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Message-ID: <20230616085922.3066990-9-j.granados@samsung.com>
Date: Fri, 16 Jun 2023 10:59:22 +0200
From: Joel Granados <j.granados@...sung.com>
To: <mcgrof@...nel.org>
CC: <linux-kselftest@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
Joel Granados <j.granados@...sung.com>
Subject: [PATCH v2 8/8] sysctl: replace child with an enumeration
This is part of the effort to remove the empty element at the end of
ctl_table structs. "child" was a deprecated elem in this struct and was
being used to differentiate between two types of ctl_tables: "normal"
and "permanently emtpy".
What changed?:
* Replace "child" with an enumeration that will have two values: the
default (0) and the permanently empty (1). The latter is left at zero
so when struct ctl_table is created with kzalloc or in a local
context, it will have the zero value by default. We document the
new enum with kdoc.
* Remove the "empty child" check from sysctl_check_table
* Remove count_subheaders function as there is no longer a need to
calculate how many headers there are for every child
* Remove the recursive call to unregister_sysctl_table as there is no
need to traverse down the child tree any longer
* Add a new SYSCTL_PERM_EMPTY_DIR binary flag
* Remove the last remanence of child from partport/procfs.c
Signed-off-by: Joel Granados <j.granados@...sung.com>
---
drivers/parport/procfs.c | 1 -
fs/proc/proc_sysctl.c | 81 +++++++++-------------------------------
include/linux/sysctl.h | 14 ++++++-
3 files changed, 30 insertions(+), 66 deletions(-)
diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index 0f2d2e1ee28e..4e5b972c3e26 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -387,7 +387,6 @@ parport_device_sysctl_template = {
.data = NULL,
.maxlen = 0,
.mode = 0555,
- .child = NULL
},
{}
}
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 07804097f997..c4ea804d862b 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -29,9 +29,8 @@ static const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;
/* Support for permanently empty directories */
-
struct ctl_table sysctl_mount_point[] = {
- { }
+ {.type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY }
};
/**
@@ -48,21 +47,14 @@ struct ctl_table_header *register_sysctl_mount_point(const char *path)
}
EXPORT_SYMBOL(register_sysctl_mount_point);
-static bool is_empty_dir(struct ctl_table_header *head)
-{
- return head->ctl_table[0].child == sysctl_mount_point;
-}
-
-static void set_empty_dir(struct ctl_dir *dir)
-{
- dir->header.ctl_table[0].child = sysctl_mount_point;
-}
-
-static void clear_empty_dir(struct ctl_dir *dir)
-
-{
- dir->header.ctl_table[0].child = NULL;
-}
+#define sysctl_is_perm_empty_ctl_table(tptr) \
+ (tptr[0].type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
+#define sysctl_is_perm_empty_ctl_header(hptr) \
+ (sysctl_is_perm_empty_ctl_table(hptr->ctl_table))
+#define sysctl_set_perm_empty_ctl_header(hptr) \
+ (hptr->ctl_table[0].type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
+#define sysctl_clear_perm_empty_ctl_header(hptr) \
+ (hptr->ctl_table[0].type = SYSCTL_TABLE_TYPE_DEFAULT)
void proc_sys_poll_notify(struct ctl_table_poll *poll)
{
@@ -230,20 +222,22 @@ static void erase_header(struct ctl_table_header *head)
static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
{
struct ctl_table *entry;
+ struct ctl_table_header *dir_h = &dir->header;
int err;
+
/* Is this a permanently empty directory? */
- if (is_empty_dir(&dir->header))
+ if (sysctl_is_perm_empty_ctl_header(dir_h))
return -EROFS;
/* Am I creating a permanently empty directory? */
- if (header->ctl_table == sysctl_mount_point) {
