[RFC PATCH 07/27] untangling ep_call_nested(): and there was much rejoicing

Al Viro
2020-10-04T02:39:43Z

fs/eventpoll.c | 43 +++++++++++--------------------------------
1 file changed, 11 insertions(+), 32 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9a6ee5991f3d..8c3b02755a50 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -439,25 +439,6 @@ static bool ep_push_nested(void *cookie)
return true;
}

-/**
- * ep_call_nested - Perform a bound (possibly) nested call, by checking
- * that the recursion limit is not exceeded, and that
- * the same nested call (by the meaning of same cookie) is
- * no re-entered.
- *
- * @nproc: Nested call core function pointer.
- * @priv: Opaque data to be passed to the @nproc callback.
- * @cookie: Cookie to be used to identify this nested call.
- *
- * Returns: Returns the code returned by the @nproc callback, or -1 if
- * the maximum recursion limit has been exceeded.
- */
-static int ep_call_nested(int (*nproc)(void *, void *, int), void *priv,
- void *cookie)
-{
- return (*nproc)(priv, cookie, nesting);
-}
-
/*
* As described in commit 0ccf831cb lockdep: annotate epoll
* the use of wait queues used by epoll is done in a very controlled
@@ -1325,7 +1306,7 @@ static void path_count_init(void)
path_count[i] = 0;
}

-static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
+static int reverse_path_check_proc(void *priv, void *cookie, int depth)
{
int error = 0;
struct file *file = priv;
@@ -1341,13 +1322,13 @@ static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
child_file = epi->ep->file;
if (is_file_epoll(child_file)) {
if (list_empty(&child_file->f_ep_links)) {
- if (path_count_inc(call_nests)) {
+ if (path_count_inc(depth)) {
error = -1;
break;
}
} else {
- error = ep_call_nested(reverse_path_check_proc,
- child_file, child_file);
+ error = reverse_path_check_proc(child_file, child_file,
+ depth + 1);
}
if (error != 0)
break;
@@ -1379,8 +1360,7 @@ static int reverse_path_check(void)
/* let's call this for all tfiles */
list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
path_count_init();
- error = ep_call_nested(reverse_path_check_proc, current_file,
- current_file);
+ error = reverse_path_check_proc(current_file, current_file, 0);
if (error)
break;
}
@@ -1886,8 +1866,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
}

/**
- * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested()
- * API, to verify that adding an epoll file inside another
+ * ep_loop_check_proc - verify that adding an epoll file inside another
* epoll structure, does not violate the constraints, in
* terms of closed loops, or too deep chains (which can
* result in excessive stack usage).
@@ -1900,7 +1879,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
* Returns: Returns zero if adding the epoll @file inside current epoll
* structure @ep does not violate the constraints, or -1 otherwise.
*/
-static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
+static int ep_loop_check_proc(void *priv, void *cookie, int depth)
{
int error = 0;
struct file *file = priv;
@@ -1912,7 +1891,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
if (!ep_push_nested(cookie)) /* limits recursion */
return -1;

- mutex_lock_nested(&ep->mtx, call_nests + 1);
+ mutex_lock_nested(&ep->mtx, depth + 1);
ep->gen = loop_check_gen;
for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
epi = rb_entry(rbp, struct epitem, rbn);
@@ -1920,8 +1899,8 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
ep_tovisit = epi->ffd.file->private_data;
if (ep_tovisit->gen == loop_check_gen)
continue;
- error = ep_call_nested(ep_loop_check_proc, epi->ffd.file,
- ep_tovisit);
+ error = ep_loop_check_proc(epi->ffd.file, ep_tovisit,
+ depth + 1);
if (error != 0)
break;
} else {
@@ -1959,7 +1938,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
*/
static int ep_loop_check(struct eventpoll *ep, struct file *file)
{
- return ep_call_nested(ep_loop_check_proc, file, ep);
+ return ep_loop_check_proc(file, ep, 0);
}

static void clear_tfile_check_list(void)
--
2.11.0