[PATCH v3 0/6] sysctl: Remove register_sysctl_table from parport

[PATCH v3 0/6] sysctl: Remove register_sysctl_table from parport

[Joel Granados]

This is part of the general push to deprecate register_sysctl_paths and
register_sysctl_table. Parport driver uses the "CHILD" pointer
in the ctl_table structure to create its directory structure. We move to
the newer register_sysctl call and remove the pointer madness.

I have separated the parport into 5 patches to clarify the different
changes needed for the 3 calls to register_sysctl_paths. I can squash
them together if need be.

We no longer export the register_sysctl_table call as parport was the
last user from outside proc_sysctl.c. Also modified documentation slightly
so register_sysctl_table is no longer mentioned.

V2:
* Added a return error value when register fails
* Made sure to free the memory on error when calling parport_proc_register
* Added a bloat-o-meter output to measure bloat
* Replaced kmalloc with kzalloc
* Added comments about testing
* Improved readability when using snprintf

Best
Joel

Joel Granados (6):
  parport: Move magic number "15" to a define
  parport: Remove register_sysctl_table from parport_proc_register
  parport: Remove register_sysctl_table from
    parport_device_proc_register
  parport: Remove register_sysctl_table from
    parport_default_proc_register
  parport: Removed sysctl related defines
  sysctl: stop exporting register_sysctl_table

 drivers/parport/procfs.c | 169 +++++++++++++++++++++------------------
 drivers/parport/share.c  |   2 +-
 fs/proc/proc_sysctl.c    |   5 +-
 include/linux/parport.h  |   2 +
 include/linux/sysctl.h   |   8 +-
 5 files changed, 95 insertions(+), 91 deletions(-)

-- 
2.30.2

[PATCH v3 1/6] parport: Move magic number "15" to a define

[Joel Granados]

Put the size of a parport name behind a define so we can use it in other
files. This is a preparation patch to be able to use this size in
parport/procfs.c.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/parport/share.c | 2 +-
 include/linux/parport.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index 62f8407923d4..2d46b1d4fd69 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -467,7 +467,7 @@ struct parport *parport_register_port(unsigned long base, int irq, int dma,
 	atomic_set(&tmp->ref_count, 1);
 	INIT_LIST_HEAD(&tmp->full_list);
 
-	name = kmalloc(15, GFP_KERNEL);
+	name = kmalloc(PARPORT_NAME_MAX_LEN, GFP_KERNEL);
 	if (!name) {
 		kfree(tmp);
 		return NULL;
diff --git a/include/linux/parport.h b/include/linux/parport.h
index a0bc9e0267b7..243c82d7f852 100644
--- a/include/linux/parport.h
+++ b/include/linux/parport.h
@@ -180,6 +180,8 @@ struct ieee1284_info {
 	struct semaphore irq;
 };
 
+#define PARPORT_NAME_MAX_LEN 15
+
 /* A parallel port */
 struct parport {
 	unsigned long base;	/* base address */
-- 
2.30.2

[PATCH v3 2/6] parport: Remove register_sysctl_table from parport_proc_register

[Joel Granados]

This is part of the general push to deprecate register_sysctl_paths and
register_sysctl_table. Register dev/parport/PORTNAME and
dev/parport/PORTNAME/devices. Temporary allocation for name is freed at
the end of the function. Remove all the struct elements that are no
longer used in the parport_device_sysctl_template struct. Add parport
specific defines that hide the base path sizes.

To make sure the resulting directory structure did not change we
made sure that `find /proc/sys/dev/ | sha1sum` was the same before and
after the change.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202305150948.pHgIh7Ql-lkp@intel.com/
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202305150948.pHgIh7Ql-lkp@intel.com/
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/parport/procfs.c | 88 +++++++++++++++++++++++++---------------
 1 file changed, 56 insertions(+), 32 deletions(-)

