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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 21/27] take the common part of ep_eventpoll_poll() and ep_item_poll() into helper
Date: Sun,  4 Oct 2020 03:39:23 +0100	[thread overview]
Message-ID: <20201004023929.2740074-21-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 reason why ep_item_poll() can't simply call ep_eventpoll_poll()
(or, better yet, call vfs_poll() in all cases) is that we need to tell
lockdep how deep into the hierarchy of ->mtx we are.  So let's add
a variant of ep_eventpoll_poll() that would take depth explicitly
and turn ep_eventpoll_poll() into wrapper for that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/eventpoll.c | 57 +++++++++++++++++++++++++++------------------------------
 1 file changed, 27 insertions(+), 30 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 39947b71f7af..a50b48d26c55 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -732,6 +732,27 @@ static int ep_eventpoll_release(struct inode *inode, struct file *file)
 static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
 			       int depth);
 
+static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int depth)
+{
+	struct eventpoll *ep = file->private_data;
+	LIST_HEAD(txlist);
+	__poll_t res;
+
+	/* Insert inside our poll wait queue */
+	poll_wait(file, &ep->poll_wait, wait);
+
+	/*
+	 * Proceed to find out if wanted events are really available inside
+	 * the ready list.
+	 */
+	mutex_lock_nested(&ep->mtx, depth);
+	ep_start_scan(ep, &txlist);
+	res = ep_read_events_proc(ep, &txlist, depth + 1);
+	ep_done_scan(ep, &txlist);
+	mutex_unlock(&ep->mtx);
+	return res;
+}
+
 /*
  * Differs from ep_eventpoll_poll() in that internal callers already have
  * the ep->mtx so we need to start from depth=1, such that mutex_lock_nested()
@@ -740,22 +761,14 @@ static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head
 static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt,
 				 int depth)
 {
-	struct eventpoll *ep;
-	LIST_HEAD(txlist);
+	struct file *file = epi->ffd.file;
 	__poll_t res;
 
 	pt->_key = epi->event.events;
-	if (!is_file_epoll(epi->ffd.file))
-		return vfs_poll(epi->ffd.file, pt) & epi->event.events;
-
-	ep = epi->ffd.file->private_data;
-	poll_wait(epi->ffd.file, &ep->poll_wait, pt);
-
-	mutex_lock_nested(&ep->mtx, depth);
-	ep_start_scan(ep, &txlist);
-	res = ep_read_events_proc(ep, &txlist, depth + 1);
-	ep_done_scan(ep, &txlist);
-	mutex_unlock(&ep->mtx);
+	if (!is_file_epoll(file))
+		res = vfs_poll(file, pt);
+	else
+		res = __ep_eventpoll_poll(file, pt, depth);
 	return res & epi->event.events;
 }
 
@@ -786,23 +799,7 @@ static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head
 
 static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait)
 {
-	struct eventpoll *ep = file->private_data;
-	LIST_HEAD(txlist);
-	__poll_t res;
-
-	/* Insert inside our poll wait queue */
-	poll_wait(file, &ep->poll_wait, wait);
-
-	/*
-	 * Proceed to find out if wanted events are really available inside
-	 * the ready list.
-	 */
-	mutex_lock(&ep->mtx);
-	ep_start_scan(ep, &txlist);
-	res = ep_read_events_proc(ep, &txlist, 1);
-	ep_done_scan(ep, &txlist);
-	mutex_unlock(&ep->mtx);
-	return res;
+	return __ep_eventpoll_poll(file, wait, 0);
 }
 
 #ifdef CONFIG_PROC_FS
-- 
2.11.0


  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   ` [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   ` Al Viro [this message]
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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