From: Martin Kepplinger <martin.kepplinger@puri.sm> To: Alan Stern <stern@rowland.harvard.edu> 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: Tue, 11 Aug 2020 09:55:54 +0200 [thread overview] Message-ID: <6f0c530f-4309-ab1e-393b-83bf8367f59e@puri.sm> (raw) In-Reply-To: <20200810141343.GA299045@rowland.harvard.edu> On 10.08.20 16:13, Alan Stern wrote: > 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. absolutely worth pointing out and I'm not yet sure about that one. > > It also doesn't get cleared in cases where the device _doesn't_ > report a Unit Attention. true. but don't we set the flag for a future UA we don't yet know of? If we would want to clear it outside of a UA, I think we'd need to keep track of a suspend/resume cycle and if we see that we *had* successfully "done requests" after resuming, we could clear it... > > Alan Stern >
next prev parent reply other threads:[~2020-08-11 7:56 UTC|newest] 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 2020-08-11 7:55 ` Martin Kepplinger [this message] 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
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