From f8f25893a477a4da4414c3e40ddd51d77fac9cfc Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@intel.com>
Date: Fri, 29 Nov 2024 13:15:37 +0100
Subject: fs: debugfs: differentiate short fops with proxy ops

Geert reported that my previous short fops debugfs changes
broke m68k, because it only has mandatory alignement of two,
so we can't stash the "is it short" information into the
pointer (as we already did with the "is it real" bit.)

Instead, exploit the fact that debugfs_file_get() called on
an already open file will already find that the fsdata is
no longer the real fops but rather the allocated data that
already distinguishes full/short ops, so only open() needs
to be able to distinguish. We can achieve that by using two
different open functions.

Unfortunately this requires another set of full file ops,
increasing the size by 536 bytes (x86-64), but that's still
a reasonable trade-off given that only converting some of
the wireless stack gained over 28k. This brings the total
cost of this to around 1k, for wins of 28k (all x86-64).

Reported-and-tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/CAMuHMdWu_9-L2Te101w8hU7H_2yobJFPXSwwUmGHSJfaPWDKiQ@mail.gmail.com
Fixes: 8dc6d81c6b2a ("debugfs: add small file operations for most files")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20241129121536.30989-2-johannes@sipsolutions.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/inode.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 38a9c7eb97e6..65e46c7b6bf1 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -455,8 +455,7 @@ struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
 					const struct file_operations *fops)
 {
 	if (WARN_ON((unsigned long)fops &
-		    (DEBUGFS_FSDATA_IS_SHORT_FOPS_BIT |
-		     DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)))
+		    DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
 		return ERR_PTR(-EINVAL);
 
 	return __debugfs_create_file(name, mode, parent, data,
@@ -471,15 +470,13 @@ struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
 					 const struct debugfs_short_fops *fops)
 {
 	if (WARN_ON((unsigned long)fops &
-		    (DEBUGFS_FSDATA_IS_SHORT_FOPS_BIT |
-		     DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)))
+		    DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
 		return ERR_PTR(-EINVAL);
 
 	return __debugfs_create_file(name, mode, parent, data,
-				fops ? &debugfs_full_proxy_file_operations :
+				fops ? &debugfs_full_short_proxy_file_operations :
 					&debugfs_noop_file_operations,
-				(const void *)((unsigned long)fops |
-					       DEBUGFS_FSDATA_IS_SHORT_FOPS_BIT));
+				fops);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_file_short);
 
-- 
cgit v1.2.3


From 24edfbdedf19998366205130cfc93158a475497e Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 29 Dec 2024 08:12:04 +0000
Subject: debugfs: fix missing mutex_destroy() in short_fops case

we need that in ->real_fops == NULL, ->short_fops != NULL case

Fixes: 8dc6d81c6b2a "debugfs: add small file operations for most files"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20241229081223.3193228-1-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 65e46c7b6bf1..e752009de929 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -229,7 +229,7 @@ static void debugfs_release_dentry(struct dentry *dentry)
 		return;
 
 	/* check it wasn't a dir (no fsdata) or automount (no real_fops) */
-	if (fsd && fsd->real_fops) {
+	if (fsd && (fsd->real_fops || fsd->short_fops)) {
 		WARN_ON(!list_empty(&fsd->cancellations));
 		mutex_destroy(&fsd->cancellations_mtx);
 	}
-- 
cgit v1.2.3


From 268b36116f2f048d2fb0cd13aa3036705fcac068 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 12 Jan 2025 08:06:45 +0000
Subject: debugfs: separate cache for debugfs inodes

Embed them into container (struct debugfs_inode_info, with nothing
else in it at the moment), set the cache up, etc.

Just the infrastructure changes letting us augment debugfs inodes
here; adding stuff will come at the next step.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20250112080705.141166-1-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/inode.c    | 40 ++++++++++++++++++++++++++++++++++------
 fs/debugfs/internal.h |  9 +++++++++
 2 files changed, 43 insertions(+), 6 deletions(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index e752009de929..5d423bd92f93 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -208,16 +208,34 @@ static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 	return 0;
 }
 
+static struct kmem_cache *debugfs_inode_cachep __ro_after_init;
+
+static void init_once(void *foo)
+{
+	struct debugfs_inode_info *info = foo;
+	inode_init_once(&info->vfs_inode);
+}
+
+static struct inode *debugfs_alloc_inode(struct super_block *sb)
+{
+	struct debugfs_inode_info *info;
+	info = alloc_inode_sb(sb, debugfs_inode_cachep, GFP_KERNEL);
+	if (!info)
+		return NULL;
+	return &info->vfs_inode;
+}
+
 static void debugfs_free_inode(struct inode *inode)
 {
 	if (S_ISLNK(inode->i_mode))
 		kfree(inode->i_link);
-	free_inode_nonrcu(inode);
+	kmem_cache_free(debugfs_inode_cachep, DEBUGFS_I(inode));
 }
 
 static const struct super_operations debugfs_super_operations = {
 	.statfs		= simple_statfs,
 	.show_options	= debugfs_show_options,
+	.alloc_inode	= debugfs_alloc_inode,
 	.free_inode	= debugfs_free_inode,
 };
 
@@ -939,12 +957,22 @@ static int __init debugfs_init(void)
 	if (retval)
 		return retval;
 
-	retval = register_filesystem(&debug_fs_type);
-	if (retval)
+	debugfs_inode_cachep = kmem_cache_create("debugfs_inode_cache",
+				sizeof(struct debugfs_inode_info), 0,
+				SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
+				init_once);
+	if (debugfs_inode_cachep == NULL) {
 		sysfs_remove_mount_point(kernel_kobj, "debug");
-	else
-		debugfs_registered = true;
+		return -ENOMEM;
+	}
 
