On Wed, Oct 24 2007, James Bottomley wrote:
> On Wed, 2007-10-24 at 12:17 -0700, Andrew Morton wrote:
> > On Wed, 24 Oct 2007 11:59:30 -0700 "Ed Lin" <ed.lin@xxxxxxxxxxx> wrote:
> >
> > > The shared tag issue was not fixed yet. Kernel panic
> > > happened while running I/O test in kernel 2.6.23
> > > (information attached). After applying the patch I posted
> > > (or the version James modified), panic disappeared.
> > > Switch back to standard kernel, panic again.
> >
> > Did either of those patches get merged in 2.6.24-rc1?
>
> No ... Jens did one instead (commit
> f3da54ba140c6427fa4a32913e1bf406f41b5dda), which now looks like it might
> not have fixed the issue.
I think there's one more bug there, for shared maps. For the locking to
work, only the tag map and tag bit map may be shared (incidentally, I
was just explaining this to Nick yesterday, but I apparently didn't
review the code well enough myself). But we also share the busy list!
The busy_list must be queue private, or we need a block_queue_tag
covering lock as well.
So we have to move the busy_list to the queue. This'll work fine, and
it'll actually also fix a problem with blk_queue_invalidate_tags() which
will invalidate tags across all shared queues. This is a bit confusing,
the low level driver should call it for each queue seperately since
otherwise you cannot kill tags on just a single queue for eg a hard
drive that stops responding. Since the function has no callers
currently, it's not an issue.
Please test.
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index a8a1810..56f2646 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -791,7 +791,6 @@ static int __blk_free_tags(struct blk_queue_tag *bqt)
retval = atomic_dec_and_test(&bqt->refcnt);
if (retval) {
BUG_ON(bqt->busy);
- BUG_ON(!list_empty(&bqt->busy_list));
kfree(bqt->tag_index);
bqt->tag_index = NULL;
@@ -903,7 +902,6 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
if (init_tag_map(q, tags, depth))
goto fail;
- INIT_LIST_HEAD(&tags->busy_list);
tags->busy = 0;
atomic_set(&tags->refcnt, 1);
return tags;
@@ -954,6 +952,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth,
*/
q->queue_tags = tags;
q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
+ INIT_LIST_HEAD(&q->tag_busy_list);
return 0;
fail:
kfree(tags);
@@ -1122,7 +1121,7 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
rq->tag = tag;
bqt->tag_index[tag] = rq;
blkdev_dequeue_request(rq);
- list_add(&rq->queuelist, &bqt->busy_list);
+ list_add(&rq->queuelist, &q->tag_busy_list);
bqt->busy++;
return 0;
}
@@ -1143,11 +1142,10 @@ EXPORT_SYMBOL(blk_queue_start_tag);
**/
void blk_queue_invalidate_tags(struct request_queue *q)
{
- struct blk_queue_tag *bqt = q->queue_tags;
struct list_head *tmp, *n;
struct request *rq;
- list_for_each_safe(tmp, n, &bqt->busy_list) {
+ list_for_each_safe(tmp, n, &q->tag_busy_list) {
rq = list_entry_rq(tmp);
if (rq->tag == -1) {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index bbf906a..8396db2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -341,7 +341,6 @@ enum blk_queue_state {
struct blk_queue_tag {
struct request **tag_index; /* map of busy tags */
unsigned long *tag_map; /* bit map of free/busy tags */
- 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 */
@@ -435,6 +434,7 @@ struct request_queue
unsigned int dma_alignment;
struct blk_queue_tag *queue_tags;
+ struct list_head tag_busy_list;
unsigned int nr_sorted;
unsigned int in_flight;
--
Jens Axboe
-
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