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Date: Thu, 26 Jan 2012 20:50:00 -0800
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: <linux-kernel@...r.kernel.org>
Cc: <linux-fsdevel@...r.kernel.org>, <netdev@...r.kernel.org>,
Damien Millescamps <damien.millescamps@...nd.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 19/29] sysctl: Rewrite proc_sys_lookup introducing find_entry and lookup_entry.
Replace the helpers that proc_sys_lookup uses with helpers that work
in terms of an entire sysctl directory. This is worse for sysctl_lock
hold times but it is much better for code clarity and the code cleanups
to come.
find_in_table is no longer needed so it is removed.
find_entry a general helper to find entries in a directory is added.
lookup_entry is a simple wrapper around find_entry that takes the
sysctl_lock increases the use count if an entry is found and drops
the sysctl_lock.
Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
fs/proc/proc_sysctl.c | 102 ++++++++++++++++++++++++++++++++++++------------
1 files changed, 76 insertions(+), 26 deletions(-)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 88d1b06..3b63f29 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -49,6 +49,55 @@ static struct ctl_table_root sysctl_table_root = {
static DEFINE_SPINLOCK(sysctl_lock);
+static int namecmp(const char *name1, int len1, const char *name2, int len2)
+{
+ int minlen;
+ int cmp;
+
+ minlen = len1;
+ if (minlen > len2)
+ minlen = len2;
+
+ cmp = memcmp(name1, name2, minlen);
+ if (cmp == 0)
+ cmp = len1 - len2;
+ return cmp;
+}
+
+static struct ctl_table *find_entry(struct ctl_table_header **phead,
+ struct ctl_table_set *set,
+ struct ctl_table_header *dir_head, struct ctl_table *dir,
+ const char *name, int namelen)
+{
+ struct ctl_table_header *head;
+ struct ctl_table *entry;
+
+ if (dir_head->set == set) {
+ for (entry = dir; entry->procname; entry++) {
+ const char *procname = entry->procname;
+ if (namecmp(procname, strlen(procname), name, namelen) == 0) {
+ *phead = dir_head;
+ return entry;
+ }
+ }
+ }
+
+ list_for_each_entry(head, &set->list, ctl_entry) {
+ if (head->unregistering)
+ continue;
+ if (head->attached_to != dir)
+ continue;
+ for (entry = head->attached_by; entry->procname; entry++) {
+ const char *procname = entry->procname;
+ if (namecmp(procname, strlen(procname), name, namelen) == 0) {
+ *phead = head;
+ return entry;
+ }
+ }
+ }
+ return NULL;
+}
+
static void init_header(struct ctl_table_header *head,
struct ctl_table_root *root, struct ctl_table_set *set,
struct ctl_table *table)
@@ -168,6 +217,32 @@ lookup_header_list(struct ctl_table_root *root, struct nsproxy *namespaces)
return &set->list;
}
+static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
+ struct ctl_table_header *dir_head,
+ struct ctl_table *dir,
+ const char *name, int namelen)
+{
+ struct ctl_table_header *head;
+ struct ctl_table *entry;
+ struct ctl_table_root *root;
+ struct ctl_table_set *set;
+
+ spin_lock(&sysctl_lock);
+ root = &sysctl_table_root;
+ do {
+ set = lookup_header_set(root, current->nsproxy);
+ entry = find_entry(&head, set, dir_head, dir, name, namelen);
+ if (entry && use_table(head))
+ *phead = head;
+ else
+ entry = NULL;
+ root = list_entry(root->root_list.next,
+ struct ctl_table_root, root_list);
+ } while (!entry && root != &sysctl_table_root);
+ spin_unlock(&sysctl_lock);
+ return entry;
+}
+
static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,
struct ctl_table_header *prev)
{
@@ -284,21 +359,6 @@ out:
return inode;
}
-static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
-{
- for ( ; p->procname; p++) {
- if (strlen(p->procname) != name->len)
- continue;
-
- if (memcmp(p->procname, name->name, name->len) != 0)
- continue;
-
- /* I have a match */
- return p;
- }
- return NULL;
-}
-
static struct ctl_table_header *grab_header(struct inode *inode)
{
struct ctl_table_header *head = PROC_I(inode)->sysctl;
@@ -328,17 +388,7 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
table = table ? table->child : &head->ctl_table[1];
- p = find_in_table(table, name);
- if (!p) {
- for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
- if (h->attached_to != table)
- continue;
- p = find_in_table(h->attached_by, name);
- if (p)
- break;
- }
- }
-
+ p = lookup_entry(&h, head, table, name->name, name->len);
if (!p)
goto out;
--
1.7.2.5
--
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