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index d740eba3c099..02c52de6e640 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -32,6 +32,13 @@
 #define PARPORT_MAX_TIMESLICE_VALUE ((unsigned long) HZ)
 #define PARPORT_MIN_SPINTIME_VALUE 1
 #define PARPORT_MAX_SPINTIME_VALUE 1000
+/*
+ * PARPORT_BASE_* is the size of the known parts of the sysctl path
+ * in dev/partport/%s/devices/%s. "dev/parport/"(12), "/devices/"(9
+ * and null char(1).
+ */
+#define PARPORT_BASE_PATH_SIZE 13
+#define PARPORT_BASE_DEVICES_PATH_SIZE 22
 
 static int do_active_device(struct ctl_table *table, int write,
 		      void *result, size_t *lenp, loff_t *ppos)
@@ -260,9 +267,6 @@ struct parport_sysctl_table {
 	struct ctl_table_header *sysctl_header;
 	struct ctl_table vars[12];
 	struct ctl_table device_dir[2];
-	struct ctl_table port_dir[2];
-	struct ctl_table parport_dir[2];
-	struct ctl_table dev_dir[2];
 };
 
 static const struct parport_sysctl_table parport_sysctl_template = {
@@ -305,7 +309,6 @@ static const struct parport_sysctl_table parport_sysctl_template = {
 			.mode		= 0444,
 			.proc_handler	= do_hardware_modes
 		},
-		PARPORT_DEVICES_ROOT_DIR,
 #ifdef CONFIG_PARPORT_1284
 		{
 			.procname	= "autoprobe",
@@ -355,18 +358,6 @@ static const struct parport_sysctl_table parport_sysctl_template = {
 		},
 		{}
 	},
-	{
-		PARPORT_PORT_DIR(NULL),
-		{}
-	},
-	{
-		PARPORT_PARPORT_DIR(NULL),
-		{}
-	},
-	{
-		PARPORT_DEV_DIR(NULL),
-		{}
-	}
 };
 
 struct parport_device_sysctl_table
@@ -473,11 +464,12 @@ parport_default_sysctl_table = {
 	}
 };
 
-
 int parport_proc_register(struct parport *port)
 {
 	struct parport_sysctl_table *t;
-	int i;
+	char *tmp_dir_path;
+	size_t tmp_path_len, port_name_len;
+	int bytes_written, i, err = 0;
 
 	t = kmemdup(&parport_sysctl_template, sizeof(*t), GFP_KERNEL);
 	if (t == NULL)
@@ -485,28 +477,60 @@ int parport_proc_register(struct parport *port)
 
 	t->device_dir[0].extra1 = port;
 
-	for (i = 0; i < 5; i++)
-		t->vars[i].extra1 = port;
-
 	t->vars[0].data = &port->spintime;
-	t->vars[5].child = t->device_dir;
-	
-	for (i = 0; i < 5; i++)
-		t->vars[6 + i].extra2 = &port->probe_info[i];
+	for (i = 0; i < 5; i++) {
+		t->vars[i].extra1 = port;
+		t->vars[5 + i].extra2 = &port->probe_info[i];
+	}
 
-	t->port_dir[0].procname = port->name;
+	port_name_len = strnlen(port->name, PARPORT_NAME_MAX_LEN);
+	/*
+	 * Allocate a buffer for two paths: dev/parport/PORT and dev/parport/PORT/devices.
+	 * We calculate for the second as that will give us enough for the first.
+	 */
+	tmp_path_len = PARPORT_BASE_DEVICES_PATH_SIZE + port_name_len;
+	tmp_dir_path = kzalloc(tmp_path_len, GFP_KERNEL);
+	if (!tmp_dir_path) {
+		err = -ENOMEM;
+		goto exit_free_t;
+	}
 
-	t->port_dir[0].child = t->vars;
-	t->parport_dir[0].child = t->port_dir;
-	t->dev_dir[0].child = t->parport_dir;
+	bytes_written = snprintf(tmp_dir_path, tmp_path_len,
+				 "dev/parport/%s/devices", port->name);
+	if (tmp_path_len <= bytes_written) {
+		err = -ENOENT;
+		goto exit_free_tmp_dir_path;
+	}
+	if (register_sysctl(tmp_dir_path, t->device_dir) == NULL) {
+		err = -ENOENT;
+		goto  exit_free_tmp_dir_path;
+	}
 
