[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20201005142118.726966971@linuxfoundation.org>
Date: Mon, 5 Oct 2020 17:27:19 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 5.8 83/85] epoll: replace ->visited/visited_list with generation count
From: Al Viro <viro@...iv.linux.org.uk>
commit 18306c404abe18a0972587a6266830583c60c928 upstream.
removes the need to clear it, along with the races.
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
fs/eventpoll.c | 27 ++++++++-------------------
1 file changed, 8 insertions(+), 19 deletions(-)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -218,8 +218,7 @@ struct eventpoll {
struct file *file;
/* used to optimize loop detection check */
- struct list_head visited_list_link;
- int visited;
+ u64 gen;
#ifdef CONFIG_NET_RX_BUSY_POLL
/* used to track busy poll napi_id */
@@ -274,6 +273,8 @@ static long max_user_watches __read_most
*/
static DEFINE_MUTEX(epmutex);
+static u64 loop_check_gen = 0;
+
/* Used to check for epoll file descriptor inclusion loops */
static struct nested_calls poll_loop_ncalls;
@@ -283,9 +284,6 @@ static struct kmem_cache *epi_cache __re
/* Slab cache used to allocate "struct eppoll_entry" */
static struct kmem_cache *pwq_cache __read_mostly;
-/* Visited nodes during ep_loop_check(), so we can unset them when we finish */
-static LIST_HEAD(visited_list);
-
/*
* List of files with newly added links, where we may need to limit the number
* of emanating paths. Protected by the epmutex.
@@ -1971,13 +1969,12 @@ static int ep_loop_check_proc(void *priv
struct epitem *epi;
mutex_lock_nested(&ep->mtx, call_nests + 1);
- ep->visited = 1;
- list_add(&ep->visited_list_link, &visited_list);
+ ep->gen = loop_check_gen;
for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
epi = rb_entry(rbp, struct epitem, rbn);
if (unlikely(is_file_epoll(epi->ffd.file))) {
ep_tovisit = epi->ffd.file->private_data;
- if (ep_tovisit->visited)
+ if (ep_tovisit->gen == loop_check_gen)
continue;
error = ep_call_nested(&poll_loop_ncalls,
ep_loop_check_proc, epi->ffd.file,
@@ -2018,18 +2015,8 @@ static int ep_loop_check_proc(void *priv
*/
static int ep_loop_check(struct eventpoll *ep, struct file *file)
{
- int ret;
- struct eventpoll *ep_cur, *ep_next;
-
- ret = ep_call_nested(&poll_loop_ncalls,
+ return ep_call_nested(&poll_loop_ncalls,
ep_loop_check_proc, file, ep, current);
- /* clear visited list */
- list_for_each_entry_safe(ep_cur, ep_next, &visited_list,
- visited_list_link) {
- ep_cur->visited = 0;
- list_del(&ep_cur->visited_list_link);
- }
- return ret;
}
static void clear_tfile_check_list(void)
@@ -2199,6 +2186,7 @@ int do_epoll_ctl(int epfd, int op, int f
error = epoll_mutex_lock(&epmutex, 0, nonblock);
if (error)
goto error_tgt_fput;
+ loop_check_gen++;
full_check = 1;
if (is_file_epoll(tf.file)) {
error = -ELOOP;
@@ -2262,6 +2250,7 @@ int do_epoll_ctl(int epfd, int op, int f
error_tgt_fput:
if (full_check) {
clear_tfile_check_list();
+ loop_check_gen++;
mutex_unlock(&epmutex);
}
Powered by blists - more mailing lists