On Tue, Jan 29 2008, Andrew Vasquez wrote:
> On Tue, 29 Jan 2008, Jens Axboe wrote:
> 
> > Great, thanks for confirming. It does look like a clear bug in cciss, it
> > just got exposed now that it uses proper end request handling. We never
> > need to clear ->data_len, since for blk_fs_request() it will be cleared
> > on init. So just setting a residual count there for blk_fs_request()
> > like cciss does is fine.
> > 
> > Anyway, it's in my pending queue for Linus.
> > 
> 
> 
> Hmm, probably not related to the block changes in your tree, but I'm
> seeing yet another problem after working (compile jobs) the machine:
> 
>       [   61.423922] BUG: spinlock recursion on CPU#2, kjournald/2317
>       [   61.427843]  lock: ffff81042c5a4988, .magic: dead4ead, .owner: 
> kjournald/2317, .owner_cpu: 2
>       [   61.427843] Pid: 2317, comm: kjournald Not tainted 2.6.24 #45
>       [   61.427843] 
>       [   61.427843] Call Trace:
>       [   61.427843]  [<ffffffff803332e1>] _raw_spin_lock+0xe9/0x12a
>       [   61.427843]  [<ffffffff80324ccf>] as_merged_requests+0xfe/0x115
>       [   61.427843]  [<ffffffff8031b558>] elv_merge_requests+0x1f/0x45
>       [   61.427843]  [<ffffffff8031e6f7>] attempt_merge+0x281/0x347
>       [   61.427843]  [<ffffffff8031f153>] __make_request+0x1e6/0x598
>       [   61.427843]  [<ffffffff8031d6ea>] generic_make_request+0x1c8/0x276
>       [   61.427843]  [<ffffffff8031d7f9>] submit_bio+0x61/0xdb
>       [   61.427843]  [<ffffffff8029b0d2>] submit_bh+0xe2/0x118
>       [   61.427843]  [<ffffffff802f69f3>] journal_do_submit_data+0x28/0x39
>       [   61.427843]  [<ffffffff802f77da>] 
> journal_commit_transaction+0xdbe/0x1394
>       [   61.427843]  [<ffffffff802381a8>] lock_timer_base+0x26/0x4e
>       [   61.427843]  [<ffffffff802fb85f>] kjournald+0x104/0x373
>       [   61.427843]  [<ffffffff80242087>] autoremove_wake_function+0x0/0x2e
>       [   61.427843]  [<ffffffff802fb75b>] kjournald+0x0/0x373
>       [   61.427843]  [<ffffffff80241cd4>] kthread+0x3d/0x61
>       [   61.427843]  [<ffffffff8020c0e8>] child_rip+0xa/0x12
>       [   61.427843]  [<ffffffff80241c97>] kthread+0x0/0x61
>       [   61.427843]  [<ffffffff8020c0de>] child_rip+0x0/0x12

Ah crap, I see the problem, nioc is most often equal to rioc. Dang.
Please try this bandaid, will push a real fix now.

diff --git a/block/as-iosched.c b/block/as-iosched.c
index b201d16..5ca55b0 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1275,9 +1275,15 @@ static void as_merged_requests(struct request_queue *q, 
struct request *req,
                         * Don't copy here but swap, because when anext is
                         * removed below, it must contain the unused context
                         */
-                       double_spin_lock(&rioc->lock, &nioc->lock, rioc < nioc);
+                       if (rioc != nioc)
+                               double_spin_lock(&rioc->lock, &nioc->lock, rioc 
< nioc);
+                       else
+                               spin_lock(&rioc->lock);
                        swap_io_context(&rioc, &nioc);
-                       double_spin_unlock(&rioc->lock, &nioc->lock, rioc < 
nioc);
+                       if (rioc != nioc)
+                               double_spin_unlock(&rioc->lock, &nioc->lock, 
rioc < nioc);
+                       else
+                               spin_unlock(&rioc->lock);
                }
        }
 

-- 
Jens Axboe

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