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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2015-01-21 10:01:39 -0500
committerSteven Rostedt <rostedt@goodmis.org>2015-02-03 12:48:43 -0500
commiteae473581cf93dad94ca833aa961c033c6a43924 (patch)
treeea0a8bbf8a30940b497dad43a858be8d1b5efb26 /kernel/trace
parentcc31004a4aa784d89054ec07b87eae05cecf7121 (diff)
tracing: Have mkdir and rmdir be part of tracefs
The tracing "instances" directory can create sub tracing buffers with mkdir, and remove them with rmdir. As a mkdir will also create all the files and directories that control the sub buffer the inode mutexes need to be released before this is done, to avoid deadlocks. It is better to let the tracing system unlock the inode mutexes before calling the functions that create the files within the new directory (or deletes the files from the one being destroyed). Now that tracing has been converted over to tracefs, the tracefs file system can be modified to accommodate this feature. It still releases the locks, but the filesystem itself can take care of the ugly business and let the user just do what it needs. The tracing system now attaches a descriptor to the directory dentry that can have userspace create or remove sub directories. If this descriptor does not exist for a dentry, then that dentry can not be used to create other directories. This descriptor holds a mkdir and rmdir method that only takes a character string as an argument. The tracefs file system will first make a copy of the dentry name before releasing the locks. Then it will pass the copied name to the methods. It is up to the tracing system that supplied the methods to handle races with duplicate names and such as all the inode mutexes would be released when the functions are called. Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c75
1 files changed, 5 insertions, 70 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b4aa936509d2..3c8913bac204 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6292,7 +6292,7 @@ static void free_trace_buffers(struct trace_array *tr)
#endif
}
-static int new_instance_create(const char *name)
+static int instance_mkdir(const char *name)
{
struct trace_array *tr;
int ret;
@@ -6362,7 +6362,7 @@ static int new_instance_create(const char *name)
}
-static int instance_delete(const char *name)
+static int instance_rmdir(const char *name)
{
struct trace_array *tr;
int found = 0;
@@ -6403,78 +6403,13 @@ static int instance_delete(const char *name)
return ret;
}
-static int instance_mkdir (struct inode *inode, struct dentry *dentry, umode_t mode)
-{
- struct dentry *parent;
- int ret;
-
- /* Paranoid: Make sure the parent is the "instances" directory */
- parent = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
- if (WARN_ON_ONCE(parent != trace_instance_dir))
- return -ENOENT;
-
- /*
- * The inode mutex is locked, but tracefs_create_dir() will also
- * take the mutex. As the instances directory can not be destroyed
- * or changed in any other way, it is safe to unlock it, and
- * let the dentry try. If two users try to make the same dir at
- * the same time, then the new_instance_create() will determine the
- * winner.
- */
- mutex_unlock(&inode->i_mutex);
-
- ret = new_instance_create(dentry->d_iname);
-
- mutex_lock(&inode->i_mutex);
-
- return ret;
-}
-
-static int instance_rmdir(struct inode *inode, struct dentry *dentry)
-{
- struct dentry *parent;
- int ret;
-
- /* Paranoid: Make sure the parent is the "instances" directory */
- parent = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
- if (WARN_ON_ONCE(parent != trace_instance_dir))
- return -ENOENT;
-
- /* The caller did a dget() on dentry */
- mutex_unlock(&dentry->d_inode->i_mutex);
-
- /*
- * The inode mutex is locked, but tracefs_create_dir() will also
- * take the mutex. As the instances directory can not be destroyed
- * or changed in any other way, it is safe to unlock it, and
- * let the dentry try. If two users try to make the same dir at
- * the same time, then the instance_delete() will determine the
- * winner.
- */
- mutex_unlock(&inode->i_mutex);
-
- ret = instance_delete(dentry->d_iname);
-
- mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
- mutex_lock(&dentry->d_inode->i_mutex);
-
- return ret;
-}
-
-static const struct inode_operations instance_dir_inode_operations = {
- .lookup = simple_lookup,
- .mkdir = instance_mkdir,
- .rmdir = instance_rmdir,
-};
-
static __init void create_trace_instances(struct dentry *d_tracer)
{
- trace_instance_dir = tracefs_create_dir("instances", d_tracer);
+ trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer,
+ instance_mkdir,
+ instance_rmdir);
if (WARN_ON(!trace_instance_dir))
return;
-
- /* Hijack the dir inode operations, to allow mkdir */
- trace_instance_dir->d_inode->i_op = &instance_dir_inode_operations;
}
static void