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@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index 0f2d2e1..4e5b972 100644 (file)
--- 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 0780409..c4ea804 100644 (file)
--- 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 @@ fail:
        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 653b66c..59d451f 100644 (file)
--- 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 */