-----Original Message-----
From: Mike Christie [mailto:michaelc@xxxxxxxxxxx]
Sent: Thursday, June 5, 2014 6:33 PM
To: KY Srinivasan
Cc: James Bottomley; linux-kernel@xxxxxxxxxxxxxxx; apw@xxxxxxxxxxxxx;
devel@xxxxxxxxxxxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; linux-
scsi@xxxxxxxxxxxxxxx; ohering@xxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
jasowang@xxxxxxxxxx
Subject: Re: [PATCH 1/1] [SCSI] Fix a bug in deriving the FLUSH_TIMEOUT
from the basic I/O timeout
On 06/04/2014 12:15 PM, KY Srinivasan wrote:
-----Original Message-----
From: James Bottomley [mailto:jbottomley@xxxxxxxxxxxxx]
Sent: Wednesday, June 4, 2014 10:02 AM
To: KY Srinivasan
Cc: linux-kernel@xxxxxxxxxxxxxxx; apw@xxxxxxxxxxxxx;
devel@xxxxxxxxxxxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; linux-
scsi@xxxxxxxxxxxxxxx; ohering@xxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
jasowang@xxxxxxxxxx
Subject: Re: [PATCH 1/1] [SCSI] Fix a bug in deriving the
FLUSH_TIMEOUT from the basic I/O timeout
On Wed, 2014-06-04 at 09:33 -0700, K. Y. Srinivasan wrote:
Commit ID: 7e660100d85af860e7ad763202fff717adcdaacd added code to
derive the FLUSH_TIMEOUT from the basic I/O timeout. However, this
patch did not use the basic I/O timeout of the device. Fix this bug.
Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
---
drivers/scsi/sd.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index
e9689d5..54150b1 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -832,7 +832,9 @@ static int sd_setup_write_same_cmnd(struct
scsi_device *sdp, struct request *rq)
static int scsi_setup_flush_cmnd(struct scsi_device *sdp, struct
request *rq) {
- rq->timeout *= SD_FLUSH_TIMEOUT_MULTIPLIER;
+ int timeout = sdp->request_queue->rq_timeout;
+
+ rq->timeout = (timeout * SD_FLUSH_TIMEOUT_MULTIPLIER);
Could you share where you found this to be a problem? It looks like
a bug in block because all inbound requests being prepared should
have a timeout set, so block would be the place to fix it.
Perhaps; what I found was that the value in rq->timeout was 0 coming
into this function and thus multiplying obviously has no effect.
I think you are right. We hit this problem because we are doing:
scsi_request_fn -> blk_peek_request -> sd_prep_fn ->
scsi_setup_flush_cmnd.
At this time request->timeout is zero so the multiplication does nothing. See
how sd_setup_write_same_cmnd will set the request->timeout at this time.
Then in scsi_request_fn we do:
scsi_request_fn -> blk_start_request -> blk_add_timer.
At this time it will set the request->timeout if something like req block pc
users (like scsi_execute() or block/scsi_ioctl.c) or the write same code
mentioned above have not set the timeout.
I don't think this is a recent change. Prior to this commit, we were setting the timeout
value in this function; it just happened to be a different constant unrelated to the I/O
timeout.