-	return retval;
+	retval = register_filesystem(&debug_fs_type);
+	if (retval) { // Really not going to happen
+		sysfs_remove_mount_point(kernel_kobj, "debug");
+		kmem_cache_destroy(debugfs_inode_cachep);
+		return retval;
+	}
+	debugfs_registered = true;
+	return 0;
 }
 core_initcall(debugfs_init);
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
index bbae4a228ef4..5cb940b0b8f6 100644
--- a/fs/debugfs/internal.h
+++ b/fs/debugfs/internal.h
@@ -11,6 +11,15 @@
 
 struct file_operations;
 
+struct debugfs_inode_info {
+	struct inode vfs_inode;
+};
+
+static inline struct debugfs_inode_info *DEBUGFS_I(struct inode *inode)
+{
+	return container_of(inode, struct debugfs_inode_info, vfs_inode);
+}
+
 /* declared over in file.c */
 extern const struct file_operations debugfs_noop_file_operations;
 extern const struct file_operations debugfs_open_proxy_file_operations;
-- 
cgit v1.2.3


From bacaaf833e964933c36ee571d8c0e9a87fae1a3e Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 12 Jan 2025 08:06:46 +0000
Subject: debugfs: move ->automount into debugfs_inode_info

... and don't bother with debugfs_fsdata for those.  Life's
simpler that way...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20250112080705.141166-2-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/inode.c    | 21 +++++----------------
 fs/debugfs/internal.h | 19 +++++++++----------
 2 files changed, 14 insertions(+), 26 deletions(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 5d423bd92f93..2f5afd7b1b94 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -246,8 +246,8 @@ static void debugfs_release_dentry(struct dentry *dentry)
 	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
 		return;
 
-	/* check it wasn't a dir (no fsdata) or automount (no real_fops) */
-	if (fsd && (fsd->real_fops || fsd->short_fops)) {
+	/* check it wasn't a dir or automount (no fsdata) */
+	if (fsd) {
 		WARN_ON(!list_empty(&fsd->cancellations));
 		mutex_destroy(&fsd->cancellations_mtx);
 	}
@@ -257,9 +257,9 @@ static void debugfs_release_dentry(struct dentry *dentry)
 
 static struct vfsmount *debugfs_automount(struct path *path)
 {
-	struct debugfs_fsdata *fsd = path->dentry->d_fsdata;
+	struct inode *inode = path->dentry->d_inode;
 
-	return fsd->automount(path->dentry, d_inode(path->dentry)->i_private);
+	return DEBUGFS_I(inode)->automount(path->dentry, inode->i_private);
 }
 
 static const struct dentry_operations debugfs_dops = {
@@ -642,23 +642,13 @@ struct dentry *debugfs_create_automount(const char *name,
 					void *data)
 {
 	struct dentry *dentry = start_creating(name, parent);
-	struct debugfs_fsdata *fsd;
 	struct inode *inode;
 
 	if (IS_ERR(dentry))
 		return dentry;
 
-	fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
-	if (!fsd) {
-		failed_creating(dentry);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	fsd->automount = f;
-
 	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
 		failed_creating(dentry);
-		kfree(fsd);
 		return ERR_PTR(-EPERM);
 	}
 
@@ -666,14 +656,13 @@ struct dentry *debugfs_create_automount(const char *name,
 	if (unlikely(!inode)) {
 		pr_err("out of free dentries, can not create automount '%s'\n",
 		       name);
-		kfree(fsd);
 		return failed_creating(dentry);
 	}
 
 	make_empty_dir_inode(inode);
 	inode->i_flags |= S_AUTOMOUNT;
 	inode->i_private = data;
-	dentry->d_fsdata = fsd;
+	DEBUGFS_I(inode)->automount = f;
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
 	d_instantiate(dentry, inode);
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
index 5cb940b0b8f6..a644e44a0ee4 100644
--- a/fs/debugfs/internal.h
+++ b/fs/debugfs/internal.h
@@ -13,6 +13,9 @@ struct file_operations;
 
 struct debugfs_inode_info {
 	struct inode vfs_inode;
+	union {
+		debugfs_automount_t automount;
+	};
 };
 
 static inline struct debugfs_inode_info *DEBUGFS_I(struct inode *inode)
@@ -29,17 +32,13 @@ extern const struct file_operations debugfs_full_short_proxy_file_operations;
 struct debugfs_fsdata {
 	const struct file_operations *real_fops;
 	const struct debugfs_short_fops *short_fops;
-	union {
-		/* automount_fn is used when real_fops is NULL */
-		debugfs_automount_t automount;
-		struct {
-			refcount_t active_users;
-			struct completion active_users_drained;
+	struct {
+		refcount_t active_users;
+		struct completion active_users_drained;
 
-			/* protect cancellations */
-			struct mutex cancellations_mtx;
-			struct list_head cancellations;
-		};
+		/* protect cancellations */
+		struct mutex cancellations_mtx;
+		struct list_head cancellations;
 	};
 };
 
-- 
cgit v1.2.3


From 95688800eefe28240204c2a0dd2bca5bf5f7f1d9 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 12 Jan 2025 08:06:48 +0000
Subject: debugfs: don't mess with bits in ->d_fsdata

The reason we need that crap is the dual use ->d_fsdata has there -
it's both holding a debugfs_fsdata reference after the first
debugfs_file_get() (actually, after the call of proxy ->open())
*and* it serves as a place to stash a reference to real file_operations
from object creation to the first open.  Oh, and it's triple use,
actually - that stashed reference might be to debugfs_short_fops.

Bugger that for a game of solidiers - just put the operations
reference into debugfs-private augmentation of inode.  And split
debugfs_full_file_operations into full and short cases, so that
debugfs_get_file() could tell one from another.

