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Subject[PATCH 77/91] block: add proper state guards to __elv_next_request
2.6.27-longterm review patch.  If anyone has any objections, please let us know.

------------------

commit 0a58e077eb600d1efd7e54ad9926a75a39d7f8ae upstream.

blk_cleanup_queue() calls elevator_exit() and after this, we can't
touch the elevator without oopsing. __elv_next_request() must check
for this state because in the refcounted queue model, we can still
call it after blk_cleanup_queue() has been called.

This was reported as causing an oops attributable to scsi.

[WT: in 2.6.27, __elv_next_request() is in elevator.c]

Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
block/clk.h | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

Index: longterm-2.6.27/block/elevator.c
===================================================================
--- longterm-2.6.27.orig/block/elevator.c 2012-02-05 22:34:32.624915301 +0100
+++ longterm-2.6.27/block/elevator.c 2012-02-05 22:34:45.849915230 +0100
@@ -729,7 +729,8 @@
return rq;
}

- if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
+ if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags) ||
+ !q->elevator->ops->elevator_dispatch_fn(q, 0))
return NULL;
}
}



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