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get rid of ep_push_nested()

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The only remaining user is loop checking.  But there we only need
to check that we have not walked into the epoll we are inserting
into - we are adding an edge to acyclic graph, so any loop being
created will have to pass through the source of that edge.

So we don't need that array of cookies - we have only one eventpoll
to watch out for.  RIP ep_push_nested(), along with the cookies
array.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-09-26 16:29:02 -04:00
parent 56c428cac5
commit 6a3890c474
1 changed files with 4 additions and 25 deletions
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29
fs/eventpoll.c
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@ -254,8 +254,7 @@ static DEFINE_MUTEX(epmutex);
static u64 loop_check_gen = 0;
/* Used to check for epoll file descriptor inclusion loops */
static void *cookies[EP_MAX_NESTS + 1];
static int nesting;
static struct eventpoll *inserting_into;
/* Slab cache used to allocate "struct epitem" */
static struct kmem_cache *epi_cache __read_mostly;
@ -424,21 +423,6 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
#endif /* CONFIG_NET_RX_BUSY_POLL */
static bool ep_push_nested(void *cookie)
{
int i;
if (nesting > EP_MAX_NESTS) /* too deep nesting */
return false;
for (i = 0; i < nesting; i++) {
if (cookies[i] == cookie) /* loop detected */
return false;
}
cookies[nesting++] = cookie;
return true;
}
/*
* As described in commit 0ccf831cb lockdep: annotate epoll
* the use of wait queues used by epoll is done in a very controlled
@ -1885,12 +1869,11 @@ static int ep_loop_check_proc(void *priv, void *cookie, int depth)
ep_tovisit = epi->ffd.file->private_data;
if (ep_tovisit->gen == loop_check_gen)
continue;
if (!ep_push_nested(ep_tovisit)) {
if (ep_tovisit == inserting_into || depth > EP_MAX_NESTS) {
error = -1;
} else {
error = ep_loop_check_proc(epi->ffd.file, ep_tovisit,
depth + 1);
nesting--;
}
if (error != 0)
break;
@ -1928,12 +1911,8 @@ static int ep_loop_check_proc(void *priv, void *cookie, int depth)
*/
static int ep_loop_check(struct eventpoll *ep, struct file *file)
{
int err;
ep_push_nested(ep); // can't fail
err = ep_loop_check_proc(file, ep, 0);
nesting--;
return err;
inserting_into = ep;
return ep_loop_check_proc(file, ep, 0);
}
static void clear_tfile_check_list(void)