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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 <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-01-18 03:15:51 -08:00
parent 076c3eed2c
commit 6a75ce167c
1 changed files with 62 additions and 36 deletions
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98
fs/proc/proc_sysctl.c
View File

@ -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;