Voila - ->d_fsdata holds NULL until the first (successful) debugfs_get_file()
and a reference to struct debugfs_fsdata afterwards.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20250112080705.141166-4-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/file.c     | 58 +++++++++++++++++++++++++--------------------------
 fs/debugfs/inode.c    | 29 +++++++-------------------
 fs/debugfs/internal.h | 12 +++--------
 3 files changed, 38 insertions(+), 61 deletions(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index eb59b01f5f25..ae014bd36a6f 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -51,7 +51,7 @@ const struct file_operations *debugfs_real_fops(const struct file *filp)
 {
 	struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata;
 
-	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT) {
+	if (!fsd) {
 		/*
 		 * Urgh, we've been called w/o a protecting
 		 * debugfs_file_get().
@@ -84,9 +84,11 @@ static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
 		return -EINVAL;
 
 	d_fsd = READ_ONCE(dentry->d_fsdata);
-	if (!((unsigned long)d_fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)) {
+	if (d_fsd) {
 		fsd = d_fsd;
 	} else {
+		struct inode *inode = dentry->d_inode;
+
 		if (WARN_ON(mode == DBGFS_GET_ALREADY))
 			return -EINVAL;
 
@@ -96,9 +98,7 @@ static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
 
 		if (mode == DBGFS_GET_SHORT) {
 			const struct debugfs_short_fops *ops;
-			ops = (void *)((unsigned long)d_fsd &
-					~DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
-			fsd->short_fops = ops;
+			ops = fsd->short_fops = DEBUGFS_I(inode)->short_fops;
 			if (ops->llseek)
 				fsd->methods |= HAS_LSEEK;
 			if (ops->read)
@@ -107,9 +107,7 @@ static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
 				fsd->methods |= HAS_WRITE;
 		} else {
 			const struct file_operations *ops;
-			ops = (void *)((unsigned long)d_fsd &
-					~DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
-			fsd->real_fops = ops;
+			ops = fsd->real_fops = DEBUGFS_I(inode)->real_fops;
 			if (ops->llseek)
 				fsd->methods |= HAS_LSEEK;
 			if (ops->read)
@@ -126,10 +124,11 @@ static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
 		INIT_LIST_HEAD(&fsd->cancellations);
 		mutex_init(&fsd->cancellations_mtx);
 
-		if (cmpxchg(&dentry->d_fsdata, d_fsd, fsd) != d_fsd) {
+		d_fsd = cmpxchg(&dentry->d_fsdata, NULL, fsd);
+		if (d_fsd) {
 			mutex_destroy(&fsd->cancellations_mtx);
 			kfree(fsd);
-			fsd = READ_ONCE(dentry->d_fsdata);
+			fsd = d_fsd;
 		}
 	}
 
@@ -226,8 +225,7 @@ void debugfs_enter_cancellation(struct file *file,
 		return;
 
 	fsd = READ_ONCE(dentry->d_fsdata);
-	if (WARN_ON(!fsd ||
-		    ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)))
+	if (WARN_ON(!fsd))
 		return;
 
 	mutex_lock(&fsd->cancellations_mtx);
@@ -258,8 +256,7 @@ void debugfs_leave_cancellation(struct file *file,
 		return;
 
 	fsd = READ_ONCE(dentry->d_fsdata);
-	if (WARN_ON(!fsd ||
-		    ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)))
+	if (WARN_ON(!fsd))
 		return;
 
 	mutex_lock(&fsd->cancellations_mtx);
@@ -427,22 +424,21 @@ static int full_proxy_release(struct inode *inode, struct file *filp)
 	 * not to leak any resources. Releasers must not assume that
 	 * ->i_private is still being meaningful here.
 	 */
-	if (real_fops && real_fops->release)
+	if (real_fops->release)
 		r = real_fops->release(inode, filp);
 
 	fops_put(real_fops);
 	return r;
 }
 
-static int full_proxy_open(struct inode *inode, struct file *filp,
-			   enum dbgfs_get_mode mode)
+static int full_proxy_open_regular(struct inode *inode, struct file *filp)
 {
 	struct dentry *dentry = F_DENTRY(filp);
 	const struct file_operations *real_fops;
 	struct debugfs_fsdata *fsd;
 	int r;
 
-	r = __debugfs_file_get(dentry, mode);
+	r = __debugfs_file_get(dentry, DBGFS_GET_REGULAR);
 	if (r)
 		return r == -EIO ? -ENOENT : r;
 
@@ -452,7 +448,7 @@ static int full_proxy_open(struct inode *inode, struct file *filp,
 	if (r)
 		goto out;
 
-	if (real_fops && !fops_get(real_fops)) {
+	if (!fops_get(real_fops)) {
 #ifdef CONFIG_MODULES
 		if (real_fops->owner &&
 		    real_fops->owner->state == MODULE_STATE_GOING) {
@@ -468,11 +464,8 @@ static int full_proxy_open(struct inode *inode, struct file *filp,
 		goto out;
 	}
 
-	if (!real_fops || real_fops->open) {
-		if (real_fops)
-			r = real_fops->open(inode, filp);
-		else
-			r = simple_open(inode, filp);
+	if (real_fops->open) {
+		r = real_fops->open(inode, filp);
 		if (r) {
 			fops_put(real_fops);
 		} else if (filp->f_op != &debugfs_full_proxy_file_operations) {
@@ -487,11 +480,6 @@ out:
 	return r;
 }
 
