linux-kernel - [PATCH] aio: simplify read

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Message-ID: <20190607175413.GA29187@redhat.com>
Date:   Fri, 7 Jun 2019 19:54:13 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Benjamin LaHaise <bcrl@...ck.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        David Laight <David.Laight@...LAB.COM>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Eric Wong <e@...24.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>, linux-aio@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] aio: simplify read_events()

Change wait_event_hrtimeout() to not call __wait_event_hrtimeout()
if timeout == 0, this matches other _timeout() helpers in wait.h.

This allows to simplify its only user, read_events(), it no longer
needs to optimize the "until == 0" case by hand.

Note: this patch doesn't use ___wait_cond_timeout because _hrtimeout()
also differs in that it returns 0 if succeeds and -ETIME on timeout.
Perhaps we should change this to make it fully compatible with other
helpers.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/aio.c             | 9 +++------
 include/linux/wait.h | 4 ++--
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 5bdbef0..2bb3f2e 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1289,12 +1289,9 @@ static long read_events(struct kioctx *ctx, long min_nr, long nr,
 	 * the ringbuffer empty. So in practice we should be ok, but it's
 	 * something to be aware of when touching this code.
 	 */
-	if (until == 0)
-		aio_read_events(ctx, min_nr, nr, event, &ret);
-	else
-		wait_event_interruptible_hrtimeout(ctx->wait,
-				aio_read_events(ctx, min_nr, nr, event, &ret),
-				until);
+	wait_event_interruptible_hrtimeout(ctx->wait,
+			aio_read_events(ctx, min_nr, nr, event, &ret),
+			until);
 	return ret;
 }
 
diff --git a/include/linux/wait.h b/include/linux/wait.h
index b6f77cf..ddb9596 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -527,7 +527,7 @@ do {										\
 ({										\
 	int __ret = 0;								\
 	might_sleep();								\
-	if (!(condition))							\
+	if (!(condition) && (timeout))						\
 		__ret = __wait_event_hrtimeout(wq_head, condition, timeout,	\
 					       TASK_UNINTERRUPTIBLE);		\
 	__ret;									\
@@ -553,7 +553,7 @@ do {										\
 ({										\
 	long __ret = 0;								\
 	might_sleep();								\
-	if (!(condition))							\
+	if (!(condition) && (timeout))						\
 		__ret = __wait_event_hrtimeout(wq, condition, timeout,		\
 					       TASK_INTERRUPTIBLE);		\
 	__ret;									\
-- 
2.5.0