Linux-SCSI Archive on lore.kernel.org
 help / color / Atom feed
From: Alan Stern <stern@rowland.harvard.edu>
To: Martin Kepplinger <martin.kepplinger@puri.sm>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Can Guo <cang@codeaurora.org>,
	martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel@puri.sm
Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release
Date: Mon, 10 Aug 2020 10:13:43 -0400
Message-ID: <20200810141343.GA299045@rowland.harvard.edu> (raw)
In-Reply-To: <60150284-be13-d373-5448-651b72a7c4c9@puri.sm>

On Mon, Aug 10, 2020 at 02:03:17PM +0200, Martin Kepplinger wrote:
> On 09.08.20 17:26, Alan Stern wrote:
> > This is a somewhat fragile approach.  You don't know for certain that 
> > scsi_noretry_cmd will be called.  Also, scsi_noretry_cmd can be called 
> > from other places.
> > 
> > It would be better to clear the expecting_media_change flag just before 
> > returning from scsi_decide_disposition.  That way its use is localized 
> > to one routine, not spread out between two.
> > 
> > Alan Stern
> > 
> 
> Hi Alan,
> 
> maybe you're right. I initially just thought that I'd allow for specific
> error codes in scsi_noretry_cmd() to return non-NULL (BUS_BUSY, PARITY,
> ERROR) despite having the flag set.
> 
> The below version works equally fine for me but I'm not sure if it's
> actually more safe.
> 
> James, when exposing a new writable sysfs option like
> "suspend_no_media_change"(?) that drivers can check before setting the
> new "expecting_media_change" flag (during resume), would this addition
> make sense to you?
> 
> thanks,
> 
>                       martin
> 
> 
> 
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -565,6 +565,18 @@ int scsi_check_sense(struct scsi_cmnd *scmd)
>  				return NEEDS_RETRY;
>  			}
>  		}
> +		if (scmd->device->expecting_media_change) {
> +			if (sshdr.asc == 0x28 && sshdr.ascq == 0x00) {
> +				/*
> +				 * clear the expecting_media_change in
> +				 * scsi_decide_disposition() because we
> +				 * need to catch possible "fail fast" overrides
> +				 * that block readahead can cause.
> +				 */
> +				return NEEDS_RETRY;
> +			}
> +		}
> +
>  		/*
>  		 * we might also expect a cc/ua if another LUN on the target
>  		 * reported a UA with an ASC/ASCQ of 3F 0E -
> @@ -1944,9 +1956,19 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd)
>  	 * the request was not marked fast fail.  Note that above,
>  	 * even if the request is marked fast fail, we still requeue
>  	 * for queue congestion conditions (QUEUE_FULL or BUSY) */
> -	if ((++scmd->retries) <= scmd->allowed
> -	    && !scsi_noretry_cmd(scmd)) {
> -		return NEEDS_RETRY;
> +	if ((++scmd->retries) <= scmd->allowed) {
> +		/*
> +		 * but scsi_noretry_cmd() cannot override the
> +		 * expecting_media_change flag.
> +		 */
> +		if (!scsi_noretry_cmd(scmd) ||
> +		    scmd->device->expecting_media_change) {
> +			scmd->device->expecting_media_change = 0;
> +			return NEEDS_RETRY;
> +		} else {
> +			/* marked fast fail and not expected. */
> +			return SUCCESS;
> +		}
>  	} else {

This may not matter...  but it's worth pointing out that 
expecting_media_change doesn't get cleared if ++scmd->retries > 
scmd->allowed.

It also doesn't get cleared in cases where the device _doesn't_ 
report a Unit Attention.

