* Re: Notify about errors during initialization [not found] <20031207051634.GB21951@one-eyed-alien.net> @ 2003-12-08 16:15 ` Alan Stern 2004-01-05 2:10 ` Matthew Dharm 0 siblings, 1 reply; 19+ messages in thread From: Alan Stern @ 2003-12-08 16:15 UTC (permalink / raw) To: Matthew Dharm; +Cc: USB Storage List, SCSI development list Cross-posted to the linux-scsi list in the hope that someone there can confirm this answer... On Sat, 6 Dec 2003, Matthew Dharm wrote: > Question: Are we guaranteed that scsi_scan_host() doesn't return until the > scanning process is complete? I'm not absolutely certain -- best to check with someone on the linux-scsi list. But a quick look through the call chain in scsi_scan.c indicates that scsi_scan_host() doesn't return until the scanning process is indeed complete. The real work is done in scsi_probe_lun() (called from scsi_probe_and_add_lun()), and that uses scsi_wait_req(). After all, it can't tell whether the LUN is there or not until it gets a reply to the INQUIRY! > I recall a problem that we had with the setting of flags and the call to > scan the host -- without pre-emption, it worked, but with pre-emption > things happened in the wrong order. Could that happen here? I don't remember that problem. But I don't think pre-emption would cause any difficulties here. All the flags should be set before we call scsi_scan_host(). If you can provide more details or a reference to what you're thinking of, I could reply in more detail. When pre-emption does cause a problem it's generally because of some assumption that the current task won't be scheduled out when it calls up() or complete() or something like that. Alan Stern ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2003-12-08 16:15 ` Notify about errors during initialization Alan Stern @ 2004-01-05 2:10 ` Matthew Dharm 2004-01-05 22:04 ` Alan Stern 0 siblings, 1 reply; 19+ messages in thread From: Matthew Dharm @ 2004-01-05 2:10 UTC (permalink / raw) To: Alan Stern; +Cc: USB Storage List, SCSI development list [-- Attachment #1: Type: text/plain, Size: 1862 bytes --] Did you ever get an answer from the linux-scsi people on this? Matt On Mon, Dec 08, 2003 at 11:15:06AM -0500, Alan Stern wrote: > Cross-posted to the linux-scsi list in the hope that someone there can > confirm this answer... > > On Sat, 6 Dec 2003, Matthew Dharm wrote: > > > Question: Are we guaranteed that scsi_scan_host() doesn't return until the > > scanning process is complete? > > I'm not absolutely certain -- best to check with someone on the linux-scsi > list. But a quick look through the call chain in scsi_scan.c indicates > that scsi_scan_host() doesn't return until the scanning process is indeed > complete. The real work is done in scsi_probe_lun() (called from > scsi_probe_and_add_lun()), and that uses scsi_wait_req(). After all, it > can't tell whether the LUN is there or not until it gets a reply to the > INQUIRY! > > > I recall a problem that we had with the setting of flags and the call to > > scan the host -- without pre-emption, it worked, but with pre-emption > > things happened in the wrong order. Could that happen here? > > I don't remember that problem. But I don't think pre-emption would cause > any difficulties here. All the flags should be set before we call > scsi_scan_host(). If you can provide more details or a reference to what > you're thinking of, I could reply in more detail. > > When pre-emption does cause a problem it's generally because of some > assumption that the current task won't be scheduled out when it calls up() > or complete() or something like that. > > Alan Stern > > > > > > -- Matthew Dharm Home: mdharm-usb@one-eyed-alien.net Maintainer, Linux USB Mass Storage Driver I'm just trying to think of a way to say "up yours" without getting fired. -- Stef User Friendly, 10/8/1998 [-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --] ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-05 2:10 ` Matthew Dharm @ 2004-01-05 22:04 ` Alan Stern 2004-01-05 22:13 ` Christoph Hellwig 0 siblings, 1 reply; 19+ messages in thread From: Alan Stern @ 2004-01-05 22:04 UTC (permalink / raw) To: James Bottomley, Matthew Dharm; +Cc: USB Storage List, SCSI development list James: Can you or someone else on the SCSI development list answer this question? When a new host is registered and scanned for devices, are we guaranteed that the scanning procedure will be finished when scsi_scan_host() returns? It sure looks that way to me, but I want to be certain -- Matt Dharm expressed some doubts. The reason for asking is so that the