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Message-ID: <f3bfe60a013827942790c89d658f63c920653437.1430414610.git.shli@fb.com>
Date: Thu, 30 Apr 2015 10:45:14 -0700
From: Shaohua Li <shli@...com>
To: <linux-kernel@...r.kernel.org>
CC: <axboe@...com>, <jmoyer@...hat.com>, <hch@....de>, <neilb@...e.de>
Subject: [PATCH 1/5] blk: clean up plug
Current code looks like inner plug gets flushed with a
blk_finish_plug(). Actually it's a nop. All requests/callbacks are added
to current->plug, while only outmost plug is assigned to current->plug.
So inner plug always has empty request/callback list, which makes
blk_flush_plug_list() a nop. This tries to make the code more clear.
Signed-off-by: Shaohua Li <shli@...com>
Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
---
block/blk-core.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index fd154b9..d51ed61 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3031,21 +3031,20 @@ void blk_start_plug(struct blk_plug *plug)
{
struct task_struct *tsk = current;
+ /*
+ * If this is a nested plug, don't actually assign it.
+ */
+ if (tsk->plug)
+ return;
+
INIT_LIST_HEAD(&plug->list);
INIT_LIST_HEAD(&plug->mq_list);
INIT_LIST_HEAD(&plug->cb_list);
-
/*
- * If this is a nested plug, don't actually assign it. It will be
- * flushed on its own.
+ * Store ordering should not be needed here, since a potential
+ * preempt will imply a full memory barrier
*/
- if (!tsk->plug) {
- /*
- * Store ordering should not be needed here, since a potential
- * preempt will imply a full memory barrier
- */
- tsk->plug = plug;
- }
+ tsk->plug = plug;
}
EXPORT_SYMBOL(blk_start_plug);
@@ -3192,10 +3191,11 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
void blk_finish_plug(struct blk_plug *plug)
{
+ if (plug != current->plug)
+ return;
blk_flush_plug_list(plug, false);
- if (plug == current->plug)
- current->plug = NULL;
+ current->plug = NULL;
}
EXPORT_SYMBOL(blk_finish_plug);
--
1.8.1
--
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