src/patches/suse-2.6.27.25/patches.suse/dm-mpath-lockdep-irqsave

   1 From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
   2 Subject: dm: Fix lock dependency warning for request based dm
   3 References: bnc#477927
   4
   5 > > From: Christof Schmitt <christof.schmitt@de.ibm.com>
   6 > >
   7 > > Testing with request based dm multipathing and lock dependency checking
   8 > > revealed this problem. Fix this by disabling interrupts when acquiring the
   9 > > map_lock from the ioctl call in __bind and __unbind.
  10 > >
  11 > > It seems that the problem has been introduced with this patch:
  12 > > http://lkml.indiana.edu/hypermail/linux/kernel/0810.0/1067.html
  13
  14 Thank you for your testing request-based dm-multipath and the patch.
  15
  16 Attached is a patch to fix it.
  17 Since request-based dm gets map_lock after taking queue_lock with
  18 interrupt disabled, we have to use save/restore variant.
  19 (By the way, although lockdep warns the deadlock possibility, currently
  20  there should be no such code path in request-based dm where request_fn
  21  is called from the interrupt context.)
  22
  23 I have done simple build and boot testings, but haven't done other
  24 testings (e.g. stress testing) yet.
  25 I will include this patch to the next update after such testings.
  26
  27 Thanks,
  28 Kiyoshi Ueda
  29
  30 Signed-off-by: Nikanth karthikesan <knikanth@suse.de>
  31
  32 Index: linux-2.6.27-SLE11_BRANCH/drivers/md/dm.c
  33 ===================================================================
  34 --- linux-2.6.27-SLE11_BRANCH.orig/drivers/md/dm.c
  35 +++ linux-2.6.27-SLE11_BRANCH/drivers/md/dm.c
  36 @@ -525,12 +525,13 @@ static int queue_io(struct mapped_device
  37  struct dm_table *dm_get_table(struct mapped_device *md)
  38  {
  39         struct dm_table *t;
  40 +       unsigned long flags;
  41
  42 -       read_lock(&md->map_lock);
  43 +       read_lock_irqsave(&md->map_lock, flags);
  44         t = md->map;
  45         if (t)
  46                 dm_table_get(t);
  47 -       read_unlock(&md->map_lock);
  48 +       read_unlock_irqrestore(&md->map_lock, flags);
  49
  50         return t;
  51  }
  52 @@ -1913,6 +1914,7 @@ static int __bind(struct mapped_device *
  53  {
  54         struct request_queue *q = md->queue;
  55         sector_t size;
  56 +       unsigned long flags;
  57
  58         size = dm_table_get_size(t);
  59
  60 @@ -1942,7 +1944,7 @@ static int __bind(struct mapped_device *
  61         if (dm_table_request_based(t) && !blk_queue_stopped(q))
  62                 stop_queue(q);
  63
  64 -       write_lock(&md->map_lock);
  65 +       write_lock_irqsave(&md->map_lock, flags);
  66         md->map = t;
  67         dm_table_set_restrictions(t, q);
  68         dm_table_set_integrity(t, md);
  69 @@ -1951,7 +1953,7 @@ static int __bind(struct mapped_device *
  70         } else {
  71                 set_disk_ro(md->disk, 0);
  72         }
  73 -       write_unlock(&md->map_lock);
  74 +       write_unlock_irqrestore(&md->map_lock, flags);
  75
  76         return 0;
  77  }
  78 @@ -1959,14 +1961,15 @@ static int __bind(struct mapped_device *
  79  static void __unbind(struct mapped_device *md)
  80  {
  81         struct dm_table *map = md->map;
  82 +       unsigned long flags;
  83
  84         if (!map)
  85                 return;
  86
  87         dm_table_event_callback(map, NULL, NULL);
  88 -       write_lock(&md->map_lock);
  89 +       write_lock_irqsave(&md->map_lock, flags);
  90         md->map = NULL;
  91 -       write_unlock(&md->map_lock);
  92 +       write_unlock_irqrestore(&md->map_lock, flags);
  93         dm_table_destroy(map);
  94  }
  95