Messages in this thread | | | Date | Wed, 5 Jan 2011 14:55:51 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH 2/2] block: fix accounting bug on cross partition merges |
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On 2011-01-04 22:00, Greg KH wrote: > On Tue, Jan 04, 2011 at 04:55:13PM +0100, Jerome Marchand wrote: >> Also add a refcount to struct hd_struct to keep the partition in >> memory as long as users exist. We use kref_test_and_get() to ensure >> we don't add a reference to a partition which is going away. > > No, don't do this, use a kref correctly and no such function should be > needed. > >> + } else { >> + part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq)); > > That is the function that should properly increment the reference count > on the object. If the object is "being removed", then it will return > NULL and you need to check that. Do that and you do not need to add:
It doesn't matter if you do it in there of after the fact, since the "lock" (RCU) is being held across the call. See my original suggestion here:
https://lkml.org/lkml/2010/12/17/275
-- Jens Axboe
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