On 2020-03-23 04:29, Daniel Wagner wrote:
> On Fri, Mar 20, 2020 at 03:24:13PM -0700, Bart Van Assche wrote:
>> Add a test that triggers the code touched by commit d0930bb8f46b ("blk-mq:
>> Fix a recently introduced regression in blk_mq_realloc_hw_ctxs()"). This
>> test only runs if a recently added fault injection feature is available,
>> namely commit 596444e75705 ("null_blk: Add support for init_hctx() fault
>> injection").
>
> [...]
>
>> +test() {
>> + local i sq=/sys/kernel/config/nullb/nullb0/submit_queues
>> +
>> + : "${TIMEOUT:=30}"
>> + if ! _init_null_blk nr_devices=0 queue_mode=2 "init_hctx=$(nproc),100,0,0"; then
>
> Doesn't make the $(nproc) the test subtil depending on the execution
> environment?
Hi Daniel,
The value $(nproc) has been chosen on purpose. The following code from
the test script:
+ echo 1 >$sq
+ nproc >$sq
triggers (nproc + 1) calls to null_init_hctx(). So injecting a failure
after (nproc) null_init_hctx() calls triggers the following pattern:
* The first blk_mq_realloc_hw_ctxs() call fails after (nproc - 1)
null_init_hctx() calls.
* The second blk_mq_realloc_hw_ctxs() call fails after (nproc - 2)
null_init_hctx() calls.
...
* The (nproc) th blk_mq_realloc_hw_ctxs() call fails after one
null_init_hctx() call.
* The (nproc + 1) th blk_mq_realloc_hw_ctxs() call succeeds.
I'm not sure to trigger this behavior without using the $(nproc) value?
Thanks,
Bart.
