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Message-Id: <1327639925-12920-20-git-send-email-ebiederm@xmission.com>
Date: Thu, 26 Jan 2012 20:51:56 -0800
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: <linux-kernel@...r.kernel.org>
Cc: <linux-fsdevel@...r.kernel.org>, <netdev@...r.kernel.org>,
Lucian Adrian Grijincu <lucian.grijincu@...il.com>,
Damien Millescamps <damien.millescamps@...nd.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 20/29] 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@...ssion.com>
---
fs/proc/proc_sysctl.c | 98 +++++++++++++++++++++++++++++++------------------
1 files changed, 62 insertions(+), 36 deletions(-)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 3b63f29..d9c3ae6 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;
--
1.7.2.5
--
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