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authorTejun Heo <htejun@gmail.com>2005-08-05 13:28:11 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-08-05 13:43:16 -0700
commitba02508248e90a9d696aebd18b48a3290235b53c (patch)
tree4167aecae57a5ceab6392e54189a271f3dfdebf8
parentc7546f8f03f5a4fa612605b6be930234d6026860 (diff)
[PATCH] blk: fix tag shrinking (revive real_max_size)
My patch in commit fa72b903f75e4f0f0b2c2feed093005167da4023 incorrectly removed blk_queue_tag->real_max_depth. The original resize implementation was incorrect in the following points. * actual allocation size of tag_index was shorter than real_max_size, but assumed to be of the same size, possibly causing memory access beyond the allocated area. * bits in tag_map between max_deptn and real_max_depth were initialized to 1's, making the tags permanently reserved. In an attempt to fix above two bugs, I had removed allocation optimization in init_tag_map and real_max_size. Tag map/index were allocated and freed immediately during resize. Unfortunately, I wasn't considering that tag map/index can be resized dynamically with tags beyond new_depth active. This led to accessing freed area after shrinking tags and led to the following bug reporting thread on linux-scsi. http://marc.theaimsgroup.com/?l=linux-scsi&m=112319898111885&w=2 To fix the problem, I've revived real_max_depth without allocation optimization in init_tag_map, and Andrew Vasquez confirmed that the problem was fixed. As Jens is not going to be available for a week, he asked me to make sure that this patch reaches you. http://marc.theaimsgroup.com/?l=linux-scsi&m=112325778530886&w=2 Also, a comment was added to make sure that real_max_size is needed for dynamic shrinking. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--drivers/block/ll_rw_blk.c18
-rw-r--r--include/linux/blkdev.h1
2 files changed, 16 insertions, 3 deletions
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index 692a5fced76..3c818544475 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -719,7 +719,7 @@ struct request *blk_queue_find_tag(request_queue_t *q, int tag)
{
struct blk_queue_tag *bqt = q->queue_tags;
- if (unlikely(bqt == NULL || tag >= bqt->max_depth))
+ if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
return NULL;
return bqt->tag_index[tag];
@@ -798,6 +798,7 @@ init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
memset(tag_index, 0, depth * sizeof(struct request *));
memset(tag_map, 0, nr_ulongs * sizeof(unsigned long));
+ tags->real_max_depth = depth;
tags->max_depth = depth;
tags->tag_index = tag_index;
tags->tag_map = tag_map;
@@ -872,11 +873,22 @@ int blk_queue_resize_tags(request_queue_t *q, int new_depth)
return -ENXIO;
/*
+ * if we already have large enough real_max_depth. just
+ * adjust max_depth. *NOTE* as requests with tag value
+ * between new_depth and real_max_depth can be in-flight, tag
+ * map can not be shrunk blindly here.
+ */
+ 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->max_depth;
+ max_depth = bqt->real_max_depth;
if (init_tag_map(q, bqt, new_depth))
return -ENOMEM;
@@ -913,7 +925,7 @@ void blk_queue_end_tag(request_queue_t *q, struct request *rq)
BUG_ON(tag == -1);
- if (unlikely(tag >= bqt->max_depth))
+ if (unlikely(tag >= bqt->real_max_depth))
/*
* This can happen after tag depth has been reduced.
* FIXME: how about a warning or info message here?
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0881b5cdee3..19bd8e7e11b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -301,6 +301,7 @@ struct blk_queue_tag {
struct list_head busy_list; /* fifo list of busy tags */
int busy; /* current depth */
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 */
};