From 6a3890c474795a4a3536e0a0c39f526e415eb212 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 26 Sep 2020 16:29:02 -0400 Subject: [PATCH] get rid of ep_push_nested() 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 --- fs/eventpoll.c | 29 ++++------------------------- 1 file changed, 4 insertions(+), 25 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 9edea39..6b1990b 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -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) -- 2.7.4