From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Marc Zyngier <maz@kernel.org>
Subject: [RFC PATCH 12/27] get rid of ep_push_nested()
Date: Sun, 4 Oct 2020 03:39:14 +0100 [thread overview]
Message-ID: <20201004023929.2740074-12-viro@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20201004023929.2740074-1-viro@ZenIV.linux.org.uk>
From: Al Viro <viro@zeniv.linux.org.uk>
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>
---
fs/eventpoll.c | 29 ++++-------------------------
1 file changed, 4 insertions(+), 25 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9edea3933790..6b1990b8b9a0 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)
--
2.11.0
next prev parent reply other threads:[~2020-10-04 2:40 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-04 2:36 [RFC][PATCHSET] epoll cleanups Al Viro
2020-10-04 2:39 ` [RFC PATCH 01/27] epoll: switch epitem->pwqlist to single-linked list Al Viro
2020-10-04 2:39 ` [RFC PATCH 02/27] epoll: get rid of epitem->nwait Al Viro
2020-10-04 2:39 ` [RFC PATCH 03/27] untangling ep_call_nested(): get rid of useless arguments Al Viro
2020-10-04 2:39 ` [RFC PATCH 04/27] untangling ep_call_nested(): it's all serialized on epmutex Al Viro
2020-10-04 2:39 ` [RFC PATCH 05/27] untangling ep_call_nested(): take pushing cookie into a helper Al Viro
2020-10-04 2:39 ` [RFC PATCH 06/27] untangling ep_call_nested(): move push/pop of cookie into the callbacks Al Viro
2020-10-04 2:39 ` [RFC PATCH 07/27] untangling ep_call_nested(): and there was much rejoicing Al Viro
2020-10-04 2:39 ` [RFC PATCH 08/27] reverse_path_check_proc(): sane arguments Al Viro
2020-10-04 2:39 ` [RFC PATCH 09/27] reverse_path_check_proc(): don't bother with cookies Al Viro
2020-10-04 2:39 ` [RFC PATCH 10/27] clean reverse_path_check_proc() a bit Al Viro
2020-10-04 2:39 ` [RFC PATCH 11/27] ep_loop_check_proc(): lift pushing the cookie into callers Al Viro
2020-10-04 2:39 ` Al Viro [this message]
2020-10-04 2:39 ` [RFC PATCH 13/27] ep_loop_check_proc(): saner calling conventions Al Viro
2020-10-04 2:39 ` [RFC PATCH 14/27] ep_scan_ready_list(): prepare to splitup Al Viro
2020-10-04 2:39 ` [RFC PATCH 15/27] lift the calls of ep_read_events_proc() into the callers Al Viro
2020-10-04 2:39 ` [RFC PATCH 16/27] lift the calls of ep_send_events_proc() " Al Viro
2020-10-04 2:39 ` [RFC PATCH 17/27] ep_send_events_proc(): fold into the caller Al Viro
2020-10-04 2:39 ` [RFC PATCH 18/27] lift locking/unlocking ep->mtx out of ep_{start,done}_scan() Al Viro
2020-10-04 2:39 ` [RFC PATCH 19/27] ep_insert(): don't open-code ep_remove() on failure exits Al Viro
2020-10-04 2:39 ` [RFC PATCH 20/27] ep_insert(): we only need tep->mtx around the insertion itself Al Viro
2020-10-04 12:56 ` [ep_insert()] 9ee1cc5666: WARNING:possible_recursive_locking_detected kernel test robot
2020-10-04 14:17 ` Al Viro
2020-10-04 14:27 ` Al Viro
2020-10-04 2:39 ` [RFC PATCH 21/27] take the common part of ep_eventpoll_poll() and ep_item_poll() into helper Al Viro
2020-10-04 2:39 ` [RFC PATCH 22/27] fold ep_read_events_proc() into the only caller Al Viro
2020-10-04 2:39 ` [RFC PATCH 23/27] ep_insert(): move creation of wakeup source past the fl_ep_links insertion Al Viro
2020-10-04 2:39 ` [RFC PATCH 24/27] convert ->f_ep_links/->fllink to hlist Al Viro
2020-10-04 2:39 ` [RFC PATCH 25/27] lift rcu_read_lock() into reverse_path_check() Al Viro
2020-10-04 2:39 ` [RFC PATCH 26/27] epoll: massage the check list insertion Al Viro
2020-10-04 2:39 ` [RFC PATCH 27/27] epoll: take epitem list out of struct file Al Viro
2020-10-05 20:37 ` Qian Cai
2020-10-05 20:49 ` Al Viro
2020-10-04 2:49 ` [RFC][PATCHSET] epoll cleanups Al Viro
2020-10-04 12:13 ` Matthew Wilcox
2020-10-04 14:15 ` Al Viro
2020-10-04 18:08 ` Linus Torvalds
2020-10-04 20:05 ` Al Viro
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