debugfs: add debugfs_lookup()
We don't always have easy access to the dentry of a file or directory we
created in debugfs. Add a helper which allows us to get a dentry we
previously created.
The motivation for this change is a problem with blktrace and the blk-mq
debugfs entries introduced in 07e4fead45e6 ("blk-mq: create debugfs
directory tree"). Namely, in some cases, the directory that blktrace
needs to create may already exist, but in other cases, it may not. We
_could_ rely on a bunch of implied knowledge to decide whether to create
the directory or not, but it's much cleaner on our end to just look it
up.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 014cc56..c0befcf 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -80,6 +80,8 @@
#if defined(CONFIG_DEBUG_FS)
+struct dentry *debugfs_lookup(const char *name, struct dentry *parent);
+
struct dentry *debugfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
@@ -181,6 +183,12 @@
* want to duplicate the design decision mistakes of procfs and devfs again.
*/
+static inline struct dentry *debugfs_lookup(const char *name,
+ struct dentry *parent)
+{
+ return ERR_PTR(-ENODEV);
+}
+
static inline struct dentry *debugfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)