linux-kernel - Re: 答复: Re: 答复: Re: [PATCH v2] scsi: Introduce sdev_printk

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Message-ID: <20180409085944.3bxu5cnvnfj43zs7@pathway.suse.cz>
Date:   Mon, 9 Apr 2018 10:59:44 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     wen.yang99@....com.cn
Cc:     sergey.senozhatsky.work@...il.com, jejb@...ux.vnet.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Bart.VanAssche@....com,
        tj@...nel.org, jiang.biao2@....com.cn, zhong.weidong@....com.cn,
        tan.hu@....com.cn
Subject: Re: 答复: Re: 答复: Re: [PATCH v2] scsi: Introduce
 sdev_printk_ratelimited tothrottlefrequent printk

On Mon 2018-04-09 10:13:43, wen.yang99@....com.cn wrote:
> That's a good idea, but it only solves part of the problem.
>  loopping printks under spinlock, there's two path:
> one path is: 

> scsi_request_fn -->  loop ->  blk_peek_request-> scsi_prep_fn -> scsi_prep_state_check -> sdev_printk

> another path is:

> scsi_request_fn -->  loop ->  sdev_printk

Is this message redundant? It seems to be printed in the same
situations as the messages in scsi_prep_state_check().

In fact, there seems to be a mismatch. scsi_request_fn() prints
about offline device also for sdev->sdev_state == SDEV_DEL.
While scsi_prep_state_check() prints about a dead device
in this case.

Would it make sense to remove the redundant dev_printk() from
scsi_request_fn()?

Then we could add a flag into struct scsi_device that
would remember if we already printed the error in
scsi_prep_state_check() for the given device. It could
be used to print the error only once.

The flag might be scsi_device_state value for which
we printed the error last time. We would need to reset
it scsi_prep_state_check() see another state.

It is a bit hairy but it really does not make much sense
to print the same error message thousand times.

Best Regards,
Petr

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