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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Al Viro <viro@ZenIV.linux.org.uk>
Subject: [PATCH 14/16 v3] tracing: Automatically mount tracefs on debugfs/tracing
Date: Mon, 26 Jan 2015 10:09:27 -0500	[thread overview]
Message-ID: <20150126151001.098069598@goodmis.org> (raw)
In-Reply-To: <20150126150913.653681560@goodmis.org>

[-- Attachment #1: 0014-tracing-Automatically-mount-tracefs-on-debugfs-traci.patch --]
[-- Type: text/plain, Size: 2840 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

As tools currently rely on the tracing directory in debugfs, we can not
just created a tracefs infrastructure and expect sysadmins to mount
the new tracefs to have their old tools work.

Instead, the debugfs tracing directory is still created and the tracefs
file system is mounted there when the debugfs filesystem is mounted.

No longer does the tracing infrastructure update the debugfs file system,
but instead interacts with the tracefs file system. But now, it still
appears to the user like nothing changed, except you also have the feature
of mounting just the tracing system without needing all of debugfs!

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index fb577a2a60ea..623791e15966 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -32,6 +32,7 @@
 #include <linux/splice.h>
 #include <linux/kdebug.h>
 #include <linux/string.h>
+#include <linux/mount.h>
 #include <linux/rwsem.h>
 #include <linux/slab.h>
 #include <linux/ctype.h>
@@ -5815,10 +5816,34 @@ static __init int register_snapshot_cmd(void)
 static inline __init int register_snapshot_cmd(void) { return 0; }
 #endif /* defined(CONFIG_TRACER_SNAPSHOT) && defined(CONFIG_DYNAMIC_FTRACE) */
 
+static struct vfsmount *trace_automount(void *ingore)
+{
+	struct vfsmount *mnt;
+	struct file_system_type *type;
+
+	/*
+	 * To maintain backward compatibility for tools that mount
+	 * debugfs to get to the tracing facility, tracefs is automatically
+	 * mounted to the debugfs/tracing directory.
+	 */
+	type = get_fs_type("tracefs");
+	if (!type)
+		return NULL;
+	mnt = vfs_kern_mount(type, 0, "tracefs", NULL);
+	put_filesystem(type);
+	if (IS_ERR(mnt))
+		return NULL;
+	mntget(mnt);
+
+	return mnt;
+}
+
 #define TRACE_TOP_DIR_ENTRY		((struct dentry *)1)
 
 struct dentry *tracing_init_dentry_tr(struct trace_array *tr)
 {
+	struct dentry *traced;
+
 	/* Top entry does not have a descriptor */
 	if (tr->dir == TRACE_TOP_DIR_ENTRY)
 		return NULL;
@@ -5831,7 +5856,16 @@ struct dentry *tracing_init_dentry_tr(struct trace_array *tr)
 		return ERR_PTR(-ENODEV);
 
 	if (tr->flags & TRACE_ARRAY_FL_GLOBAL) {
-		tr->dir = debugfs_create_dir("tracing", NULL);
+		/*
+		 * As there may still be users that expect the tracing
+		 * files to exist in debugfs/tracing, we must automount
+		 * the tracefs file system there, so older tools still
+		 * work with the newer kerenl.
+		 */
+		traced = debugfs_create_automount("tracing", NULL,
+						  trace_automount, NULL);
+		if (!traced)
+			return ERR_PTR(-ENOMEM);
 		tr->dir = TRACE_TOP_DIR_ENTRY;
 		return NULL;
 	}
-- 
2.1.4



  parent reply	other threads:[~2015-01-26 15:10 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-26 15:09 [PATCH 00/16 v3] tracing: Add new file system tracefs Steven Rostedt
2015-01-26 15:09 ` [PATCH 01/16 v3] debugfs_{mkdir,create,link}(): get rid of redundant argument Steven Rostedt
2015-01-26 15:09 ` [PATCH 02/16 v3] debugfs: split the beginning and the end of __create_file() off Steven Rostedt
2015-01-26 15:09 ` [PATCH 03/16 v3] debugfs: kill __create_file() Steven Rostedt
2015-01-26 15:09 ` [PATCH 04/16 v3] fold debugfs_link() into caller Steven Rostedt
2015-01-26 15:09 ` [PATCH 05/16 v3] debugfs_mknod(): get rid useless arguments Steven Rostedt
2015-01-26 15:09 ` [PATCH 06/16 v3] fold debugfs_mkdir() into caller Steven Rostedt
2015-01-26 15:09 ` [PATCH 07/16 v3] fold debugfs_create() " Steven Rostedt
2015-01-26 15:09 ` [PATCH 08/16 v3] fold debugfs_mknod() into callers Steven Rostedt
2015-01-26 15:09 ` [PATCH 09/16 v3] debugfs: take mode-dependent parts of debugfs_get_inode() " Steven Rostedt
2015-01-26 15:09 ` [PATCH 10/16 v3] debugfs: split end_creating() into success and failure cases Steven Rostedt
2015-01-26 15:09 ` [PATCH 11/16 v3] new primitive: debugfs_create_automount() Steven Rostedt
2015-01-26 15:09 ` [PATCH 12/16 v3] tracefs: Add new tracefs file system Steven Rostedt
2015-01-26 15:09 ` [PATCH 13/16 v3] tracing: Convert the tracing facility over to use tracefs Steven Rostedt
2015-01-26 15:09 ` Steven Rostedt [this message]
2015-01-26 15:09 ` [PATCH 15/16 v3] tracefs: Add directory /sys/kernel/tracing Steven Rostedt
2015-01-26 15:09 ` [PATCH 16/16 v3] tracing: Have mkdir and rmdir be part of tracefs Steven Rostedt
2015-01-26 19:30 ` [PATCH 00/16 v3] tracing: Add new file system tracefs Al Viro
2015-01-26 20:42   ` Steven Rostedt
2015-01-26 20:44     ` Steven Rostedt
2015-01-26 20:58       ` Steven Rostedt
2015-01-26 21:44         ` Al Viro
2015-01-26 21:46     ` Al Viro
2015-01-26 23:02       ` Al Viro
2015-01-26 23:39         ` Steven Rostedt
2015-01-26 23:43       ` Steven Rostedt
2015-01-26 23:49         ` Steven Rostedt
2015-01-27  0:39           ` Steven Rostedt
2015-01-27  4:34             ` Al Viro
2015-01-27 15:15               ` Steven Rostedt
2015-01-27  0:37         ` Al Viro
2015-01-27  1:02           ` Steven Rostedt
2015-01-27  1:03             ` Steven Rostedt
2015-01-27  4:38               ` Al Viro
2015-01-27 15:19                 ` Steven Rostedt
2015-01-27 15:44                   ` Steven Rostedt
2015-01-26 21:40   ` Al Viro
2015-01-26 23:37     ` Steven Rostedt
2015-01-27  2:34       ` Steven Rostedt
2015-01-27  4:46         ` Al Viro

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