-	t->sysctl_header = register_sysctl_table(t->dev_dir);
+	tmp_path_len = PARPORT_BASE_PATH_SIZE + port_name_len;
+	bytes_written = snprintf(tmp_dir_path, tmp_path_len,
+				 "dev/parport/%s", port->name);
+	if (tmp_path_len <= bytes_written) {
+		err = -ENOENT;
+		goto exit_free_tmp_dir_path;
+	}
+
+	t->sysctl_header = register_sysctl(tmp_dir_path, t->vars);
 	if (t->sysctl_header == NULL) {
-		kfree(t);
-		t = NULL;
+		err = -ENOENT;
+		goto exit_free_tmp_dir_path;
 	}
+
 	port->sysctl_table = t;
+
+	kfree(tmp_dir_path);
 	return 0;
+
+exit_free_tmp_dir_path:
+	kfree(tmp_dir_path);
+
+exit_free_t:
+	kfree(t);
+	return err;
 }
 
 int parport_proc_unregister(struct parport *port)
-- 
2.30.2

[PATCH v3 3/6] parport: Remove register_sysctl_table from parport_device_proc_register

[Joel Granados]

This is part of the general push to deprecate register_sysctl_paths and
register_sysctl_table. We use a temp allocation to include both port and
device name in proc. Allocated mem is freed at the end. The unused
parport_device_sysctl_template struct elements that are not used are
removed.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202305150948.pHgIh7Ql-lkp@intel.com/
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202305150948.pHgIh7Ql-lkp@intel.com/
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/parport/procfs.c | 56 +++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index 02c52de6e640..a2b58da1fe86 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -384,6 +384,7 @@ parport_device_sysctl_template = {
 			.extra1		= (void*) &parport_min_timeslice_value,
 			.extra2		= (void*) &parport_max_timeslice_value
 		},
+		{}
 	},
 	{
 		{
@@ -394,22 +395,6 @@ parport_device_sysctl_template = {
 			.child		= NULL
 		},
 		{}
-	},
-	{
-		PARPORT_DEVICES_ROOT_DIR,
-		{}
-	},
-	{
-		PARPORT_PORT_DIR(NULL),
-		{}
-	},
-	{
-		PARPORT_PARPORT_DIR(NULL),
-		{}
-	},
-	{
-		PARPORT_DEV_DIR(NULL),
-		{}
 	}
 };
 
@@ -546,30 +531,53 @@ int parport_proc_unregister(struct parport *port)
 
 int parport_device_proc_register(struct pardevice *device)
 {
+	int bytes_written, err = 0;
 	struct parport_device_sysctl_table *t;
 	struct parport * port = device->port;
+	size_t port_name_len, device_name_len, tmp_dir_path_len;
+	char *tmp_dir_path;
 	
 	t = kmemdup(&parport_device_sysctl_template, sizeof(*t), GFP_KERNEL);
 	if (t == NULL)
 		return -ENOMEM;
 
-	t->dev_dir[0].child = t->parport_dir;
-	t->parport_dir[0].child = t->port_dir;
-	t->port_dir[0].procname = port->name;
-	t->port_dir[0].child = t->devices_root_dir;
-	t->devices_root_dir[0].child = t->device_dir;
+	port_name_len = strnlen(port->name, PARPORT_NAME_MAX_LEN);
+	device_name_len = strnlen(device->name, PATH_MAX);
+
+	/* Allocate a buffer for two paths: dev/parport/PORT/devices/DEVICE. */
+	tmp_dir_path_len = PARPORT_BASE_DEVICES_PATH_SIZE + port_name_len + device_name_len;
+	tmp_dir_path = kzalloc(tmp_dir_path_len, GFP_KERNEL);
+	if (!tmp_dir_path) {
+		err = -ENOMEM;
+		goto exit_free_t;
+	}
+
+	bytes_written = snprintf(tmp_dir_path, tmp_dir_path_len, "dev/parport/%s/devices/%s",
+				 port->name, device->name);
+	if (tmp_dir_path_len <= bytes_written) {
+		err = -ENOENT;
+		goto exit_free_path;
+	}
 
