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Date: Mon, 10 Jan 2011 11:47:20 -0800 (PST)
From: Luben Tuikov <ltuikov@...oo.com>
To: jaxboe@...ionio.com, linux-scsi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] [BLOCK] Tags should form increasing sequence
Signed-off-by: Luben Tuikov <ltuikov@...oo.com>
---
block/blk-tag.c | 19 +++++++++++++++----
include/linux/blkdev.h | 1 +
2 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/block/blk-tag.c b/block/blk-tag.c
index ece65fc..744cea6 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -130,6 +130,7 @@ init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
tags->max_depth = depth;
tags->tag_index = tag_index;
tags->tag_map = tag_map;
+ tags->last_tag = -1;
return 0;
fail:
@@ -222,7 +223,7 @@ int blk_queue_resize_tags(struct request_queue *q, int new_depth)
struct blk_queue_tag *bqt = q->queue_tags;
struct request **tag_index;
unsigned long *tag_map;
- int max_depth, nr_ulongs;
+ int max_depth, nr_ulongs, last_tag;
if (!bqt)
return -ENXIO;
@@ -251,6 +252,7 @@ int blk_queue_resize_tags(struct request_queue *q, int new_depth)
tag_index = bqt->tag_index;
tag_map = bqt->tag_map;
max_depth = bqt->real_max_depth;
+ last_tag = bqt->last_tag;
if (init_tag_map(q, bqt, new_depth))
return -ENOMEM;
@@ -258,6 +260,7 @@ int blk_queue_resize_tags(struct request_queue *q, int new_depth)
memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
+ bqt->last_tag = last_tag;
kfree(tag_index);
kfree(tag_map);
@@ -337,7 +340,7 @@ EXPORT_SYMBOL(blk_queue_end_tag);
int blk_queue_start_tag(struct request_queue *q, struct request *rq)
{
struct blk_queue_tag *bqt = q->queue_tags;
- unsigned max_depth;
+ int max_depth;
int tag;
if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
@@ -358,18 +361,26 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
max_depth = bqt->max_depth;
if (!rq_is_sync(rq) && max_depth > 1) {
max_depth -= 2;
- if (!max_depth)
+ if (max_depth <= 0)
max_depth = 1;
if (q->in_flight[BLK_RW_ASYNC] > max_depth)
return 1;
}
+ if (bqt->last_tag == bqt->max_depth-1)
+ bqt->last_tag = -1;
+
do {
- tag = find_first_zero_bit(bqt->tag_map, max_depth);
+ tag = find_next_zero_bit(bqt->tag_map,
+ max_depth,
+ bqt->last_tag+1);
if (tag >= max_depth)
return 1;
} while (test_and_set_bit_lock(tag, bqt->tag_map));
+
+ bqt->last_tag = tag;
+
/*
* We need lock ordering semantics given by test_and_set_bit_lock.
* See blk_queue_end_tag for details.
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 36ab42c..852dc45 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -224,6 +224,7 @@ struct blk_queue_tag {
int max_depth; /* what we will send to device */
int real_max_depth; /* what the array can hold */
atomic_t refcnt; /* map can be shared */
+ int last_tag;
};
#define BLK_SCSI_MAX_CMDS (256)
--
1.7.2.2.165.gbc382
--
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