path, struct dentry *dentry, int mode,
+	       dev_t dev)
 {
-	switch (mode & S_IFMT) {
-	case S_IFREG:
-	case S_IFCHR:
-	case S_IFBLK:
-	case S_IFIFO:
-	case S_IFSOCK:
-	case 0: /* zero mode translates to S_IFREG */
-		return 0;
-	case S_IFDIR:
-		return -EPERM;
-	default:
-		return -EINVAL;
+	int error = mnt_want_write(dir_path->mnt);
+
+	if (!error) {
+		error = vfs_mknod(dir_path->dentry->d_inode, dentry, mode, dev);
+		mnt_drop_write(dir_path->mnt);
 	}
+
+	return error;
 }
+EXPORT_SYMBOL(path_mknod);
 
 asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
 				unsigned dev)
@@ -2080,26 +2091,22 @@ asmlinkage long sys_mknodat(int dfd, con
 	}
 	if (!IS_POSIXACL(nd.path.dentry->d_inode))
 		mode &= ~current->fs->umask;
-	error = may_mknod(mode);
-	if (error)
-		goto out_dput;
-	error = mnt_want_write(nd.path.mnt);
-	if (error)
-		goto out_dput;
 	switch (mode & S_IFMT) {
-		case 0: case S_IFREG:
-			error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
-			break;
-		case S_IFCHR: case S_IFBLK:
-			error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
-					new_decode_dev(dev));
-			break;
-		case S_IFIFO: case S_IFSOCK:
-			error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
-			break;
+	case 0: case S_IFREG:
+		error = path_create(&nd.path, dentry, mode, &nd);
+		break;
+	case S_IFCHR: case S_IFBLK:
+		error = path_mknod(&nd.path, dentry, mode, new_decode_dev(dev));
+		break;
+	case S_IFIFO: case S_IFSOCK:
+		error = path_mknod(&nd.path, dentry, mode, 0);
+		break;
+	case S_IFDIR:
+		error = -EPERM;
+		break;
+	default:
+		error = -EINVAL;
 	}
-	mnt_drop_write(nd.path.mnt);
-out_dput:
 	dput(dentry);
 out_unlock:
 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
@@ -2966,11 +2973,9 @@ EXPORT_SYMBOL(permission);
 EXPORT_SYMBOL(vfs_permission);
 EXPORT_SYMBOL(file_permission);
 EXPORT_SYMBOL(unlock_rename);
-EXPORT_SYMBOL(vfs_create);
 EXPORT_SYMBOL(vfs_follow_link);
 EXPORT_SYMBOL(vfs_link);
 EXPORT_SYMBOL(vfs_mkdir);
-EXPORT_SYMBOL(vfs_mknod);
 EXPORT_SYMBOL(generic_permission);
 EXPORT_SYMBOL(vfs_readlink);
 EXPORT_SYMBOL(vfs_rename);
Index: vfs-2.6/include/linux/fs.h
===================================================================
--- vfs-2.6.orig/include/linux/fs.h	2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/include/linux/fs.h	2008-04-02 21:10:17.000000000 +0200
@@ -1123,9 +1123,9 @@ extern void unlock_super(struct super_bl
  * VFS helper functions..
  */
 extern int vfs_permission(struct nameidata *, int);
-extern int vfs_create(struct inode *, struct dentry *, int, struct nameidata *);
+extern int path_create(struct path *, struct dentry *, int, struct nameidata *);
 extern int vfs_mkdir(struct inode *, struct dentry *, int);
-extern int vfs_mknod(struct inode *, struct dentry *, int, dev_t);
+extern int path_mknod(struct path *, struct dentry *, int, dev_t);
 extern int vfs_symlink(struct inode *, struct dentry *, const char *, int);
 extern int vfs_link(struct dentry *, struct inode *, struct dentry *);
 extern int vfs_rmdir(struct inode *, struct dentry *);
Index: vfs-2.6/fs/ecryptfs/inode.c
===================================================================
--- vfs-2.6.orig/fs/ecryptfs/inode.c	2008-04-02 21:10:15.000000000 +0200
+++ vfs-2.6/fs/ecryptfs/inode.c	2008-04-02 21:10:17.000000000 +0200
@@ -67,7 +67,7 @@ static void unlock_dir(struct dentry *di
  * Returns zero on success; non-zero on error condition
  */
 static int
-ecryptfs_create_underlying_file(struct inode *lower_dir_inode,
+ecryptfs_create_underlying_file(struct dentry *lower_dir_dentry,
 				struct dentry *dentry, int mode,
 				struct nameidata *nd)
 {
@@ -79,9 +79,9 @@ ecryptfs_create_underlying_file(struct i
 
 	dentry_save = nd->path.dentry;
 	vfsmount_save = nd->path.mnt;
-	nd->path.dentry = lower_dentry;
+	nd->path.dentry = lower_dir_dentry;
 	nd->path.mnt = lower_mnt;
-	rc = vfs_create(lower_dir_inode, lower_dentry, mode, nd);
+	rc = path_create(&nd->path, lower_dentry, mode, nd);
 	nd->path.dentry = dentry_save;
 	nd->path.mnt = vfsmount_save;
 	return rc;
@@ -117,7 +117,7 @@ ecryptfs_do_create(struct inode *directo
 		rc = PTR_ERR(lower_dir_dentry);
 		goto out;
 	}
-	rc = ecryptfs_create_underlying_file(lower_dir_dentry->d_inode,
+	rc = ecryptfs_create_underlying_file(lower_dir_dentry,
 					     ecryptfs_dentry, mode, nd);
 	if (rc) {
 		printk(KERN_ERR "%s: Failure to create dentry in lower fs; "
@@ -535,20 +535,21 @@ ecryptfs_mknod(struct inode *dir, struct
 {
 	int rc;
 	struct dentry *lower_dentry;
-	struct dentry *lower_dir_dentry;
+	struct path lower_dir;
 
