releases/2.6.23.2/block-fix-bad-sharing-of-tag-busy-list-on-queues-with-shared-tag-maps.patch

   1 From stable-bounces@linux.kernel.org Tue Oct 30 03:21:13 2007
   2 From: Jens Axboe <jens.axboe@oracle.com>
   3 Date: Tue, 30 Oct 2007 11:18:15 +0100
   4 Subject: BLOCK: Fix bad sharing of tag busy list on queues with shared tag maps
   5 To: stable@kernel.org
   6 Message-ID: <20071030101815.GO4993@kernel.dk>
   7 Content-Disposition: inline
   8
   9 From: Jens Axboe <jens.axboe@oracle.com>
  10
  11 patch 6eca9004dfcb274a502438a591df5b197690afb1 in mainline.
  12
  13 For the locking to work, only the tag map and tag bit map may be shared
  14 (incidentally, I was just explaining this to Nick yesterday, but I
  15 apparently didn't review the code well enough myself). But we also share
  16 the busy list!  The busy_list must be queue private, or we need a
  17 block_queue_tag covering lock as well.
  18
  19 So we have to move the busy_list to the queue. This'll work fine, and
  20 it'll actually also fix a problem with blk_queue_invalidate_tags() which
  21 will invalidate tags across all shared queues. This is a bit confusing,
  22 the low level driver should call it for each queue seperately since
  23 otherwise you cannot kill tags on just a single queue for eg a hard
  24 drive that stops responding. Since the function has no callers
  25 currently, it's not an issue.
  26
  27 This is fixed with commit 6eca9004dfcb274a502438a591df5b197690afb1 in
  28 Linus' tree.
  29
  30 Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
  31 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  32
  33 ---
  34  block/ll_rw_blk.c      |    8 +++-----
  35  include/linux/blkdev.h |    2 +-
  36  2 files changed, 4 insertions(+), 6 deletions(-)
  37
  38 --- a/block/ll_rw_blk.c
  39 +++ b/block/ll_rw_blk.c
  40 @@ -819,7 +819,6 @@ static int __blk_free_tags(struct blk_qu
  41         retval = atomic_dec_and_test(&bqt->refcnt);
  42         if (retval) {
  43                 BUG_ON(bqt->busy);
  44 -               BUG_ON(!list_empty(&bqt->busy_list));
  45
  46                 kfree(bqt->tag_index);
  47                 bqt->tag_index = NULL;
  48 @@ -931,7 +930,6 @@ static struct blk_queue_tag *__blk_queue
  49         if (init_tag_map(q, tags, depth))
  50                 goto fail;
  51
  52 -       INIT_LIST_HEAD(&tags->busy_list);
  53         tags->busy = 0;
  54         atomic_set(&tags->refcnt, 1);
  55         return tags;
  56 @@ -982,6 +980,7 @@ int blk_queue_init_tags(struct request_q
  57          */
  58         q->queue_tags = tags;
  59         q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
  60 +       INIT_LIST_HEAD(&q->tag_busy_list);
  61         return 0;
  62  fail:
  63         kfree(tags);
  64 @@ -1152,7 +1151,7 @@ int blk_queue_start_tag(struct request_q
  65         rq->tag = tag;
  66         bqt->tag_index[tag] = rq;
  67         blkdev_dequeue_request(rq);
  68 -       list_add(&rq->queuelist, &bqt->busy_list);
  69 +       list_add(&rq->queuelist, &q->tag_busy_list);
  70         bqt->busy++;
  71         return 0;
  72  }
  73 @@ -1173,11 +1172,10 @@ EXPORT_SYMBOL(blk_queue_start_tag);
  74   **/
  75  void blk_queue_invalidate_tags(struct request_queue *q)
  76  {
  77 -       struct blk_queue_tag *bqt = q->queue_tags;
  78         struct list_head *tmp, *n;
  79         struct request *rq;
  80
  81 -       list_for_each_safe(tmp, n, &bqt->busy_list) {
  82 +       list_for_each_safe(tmp, n, &q->tag_busy_list) {
  83                 rq = list_entry_rq(tmp);
  84
  85                 if (rq->tag == -1) {
  86 --- a/include/linux/blkdev.h
  87 +++ b/include/linux/blkdev.h
  88 @@ -356,7 +356,6 @@ enum blk_queue_state {
  89  struct blk_queue_tag {
  90         struct request **tag_index;     /* map of busy tags */
  91         unsigned long *tag_map;         /* bit map of free/busy tags */
  92 -       struct list_head busy_list;     /* fifo list of busy tags */
  93         int busy;                       /* current depth */
  94         int max_depth;                  /* what we will send to device */
  95         int real_max_depth;             /* what the array can hold */
  96 @@ -451,6 +450,7 @@ struct request_queue
  97         unsigned int            dma_alignment;
  98
  99         struct blk_queue_tag    *queue_tags;
 100 +       struct list_head        tag_busy_list;
 101
 102         unsigned int            nr_sorted;
 103         unsigned int            in_flight;