+ if (sysctl_is_perm_empty_ctl_table(header->ctl_table)) {
if (!RB_EMPTY_ROOT(&dir->root))
return -EINVAL;
- set_empty_dir(dir);
+ sysctl_set_perm_empty_ctl_header(dir_h);
}
- dir->header.nreg++;
+ dir_h->nreg++;
header->parent = dir;
err = insert_links(header);
if (err)
@@ -259,9 +253,9 @@ static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
put_links(header);
fail_links:
if (header->ctl_table == sysctl_mount_point)
- clear_empty_dir(dir);
+ sysctl_clear_perm_empty_ctl_header(dir_h);
header->parent = NULL;
- drop_sysctl_table(&dir->header);
+ drop_sysctl_table(dir_h);
return err;
}
@@ -479,7 +473,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
inode->i_mode |= S_IFDIR;
inode->i_op = &proc_sys_dir_operations;
inode->i_fop = &proc_sys_dir_file_operations;
- if (is_empty_dir(head))
+ if (sysctl_is_perm_empty_ctl_header(head))
make_empty_dir_inode(inode);
}
@@ -1136,9 +1130,6 @@ static int sysctl_check_table(const char *path, struct ctl_table *table)
struct ctl_table *entry;
int err = 0;
list_for_each_table_entry(entry, table) {
- if (entry->child)
- err |= sysctl_err(path, entry, "Not a file");
-
if ((entry->proc_handler == proc_dostring) ||
(entry->proc_handler == proc_dobool) ||
(entry->proc_handler == proc_dointvec) ||
@@ -1465,25 +1456,6 @@ void __init __register_sysctl_init(const char *path, struct ctl_table *table,
kmemleak_not_leak(hdr);
}
-static int count_subheaders(struct ctl_table *table)
-{
- int has_files = 0;
- int nr_subheaders = 0;
- struct ctl_table *entry;
-
- /* special case: no directory and empty directory */
- if (!table || !table->procname)
- return 1;
-
- list_for_each_table_entry(entry, table) {
- if (entry->child)
- nr_subheaders += count_subheaders(entry->child);
- else
- has_files = 1;
- }
- return nr_subheaders + has_files;
-}
-
static void put_links(struct ctl_table_header *header)
{
struct ctl_table_set *root_set = &sysctl_table_root.default_set;
@@ -1546,28 +1518,11 @@ static void drop_sysctl_table(struct ctl_table_header *header)
*/
void unregister_sysctl_table(struct ctl_table_header * header)
{
- int nr_subheaders;
might_sleep();
if (header == NULL)
return;
- nr_subheaders = count_subheaders(header->ctl_table_arg);
- if (unlikely(nr_subheaders > 1)) {
- struct ctl_table_header **subheaders;
- int i;
-
- subheaders = (struct ctl_table_header **)(header + 1);
- for (i = nr_subheaders -1; i >= 0; i--) {
- struct ctl_table_header *subh = subheaders[i];
- struct ctl_table *table = subh->ctl_table_arg;
- unregister_sysctl_table(subh);
- kfree(table);
- }
- kfree(header);
- return;
- }
-
spin_lock(&sysctl_lock);
drop_sysctl_table(header);
spin_unlock(&sysctl_lock);
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 653b66c762b1..59d451f455bf 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -137,7 +137,17 @@ struct ctl_table {
void *data;
int maxlen;
umode_t mode;
- struct ctl_table *child; /* Deprecated */
+ /**
+ * enum type - Enumeration to differentiate between ctl target types
+ * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations
+ * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently
+ * empty directory target to serve
+ * as mount point.
+ */
+ enum {
+ SYSCTL_TABLE_TYPE_DEFAULT,
+ SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY
+ } type;
proc_handler *proc_handler; /* Callback for text formatting */
struct ctl_table_poll *poll;
void *extra1;
@@ -229,7 +239,7 @@ extern int unaligned_enabled;
extern int unaligned_dump_stack;
extern int no_unaligned_warning;
-extern struct ctl_table sysctl_mount_point[];
+#define SYSCTL_PERM_EMPTY_DIR (1 << 0)
#else /* CONFIG_SYSCTL */
--
2.30.2
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