From 076c3eed2c31773200b082568957fd8852ae93d7 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Mon, 9 Jan 2012 21:42:02 -0800 Subject: [PATCH] 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 --- fs/proc/proc_sysctl.c | 102 +++++++++++++++++++++++++++++++----------- 1 file changed, 76 insertions(+), 26 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 88d1b06cc5c0..3b63f298ce28 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; -- 2.20.1