-	t->device_dir[0].procname = device->name;
-	t->device_dir[0].child = t->vars;
 	t->vars[0].data = &device->timeslice;
 
-	t->sysctl_header = register_sysctl_table(t->dev_dir);
+	t->sysctl_header = register_sysctl(tmp_dir_path, t->vars);
 	if (t->sysctl_header == NULL) {
 		kfree(t);
 		t = NULL;
 	}
 	device->sysctl_table = t;
+
+	kfree(tmp_dir_path);
 	return 0;
+
+exit_free_path:
+	kfree(tmp_dir_path);
+
+exit_free_t:
+	kfree(t);
+
+	return err;
 }
 
 int parport_device_proc_unregister(struct pardevice *device)
-- 
2.30.2

[PATCH v3 4/6] parport: Remove register_sysctl_table from parport_default_proc_register

[Joel Granados]

This is part of the general push to deprecate register_sysctl_paths and
register_sysctl_table. Simply change the full path "dev/parport/default"
to point to an already existing set of table entries (vars). We also
remove the unused elements from parport_default_table.

To make sure the resulting directory structure did not change we
made sure that `find /proc/sys/dev/ | sha1sum` was the same before and
after the change.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/parport/procfs.c | 18 +-----------------
 1 file changed, 1 insertion(+), 17 deletions(-)

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index a2b58da1fe86..5a58a7852464 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -430,22 +430,6 @@ parport_default_sysctl_table = {
 			.extra2		= (void*) &parport_max_spintime_value
 		},
 		{}
-	},
-	{
-		{
-			.procname	= "default",
-			.mode		= 0555,
-			.child		= parport_default_sysctl_table.vars
-		},
-		{}
-	},
-	{
-		PARPORT_PARPORT_DIR(parport_default_sysctl_table.default_dir),
-		{}
-	},
-	{
-		PARPORT_DEV_DIR(parport_default_sysctl_table.parport_dir),
-		{}
 	}
 };
 
@@ -596,7 +580,7 @@ static int __init parport_default_proc_register(void)
 	int ret;
 
 	parport_default_sysctl_table.sysctl_header =
-		register_sysctl_table(parport_default_sysctl_table.dev_dir);
+		register_sysctl("dev/parport/default", parport_default_sysctl_table.vars);
 	if (!parport_default_sysctl_table.sysctl_header)
 		return -ENOMEM;
 	ret = parport_bus_init();
-- 
2.30.2

[PATCH v3 5/6] parport: Removed sysctl related defines

[Joel Granados]

The partport driver used to rely on defines to include different
directories in sysctl. Now that we have made the transition to
register_sysctl from regsiter_sysctl_table, they are no longer needed.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/parport/procfs.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index 5a58a7852464..f985248b2c5b 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -243,13 +243,6 @@ do {									\
 	return 0;
 }
 
-#define PARPORT_PORT_DIR(CHILD) { .procname = NULL, .mode = 0555, .child = CHILD }
-#define PARPORT_PARPORT_DIR(CHILD) { .procname = "parport", \
-                                     .mode = 0555, .child = CHILD }
-#define PARPORT_DEV_DIR(CHILD) { .procname = "dev", .mode = 0555, .child = CHILD }
-#define PARPORT_DEVICES_ROOT_DIR  {  .procname = "devices", \
-                                    .mode = 0555, .child = NULL }
-
 static const unsigned long parport_min_timeslice_value =
 PARPORT_MIN_TIMESLICE_VALUE;
 
-- 
2.30.2

[PATCH v3 6/6] sysctl: stop exporting register_sysctl_table

[Joel Granados]

We make register_sysctl_table static because the only function calling
it is in fs/proc/proc_sysctl.c (__register_sysctl_base). We remove it
from the sysctl.h header and modify the documentation in both the header
and proc_sysctl.c files to mention "register_sysctl" instead of
"register_sysctl_table".

