> On Apr 5, 2017, at 8:18 AM, Mauricio Faria de Oliveira > <[email protected]> wrote: > > 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 <[email protected]> > Fixes: 08024885a2a3 ("ses: Add power_status to SES device slot") > --- > > v2: > - remove module parameter. > - better return values for -1/uninitalized power_status. > (thanks: Dan Williams <[email protected]>) > > drivers/misc/enclosure.c | 7 ++++++- > drivers/scsi/ses.c | 1 - > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/misc/enclosure.c b/drivers/misc/enclosure.c > index 65fed7146e9b..d3fe3ea902d4 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 +594,11 @@ static ssize_t get_component_power_status(struct device > *cdev, > > 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"); > } > > diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c > index 50adabbb5808..f1cdf32d7514 100644 > --- a/drivers/scsi/ses.c > +++ b/drivers/scsi/ses.c > @@ -548,7 +548,6 @@ 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 (addl_desc_ptr) > ses_process_descriptor( > ecomp, > -- > 1.8.3.1 >
Reviewed-by: Song Liu <[email protected]>
