Commit 805b5d5e authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
Browse files

[PATCH] sysctl: factor out sysctl_head_next from do_sysctl 



The current logic to walk through the list of sysctl table headers is slightly
painful and implement in a way it cannot be used by code outside sysctl.c

I am in the process of implementing a version of the sysctl proc support that
instead of using the proc generic non-caching monster, just uses the existing
sysctl data structure as backing store for building the dcache entries and for
doing directory reads.  To use the existing data structures however I need a
way to get at them.

[akpm@osdl.org: warning fix]
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0b4d4147

include/linux/sysctl.h

+4 −0
Original line number Diff line number Diff line
@@ -924,6 +924,10 @@ enum 
#ifdef __KERNEL__

#include <linux/list.h>



/* For the /proc/sys support */

extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev);

extern void sysctl_head_finish(struct ctl_table_header *prev);



extern void sysctl_init(void);



typedef struct ctl_table ctl_table;

kernel/sysctl.c

+43 −17
Original line number Diff line number Diff line
@@ -1070,6 +1070,42 @@ static void start_unregistering(struct ctl_table_header *p) 
	list_del_init(&p->ctl_entry);

}



void sysctl_head_finish(struct ctl_table_header *head)

{

	if (!head)

		return;

	spin_lock(&sysctl_lock);

	unuse_table(head);

	spin_unlock(&sysctl_lock);

}



struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev)

{

	struct ctl_table_header *head;

	struct list_head *tmp;

	spin_lock(&sysctl_lock);

	if (prev) {

		tmp = &prev->ctl_entry;

		unuse_table(prev);

		goto next;

	}

	tmp = &root_table_header.ctl_entry;

	for (;;) {

		head = list_entry(tmp, struct ctl_table_header, ctl_entry);



		if (!use_table(head))

			goto next;

		spin_unlock(&sysctl_lock);

		return head;

	next:

		tmp = tmp->next;

		if (tmp == &root_table_header.ctl_entry)

			break;

	}

	spin_unlock(&sysctl_lock);

	return NULL;

}



void __init sysctl_init(void)

{

#ifdef CONFIG_PROC_SYSCTL
@@ -1081,7 +1117,7 @@ void __init sysctl_init(void) 
int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *oldlenp,

	       void __user *newval, size_t newlen)

{

	struct list_head *tmp;

	struct ctl_table_header *head;

	int error = -ENOTDIR;



	if (nlen <= 0 || nlen >= CTL_MAXNAME)
@@ -1091,26 +1127,16 @@ int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *ol 
		if (!oldlenp || get_user(old_len, oldlenp))

			return -EFAULT;

	}

	spin_lock(&sysctl_lock);

	tmp = &root_table_header.ctl_entry;

	do {

		struct ctl_table_header *head =

			list_entry(tmp, struct ctl_table_header, ctl_entry);



		if (!use_table(head))

			continue;



		spin_unlock(&sysctl_lock);



	for (head = sysctl_head_next(NULL); head;

			head = sysctl_head_next(head)) {

		error = parse_table(name, nlen, oldval, oldlenp, 

					newval, newlen, head->ctl_table);



		spin_lock(&sysctl_lock);

		unuse_table(head);

		if (error != -ENOTDIR)

		if (error != -ENOTDIR) {

			sysctl_head_finish(head);

			break;

	} while ((tmp = tmp->next) != &root_table_header.ctl_entry);

	spin_unlock(&sysctl_lock);

		}

	}

	return error;

}

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