-static int full_proxy_open_regular(struct inode *inode, struct file *filp)
-{
-	return full_proxy_open(inode, filp, DBGFS_GET_REGULAR);
-}
-
 const struct file_operations debugfs_full_proxy_file_operations = {
 	.open = full_proxy_open_regular,
 	.release = full_proxy_release,
@@ -504,7 +492,17 @@ const struct file_operations debugfs_full_proxy_file_operations = {
 
 static int full_proxy_open_short(struct inode *inode, struct file *filp)
 {
-	return full_proxy_open(inode, filp, DBGFS_GET_SHORT);
+	struct dentry *dentry = F_DENTRY(filp);
+	int r;
+
+	r = __debugfs_file_get(dentry, DBGFS_GET_SHORT);
+	if (r)
+		return r == -EIO ? -ENOENT : r;
+	r = debugfs_locked_down(inode, filp, NULL);
+	if (!r)
+		r = simple_open(inode, filp);
+	debugfs_file_put(dentry);
+	return r;
 }
 
 const struct file_operations debugfs_full_short_proxy_file_operations = {
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 2f5afd7b1b94..c4e8b7f758e0 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -243,15 +243,10 @@ static void debugfs_release_dentry(struct dentry *dentry)
 {
 	struct debugfs_fsdata *fsd = dentry->d_fsdata;
 
-	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
-		return;
-
-	/* check it wasn't a dir or automount (no fsdata) */
 	if (fsd) {
 		WARN_ON(!list_empty(&fsd->cancellations));
 		mutex_destroy(&fsd->cancellations_mtx);
 	}
-
 	kfree(fsd);
 }
 
@@ -459,9 +454,10 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 	inode->i_private = data;
 
 	inode->i_op = &debugfs_file_inode_operations;
+	if (!real_fops)
+		proxy_fops = &debugfs_noop_file_operations;
 	inode->i_fop = proxy_fops;
-	dentry->d_fsdata = (void *)((unsigned long)real_fops |
-				DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
+	DEBUGFS_I(inode)->raw = real_fops;
 
 	d_instantiate(dentry, inode);
 	fsnotify_create(d_inode(dentry->d_parent), dentry);
@@ -472,13 +468,8 @@ struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
 					struct dentry *parent, void *data,
 					const struct file_operations *fops)
 {
-	if (WARN_ON((unsigned long)fops &
-		    DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
-		return ERR_PTR(-EINVAL);
-
 	return __debugfs_create_file(name, mode, parent, data,
-				fops ? &debugfs_full_proxy_file_operations :
-					&debugfs_noop_file_operations,
+				&debugfs_full_proxy_file_operations,
 				fops);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_file_full);
@@ -487,13 +478,8 @@ struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
 					 struct dentry *parent, void *data,
 					 const struct debugfs_short_fops *fops)
 {
-	if (WARN_ON((unsigned long)fops &
-		    DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
-		return ERR_PTR(-EINVAL);
-
 	return __debugfs_create_file(name, mode, parent, data,
-				fops ? &debugfs_full_short_proxy_file_operations :
-					&debugfs_noop_file_operations,
+				&debugfs_full_short_proxy_file_operations,
 				fops);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_file_short);
@@ -531,8 +517,7 @@ struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
 {
 
 	return __debugfs_create_file(name, mode, parent, data,
-				fops ? &debugfs_open_proxy_file_operations :
-					&debugfs_noop_file_operations,
+				&debugfs_open_proxy_file_operations,
 				fops);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
@@ -737,7 +722,7 @@ static void __debugfs_file_removed(struct dentry *dentry)
 	 */
 	smp_mb();
 	fsd = READ_ONCE(dentry->d_fsdata);
-	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
+	if (!fsd)
 		return;
 
 	/* if this was the last reference, we're done */
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
index 011ef8b1a99a..8d2de647b42c 100644
--- a/fs/debugfs/internal.h
+++ b/fs/debugfs/internal.h
@@ -14,6 +14,9 @@ struct file_operations;
 struct debugfs_inode_info {
 	struct inode vfs_inode;
 	union {
+		const void *raw;
+		const struct file_operations *real_fops;
+		const struct debugfs_short_fops *short_fops;
 		debugfs_automount_t automount;
 	};
 };
@@ -51,15 +54,6 @@ enum {
 	HAS_IOCTL = 16
 };
 
-/*
- * A dentry's ->d_fsdata either points to the real fops or to a
- * dynamically allocated debugfs_fsdata instance.
- * In order to distinguish between these two cases, a real fops
- * pointer gets its lowest bit set.
- */
-#define DEBUGFS_FSDATA_IS_REAL_FOPS_BIT BIT(0)
-
-/* Access BITS */
 #define DEBUGFS_ALLOW_API	BIT(0)
 #define DEBUGFS_ALLOW_MOUNT	BIT(1)
 
-- 
cgit v1.2.3


From 12c92098932b4bbf38396e9aed0a343d35437a21 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 12 Jan 2025 08:06:49 +0000
Subject: debugfs: allow to store an additional opaque pointer at file creation

Set by debugfs_create_file_aux(name, mode, parent, data, aux, fops).
Plain debugfs_create_file() has it set to NULL.
Accessed by debugfs_get_aux(file).

Convenience macros for numeric opaque data - debugfs_create_file_aux_num
and debugfs_get_aux_num, resp.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20250112080705.141166-5-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/file.c       |  6 ++++++
 fs/debugfs/inode.c      | 14 +++++++++-----
 fs/debugfs/internal.h   |  1 +
 include/linux/debugfs.h | 27 ++++++++++++++++++++++++++-
 4 files changed, 42 insertions(+), 6 deletions(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index ae014bd36a6f..e33cc77699cd 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -47,6 +47,12 @@ const struct file_operations debugfs_noop_file_operations = {
 
 #define F_DENTRY(filp) ((filp)->f_path.dentry)
 
+const void *debugfs_get_aux(const struct file *file)
+{
+	return DEBUGFS_I(file_inode(file))->aux;
+}
+EXPORT_SYMBOL_GPL(debugfs_get_aux);
+
 const struct file_operations *debugfs_real_fops(const struct file *filp)
 {
 	struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata;
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c4e8b7f758e0..51d4c3e9d422 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -424,6 +424,7 @@ static struct dentry *end_creating(struct dentry *dentry)
 
