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SubjectRe: [PATCH 05/10] block: remove per-queue plugging
On Mon, 18 Apr 2011 08:19:22 +1000 NeilBrown <neilb@suse.de> wrote:

> So can we please have my original patch applied? (Revised version using
> list_splice_init included below).

I hadn't adjusted that one properly for the recent code shuffling.
This one is actually tested...

Thanks,
NeilBrown

From 325b1c12b6165002022bd7b599f95c0331491cb3 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Mon, 18 Apr 2011 14:06:05 +1000
Subject: [PATCH] Enhance new plugging support to support general callbacks.

md/raid requires an unplug callback, but as it does not uses
requests the current code cannot provide one.

So allow arbitrary callbacks to be attached to the blk_plug.

Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
---
block/blk-core.c | 20 ++++++++++++++++++++
include/linux/blkdev.h | 7 ++++++-
2 files changed, 26 insertions(+), 1 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 78b7b0c..77edf05 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2638,6 +2638,7 @@ void blk_start_plug(struct blk_plug *plug)

plug->magic = PLUG_MAGIC;
INIT_LIST_HEAD(&plug->list);
+ INIT_LIST_HEAD(&plug->cb_list);
plug->should_sort = 0;

/*
@@ -2678,6 +2679,24 @@ static void queue_unplugged(struct request_queue *q, unsigned int depth,
q->unplugged_fn(q);
}

+static void flush_plug_callbacks(struct blk_plug *plug)
+{
+ LIST_HEAD(callbacks);
+
+ if (list_empty(&plug->cb_list))
+ return;
+
+ list_splice_init(&plug->cb_list, &callbacks);
+
+ while (!list_empty(&callbacks)) {
+ struct blk_plug_cb *cb = list_first_entry(&callbacks,
+ struct blk_plug_cb,
+ list);
+ list_del(&cb->list);
+ cb->callback(cb);
+ }
+}
+
void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
{
struct request_queue *q;
@@ -2688,6 +2707,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)

BUG_ON(plug->magic != PLUG_MAGIC);

+ flush_plug_callbacks(plug);
if (list_empty(&plug->list))
return;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index ec0357d..f3f7879 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -860,8 +860,13 @@ extern void blk_put_queue(struct request_queue *);
struct blk_plug {
unsigned long magic;
struct list_head list;
+ struct list_head cb_list;
unsigned int should_sort;
};
+struct blk_plug_cb {
+ struct list_head list;
+ void (*callback)(struct blk_plug_cb *);
+};

extern void blk_start_plug(struct blk_plug *);
extern void blk_finish_plug(struct blk_plug *);
@@ -887,7 +892,7 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk)
{
struct blk_plug *plug = tsk->plug;

- return plug && !list_empty(&plug->list);
+ return plug && (!list_empty(&plug->list) || !list_empty(&plug->cb_list));
}

/*
--
1.7.3.4


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