[PATCH] relayfs: export relayfs_create_file() with fileops param

This patch adds a mandatory fileops param to relayfs_create_file() and exports
that function so that clients can use it to create files defined by their own
set of file operations, in relayfs.  The purpose is to allow relayfs
applications to create their own set of 'control' files alongside their relay
files in relayfs rather than having to create them in /proc or debugfs for
instance.  relayfs_create_file() is also used by relay_open_buf() to create
the relay files for a channel.  In this case, a pointer to
relayfs_file_operations is passed in, along with a pointer to the buffer
associated with the file.
Signed-off-by: Tom Zanussi <zanussi@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/relayfs/inode.c

@@ -33,7 +33,9 @@ static struct backing_dev_info		relayfs_backing_dev_info = {
 	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
 };
 
-static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
+static struct inode *relayfs_get_inode(struct super_block *sb,
+				       int mode,
+ 				       struct file_operations *fops,
 				       void *data)
 {
 	struct inode *inode;
@@ -51,8 +53,8 @@ static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 	switch (mode & S_IFMT) {
 	case S_IFREG:
-		inode->i_fop = &relayfs_file_operations;
-		RELAYFS_I(inode)->buf = data;
+		inode->i_fop = fops;
+		RELAYFS_I(inode)->data = data;
 		break;
 	case S_IFDIR:
 		inode->i_op = &simple_dir_inode_operations;
@@ -73,6 +75,7 @@ static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
  *	@name: the name of the file to create
  *	@parent: parent directory
  *	@mode: mode
+ *	@fops: file operations to use for the file
  *	@data: user-associated data for this file
  *
  *	Returns the new dentry, NULL on failure
@@ -82,6 +85,7 @@ static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
 static struct dentry *relayfs_create_entry(const char *name,
 					   struct dentry *parent,
 					   int mode,
+					   struct file_operations *fops,
 					   void *data)
 {
 	struct dentry *d;
@@ -117,7 +121,7 @@ static struct dentry *relayfs_create_entry(const char *name,
 		goto release_mount;
 	}
 
-	inode = relayfs_get_inode(parent->d_inode->i_sb, mode, data);
+	inode = relayfs_get_inode(parent->d_inode->i_sb, mode, fops, data);
 	if (!inode) {
 		d = NULL;
 		goto release_mount;
@@ -145,20 +149,26 @@ static struct dentry *relayfs_create_entry(const char *name,
  *	@name: the name of the file to create
  *	@parent: parent directory
  *	@mode: mode, if not specied the default perms are used
+ *	@fops: file operations to use for the file
  *	@data: user-associated data for this file
  *
  *	Returns file dentry if successful, NULL otherwise.
  *
  *	The file will be created user r on behalf of current user.
  */
-struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
-				   int mode, void *data)
+struct dentry *relayfs_create_file(const char *name,
+				   struct dentry *parent,
+				   int mode,
+				   struct file_operations *fops,
+				   void *data)
 {
+	BUG_ON(!fops);
+
 	if (!mode)
 		mode = S_IRUSR;
 	mode = (mode & S_IALLUGO) | S_IFREG;
 
-	return relayfs_create_entry(name, parent, mode, data);
+	return relayfs_create_entry(name, parent, mode, fops, data);
 }
 
 /**
@@ -173,7 +183,7 @@ struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
 struct dentry *relayfs_create_dir(const char *name, struct dentry *parent)
 {
 	int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
-	return relayfs_create_entry(name, parent, mode, NULL);
+	return relayfs_create_entry(name, parent, mode, NULL, NULL);
 }
 
 /**
@@ -234,7 +244,7 @@ int relayfs_remove_dir(struct dentry *dentry)
  */
 static int relayfs_open(struct inode *inode, struct file *filp)
 {
-	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+	struct rchan_buf *buf = RELAYFS_I(inode)->data;
 	kref_get(&buf->kref);
 
 	return 0;
@@ -250,7 +260,7 @@ static int relayfs_open(struct inode *inode, struct file *filp)
 static int relayfs_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	struct inode *inode = filp->f_dentry->d_inode;
-	return relay_mmap_buf(RELAYFS_I(inode)->buf, vma);
+	return relay_mmap_buf(RELAYFS_I(inode)->data, vma);
 }
 