 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 				struct dentry *parent, void *data,
+				const void *aux,
 				const struct file_operations *proxy_fops,
 				const void *real_fops)
 {
@@ -458,6 +459,7 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 		proxy_fops = &debugfs_noop_file_operations;
 	inode->i_fop = proxy_fops;
 	DEBUGFS_I(inode)->raw = real_fops;
+	DEBUGFS_I(inode)->aux = aux;
 
 	d_instantiate(dentry, inode);
 	fsnotify_create(d_inode(dentry->d_parent), dentry);
@@ -466,19 +468,21 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 
 struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
 					struct dentry *parent, void *data,
+					const void *aux,
 					const struct file_operations *fops)
 {
-	return __debugfs_create_file(name, mode, parent, data,
+	return __debugfs_create_file(name, mode, parent, data, aux,
 				&debugfs_full_proxy_file_operations,
 				fops);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_file_full);
 
 struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
-					 struct dentry *parent, void *data,
-					 const struct debugfs_short_fops *fops)
+					struct dentry *parent, void *data,
+					const void *aux,
+					const struct debugfs_short_fops *fops)
 {
-	return __debugfs_create_file(name, mode, parent, data,
+	return __debugfs_create_file(name, mode, parent, data, aux,
 				&debugfs_full_short_proxy_file_operations,
 				fops);
 }
@@ -516,7 +520,7 @@ struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
 				   const struct file_operations *fops)
 {
 
-	return __debugfs_create_file(name, mode, parent, data,
+	return __debugfs_create_file(name, mode, parent, data, NULL,
 				&debugfs_open_proxy_file_operations,
 				fops);
 }
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
index 8d2de647b42c..93483fe84425 100644
--- a/fs/debugfs/internal.h
+++ b/fs/debugfs/internal.h
@@ -19,6 +19,7 @@ struct debugfs_inode_info {
 		const struct debugfs_short_fops *short_fops;
 		debugfs_automount_t automount;
 	};
+	const void *aux;
 };
 
 static inline struct debugfs_inode_info *DEBUGFS_I(struct inode *inode)
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 59444b495d49..7c97417d73b5 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -79,9 +79,11 @@ struct debugfs_short_fops {
 
 struct dentry *debugfs_create_file_full(const char *name, umode_t mode,
 					struct dentry *parent, void *data,
+					const void *aux,
 					const struct file_operations *fops);
 struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
 					 struct dentry *parent, void *data,
+					 const void *aux,
 					 const struct debugfs_short_fops *fops);
 
 /**
@@ -126,7 +128,15 @@ struct dentry *debugfs_create_file_short(const char *name, umode_t mode,
 		 const struct debugfs_short_fops *: debugfs_create_file_short,	\
 		 struct file_operations *: debugfs_create_file_full,		\
 		 struct debugfs_short_fops *: debugfs_create_file_short)	\
-		(name, mode, parent, data, fops)
+		(name, mode, parent, data, NULL, fops)
+
+#define debugfs_create_file_aux(name, mode, parent, data, aux, fops)		\
+	_Generic(fops,								\
+		 const struct file_operations *: debugfs_create_file_full,	\
+		 const struct debugfs_short_fops *: debugfs_create_file_short,	\
+		 struct file_operations *: debugfs_create_file_full,		\
+		 struct debugfs_short_fops *: debugfs_create_file_short)	\
+		(name, mode, parent, data, aux, fops)
 
 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
 				   struct dentry *parent, void *data,
@@ -153,6 +163,7 @@ void debugfs_remove(struct dentry *dentry);
 void debugfs_lookup_and_remove(const char *name, struct dentry *parent);
 
 const struct file_operations *debugfs_real_fops(const struct file *filp);
+const void *debugfs_get_aux(const struct file *file);
 
 int debugfs_file_get(struct dentry *dentry);
 void debugfs_file_put(struct dentry *dentry);
@@ -259,6 +270,14 @@ static inline struct dentry *debugfs_lookup(const char *name,
 	return ERR_PTR(-ENODEV);
 }
 
+static inline struct dentry *debugfs_create_file_aux(const char *name,
+					umode_t mode, struct dentry *parent,
+					void *data, void *aux,
+					const void *fops)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline struct dentry *debugfs_create_file(const char *name, umode_t mode,
 					struct dentry *parent, void *data,
 					const void *fops)
@@ -312,6 +331,7 @@ static inline void debugfs_lookup_and_remove(const char *name,
 { }
 
 const struct file_operations *debugfs_real_fops(const struct file *filp);
+void *debugfs_get_aux(const struct file *file);
 
 static inline int debugfs_file_get(struct dentry *dentry)
 {
@@ -452,6 +472,11 @@ static inline ssize_t debugfs_read_file_str(struct file *file,
 
 #endif
 
+#define debugfs_create_file_aux_num(name, mode, parent, data, n, fops) \
+	debugfs_create_file_aux(name, mode, parent, data, \
+				(void *)(unsigned long)n, fops)
+#define debugfs_get_aux_num(f) (unsigned long)debugfs_get_aux(f)
+
 /**
  * debugfs_create_xul - create a debugfs file that is used to read and write an
  * unsigned long value, formatted in hexadecimal
-- 
cgit v1.2.3


From f7862dfef6612b87b2ad8352c4d73886f09456d6 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 12 Jan 2025 08:07:05 +0000
Subject: saner replacement for debugfs_rename()

Existing primitive has several problems:
	1) calling conventions are clumsy - it returns a dentry reference
that is either identical to its second argument or is an ERR_PTR(-E...);
in both cases no refcount changes happen.  Inconvenient for users and
bug-prone; it would be better to have it return 0 on success and -E... on
failure.
	2) it allows cross-directory moves; however, no such caller have
ever materialized and considering the way debugfs is used, it's unlikely
to happen in the future.  What's more, any such caller would have fun
issues to deal with wrt interplay with recursive removal.  It also makes
the calling conventions clumsier...
	3) tautological rename fails; the callers have no race-free way
to deal with that.
	4) new name must have been formed by the caller; quite a few
callers have it done by sprintf/kasprintf/etc., ending up with considerable
boilerplate.