usb-storage driver can test whether any devices were found. Depressingly often some incompatibility causes the scan to fail, and when that happens it would be nice to put a notification in the system log, unregister the host, and generally avoid loading the driver as though everything was okay. Thanks, Alan Stern > > On Sat, 6 Dec 2003, Matthew Dharm wrote: > > > > > Question: Are we guaranteed that scsi_scan_host() doesn't return until the > > > scanning process is complete? > > > > > I recall a problem that we had with the setting of flags and the call to > > > scan the host -- without pre-emption, it worked, but with pre-emption > > > things happened in the wrong order. Could that happen here? ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-05 22:04 ` Alan Stern @ 2004-01-05 22:13 ` Christoph Hellwig 2004-01-05 23:32 ` Mike Anderson 0 siblings, 1 reply; 19+ messages in thread From: Christoph Hellwig @ 2004-01-05 22:13 UTC (permalink / raw) To: Alan Stern Cc: James Bottomley, Matthew Dharm, USB Storage List, SCSI development list On Mon, Jan 05, 2004 at 05:04:59PM -0500, Alan Stern wrote: > James: > > Can you or someone else on the SCSI development list answer this question? > > When a new host is registered and scanned for devices, are we guaranteed > that the scanning procedure will be finished when scsi_scan_host() > returns? With the current code the scanning activity has finished when we return. But I'm not sure whether we should document that assumption - if we're moving to parallel scanning that assumption might soon be void. > The reason for asking is so that the usb-storage driver can test whether > any devices were found. Depressingly often some incompatibility causes > the scan to fail, and when that happens it would be nice to put a > notification in the system log, unregister the host, and generally avoid > loading the driver as though everything was okay. Hmm. maybe we should guarantee that scsi_scan_host will have finished and introduce a scsi_scan_host_parallel when we go down that route. Or do it the other way and add a serialized version for usb-storage.. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-05 22:13 ` Christoph Hellwig @ 2004-01-05 23:32 ` Mike Anderson 2004-01-06 16:17 ` Christoph Hellwig 0 siblings, 1 reply; 19+ messages in thread From: Mike Anderson @ 2004-01-05 23:32 UTC (permalink / raw) To: Christoph Hellwig Cc: Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list Christoph Hellwig [hch@infradead.org] wrote: > On Mon, Jan 05, 2004 at 05:04:59PM -0500, Alan Stern wrote: > > James: > > > > Can you or someone else on the SCSI development list answer this question? > > > > When a new host is registered and scanned for devices, are we guaranteed > > that the scanning procedure will be finished when scsi_scan_host() > > returns? > > With the current code the scanning activity has finished when we return. > But I'm not sure whether we should document that assumption - if we're > moving to parallel scanning that assumption might soon be void. > It would appear that saying the scan requested by scsi_scan_host is completed when the function returns would be the expected result. The LLDD writer should be aware that once scsi_add_host has been called hotplug events to user space could allow the user space to scan and delete devices through sysfs making assumptions on devices found or not found iffy. > > The reason for asking is so that the usb-storage driver can test whether > > any devices were found. Depressingly often some incompatibility causes > > the scan to fail, and when that happens it would be nice to put a > > notification in the system log, unregister the host, and generally avoid > > loading the driver as though everything was okay. > > Hmm. maybe we should guarantee that scsi_scan_host will have finished > and introduce a scsi_scan_host_parallel when we go down that route. Or > do it the other way and add a serialized version for usb-storage.. I thought we where moving to not calling a scan api from the LLDD and using hotplug events. Then user space would define the scan policy it wanted. -andmike -- Michael Anderson andmike@us.ibm.com ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-05 23:32 ` Mike Anderson @ 2004-01-06 16:17 ` Christoph Hellwig 2004-01-06 17:15 ` Patrick Mansfield 0 siblings, 1 reply; 19+ messages in thread From: Christoph Hellwig @ 2004-01-06 16:17 UTC (permalink / raw) To: Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list On Mon, Jan 05, 2004 at 03:32:21PM -0800, Mike Anderson wrote: > It would appear that saying the