From 6a75ce167c53b41f15088d3c2c7e51c89dc8798a Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 18 Jan 2012 03:15:51 -0800 Subject: sysctl: Rewrite proc_sys_readdir in terms of first_entry and next_entry Replace sysctl_head_next with first_entry and next_entry. These new iterators operate at the level of sysctl table entries and filter out any sysctl tables that should not be shown. Utilizing two specialized functions instead of a single function removes conditionals for handling awkward special cases that only come up at the beginning of iteration, making the iterators easier to read and understand. Signed-off-by: Eric W. Biederman --- fs/proc/proc_sysctl.c | 98 ++++++++++++++++++++++++++++++++------------------- 1 file changed, 62 insertions(+), 36 deletions(-) (limited to 'fs/proc/proc_sysctl.c') diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 3b63f298ce2..d9c3ae6afe4 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -243,31 +243,25 @@ static struct ctl_table *lookup_entry(struct ctl_table_header **phead, return entry; } -static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces, - struct ctl_table_header *prev) +static struct ctl_table_header *next_usable_entry(struct ctl_table *dir, + struct ctl_table_root *root, struct list_head *tmp) { - struct ctl_table_root *root; + struct nsproxy *namespaces = current->nsproxy; struct list_head *header_list; struct ctl_table_header *head; - struct list_head *tmp; - spin_lock(&sysctl_lock); - if (prev) { - head = prev; - tmp = &prev->ctl_entry; - unuse_table(prev); - goto next; - } - tmp = &root_table_header.ctl_entry; + goto next; for (;;) { head = list_entry(tmp, struct ctl_table_header, ctl_entry); + root = head->root; - if (!use_table(head)) + if (head->attached_to != dir || + !head->attached_by->procname || + !use_table(head)) goto next; - spin_unlock(&sysctl_lock); + return head; next: - root = head->root; tmp = tmp->next; header_list = lookup_header_list(root, namespaces); if (tmp != header_list) @@ -283,13 +277,53 @@ static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces, tmp = header_list->next; } out: - spin_unlock(&sysctl_lock); return NULL; } -static struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev) +static void first_entry( + struct ctl_table_header *dir_head, struct ctl_table *dir, + struct ctl_table_header **phead, struct ctl_table **pentry) { - return __sysctl_head_next(current->nsproxy, prev); + struct ctl_table_header *head = dir_head; + struct ctl_table *entry = dir; + + spin_lock(&sysctl_lock); + if (entry->procname) { + use_table(head); + } else { + head = next_usable_entry(dir, &sysctl_table_root, + &sysctl_table_root.default_set.list); + if (head) + entry = head->attached_by; + } + spin_unlock(&sysctl_lock); + *phead = head; + *pentry = entry; +} + +static void next_entry(struct ctl_table *dir, + struct ctl_table_header **phead, struct ctl_table **pentry) +{ + struct ctl_table_header *head = *phead; + struct ctl_table *entry = *pentry; + + entry++; + if (!entry->procname) { + struct ctl_table_root *root = head->root; + struct list_head *tmp = &head->ctl_entry; + if (head->attached_to != dir) { + root = &sysctl_table_root; + tmp = &sysctl_table_root.default_set.list; + } + spin_lock(&sysctl_lock); + unuse_table(head); + head = next_usable_entry(dir, root, tmp); + spin_unlock(&sysctl_lock); + if (head) + entry = head->attached_by; + } + *phead = head; + *pentry = entry; } void register_sysctl_root(struct ctl_table_root *root) @@ -533,20 +567,17 @@ static int scan(struct ctl_table_header *head, ctl_table *table, unsigned long *pos, struct file *file, void *dirent, filldir_t filldir) { + int res; - for (; table->procname; table++, (*pos)++) { - int res; + if ((*pos)++ < file->f_pos) + return 0; - if (*pos < file->f_pos) - continue; + res = proc_sys_fill_cache(file, dirent, filldir, head, table); - res = proc_sys_fill_cache(file, dirent, filldir, head, table); - if (res) - return res; + if (res == 0) + file->f_pos = *pos; - file->f_pos = *pos + 1; - } - return 0; + return res; } static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) @@ -556,6 +587,7 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) struct ctl_table_header *head = grab_header(inode); struct ctl_table *table = PROC_I(inode)->sysctl_entry; struct ctl_table_header *h = NULL; + struct ctl_table *entry; unsigned long pos; int ret = -EINVAL; @@ -585,14 +617,8 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) } pos = 2; - ret = scan(head, table, &pos, filp, dirent, filldir); - if (ret) - goto out; - - for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) { - if (h->attached_to != table) - continue; - ret = scan(h, h->attached_by, &pos, filp, dirent, filldir); + for (first_entry(head, table, &h, &entry); h; next_entry(table, &h, &entry)) { + ret = scan(h, entry, &pos, filp, dirent, filldir); if (ret) { sysctl_head_finish(h); break; -- cgit v1.2.3