Proposed replacement: int debugfs_change_name(dentry, fmt, ...).  All callers
convert to that easily, and it's simpler internally.

IMO debugfs_rename() should go; if we ever get a real-world use case for
cross-directory moves in debugfs, we can always look into the right way
to handle that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20250112080705.141166-21-viro@zeniv.linux.org.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 Documentation/filesystems/debugfs.rst             |  12 +--
 drivers/net/bonding/bond_debugfs.c                |   9 +-
 drivers/net/ethernet/amd/xgbe/xgbe-debugfs.c      |  19 +---
 drivers/net/ethernet/marvell/skge.c               |   5 +-
 drivers/net/ethernet/marvell/sky2.c               |   5 +-
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   6 +-
 drivers/opp/debugfs.c                             |  10 +-
 fs/debugfs/inode.c                                | 106 ++++++++++------------
 include/linux/debugfs.h                           |   9 +-
 mm/shrinker_debug.c                               |  16 +---
 net/hsr/hsr_debugfs.c                             |   9 +-
 net/mac80211/debugfs_netdev.c                     |  11 +--
 net/wireless/core.c                               |   5 +-
 13 files changed, 77 insertions(+), 145 deletions(-)

(limited to 'fs/debugfs/inode.c')

diff --git a/Documentation/filesystems/debugfs.rst b/Documentation/filesystems/debugfs.rst
index dc35da8b8792..f7f977ffbf8d 100644
--- a/Documentation/filesystems/debugfs.rst
+++ b/Documentation/filesystems/debugfs.rst
@@ -211,18 +211,16 @@ seq_file content.
 
 There are a couple of other directory-oriented helper functions::
 
-    struct dentry *debugfs_rename(struct dentry *old_dir,
-    				  struct dentry *old_dentry,
-		                  struct dentry *new_dir,
-				  const char *new_name);
+    struct dentry *debugfs_change_name(struct dentry *dentry,
+					  const char *fmt, ...);
 
     struct dentry *debugfs_create_symlink(const char *name,
                                           struct dentry *parent,
 				      	  const char *target);
 
-A call to debugfs_rename() will give a new name to an existing debugfs
-file, possibly in a different directory.  The new_name must not exist prior
-to the call; the return value is old_dentry with updated information.
+A call to debugfs_change_name() will give a new name to an existing debugfs
+file, always in the same directory.  The new_name must not exist prior
+to the call; the return value is 0 on success and -E... on failuer.
 Symbolic links can be created with debugfs_create_symlink().
 
 There is one important thing that all debugfs users must take into account:
diff --git a/drivers/net/bonding/bond_debugfs.c b/drivers/net/bonding/bond_debugfs.c
index b19492a7f6ad..8adbec7c5084 100644
--- a/drivers/net/bonding/bond_debugfs.c
+++ b/drivers/net/bonding/bond_debugfs.c
@@ -63,13 +63,8 @@ void bond_debug_unregister(struct bonding *bond)
 
 void bond_debug_reregister(struct bonding *bond)
 {
-	struct dentry *d;
-
-	d = debugfs_rename(bonding_debug_root, bond->debug_dir,
-			   bonding_debug_root, bond->dev->name);
-	if (!IS_ERR(d)) {
-		bond->debug_dir = d;
-	} else {
+	int err = debugfs_change_name(bond->debug_dir, "%s", bond->dev->name);
+	if (err) {
 		netdev_warn(bond->dev, "failed to reregister, so just unregister old one\n");
 		bond_debug_unregister(bond);
 	}
diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-debugfs.c b/drivers/net/ethernet/amd/xgbe/xgbe-debugfs.c
index b0a6c96b6ef4..b35808d3d07f 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-debugfs.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-debugfs.c
@@ -505,21 +505,6 @@ void xgbe_debugfs_exit(struct xgbe_prv_data *pdata)
 
 void xgbe_debugfs_rename(struct xgbe_prv_data *pdata)
 {
-	char *buf;
-
-	if (!pdata->xgbe_debugfs)
-		return;
-
-	buf = kasprintf(GFP_KERNEL, "amd-xgbe-%s", pdata->netdev->name);
-	if (!buf)
-		return;
-
-	if (!strcmp(pdata->xgbe_debugfs->d_name.name, buf))
-		goto out;
-
-	debugfs_rename(pdata->xgbe_debugfs->d_parent, pdata->xgbe_debugfs,
-		       pdata->xgbe_debugfs->d_parent, buf);
-
-out:
-	kfree(buf);
+	debugfs_change_name(pdata->xgbe_debugfs,
+			    "amd-xgbe-%s", pdata->netdev->name);
 }
diff --git a/drivers/net/ethernet/marvell/skge.c b/drivers/net/ethernet/marvell/skge.c
index 25bf6ec44289..a1bada9eaaf6 100644
--- a/drivers/net/ethernet/marvell/skge.c
+++ b/drivers/net/ethernet/marvell/skge.c
@@ -3742,10 +3742,7 @@ static int skge_device_event(struct notifier_block *unused,
 	skge = netdev_priv(dev);
 	switch (event) {
 	case NETDEV_CHANGENAME:
-		if (skge->debugfs)
-			skge->debugfs = debugfs_rename(skge_debug,
-						       skge->debugfs,
-						       skge_debug, dev->name);
+		debugfs_change_name(skge->debugfs, "%s", dev->name);
 		break;
 