scan requested by scsi_scan_host is > completed when the function returns would be the expected result. The > LLDD writer should be aware that once scsi_add_host has been called > hotplug events to user space could allow the user space to scan and > delete devices through sysfs making assumptions on devices found or not > found iffy. > ... > I thought we where moving to not calling a scan api from the LLDD and > using hotplug events. Then user space would define the scan policy it > wanted. My idea was that in the brave new hotplug world scsi_scan_host would do nothing but simply sending a SCAN hotplug even. With that design we'd have a hard time to find out when the scanning has finished in kernelspace. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-06 16:17 ` Christoph Hellwig @ 2004-01-06 17:15 ` Patrick Mansfield 2004-01-06 17:18 ` Christoph Hellwig 2004-01-06 18:07 ` Sysfs attribute file for max_sectors Alan Stern 0 siblings, 2 replies; 19+ messages in thread From: Patrick Mansfield @ 2004-01-06 17:15 UTC (permalink / raw) To: Christoph Hellwig Cc: Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list On Tue, Jan 06, 2004 at 04:17:31PM +0000, Christoph Hellwig wrote: > My idea was that in the brave new hotplug world scsi_scan_host would > do nothing but simply sending a SCAN hotplug even. With that design > we'd have a hard time to find out when the scanning has finished in > kernelspace. Why not trigger off the scsi_host hotplug event? Though we will have races similiar to udev where the sysfs attribute files are created after the hotplug event - we really ought to have a device_init/setup, create the sysfs files, then device_add/enable. For user space scanning, we could special case the USB driver to check that we find the expected number of targets. -- Patrick Mansfield ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-06 17:15 ` Patrick Mansfield @ 2004-01-06 17:18 ` Christoph Hellwig 2004-01-06 18:08 ` Mike Anderson 2004-01-06 18:07 ` Sysfs attribute file for max_sectors Alan Stern 1 sibling, 1 reply; 19+ messages in thread From: Christoph Hellwig @ 2004-01-06 17:18 UTC (permalink / raw) To: Patrick Mansfield Cc: Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list On Tue, Jan 06, 2004 at 09:15:39AM -0800, Patrick Mansfield wrote: > Why not trigger off the scsi_host hotplug event? Though we will have races > similiar to udev where the sysfs attribute files are created after the > hotplug event - we really ought to have a device_init/setup, create the > sysfs files, then device_add/enable. Because some drivers (like the ieee1394) don't want scanning to happen. They can easily chose that by not sending a scan event. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-06 17:18 ` Christoph Hellwig @ 2004-01-06 18:08 ` Mike Anderson 2004-01-06 18:08 ` Christoph Hellwig 0 siblings, 1 reply; 19+ messages in thread From: Mike Anderson @ 2004-01-06 18:08 UTC (permalink / raw) To: Christoph Hellwig Cc: Patrick Mansfield, Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list Christoph Hellwig [hch@infradead.org] wrote: > On Tue, Jan 06, 2004 at 09:15:39AM -0800, Patrick Mansfield wrote: > > Why not trigger off the scsi_host hotplug event? Though we will have races > > similiar to udev where the sysfs attribute files are created after the > > hotplug event - we really ought to have a device_init/setup, create the > > sysfs files, then device_add/enable. > > Because some drivers (like the ieee1394) don't want scanning to happen. > They can easily chose that by not sending a scan event. > Couldn't the user space also set the policy to scan or not scan? It would seem that user space would be more flexible and not need a new api (Just do not call scsi_scan_host). -andmike -- Michael Anderson andmike@us.ibm.com ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-06 18:08 ` Mike Anderson @ 2004-01-06 18:08 ` Christoph Hellwig 2004-01-06 19:04 ` Mike Anderson 0 siblings, 1 reply; 19+ messages in thread From: Christoph Hellwig @ 2004-01-06 18:08 UTC (permalink / raw) To: Christoph Hellwig, Patrick Mansfield, Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list On Tue, Jan 06, 2004 at 10:08:14AM -0800, Mike Anderson wrote: > > Because some drivers (like the ieee1394) don't want scanning to happen. > > They can easily chose that by not sending a scan event. > > > > Couldn't the user space also set the policy to scan or not scan? It > would seem that user space would be more flexible and not need a new > api (Just do not call scsi_scan_host). For ieee1394 scanning doesn't make any sense, so I don't see why it should scan at all. And I don't understand that API argument at all. With my suggestion scsi_scan_host would be changed to send the hotplug even - not change in API at all. