Re: [PATCH 1/6] xattr consolidation v2 - generic xattr API

[Will Dyson]

On Mon, 20 Sep 2004 19:07:21 -0400 (EDT), James Morris
<jmorris@xxxxxxxxxx> wrote:

> > For example:
> >
> > /*
> > In order to implement different sets of xattr operations for each
> > xattr prefix, a filesystem should create a null-terminated array of
> > struct xattr_handler (one for each prefix) and hang a pointer to it
> > off of the s_xattr field of the superblock. The generic_fooxattr
> > functions will search this list for a xattr_handler with a prefix
> > field that matches the prefix of the xattr we are dealing with and
> > call the apropriate function pointer from that xattr_handler.
> > */
> 
> The above is inaccurate.  e.g. not all of the generic functions search for
> a matching xattr handler.

Ok. You see the difficulty of documenting code that someone else
wrote.  Please consider the following:

--- xattr.c.old	2004-09-20 22:39:18.000000000 -0400
+++ xattr.c	2004-09-20 23:13:53.000000000 -0400
@@ -359,11 +359,24 @@
 	return *a_prefix ? NULL : a;
 }
 
+/*
+ * In order to implement different sets of xattr operations for each xattr
+ * prefix, a filesystem should create a null-terminated array of struct
+ * xattr_handler (one for each prefix) and hang a pointer to it off of the
+ * s_xattr field of the superblock.
+ *
+ * The generic_fooxattr() functions will use this list to dispatch xattr
+ * operations to the correct xattr_handler.
+ */
+
 #define for_each_xattr_handler(handlers, handler)		\
 		for ((handler) = *(handlers)++;			\
 			(handler) != NULL;			\
 			(handler) = *(handlers)++)	
 			
+/*
+ * Find the xattr_handler with the matching prefix
+ */
 static struct xattr_handler *xattr_resolve_name(struct xattr_handler
**handlers, const char **name)
 {
 	struct xattr_handler *handler;
@@ -381,6 +394,9 @@
 	return handler;
 }
 
+/*
+ * Find the handler for the prefix and dispatch the operation through it
+ */
 ssize_t generic_getxattr(struct dentry *dentry, const char *name,
void *buffer, size_t size)
 {
 	struct xattr_handler *handler;
@@ -392,6 +408,10 @@
 	return handler->get(inode, name, buffer, size);
 }
 
+/*
+ * Combine the results of the list() function from every xattr_handler in the
+ * list.
+ */
 ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t
buffer_size)
 {
 	struct inode *inode = dentry->d_inode;
@@ -417,6 +437,9 @@
 	return size;
 }
 
+/*
+ * Find the handler for the prefix and dispatch the operation through it
+ */
 int generic_setxattr(struct dentry *dentry, const char *name, const
void *value, size_t size, int flags)
 {
 	struct xattr_handler *handler;
@@ -430,6 +453,9 @@
 	return handler->set(inode, name, value, size, flags);
 }
 
+/*
+ * Find the handler for the prefix and dispatch the operation through it
+ */
 int generic_removexattr(struct dentry *dentry, const char *name)
 {
 	struct xattr_handler *handler;


-- 
Will Dyson - Consultant
http://www.lucidts.com/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/