 	case NETDEV_GOING_DOWN:
diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
index 988fa28cfb5f..d7121c836508 100644
--- a/drivers/net/ethernet/marvell/sky2.c
+++ b/drivers/net/ethernet/marvell/sky2.c
@@ -4494,10 +4494,7 @@ static int sky2_device_event(struct notifier_block *unused,
 
 	switch (event) {
 	case NETDEV_CHANGENAME:
-		if (sky2->debugfs) {
-			sky2->debugfs = debugfs_rename(sky2_debug, sky2->debugfs,
-						       sky2_debug, dev->name);
-		}
+		debugfs_change_name(sky2->debugfs, "%s", dev->name);
 		break;
 
 	case NETDEV_GOING_DOWN:
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index c81ea8cdfe6e..82e2908016bd 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -6489,11 +6489,7 @@ static int stmmac_device_event(struct notifier_block *unused,
 
 	switch (event) {
 	case NETDEV_CHANGENAME:
-		if (priv->dbgfs_dir)
-			priv->dbgfs_dir = debugfs_rename(stmmac_fs_dir,
-							 priv->dbgfs_dir,
-							 stmmac_fs_dir,
-							 dev->name);
+		debugfs_change_name(priv->dbgfs_dir, "%s", dev->name);
 		break;
 	}
 done:
diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c
index 105de7c3274a..8fc6238b1728 100644
--- a/drivers/opp/debugfs.c
+++ b/drivers/opp/debugfs.c
@@ -217,7 +217,7 @@ static void opp_migrate_dentry(struct opp_device *opp_dev,
 {
 	struct opp_device *new_dev = NULL, *iter;
 	const struct device *dev;
-	struct dentry *dentry;
+	int err;
 
 	/* Look for next opp-dev */
 	list_for_each_entry(iter, &opp_table->dev_list, node)
@@ -234,16 +234,14 @@ static void opp_migrate_dentry(struct opp_device *opp_dev,
 
 	opp_set_dev_name(dev, opp_table->dentry_name);
 
-	dentry = debugfs_rename(rootdir, opp_dev->dentry, rootdir,
-				opp_table->dentry_name);
-	if (IS_ERR(dentry)) {
+	err = debugfs_change_name(opp_dev->dentry, "%s", opp_table->dentry_name);
+	if (err) {
 		dev_err(dev, "%s: Failed to rename link from: %s to %s\n",
 			__func__, dev_name(opp_dev->dev), dev_name(dev));
 		return;
 	}
 
-	new_dev->dentry = dentry;
-	opp_table->dentry = dentry;
+	new_dev->dentry = opp_table->dentry = opp_dev->dentry;
 }
 
 /**
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 51d4c3e9d422..75715d8877ee 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -830,76 +830,70 @@ void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
 EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
 
 /**
- * debugfs_rename - rename a file/directory in the debugfs filesystem
- * @old_dir: a pointer to the parent dentry for the renamed object. This
- *          should be a directory dentry.
- * @old_dentry: dentry of an object to be renamed.
- * @new_dir: a pointer to the parent dentry where the object should be
- *          moved. This should be a directory dentry.
- * @new_name: a pointer to a string containing the target name.
+ * debugfs_change_name - rename a file/directory in the debugfs filesystem
+ * @dentry: dentry of an object to be renamed.
+ * @fmt: format for new name
  *
  * This function renames a file/directory in debugfs.  The target must not
  * exist for rename to succeed.
  *
- * This function will return a pointer to old_dentry (which is updated to
- * reflect renaming) if it succeeds. If an error occurs, ERR_PTR(-ERROR)
- * will be returned.
+ * This function will return 0 on success and -E... on failure.
  *
  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
  * returned.
  */
-struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
-		struct dentry *new_dir, const char *new_name)
+int __printf(2, 3) debugfs_change_name(struct dentry *dentry, const char *fmt, ...)
 {
-	int error;
-	struct dentry *dentry = NULL, *trap;
+	int error = 0;
+	const char *new_name;
 	struct name_snapshot old_name;
+	struct dentry *parent, *target;
+	struct inode *dir;
+	va_list ap;
 
-	if (IS_ERR(old_dir))
-		return old_dir;
-	if (IS_ERR(new_dir))
-		return new_dir;
-	if (IS_ERR_OR_NULL(old_dentry))
-		return old_dentry;
-
-	trap = lock_rename(new_dir, old_dir);
-	/* Source or destination directories don't exist? */
-	if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
-		goto exit;
-	/* Source does not exist, cyclic rename, or mountpoint? */
-	if (d_really_is_negative(old_dentry) || old_dentry == trap ||
-	    d_mountpoint(old_dentry))
-		goto exit;
-	dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
-	/* Lookup failed, cyclic rename or target exists? */
-	if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
-		goto exit;
-
-	take_dentry_name_snapshot(&old_name, old_dentry);
-
-	error = simple_rename(&nop_mnt_idmap, d_inode(old_dir), old_dentry,
-			      d_inode(new_dir), dentry, 0);
-	if (error) {
-		release_dentry_name_snapshot(&old_name);
-		goto exit;
+	if (IS_ERR_OR_NULL(dentry))
+		return 0;
+
+	va_start(ap, fmt);
+	new_name = kvasprintf_const(GFP_KERNEL, fmt, ap);
+	va_end(ap);
+	if (!new_name)
+		return -ENOMEM;
+
+	parent = dget_parent(dentry);
+	dir = d_inode(parent);
+	inode_lock(dir);
+
+	take_dentry_name_snapshot(&old_name, dentry);
+
+	if (WARN_ON_ONCE(dentry->d_parent != parent)) {
+		error = -EINVAL;
+		goto out;
+	}
+	if (strcmp(old_name.name.name, new_name) == 0)
+		goto out;
+	target = lookup_one_len(new_name, parent, strlen(new_name));
+	if (IS_ERR(target)) {
+		error = PTR_ERR(target);
+		goto out;
 	}
-	d_move(old_dentry, dentry);
-	fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
-		d_is_dir(old_dentry),
-		NULL, old_dentry);
+	if (d_really_is_positive(target)) {
+		dput(target);
+		error = -EINVAL;
+		goto out;
+	}
+	simple_rename_timestamp(dir, dentry, dir, target);
+	d_move(dentry, target);
+	dput(target);
+	fsnotify_move(dir, dir, &old_name.name, d_is_dir(dentry), NULL, dentry);
+out:
 	release_dentry_name_snapshot(&old_name);
-	unlock_rename(new_dir, old_dir);
-	dput(dentry);
-	return old_dentry;
-exit:
-	if (dentry && !IS_ERR(dentry))
-		dput(dentry);
-	unlock_rename(new_dir, old_dir);
-	if (IS_ERR(dentry))
-		return dentry;
-	return ERR_PTR(-EINVAL);
+	inode_unlock(dir);
+	dput(parent);
+	kfree_const(new_name);
+	return error;
 }
-EXPORT_SYMBOL_GPL(debugfs_rename);
+EXPORT_SYMBOL_GPL(debugfs_change_name);
 