This plus the commits that remove register_sysctl_table from parport
save 217 bytes:

./scripts/bloat-o-meter .bsysctl/vmlinux.old .bsysctl/vmlinux.new
add/remove: 0/1 grow/shrink: 5/1 up/down: 458/-675 (-217)
Function                                     old     new   delta
__register_sysctl_base                         8     286    +278
parport_proc_register                        268     379    +111
parport_device_proc_register                 195     247     +52
kzalloc.constprop                            598     608     +10
parport_default_proc_register                 62      69      +7
register_sysctl_table                        291       -    -291
parport_sysctl_template                     1288     904    -384
Total: Before=8603076, After=8602859, chg -0.00%

Signed-off-by: Joel Granados <j.granados@samsung.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 fs/proc/proc_sysctl.c  | 5 ++---
 include/linux/sysctl.h | 8 +-------
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 8038833ff5b0..f8f19e000d76 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1582,7 +1582,7 @@ static int register_leaf_sysctl_tables(const char *path, char *pos,
  * array. A completely 0 filled entry terminates the table.
  * We are slowly deprecating this call so avoid its use.
  */
-struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
+static struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
 {
 	struct ctl_table *ctl_table_arg = table;
 	int nr_subheaders = count_subheaders(table);
@@ -1634,7 +1634,6 @@ struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
 	header = NULL;
 	goto out;
 }
-EXPORT_SYMBOL(register_sysctl_table);
 
 int __register_sysctl_base(struct ctl_table *base_table)
 {
@@ -1700,7 +1699,7 @@ static void drop_sysctl_table(struct ctl_table_header *header)
 
 /**
  * unregister_sysctl_table - unregister a sysctl table hierarchy
- * @header: the header returned from register_sysctl_table
+ * @header: the header returned from register_sysctl or __register_sysctl_table
  *
  * Unregisters the sysctl table and all children. proc entries may not
  * actually be removed until they are no longer used by anyone.
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 3d08277959af..218e56a26fb0 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -89,7 +89,7 @@ int proc_do_static_key(struct ctl_table *table, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
 
 /*
- * Register a set of sysctl names by calling register_sysctl_table
+ * Register a set of sysctl names by calling register_sysctl
  * with an initialised array of struct ctl_table's.  An entry with 
  * NULL procname terminates the table.  table->de will be
  * set up by the registration and need not be initialised in advance.
@@ -222,7 +222,6 @@ struct ctl_table_header *__register_sysctl_table(
 	struct ctl_table_set *set,
 	const char *path, struct ctl_table *table);
 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
-struct ctl_table_header *register_sysctl_table(struct ctl_table * table);
 void unregister_sysctl_table(struct ctl_table_header * table);
 
 extern int sysctl_init_bases(void);
@@ -257,11 +256,6 @@ static inline int __register_sysctl_base(struct ctl_table *base_table)
 
 #define register_sysctl_base(table) __register_sysctl_base(table)
 
-static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
-{
-	return NULL;
-}
-
 static inline void register_sysctl_init(const char *path, struct ctl_table *table)
 {
 }
-- 
2.30.2

Re: [PATCH v3 0/6] sysctl: Remove register_sysctl_table from parport

[Luis Chamberlain]

On Tue, May 16, 2023 at 06:28:57PM +0200, Joel Granados wrote:
> This is part of the general push to deprecate register_sysctl_paths and
> register_sysctl_table. Parport driver uses the "CHILD" pointer
> in the ctl_table structure to create its directory structure. We move to
> the newer register_sysctl call and remove the pointer madness.
> 
> I have separated the parport into 5 patches to clarify the different
> changes needed for the 3 calls to register_sysctl_paths. I can squash
> them together if need be.
> 
> We no longer export the register_sysctl_table call as parport was the
> last user from outside proc_sysctl.c. Also modified documentation slightly
> so register_sysctl_table is no longer mentioned.
> 
> V2:
> * Added a return error value when register fails
> * Made sure to free the memory on error when calling parport_proc_register
> * Added a bloat-o-meter output to measure bloat
> * Replaced kmalloc with kzalloc
> * Added comments about testing
> * Improved readability when using snprintf

Thanks, applied and pushed!

  Luis