[PATCH 01/10] fs: implement mknod

[Sascha Hauer <s.hauer@pengutronix.de>]

This implements mknod for the barebox VFS. Use the cdevname for
connecting a device special node with a cdev. In Linux this is done with
major/minor numbers which shouldn't be necessary for barebox as we do
not intend to mount filesystems which contain device special nodes, but
instead create them in ramfs. If a mounted filesystem contains special
nodes then these won't work with barebox.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 fs/devfs.c         | 13 +++++++++++++
 fs/fs.c            | 35 +++++++++++++++++++++++++++++++++++
 include/fcntl.h    |  6 ++++++
 include/linux/fs.h | 13 +++++++++++++
 4 files changed, 67 insertions(+)

diff --git a/fs/devfs.c b/fs/devfs.c
index 15c7a63d3949a5fa7c5ec15f58bc9f4c53b7852b..be3272be49e66eb843823b3ff664a1565f326790 100644
--- a/fs/devfs.c
+++ b/fs/devfs.c
@@ -103,6 +103,12 @@ static int devfs_open(struct inode *inode, struct file *f)
 	struct devfs_inode *node = container_of(inode, struct devfs_inode, inode);
 	struct cdev *cdev = node->cdev;
 
+	if (inode->cdevname) {
+		cdev = cdev_by_name(inode->cdevname);
+		if (!cdev)
+			return -ENOENT;
+	}
+
 	f->f_size = cdev->flags & DEVFS_IS_CHARACTER_DEV ?
 			FILE_SIZE_STREAM : cdev->size;
 	f->private_data = cdev;
@@ -188,6 +194,13 @@ static const struct file_operations devfs_file_operations = {
 	.memmap = devfs_memmap,
 };
 
+void init_special_inode(struct inode *inode, umode_t mode, const char *cdevname)
+{
+	inode->i_mode = mode;
+	inode->i_fop = &devfs_file_operations;
+	inode->cdevname = strdup(cdevname);
+}
+
 static int devfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct devfs_inode *dinode;
diff --git a/fs/fs.c b/fs/fs.c
index 528299e039d2d73b76c363b7ece32b6255d925f1..bfcfadff7fa76de17c68a0dca4843aa02cb62b6d 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -826,6 +826,8 @@ static int dentry_delete_subtree(struct super_block *sb, struct dentry *parent)
 
 static void destroy_inode(struct inode *inode)
 {
+	free(inode->cdevname);
+
 	if (inode->i_sb->s_op->destroy_inode)
 		inode->i_sb->s_op->destroy_inode(inode);
 	else
@@ -2745,6 +2747,39 @@ int openat(int dirfd, const char *pathname, int flags)
 }
 EXPORT_SYMBOL(openat);
 
+static int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
+		     const char *cdevname)
+{
+	int error;
+
+	if (!dir->i_op->mknod)
+		return -EPERM;
+
+	error = dir->i_op->mknod(dir, dentry, mode, cdevname);
+
+	return error;
+}
+
+int mknodat(int dirfd, const char *pathname, mode_t mode, const char *devname)
+{
+	struct dentry *dentry;
+	struct path path;
+	int error;
+
+	dentry = filename_create(dirfd, getname(pathname), &path, 0);
+	if (IS_ERR(dentry)) {
+		error = PTR_ERR(dentry);
+		goto out;
+	}
+
+	error = vfs_mknod(path.dentry->d_inode, dentry, mode, devname);
+
+	dput(dentry);
+	path_put(&path);
+out:
+	return errno_set(error);
+}
+
 int unlinkat(int dirfd, const char *pathname, int flags)
 {
 	int ret;
diff --git a/include/fcntl.h b/include/fcntl.h
index db7926ee25fbe14607063d420697964801cd8321..57c01002cc9290bfae53f3b5be5615eda874c720 100644
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -46,6 +46,8 @@ static inline int openat(int dirfd, const char *pathname, int flags, ...)
 }
 #endif
 
+int mknodat(int dirfd, const char *pathname, mode_t mode, const char *devname);
+
 static inline int open(const char *pathname, int flags, ...)
 {
 	return openat(AT_FDCWD, pathname, flags);
@@ -56,4 +58,8 @@ static inline int creat(const char *pathname, mode_t mode)
 	return open(pathname, O_CREAT | O_WRONLY | O_TRUNC);
 }
 
+static inline int mknod(const char *pathname, mode_t mode, const char *devname)
+{
+	return mknodat(AT_FDCWD, pathname, mode, devname);
+}
 #endif /* __FCNTL_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed4332c79d496b18b37b120b6008e1e474316e76..f6b8f6a8e08b7e56716005453d6f9c4488ba853f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -149,6 +149,8 @@ struct inode {
 
 	char			*i_link;
 
+	char			*cdevname;
+
 	void			*i_private; /* fs or device private pointer */
 };
 
@@ -429,6 +431,16 @@ void ihold(struct inode *inode);
 void inc_nlink(struct inode *inode);
 void clear_nlink(struct inode *inode);
 void set_nlink(struct inode *inode, unsigned int nlink);
+#ifdef CONFIG_FS_DEVFS
+void init_special_inode(struct inode *inode, umode_t mode, const char *cdevname);
+#else
+static inline void init_special_inode(struct inode *inode, umode_t mode,
+				      const char *cdevname)
+{
+}
+#endif
+
+struct cdev;
 
 struct inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
@@ -436,6 +448,7 @@ struct inode_operations {
 	const char *(*get_link) (struct dentry *dentry, struct inode *inode);
 
 	int (*create) (struct inode *,struct dentry *, umode_t);
+	int (*mknod) (struct inode *,struct dentry *, umode_t, const char *name);
 	int (*link) (struct dentry *,struct inode *,struct dentry *);
 	int (*unlink) (struct inode *,struct dentry *);
 	int (*symlink) (struct inode *,struct dentry *,const char *);

-- 
2.47.3