[PATCH] relayfs: add support for global relay buffers

This patch adds the optional is_global outparam to the create_buf_file()
callback.  This can be used by clients to create a single global relayfs
buffer instead of the default per-cpu buffers.  This was suggested as being
useful for certain debugging applications where it's more convenient to be
able to get all the data from a single channel without having to go to the
bother of dealing with per-cpu files.

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>

1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/relayfs_fs.h b/include/linux/relayfs_fs.h
index 8c2177105857..30f45511b40d 100644
--- a/include/linux/relayfs_fs.h
+++ b/include/linux/relayfs_fs.h
@@ -116,6 +116,7 @@ struct rchan_callbacks
          * @parent: the parent of the file to create
          * @mode: the mode of the file to create
          * @buf: the channel buffer
+         * @is_global: outparam - set non-zero if the buffer should be global
          *
          * Called during relay_open(), once for each per-cpu buffer,
          * to allow the client to create a file to be used to
@@ -126,12 +127,17 @@ struct rchan_callbacks
          * The callback should return the dentry of the file created
          * to represent the relay buffer.
          *
+         * Setting the is_global outparam to a non-zero value will
+         * cause relay_open() to create a single global buffer rather
+         * than the default set of per-cpu buffers.
+         *
          * See Documentation/filesystems/relayfs.txt for more info.
          */
         struct dentry *(*create_buf_file)(const char *filename,
                                           struct dentry *parent,
                                           int mode,
-                                          struct rchan_buf *buf);
+                                          struct rchan_buf *buf,
+                                          int *is_global);
 
         /*
          * remove_buf_file - remove file representing a relayfs channel buffer