From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mauricio Faria de Oliveira Subject: [PATCH] scsi: ses: don't get power status of SES device slot on probe Date: Wed, 29 Mar 2017 22:02:10 -0300 Message-ID: <1490835730-13181-1-git-send-email-mauricfo@linux.vnet.ibm.com> Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:54554 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933094AbdC3BCW (ORCPT ); Wed, 29 Mar 2017 21:02:22 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2U0xB8n062092 for ; Wed, 29 Mar 2017 21:02:21 -0400 Received: from e24smtp02.br.ibm.com (e24smtp02.br.ibm.com [32.104.18.86]) by mx0a-001b2d01.pphosted.com with ESMTP id 29gfqgbycm-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 29 Mar 2017 21:02:21 -0400 Received: from localhost by e24smtp02.br.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 29 Mar 2017 22:02:19 -0300 Received: from d24av03.br.ibm.com (d24av03.br.ibm.com [9.8.31.95]) by d24relay02.br.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v2U12HYI17629300 for ; Wed, 29 Mar 2017 22:02:17 -0300 Received: from d24av03.br.ibm.com (localhost [127.0.0.1]) by d24av03.br.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v2U12HBx009861 for ; Wed, 29 Mar 2017 22:02:17 -0300 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org, jejb@linux.vnet.ibm.com, martin.petersen@oracle.com, songliubraving@fb.com Cc: dan.j.williams@intel.com, axboe@fb.com, hare@suse.de, hch@lst.de, gpiccoli@linux.vnet.ibm.com 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) Another downside is that the SCSI device class lock is held during the executions of ses_enclosure_data_process() since it's a callee of ses_intf_add(), which is executed under that lock in device_add(). This ends up blocking the parallel SCSI scan functionality because device_add() depends on that lock, and also the removal of devices via device_del() (e.g., during an enclosure reboot). 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. So, for out-of-tree modules and people still interested in this behavior (in case I might have missed something about it, other than the total probe time impact): let's add a module parameter to keep that check turned on (disabled by default). Also, 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 Fixes: 08024885a2a3 ("ses: Add power_status to SES device slot") --- drivers/misc/enclosure.c | 6 +++++- drivers/scsi/ses.c | 9 ++++++++- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/misc/enclosure.c b/drivers/misc/enclosure.c index 65fed7146e9b..d3a8a13c4247 100644 --- a/drivers/misc/enclosure.c +++ b/drivers/misc/enclosure.c @@ -148,7 +148,7 @@ struct enclosure_device * 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); @@ -594,6 +594,10 @@ static ssize_t get_component_power_status(struct device *cdev, if (edev->cb->get_power_status) edev->cb->get_power_status(edev, ecomp); + + if (ecomp->power_status == -1) + return -EINVAL; + return snprintf(buf, 40, "%s\n", ecomp->power_status ? "on" : "off"); } diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c index 50adabbb5808..2fafefd419c1 100644 --- a/drivers/scsi/ses.c +++ b/drivers/scsi/ses.c @@ -36,6 +36,12 @@ #include +static bool power_status_on_probe; /* default: false, 0. */ +module_param(power_status_on_probe, bool, 0644); +MODULE_PARM_DESC(power_status_on_probe, "get power status of SES device slots " + "(enclosure components) at probe time " + "(warning: may delay total probe time)"); + struct ses_device { unsigned char *page1; unsigned char *page1_types; @@ -548,7 +554,8 @@ static void ses_enclosure_data_process(struct enclosure_device *edev, ecomp = &edev->component[components++]; if (!IS_ERR(ecomp)) { - ses_get_power_status(edev, ecomp); + if (power_status_on_probe) + ses_get_power_status(edev, ecomp); if (addl_desc_ptr) ses_process_descriptor( ecomp, -- 1.8.3.1