* Patch "scsi: ses: don't get power status of SES device slot on probe" has been added to the 4.9-stable tree
@ 2018-03-18 16:04 gregkh
0 siblings, 0 replies; only message in thread
From: gregkh @ 2018-03-18 16:04 UTC (permalink / raw)
To: mauricfo, alexander.levin, dan.j.williams, gregkh,
martin.petersen, songliubraving
Cc: stable, stable-commits
This is a note to let you know that I've just added the patch titled
scsi: ses: don't get power status of SES device slot on probe
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
scsi-ses-don-t-get-power-status-of-ses-device-slot-on-probe.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
>From foo@baz Sun Mar 18 16:55:33 CET 2018
From: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Date: Wed, 5 Apr 2017 12:18:19 -0300
Subject: scsi: ses: don't get power status of SES device slot on probe
From: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
[ Upstream commit 75106523f39751390b5789b36ee1d213b3af1945 ]
The commit 08024885a2a3 ("ses: Add power_status to SES device slot")
introduced the 'power_status' attribute to enclosure components and
the associated callbacks.
There are 2 callbacks available to get the power status of a device:
1) ses_get_power_status() for 'struct enclosure_component_callbacks'
2) get_component_power_status() for the sysfs device attribute
(these are available for kernel-space and user-space, respectively.)
However, despite both methods being available to get power status
on demand, that commit also introduced a call to get power status
in ses_enclosure_data_process().
This dramatically increased the total probe time for SCSI devices
on larger configurations, because ses_enclosure_data_process() is
called several times during the SCSI devices probe and loops over
the component devices (but that is another problem, another patch).
That results in a tremendous continuous hammering of SCSI Receive
Diagnostics commands to the enclosure-services device, which does
delay the total probe time for the SCSI devices __significantly__:
Originally, ~34 minutes on a system attached to ~170 disks:
[ 9214.490703] mpt3sas version 13.100.00.00 loaded
...
[11256.580231] scsi 17:0:177:0: qdepth(16), tagged(1), simple(0),
ordered(0), scsi_level(6), cmd_que(1)
With this patch, it decreased to ~2.5 minutes -- a 13.6x faster
[ 1002.992533] mpt3sas version 13.100.00.00 loaded
...
[ 1151.978831] scsi 11:0:177:0: qdepth(16), tagged(1), simple(0),
ordered(0), scsi_level(6), cmd_que(1)
Back to the commit discussion.. on the ses_get_power_status() call
introduced in ses_enclosure_data_process(): impact of removing it.
That may possibly be in place to initialize the power status value
on device probe. However, those 2 functions available to retrieve
that value _do_ automatically refresh/update it. So the potential
benefit would be a direct access of the 'power_status' field which
does not use the callbacks...
But the only reader of 'struct enclosure_component::power_status'
is the get_component_power_status() callback for sysfs attribute,
and it _does_ check for and call the .get_power_status callback,
(which indeed is defined and implemented by that commit), so the
power status value is, again, automatically updated.
So, the remaining potential for a direct/non-callback access to
the power_status attribute would be out-of-tree modules -- well,
for those, if they are for whatever reason interested in values
that are set during device probe and not up-to-date by the time
they need it.. well, that would be curious.
Well, to handle that more properly, set the initial power state
value to '-1' (i.e., uninitialized) instead of '1' (power 'on'),
and check for it in that callback which may do an direct access
to the field value _if_ a callback function is not defined.
Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Fixes: 08024885a2a3 ("ses: Add power_status to SES device slot")
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/misc/enclosure.c | 7 ++++++-
drivers/scsi/ses.c | 1 -
2 files changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/misc/enclosure.c
+++ b/drivers/misc/enclosure.c
@@ -148,7 +148,7 @@ enclosure_register(struct device *dev, c
for (i = 0; i < components; i++) {
edev->component[i].number = -1;
edev->component[i].slot = -1;
- edev->component[i].power_status = 1;
+ edev->component[i].power_status = -1;
}
mutex_lock(&container_list_lock);
@@ -600,6 +600,11 @@ static ssize_t get_component_power_statu
if (edev->cb->get_power_status)
edev->cb->get_power_status(edev, ecomp);
+
+ /* If still uninitialized, the callback failed or does not exist. */
+ if (ecomp->power_status == -1)
+ return (edev->cb->get_power_status) ? -EIO : -ENOTTY;
+
return snprintf(buf, 40, "%s\n", ecomp->power_status ? "on" : "off");
}
--- a/drivers/scsi/ses.c
+++ b/drivers/scsi/ses.c
@@ -548,7 +548,6 @@ static void ses_enclosure_data_process(s
ecomp = &edev->component[components++];
if (!IS_ERR(ecomp)) {
- ses_get_power_status(edev, ecomp);
if (addl_desc_ptr)
ses_process_descriptor(
ecomp,
Patches currently in stable-queue which might be from mauricfo@linux.vnet.ibm.com are
queue-4.9/scsi-ses-don-t-get-power-status-of-ses-device-slot-on-probe.patch
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2018-03-18 16:04 Patch "scsi: ses: don't get power status of SES device slot on probe" has been added to the 4.9-stable tree gregkh
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