The patch titled
Subject: epoll: rename global epmutex
has been added to the -mm mm-nonmm-unstable branch. Its filename is
epoll-rename-global-epmutex.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/epoll-rename-global-epmutex.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: epoll: rename global epmutex
Date: Tue, 11 Apr 2023 16:41:59 -0700
As of 4f04cbaf128 ("epoll: use refcount to reduce ep_mutex contention"),
this lock is now specific to nesting cases - inserting an epoll fd onto
another epoll fd. Rename the lock to be less generic.
Link: https://lkml.kernel.org/r/20230411234159.20421-1-dave@xxxxxxxxxxxx
Signed-off-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
--- a/fs/eventpoll.c~epoll-rename-global-epmutex
+++ a/fs/eventpoll.c
@@ -43,7 +43,7 @@
* LOCKING:
* There are three level of locking required by epoll :
*
- * 1) epmutex (mutex)
+ * 1) epnested_mutex (mutex)
* 2) ep->mtx (mutex)
* 3) ep->lock (rwlock)
*
@@ -57,8 +57,8 @@
* we need a lock that will allow us to sleep. This lock is a
* mutex (ep->mtx). It is acquired during the event transfer loop,
* during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
- * The epmutex is acquired when inserting an epoll fd onto another epoll
- * fd. We do this so that we walk the epoll tree and ensure that this
+ * The epnested_mutex is acquired when inserting an epoll fd onto another
+ * epoll fd. We do this so that we walk the epoll tree and ensure that this
* insertion does not create a cycle of epoll file descriptors, which
* could lead to deadlock. We need a global mutex to prevent two
* simultaneous inserts (A into B and B into A) from racing and
@@ -74,9 +74,9 @@
* of epoll file descriptors, we use the current recursion depth as
* the lockdep subkey.
* It is possible to drop the "ep->mtx" and to use the global
- * mutex "epmutex" (together with "ep->lock") to have it working,
+ * mutex "epnested_mutex" (together with "ep->lock") to have it working,
* but having "ep->mtx" will make the interface more scalable.
- * Events that require holding "epmutex" are very rare, while for
+ * Events that require holding "epnested_mutex" are very rare, while for
* normal operations the epoll private "ep->mtx" will guarantee
* a better scalability.
*/
@@ -248,7 +248,7 @@ struct ep_pqueue {
static long max_user_watches __read_mostly;
/* Used for cycles detection */
-static DEFINE_MUTEX(epmutex);
+static DEFINE_MUTEX(epnested_mutex);
static u64 loop_check_gen = 0;
@@ -263,7 +263,7 @@ static struct kmem_cache *pwq_cache __re
/*
* List of files with newly added links, where we may need to limit the number
- * of emanating paths. Protected by the epmutex.
+ * of emanating paths. Protected by the epnested_mutex.
*/
struct epitems_head {
struct hlist_head epitems;
@@ -1337,7 +1337,7 @@ static void ep_rbtree_insert(struct even
* is connected to n file sources. In this case each file source has 1 path
* of length 1. Thus, the numbers below should be more than sufficient. These
* path limits are enforced during an EPOLL_CTL_ADD operation, since a modify
- * and delete can't add additional paths. Protected by the epmutex.
+ * and delete can't add additional paths. Protected by the epnested_mutex.
*/
static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 };
static int path_count[PATH_ARR_SIZE];
@@ -2167,7 +2167,7 @@ int do_epoll_ctl(int epfd, int op, int f
* We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when
* the epoll file descriptor is attaching directly to a wakeup source,
* unless the epoll file descriptor is nested. The purpose of taking the
- * 'epmutex' on add is to prevent complex toplogies such as loops and
+ * 'epnested_mutex' on add is to prevent complex toplogies such as loops and
* deep wakeup paths from forming in parallel through multiple
* EPOLL_CTL_ADD operations.
*/
@@ -2178,7 +2178,7 @@ int do_epoll_ctl(int epfd, int op, int f
if (READ_ONCE(f.file->f_ep) || ep->gen == loop_check_gen ||
is_file_epoll(tf.file)) {
mutex_unlock(&ep->mtx);
- error = epoll_mutex_lock(&epmutex, 0, nonblock);
+ error = epoll_mutex_lock(&epnested_mutex, 0, nonblock);
if (error)
goto error_tgt_fput;
loop_check_gen++;
@@ -2239,7 +2239,7 @@ error_tgt_fput:
if (full_check) {
clear_tfile_check_list();
loop_check_gen++;
- mutex_unlock(&epmutex);
+ mutex_unlock(&epnested_mutex);
}
fdput(tf);
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
epoll-rename-global-epmutex.patch
