[PATCH] blk: remove blk_queue_tag->real_max_depth optimization
blk_queue_tag->real_max_depth was used to optimize out unnecessary
allocations/frees on tag resize. However, the whole thing was very broken -
tag_map was never allocated to real_max_depth resulting in access beyond the
end of the map, bits in [max_depth..real_max_depth] were set when initializing
a map and copied when resizing resulting in pre-occupied tags.
As the gain of the optimization is very small, well, almost nill, remove the
whole thing.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index 808390c..896d17c 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -717,7 +717,7 @@
{
struct blk_queue_tag *bqt = q->queue_tags;
- if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
+ if (unlikely(bqt == NULL || tag >= bqt->max_depth))
return NULL;
return bqt->tag_index[tag];
@@ -775,9 +775,9 @@
static int
init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
{
- int bits, i;
struct request **tag_index;
unsigned long *tag_map;
+ int nr_ulongs;
if (depth > q->nr_requests * 2) {
depth = q->nr_requests * 2;
@@ -789,24 +789,17 @@
if (!tag_index)
goto fail;
- bits = (depth / BLK_TAGS_PER_LONG) + 1;
- tag_map = kmalloc(bits * sizeof(unsigned long), GFP_ATOMIC);
+ nr_ulongs = ALIGN(depth, BLK_TAGS_PER_LONG) / BLK_TAGS_PER_LONG;
+ tag_map = kmalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
if (!tag_map)
goto fail;
memset(tag_index, 0, depth * sizeof(struct request *));
- memset(tag_map, 0, bits * sizeof(unsigned long));
+ memset(tag_map, 0, nr_ulongs * sizeof(unsigned long));
tags->max_depth = depth;
- tags->real_max_depth = bits * BITS_PER_LONG;
tags->tag_index = tag_index;
tags->tag_map = tag_map;
- /*
- * set the upper bits if the depth isn't a multiple of the word size
- */
- for (i = depth; i < bits * BLK_TAGS_PER_LONG; i++)
- __set_bit(i, tag_map);
-
return 0;
fail:
kfree(tag_index);
@@ -871,32 +864,24 @@
struct blk_queue_tag *bqt = q->queue_tags;
struct request **tag_index;
unsigned long *tag_map;
- int bits, max_depth;
+ int max_depth, nr_ulongs;
if (!bqt)
return -ENXIO;
/*
- * don't bother sizing down
- */
- if (new_depth <= bqt->real_max_depth) {
- bqt->max_depth = new_depth;
- return 0;
- }
-
- /*
* save the old state info, so we can copy it back
*/
tag_index = bqt->tag_index;
tag_map = bqt->tag_map;
- max_depth = bqt->real_max_depth;
+ max_depth = bqt->max_depth;
if (init_tag_map(q, bqt, new_depth))
return -ENOMEM;
memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
- bits = max_depth / BLK_TAGS_PER_LONG;
- memcpy(bqt->tag_map, tag_map, bits * sizeof(unsigned long));
+ nr_ulongs = ALIGN(max_depth, BLK_TAGS_PER_LONG) / BLK_TAGS_PER_LONG;
+ memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
kfree(tag_index);
kfree(tag_map);
@@ -926,7 +911,7 @@
BUG_ON(tag == -1);
- if (unlikely(tag >= bqt->real_max_depth))
+ if (unlikely(tag >= bqt->max_depth))
return;
if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {