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sysctl: Rewrite proc_sys_lookup introducing find_entry and lookup_entry.

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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@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-01-09 21:42:02 -08:00
parent a194558e86
commit 076c3eed2c
1 changed files with 76 additions and 26 deletions
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102
fs/proc/proc_sysctl.c
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@ -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;