 /**
  * debugfs_initialized - Tells whether debugfs has been registered
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 68e9c6cbd835..fa2568b4380d 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -175,8 +175,7 @@ ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
 ssize_t debugfs_attr_write_signed(struct file *file, const char __user *buf,
 			size_t len, loff_t *ppos);
 
-struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
-                struct dentry *new_dir, const char *new_name);
+int debugfs_change_name(struct dentry *dentry, const char *fmt, ...) __printf(2, 3);
 
 void debugfs_create_u8(const char *name, umode_t mode, struct dentry *parent,
 		       u8 *value);
@@ -361,10 +360,10 @@ static inline ssize_t debugfs_attr_write_signed(struct file *file,
 	return -ENODEV;
 }
 
-static inline struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
-                struct dentry *new_dir, char *new_name)
+static inline int __printf(2, 3) debugfs_change_name(struct dentry *dentry,
+					const char *fmt, ...)
 {
-	return ERR_PTR(-ENODEV);
+	return -ENODEV;
 }
 
 static inline void debugfs_create_u8(const char *name, umode_t mode,
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index 4a85b94d12ce..794bd433cce0 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -195,8 +195,6 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
 
 int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
 {
-	struct dentry *entry;
-	char buf[128];
 	const char *new, *old;
 	va_list ap;
 	int ret = 0;
@@ -213,18 +211,8 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
 	old = shrinker->name;
 	shrinker->name = new;
 
-	if (shrinker->debugfs_entry) {
-		snprintf(buf, sizeof(buf), "%s-%d", shrinker->name,
-			 shrinker->debugfs_id);
-
-		entry = debugfs_rename(shrinker_debugfs_root,
-				       shrinker->debugfs_entry,
-				       shrinker_debugfs_root, buf);
-		if (IS_ERR(entry))
-			ret = PTR_ERR(entry);
-		else
-			shrinker->debugfs_entry = entry;
-	}
+	ret = debugfs_change_name(shrinker->debugfs_entry, "%s-%d",
+			shrinker->name, shrinker->debugfs_id);
 
 	mutex_unlock(&shrinker_mutex);
 
diff --git a/net/hsr/hsr_debugfs.c b/net/hsr/hsr_debugfs.c
index 1a195efc79cd..5b2cfac3b2ba 100644
--- a/net/hsr/hsr_debugfs.c
+++ b/net/hsr/hsr_debugfs.c
@@ -57,14 +57,11 @@ DEFINE_SHOW_ATTRIBUTE(hsr_node_table);
 void hsr_debugfs_rename(struct net_device *dev)
 {
 	struct hsr_priv *priv = netdev_priv(dev);
-	struct dentry *d;
+	int err;
 
-	d = debugfs_rename(hsr_debugfs_root_dir, priv->node_tbl_root,
-			   hsr_debugfs_root_dir, dev->name);
-	if (IS_ERR(d))
+	err = debugfs_change_name(priv->node_tbl_root, "%s", dev->name);
+	if (err)
 		netdev_warn(dev, "failed to rename\n");
-	else
-		priv->node_tbl_root = d;
 }
 
 /* hsr_debugfs_init - create hsr node_table file for dumping
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index a9bc2fd59f55..9fa38c489edc 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -1025,16 +1025,7 @@ void ieee80211_debugfs_remove_netdev(struct ieee80211_sub_if_data *sdata)
 
 void ieee80211_debugfs_rename_netdev(struct ieee80211_sub_if_data *sdata)
 {
-	struct dentry *dir;
-	char buf[10 + IFNAMSIZ];
-
-	dir = sdata->vif.debugfs_dir;
-
-	if (IS_ERR_OR_NULL(dir))
-		return;
-
-	sprintf(buf, "netdev:%s", sdata->name);
-	debugfs_rename(dir->d_parent, dir, dir->d_parent, buf);
+	debugfs_change_name(sdata->vif.debugfs_dir, "netdev:%s", sdata->name);
 }
 
 void ieee80211_debugfs_recreate_netdev(struct ieee80211_sub_if_data *sdata,
diff --git a/net/wireless/core.c b/net/wireless/core.c
index afbdc549fb4a..9130cb872ed3 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -143,10 +143,7 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
 	if (result)
 		return result;
 
-	if (!IS_ERR_OR_NULL(rdev->wiphy.debugfsdir))
-		debugfs_rename(rdev->wiphy.debugfsdir->d_parent,
-			       rdev->wiphy.debugfsdir,
-			       rdev->wiphy.debugfsdir->d_parent, newname);
+	debugfs_change_name(rdev->wiphy.debugfsdir, "%s", newname);
 
 	nl80211_notify_wiphy(rdev, NL80211_CMD_NEW_WIPHY);
 
-- 
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