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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 02/27] epoll: get rid of epitem->nwait
Date: Sun,  4 Oct 2020 03:39:04 +0100	[thread overview]
Message-ID: <20201004023929.2740074-2-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>

we use it only to indicate allocation failures within queueing
callback back to ep_insert().  Might as well use epq.epi for that
reporting...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/eventpoll.c | 46 ++++++++++++++++++++--------------------------
 1 file changed, 20 insertions(+), 26 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index ae41868d9b35..44aca681d897 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -172,9 +172,6 @@ struct epitem {
 	/* The file descriptor information this item refers to */
 	struct epoll_filefd ffd;
 
-	/* Number of active wait queue attached to poll operations */
-	int nwait;
-
 	/* List containing poll wait queues */
 	struct eppoll_entry *pwqlist;
 
@@ -351,12 +348,6 @@ static inline struct epitem *ep_item_from_wait(wait_queue_entry_t *p)
 	return container_of(p, struct eppoll_entry, wait)->base;
 }
 
-/* Get the "struct epitem" from an epoll queue wrapper */
-static inline struct epitem *ep_item_from_epqueue(poll_table *p)
-{
-	return container_of(p, struct ep_pqueue, pt)->epi;
-}
-
 /* Initialize the poll safe wake up structure */
 static void ep_nested_calls_init(struct nested_calls *ncalls)
 {
@@ -1307,24 +1298,28 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v
 static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
 				 poll_table *pt)
 {
-	struct epitem *epi = ep_item_from_epqueue(pt);
+	struct ep_pqueue *epq = container_of(pt, struct ep_pqueue, pt);
+	struct epitem *epi = epq->epi;
 	struct eppoll_entry *pwq;
 
-	if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
-		init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
-		pwq->whead = whead;
-		pwq->base = epi;
-		if (epi->event.events & EPOLLEXCLUSIVE)
-			add_wait_queue_exclusive(whead, &pwq->wait);
-		else
-			add_wait_queue(whead, &pwq->wait);
-		pwq->next = epi->pwqlist;
-		epi->pwqlist = pwq;
-		epi->nwait++;
-	} else {
-		/* We have to signal that an error occurred */
-		epi->nwait = -1;
+	if (unlikely(!epi))	// an earlier allocation has failed
+		return;
+
+	pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL);
+	if (unlikely(!pwq)) {
+		epq->epi = NULL;
+		return;
 	}
+
+	init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
+	pwq->whead = whead;
+	pwq->base = epi;
+	if (epi->event.events & EPOLLEXCLUSIVE)
+		add_wait_queue_exclusive(whead, &pwq->wait);
+	else
+		add_wait_queue(whead, &pwq->wait);
+	pwq->next = epi->pwqlist;
+	epi->pwqlist = pwq;
 }
 
 static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
@@ -1510,7 +1505,6 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 	epi->ep = ep;
 	ep_set_ffd(&epi->ffd, tfile, fd);
 	epi->event = *event;
-	epi->nwait = 0;
 	epi->next = EP_UNACTIVE_PTR;
 	if (epi->event.events & EPOLLWAKEUP) {
 		error = ep_create_wakeup_source(epi);
@@ -1555,7 +1549,7 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 	 * high memory pressure.
 	 */
 	error = -ENOMEM;
-	if (epi->nwait < 0)
+	if (!epq.epi)
 		goto error_unregister;
 
 	/* We have to drop the new item inside our item list to keep track of it */
-- 
2.11.0


  reply	other threads:[~2020-10-04  2:41 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   ` Al Viro [this message]
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   ` [RFC PATCH 12/27] get rid of ep_push_nested() Al Viro
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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