 /**
@@ -264,7 +274,7 @@ static unsigned int relayfs_poll(struct file *filp, poll_table *wait)
 {
 	unsigned int mask = 0;
 	struct inode *inode = filp->f_dentry->d_inode;
-	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+	struct rchan_buf *buf = RELAYFS_I(inode)->data;
 
 	if (buf->finalized)
 		return POLLERR;
@@ -288,7 +298,7 @@ static unsigned int relayfs_poll(struct file *filp, poll_table *wait)
  */
 static int relayfs_release(struct inode *inode, struct file *filp)
 {
-	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+	struct rchan_buf *buf = RELAYFS_I(inode)->data;
 	kref_put(&buf->kref, relay_remove_buf);
 
 	return 0;
@@ -450,7 +460,7 @@ static ssize_t relayfs_read(struct file *filp,
 			    loff_t *ppos)
 {
 	struct inode *inode = filp->f_dentry->d_inode;
-	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+	struct rchan_buf *buf = RELAYFS_I(inode)->data;
 	size_t read_start, avail;
 	ssize_t ret = 0;
 	void *from;
@@ -485,7 +495,7 @@ static struct inode *relayfs_alloc_inode(struct super_block *sb)
 	struct relayfs_inode_info *p = kmem_cache_alloc(relayfs_inode_cachep, SLAB_KERNEL);
 	if (!p)
 		return NULL;
-	p->buf = NULL;
+	p->data = NULL;
 
 	return &p->vfs_inode;
 }
@@ -531,7 +541,7 @@ static int relayfs_fill_super(struct super_block * sb, void * data, int silent)
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	sb->s_magic = RELAYFS_MAGIC;
 	sb->s_op = &relayfs_ops;
-	inode = relayfs_get_inode(sb, mode, NULL);
+	inode = relayfs_get_inode(sb, mode, NULL, NULL);
 
 	if (!inode)
 		return -ENOMEM;
@@ -589,6 +599,7 @@ module_exit(exit_relayfs_fs)
 EXPORT_SYMBOL_GPL(relayfs_file_operations);
 EXPORT_SYMBOL_GPL(relayfs_create_dir);
 EXPORT_SYMBOL_GPL(relayfs_remove_dir);
+EXPORT_SYMBOL_GPL(relayfs_create_file);
 
 MODULE_AUTHOR("Tom Zanussi <zanussi@us.ibm.com> and Karim Yaghmour <karim@opersys.com>");
 MODULE_DESCRIPTION("Relay Filesystem");

fs/relayfs/relay.c

@@ -176,7 +176,8 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan,
  		return NULL;
 
 	/* Create file in fs */
-	dentry = relayfs_create_file(filename, parent, S_IRUSR, buf);
+	dentry = relayfs_create_file(filename, parent, S_IRUSR,
+				     &relayfs_file_operations, buf);
  	if (!dentry) {
  		relay_destroy_buf(buf);
 		return NULL;

fs/relayfs/relay.h

 #ifndef _RELAY_H
 #define _RELAY_H
 
-struct dentry *relayfs_create_file(const char *name,
-				   struct dentry *parent,
-				   int mode,
-				   void *data);
 extern int relayfs_remove(struct dentry *dentry);
 extern int relay_buf_empty(struct rchan_buf *buf);
 extern void relay_destroy_channel(struct kref *kref);

include/linux/relayfs_fs.h

@@ -70,7 +70,7 @@ struct rchan
 struct relayfs_inode_info
 {
 	struct inode vfs_inode;
-	struct rchan_buf *buf;
+	void *data;
 };
 
 static inline struct relayfs_inode_info *RELAYFS_I(struct inode *inode)
@@ -148,6 +148,11 @@ extern size_t relay_switch_subbuf(struct rchan_buf *buf,
 extern struct dentry *relayfs_create_dir(const char *name,
 					 struct dentry *parent);
 extern int relayfs_remove_dir(struct dentry *dentry);
+extern struct dentry *relayfs_create_file(const char *name,
+					  struct dentry *parent,
+					  int mode,
+					  struct file_operations *fops,
+					  void *data);
 
 /**
  *	relay_write - write data into the channel