Alan Stern

  reply index

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 11:10 Martin Kepplinger
2020-06-24 13:33 ` Bart Van Assche
2020-06-25  8:16   ` Martin Kepplinger
2020-06-25 14:52     ` Alan Stern
2020-06-26  3:53     ` Bart Van Assche
2020-06-26 15:07     ` Bart Van Assche
2020-06-26 15:44       ` Alan Stern
2020-06-28  2:37         ` Bart Van Assche
2020-06-28 13:10           ` Alan Stern
2020-06-29  9:42         ` Martin Kepplinger
2020-06-29 16:15           ` Alan Stern
2020-06-29 16:56             ` Bart Van Assche
2020-06-29 17:40               ` Alan Stern
2020-06-30  3:33             ` Martin Kepplinger
2020-06-30 13:38               ` Alan Stern
2020-06-30 15:59             ` Bart Van Assche
2020-06-30 18:02               ` Alan Stern
2020-06-30 19:23                 ` Bart Van Assche
2020-06-30 19:38                   ` Alan Stern
2020-06-30 23:31                     ` Bart Van Assche
2020-07-01  0:49                       ` Alan Stern
2020-07-06 16:41                         ` Alan Stern
2020-07-28  7:02                           ` Martin Kepplinger
2020-07-28 20:02                             ` Alan Stern
2020-07-29 14:12                               ` Martin Kepplinger
2020-07-29 14:32                                 ` Alan Stern
2020-07-29 14:44                                   ` Martin K. Petersen
2020-07-29 14:56                                     ` Alan Stern
2020-07-29 14:46                                   ` James Bottomley
2020-07-29 14:53                                     ` James Bottomley
2020-07-29 15:40                                       ` Martin Kepplinger
2020-07-29 15:44                                         ` James Bottomley
2020-07-29 16:43                                           ` Martin Kepplinger
2020-07-29 18:25                                             ` Alan Stern
2020-07-29 18:29                                               ` James Bottomley
2020-07-30  8:52                                                 ` Martin Kepplinger
2020-07-30  8:54                                                   ` Martin Kepplinger
2020-07-30 15:10                                                   ` Alan Stern
2020-08-04  9:39                                                     ` Martin Kepplinger
2020-08-07  9:51                                                       ` Martin Kepplinger
2020-08-07 14:30                                                         ` Alan Stern
2020-08-08  6:59                                                           ` Martin Kepplinger
2020-08-08 15:05                                                             ` Alan Stern
2020-08-09  9:20                                                               ` Martin Kepplinger
2020-08-09 15:26                                                                 ` Alan Stern
2020-08-10 12:03                                                                   ` Martin Kepplinger
2020-08-10 14:13                                                                     ` Alan Stern [this message]
2020-08-11  7:55                                                                       ` Martin Kepplinger
2020-08-11 13:48                                                                         ` Alan Stern
2020-08-23 14:57                                                                         ` [PATCH] block: Fix bug in runtime-resume handling Alan Stern
2020-08-24 17:48                                                                           ` Bart Van Assche
2020-08-24 20:13                                                                             ` Alan Stern
2020-08-26  7:48                                                                               ` Martin Kepplinger
2020-08-27 17:42                                                                                 ` Martin Kepplinger
2020-08-27 20:29                                                                                   ` Alan Stern
2020-08-29  7:24                                                                                     ` Martin Kepplinger
2020-08-29 15:26                                                                                       ` Alan Stern
2020-08-29 16:33                                                                                         ` Martin Kepplinger
2020-08-29 18:56                                                                                           ` Alan Stern
2020-08-30  0:38                                                                                             ` Bart Van Assche
2020-08-30  1:06                                                                                               ` Alan Stern
2020-07-29 15:40                                       ` [PATCH] scsi: sd: add runtime pm to open / release Alan Stern
2020-07-29 15:49                                         ` James Bottomley
2020-07-29 16:17                                           ` Alan Stern
2020-07-29 15:52                                         ` Martin Kepplinger
2020-07-29 18:10                                   ` Douglas Gilbert
2020-07-30  8:05             ` Martin Kepplinger
2020-07-30 15:14               ` Alan Stern

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200810141343.GA299045@rowland.harvard.edu \
    --to=stern@rowland.harvard.edu \
    --cc=James.Bottomley@hansenpartnership.com \
    --cc=bvanassche@acm.org \
    --cc=cang@codeaurora.org \
    --cc=kernel@puri.sm \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-scsi@vger.kernel.org \
    --cc=martin.kepplinger@puri.sm \
    --cc=martin.petersen@oracle.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-SCSI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-scsi/0 linux-scsi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-scsi linux-scsi/ https://lore.kernel.org/linux-scsi \
		linux-scsi@vger.kernel.org
	public-inbox-index linux-scsi

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-scsi


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git