Il 30/05/2014 10:15, Liu Ping Fan ha scritto:
When running io stress test on large latency scsi-disk, e.g guest with virtscsi
on a nfs image. It can trigger the BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
in blk_start_request().
Since there is a race between latency "finishing" scmd and the re-allocated scmd.
I.e a request is still referred by a scmd, but we had turn it back to
slab.
This series introduces the ref on scmd to exclude this issue, and the following is ref rules.
inc ref rules is like the following:
When setup a scmd, inited as 1. When add a timer inc 1.
dec ref rules is like the following:
-for the normal ref
scsi_done() will drop the ref when fail to acquire REQ_ATOM_COMPLETE immediately
or drop the ref by scsi_end_request()
or drop by return SUCCESS_REMOVE
-for a timer ref
when deleting timer, if !list_empty(timeout_list), then there is a timer ref, and
drop it.
patch1-2: fix the current potential bug
patch3~6: prepare for the mechanism for the ref
patch7: the ref rules core
patch8-9: e.g and test-issue for the new mechanism. Since lack of many virtscsi background,
patch8 may be poor and need to be improved :)
Note: all the patches are based on rhel7, whose kernel version is linux-3.10.
I will rebase them onto the latest commit if my method is practical.
This series is not necessary, this is a bug in the virtscsi driver. I
have a ten line patch to fix it, but I haven't yet tested it properly.
Paolo
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