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
-	lower_dir_dentry = lock_parent(lower_dentry);
-	rc = vfs_mknod(lower_dir_dentry->d_inode, lower_dentry, mode, dev);
+	lower_dir.mnt = ecryptfs_dentry_to_lower_mnt(dentry);
+	lower_dir.dentry = lock_parent(lower_dentry);
+	rc = path_mknod(&lower_dir, lower_dentry, mode, dev);
 	if (rc || !lower_dentry->d_inode)
 		goto out;
 	rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb, 0);
 	if (rc)
 		goto out;
-	fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
-	fsstack_copy_inode_size(dir, lower_dir_dentry->d_inode);
+	fsstack_copy_attr_times(dir, lower_dir.dentry->d_inode);
+	fsstack_copy_inode_size(dir, lower_dir.dentry->d_inode);
 out:
-	unlock_dir(lower_dir_dentry);
+	unlock_dir(lower_dir.dentry);
 	if (!dentry->d_inode)
 		d_drop(dentry);
 	return rc;
Index: vfs-2.6/fs/nfsd/vfs.c
===================================================================
--- vfs-2.6.orig/fs/nfsd/vfs.c	2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/fs/nfsd/vfs.c	2008-04-02 21:10:17.000000000 +0200
@@ -1185,6 +1185,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
 		char *fname, int flen, struct iattr *iap,
 		int type, dev_t rdev, struct svc_fh *resfhp)
 {
+	struct path 	dir_path;
 	struct dentry	*dentry, *dchild = NULL;
 	struct inode	*dirp;
 	__be32		err;
@@ -1249,13 +1250,12 @@ nfsd_create(struct svc_rqst *rqstp, stru
 		iap->ia_mode = 0;
 	iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
 
-	/*
-	 * Get the dir op function pointer.
-	 */
+	dir_path.mnt = fhp->fh_export->ex_path.mnt;
+	dir_path.dentry = dentry;
 	err = 0;
 	switch (type) {
 	case S_IFREG:
-		host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
+		host_err = path_create(&dir_path, dchild, iap->ia_mode, NULL);
 		break;
 	case S_IFDIR:
 		host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
@@ -1264,11 +1264,7 @@ nfsd_create(struct svc_rqst *rqstp, stru
 	case S_IFBLK:
 	case S_IFIFO:
 	case S_IFSOCK:
-		host_err = mnt_want_write(fhp->fh_export->ex_path.mnt);
-		if (host_err)
-			break;
-		host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
-		mnt_drop_write(fhp->fh_export->ex_path.mnt);
+		host_err = path_mknod(&dir_path, dchild, iap->ia_mode, rdev);
 		break;
 	default:
 	        printk("nfsd: bad file type %o in nfsd_create\n", type);
@@ -1311,6 +1307,7 @@ nfsd_create_v3(struct svc_rqst *rqstp, s
 		struct svc_fh *resfhp, int createmode, u32 *verifier,
 	        int *truncp, int *created)
 {
+	struct path 	dir_path;
 	struct dentry	*dentry, *dchild = NULL;
 	struct inode	*dirp;
 	__be32		err;
@@ -1397,7 +1394,9 @@ nfsd_create_v3(struct svc_rqst *rqstp, s
 		goto out;
 	}
 
-	host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
+	dir_path.mnt = fhp->fh_export->ex_path.mnt;
+	dir_path.dentry = dentry;
+	host_err = path_create(&dir_path, dchild, iap->ia_mode, NULL);
 	if (host_err < 0)
 		goto out_nfserr;
 	if (created)
Index: vfs-2.6/ipc/mqueue.c
===================================================================
--- vfs-2.6.orig/ipc/mqueue.c	2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/ipc/mqueue.c	2008-04-02 21:10:17.000000000 +0200
@@ -599,6 +599,7 @@ static struct file *do_create(struct den
 {
 	struct mq_attr attr;
 	struct file *result;
+	struct path dir_path;
 	int ret;
 
 	if (u_attr) {
@@ -616,7 +617,10 @@ static struct file *do_create(struct den
 	ret = mnt_want_write(mqueue_mnt);
 	if (ret)
 		goto out;
-	ret = vfs_create(dir->d_inode, dentry, mode, NULL);
+
+	dir_path.mnt = mqueue_mnt;
+	dir_path.dentry = dir;
+	ret = path_create(&dir_path, dentry, mode, NULL);
 	dentry->d_fsdata = NULL;
 	if (ret)
 		goto out_drop_write;
Index: vfs-2.6/net/unix/af_unix.c
===================================================================
--- vfs-2.6.orig/net/unix/af_unix.c	2008-04-02 21:10:14.000000000 +0200
+++ vfs-2.6/net/unix/af_unix.c	2008-04-02 21:10:17.000000000 +0200
@@ -819,11 +819,7 @@ static int unix_bind(struct socket *sock
 		 */
 		mode = S_IFSOCK |
 		       (SOCK_INODE(sock)->i_mode & ~current->fs->umask);
-		err = mnt_want_write(nd.path.mnt);
-		if (err)
-			goto out_mknod_dput;
-		err = vfs_mknod(nd.path.dentry->d_inode, dentry, mode, 0);
-		mnt_drop_write(nd.path.mnt);
+		err = path_mknod(&nd.path, dentry, mode, 0);
 		if (err)
 			goto out_mknod_dput;
 		mutex_unlock(&nd.path.dentry->d_inode->i_mutex);

--