[PATCH 2/2] fs: add documentation to simple_xattr functions

[Aristeu Rozanski]

Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Hillf Danton <dhillf@xxxxxxxxx>
Cc: Lennart Poettering <lpoetter@xxxxxxxxxx>
Signed-off-by: Aristeu Rozanski <aris@xxxxxxxxxx>

---
 Documentation/filesystems/00-INDEX         |    3 ++
 Documentation/filesystems/simple_xattr.txt |   42 +++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

Index: github/Documentation/filesystems/00-INDEX
===================================================================
--- github.orig/Documentation/filesystems/00-INDEX	2012-09-05 11:51:50.870969722 -0400
+++ github/Documentation/filesystems/00-INDEX	2012-09-05 12:10:46.250211947 -0400
@@ -96,6 +96,9 @@
 	- how to use the seq_file API
 sharedsubtree.txt
 	- a description of shared subtrees for namespaces.
+simple_xattr.txt
+	- description of extended attributes for memory backed filesystems
+	  like tmpfs and cgroup filesystem.
 spufs.txt
 	- info and mount options for the SPU filesystem used on Cell.
 sysfs-pci.txt
Index: github/Documentation/filesystems/simple_xattr.txt
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ github/Documentation/filesystems/simple_xattr.txt	2012-09-05 12:10:46.250211947 -0400
@@ -0,0 +1,42 @@
+Simple Extended Attributes for Memory Backed Filesystems Interface
+==================================================================
+
+Implements extended attributes storage using kernel memory.  Users of these
+functions are strongly advised against allowing user or any other kind of
+extended attributes that can be manipulated by unprivileged users, since it'd
+be trivial to exhaust kernel memory.
+
+The filesystem implementation is responsible by storing a simple_xattrs
+structure for every directory and file and to implement setxattr() and
+getxattr() calls. Also, setxattr() should filter off by name the unsupported
+types.
+
+void simple_xattrs_init(struct simple_xattrs *xattrs)
+- Initializes a pre allocated structure
+
+void simple_xattrs_free(struct simple_xattrs *xattrs)
+- Frees up all the extended attributes and any resources allocated by
+  simple_xattrs_init
+
+struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
+- Allocates a extended attribute entry
+
+void simple_xattr_list_add(struct simple_xattrs *xattrs,
+                          struct simple_xattr *new_xattr)
+int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
+- Adds and removes an extended attribute from the list
+
+int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
+                    void *buffer, size_t size);
+- Returns the value of an extended attribute searching by name
+
+int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
+                    const void *value, size_t size, int flags);
+- Sets a new value for a given extended attribute. Specifying value as
+  NULL will remove the entry.  If XATTR_CREATE is set in flags, no extended
+  attribute with the same name may exist.  If XATTR_REPLACE is set, the
+  extended attribute has to exist or the operation will fail
+
+ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
+                         size_t size);
+- Lists the existing extended attributes names in a given buffer

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