Patch "debugfs: introduce a public file_operations accessor" has been added to the 4.7-stable tree

PATCH [email protected] 1 participant 1 message Oct 20, 2016

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2016-10-20 13:29 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

debugfs: introduce a public file_operations accessor

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
debugfs-introduce-a-public-file_operations-accessor.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 86f0e06767dda7863d6d2a8f0b3b857e6ea876a0 Mon Sep 17 00:00:00 2001

From: Christian Lamparter <[email protected]>
Date: Sat, 17 Sep 2016 21:43:01 +0200
Subject: debugfs: introduce a public file_operations accessor

From: Christian Lamparter <[email protected]>

commit 86f0e06767dda7863d6d2a8f0b3b857e6ea876a0 upstream.

This patch introduces an accessor which can be used by the users of debugfs (drivers, fs, ...) to get the original file_operations struct. It also removes the REAL_FOPS_DEREF macro in file.c and converts the code to use the public version.

Previously, REAL_FOPS_DEREF was only available within the file.c of debugfs. But having a public getter available for debugfs users is important as some drivers (carl9170 and b43) use the pointer of the original file_operations in conjunction with container_of() within their debugfs implementations.

Reviewed-by Nicolai Stange <[email protected]>

Signed-off-by Christian Lamparter <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 fs/debugfs/file.c       |   13 +++++--------
 include/linux/debugfs.h |   17 +++++++++++++++++
 2 files changed, 22 insertions(+), 8 deletions(-)

fs/debugfs/file.c +5 -8

@@ -97,9 +97,6 @@ EXPORT_SYMBOL_GPL(debugfs_use_file_finis
 
 #define F_DENTRY(filp) ((filp)->f_path.dentry)
 
-#define REAL_FOPS_DEREF(dentry)					\
-	((const struct file_operations *)(dentry)->d_fsdata)
-
 static int open_proxy_open(struct inode *inode, struct file *filp)
 {
 	const struct dentry *dentry = F_DENTRY(filp);

@@ -112,7 +109,7 @@ static int open_proxy_open(struct inode
 		goto out;
 	}
 
-	real_fops = REAL_FOPS_DEREF(dentry);
+	real_fops = debugfs_real_fops(filp);
 	real_fops = fops_get(real_fops);
 	if (!real_fops) {
 		/* Huh? Module did not clean up after itself at exit? */

@@ -143,7 +140,7 @@ static ret_type full_proxy_ ## name(prot
 {									\
 	const struct dentry *dentry = F_DENTRY(filp);			\
 	const struct file_operations *real_fops =			\
-		REAL_FOPS_DEREF(dentry);				\
+		debugfs_real_fops(filp);				\
 	int srcu_idx;							\
 	ret_type r;							\
 									\

@@ -176,7 +173,7 @@ static unsigned int full_proxy_poll(stru
 				struct poll_table_struct *wait)
 {
 	const struct dentry *dentry = F_DENTRY(filp);
-	const struct file_operations *real_fops = REAL_FOPS_DEREF(dentry);
+	const struct file_operations *real_fops = debugfs_real_fops(filp);
 	int srcu_idx;
 	unsigned int r = 0;

@@ -193,7 +190,7 @@ static unsigned int full_proxy_poll(stru
 static int full_proxy_release(struct inode *inode, struct file *filp)
 {
 	const struct dentry *dentry = F_DENTRY(filp);
-	const struct file_operations *real_fops = REAL_FOPS_DEREF(dentry);
+	const struct file_operations *real_fops = debugfs_real_fops(filp);
 	const struct file_operations *proxy_fops = filp->f_op;
 	int r = 0;

@@ -241,7 +238,7 @@ static int full_proxy_open(struct inode
 		goto out;
 	}
 
-	real_fops = REAL_FOPS_DEREF(dentry);
+	real_fops = debugfs_real_fops(filp);
 	real_fops = fops_get(real_fops);
 	if (!real_fops) {
 		/* Huh? Module did not cleanup after itself at exit? */

include/linux/debugfs.h +17 -0

@@ -45,6 +45,23 @@ extern struct dentry *arch_debugfs_dir;
 
 extern struct srcu_struct debugfs_srcu;
 
+/**
+ * debugfs_real_fops - getter for the real file operation
+ * @filp: a pointer to a struct file
+ *
+ * Must only be called under the protection established by
+ * debugfs_use_file_start().
+ */
+static inline const struct file_operations *debugfs_real_fops(struct file *filp)
+	__must_hold(&debugfs_srcu)
+{
+	/*
+	 * Neither the pointer to the struct file_operations, nor its
+	 * contents ever change -- srcu_dereference() is not needed here.
+	 */
+	return filp->f_path.dentry->d_fsdata;
+}
+
 #if defined(CONFIG_DEBUG_FS)
 
 struct dentry *debugfs_create_file(const char *name, umode_t mode,

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/b43-fix-debugfs-crash.patch queue-4.7/carl9170-fix-debugfs-crashes.patch queue-4.7/b43legacy-fix-debugfs-crash.patch queue-4.7/debugfs-introduce-a-public-file_operations-accessor.patch