From c64688081490321f2d23a292ef24e60bb321f3f1 Mon Sep 17 00:00:00 2001 From: Nicolai Stange Date: Tue, 22 Mar 2016 14:11:15 +0100 Subject: debugfs: add support for self-protecting attribute file fops In order to protect them against file removal issues, debugfs_create_file() creates a lifetime managing proxy around each struct file_operations handed in. In cases where this struct file_operations is able to manage file lifetime by itself already, the proxy created by debugfs is a waste of resources. The most common class of struct file_operations given to debugfs are those defined by means of the DEFINE_SIMPLE_ATTRIBUTE() macro. Introduce a DEFINE_DEBUGFS_ATTRIBUTE() macro to allow any struct file_operations of this class to be easily made file lifetime aware and thus, to be operated unproxied. Specifically, introduce debugfs_attr_read() and debugfs_attr_write() which wrap simple_attr_read() and simple_attr_write() under the protection of a debugfs_use_file_start()/debugfs_use_file_finish() pair. Make DEFINE_DEBUGFS_ATTRIBUTE() set the defined struct file_operations' ->read() and ->write() members to these wrappers. Export debugfs_create_file_unsafe() in order to allow debugfs users to create their files in non-proxying operation mode. Signed-off-by: Nicolai Stange Signed-off-by: Greg Kroah-Hartman --- fs/debugfs/file.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'fs/debugfs/file.c') diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index 6eb58a8ed03c..8ef56d9499a4 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -284,6 +284,34 @@ const struct file_operations debugfs_full_proxy_file_operations = { .open = full_proxy_open, }; +ssize_t debugfs_attr_read(struct file *file, char __user *buf, + size_t len, loff_t *ppos) +{ + ssize_t ret; + int srcu_idx; + + ret = debugfs_use_file_start(F_DENTRY(file), &srcu_idx); + if (likely(!ret)) + ret = simple_attr_read(file, buf, len, ppos); + debugfs_use_file_finish(srcu_idx); + return ret; +} +EXPORT_SYMBOL_GPL(debugfs_attr_read); + +ssize_t debugfs_attr_write(struct file *file, const char __user *buf, + size_t len, loff_t *ppos) +{ + ssize_t ret; + int srcu_idx; + + ret = debugfs_use_file_start(F_DENTRY(file), &srcu_idx); + if (likely(!ret)) + ret = simple_attr_write(file, buf, len, ppos); + debugfs_use_file_finish(srcu_idx); + return ret; +} +EXPORT_SYMBOL_GPL(debugfs_attr_write); + static struct dentry *debugfs_create_mode(const char *name, umode_t mode, struct dentry *parent, void *value, const struct file_operations *fops, -- cgit v1.2.3