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Notify about errors during initialization 2004-01-06 18:08 ` Christoph Hellwig @ 2004-01-06 19:04 ` Mike Anderson 0 siblings, 0 replies; 19+ messages in thread From: Mike Anderson @ 2004-01-06 19:04 UTC (permalink / raw) To: Christoph Hellwig Cc: Patrick Mansfield, Alan Stern, James Bottomley, Matthew Dharm, USB Storage List, SCSI development list Christoph Hellwig [hch@infradead.org] wrote: > On Tue, Jan 06, 2004 at 10:08:14AM -0800, Mike Anderson wrote: > > > Because some drivers (like the ieee1394) don't want scanning to happen. > > > They can easily chose that by not sending a scan event. > > > > > > > Couldn't the user space also set the policy to scan or not scan? It > > would seem that user space would be more flexible and not need a new > > api (Just do not call scsi_scan_host). > > For ieee1394 scanning doesn't make any sense, so I don't see why it should > scan at all. > > And I don't understand that API argument at all. With my suggestion > scsi_scan_host would be changed to send the hotplug even - not change in > API at all. ok, I was reading two replies back when you mentioned "scsi_scan_host_parallel". I re-read the last reply and see that scsi_scan_host would just send a scan event. -andmike -- Michael Anderson andmike@us.ibm.com ^ permalink raw reply [flat|nested] 19+ messages in thread
* Sysfs attribute file for max_sectors 2004-01-06 17:15 ` Patrick Mansfield 2004-01-06 17:18 ` Christoph Hellwig @ 2004-01-06 18:07 ` Alan Stern 2004-01-06 18:23 ` James Bottomley 1 sibling, 1 reply; 19+ messages in thread From: Alan Stern @ 2004-01-06 18:07 UTC (permalink / raw) To: Patrick Mansfield Cc: Christoph Hellwig, James Bottomley, Matthew Dharm, SCSI development list, USB Storage List Some USB Mass Storage devices need max_sectors set as low as 64 KB per transfer. Many devices don't have this restriction, though, and it would be nice to give users an easy way to change the value. Especially if we play it safe by starting with the default value set low; that way more capable devices wouldn't have to be penalized. The simplest way to export max_sectors to user processes is as a sysfs attribute. We have code that will do this for USB devices, but perhaps it would be better as a general feature available for all SCSI devices. What's your feeling? Should max_sectors be exported for all SCSI devices or only for USB mass storage devices? Alan Stern ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Sysfs attribute file for max_sectors 2004-01-06 18:07 ` Sysfs attribute file for max_sectors Alan Stern @ 2004-01-06 18:23 ` James Bottomley 2004-01-06 19:31 ` Alan Stern 0 siblings, 1 reply; 19+ messages in thread From: James Bottomley @ 2004-01-06 18:23 UTC (permalink / raw) To: Alan Stern Cc: Patrick Mansfield, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List On Tue, 2004-01-06 at 12:07, Alan Stern wrote: > Some USB Mass Storage devices need max_sectors set as low as 64 KB per > transfer. Many devices don't have this restriction, though, and it would > be nice to give users an easy way to change the value. Especially if we > play it safe by starting with the default value set low; that way more > capable devices wouldn't have to be penalized. This is treading on dangerous ground. Setting max_sectors too high is a sure fire way to hang a driver. Its value isn't really "policy" which belongs in user land, its an expression of a driver constraint. > The simplest way to export max_sectors to user processes is as a sysfs > attribute. We have code that will do this for USB devices, but perhaps it > would be better as a general feature available for all SCSI devices. > > What's your feeling? Should max_sectors be exported for all SCSI devices > or only for USB mass storage devices? The value is useful to know for all drivers, so exporting it in sysfs should be fine. If you want to do an attribute override in usb-storage, you can...but I'd be very careful not to let the user set it to an obviously wrong value (like larger than the sg array or something). James ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Sysfs attribute file for max_sectors 2004-01-06 18:23 ` James Bottomley @ 2004-01-06 19:31 ` Alan Stern 2004-01-06 19:47 ` James Bottomley 2004-01-06 21:11 ` Patrick Mansfield 0 siblings, 2 replies; 19+ messages in thread From: Alan Stern @ 2004-01-06 19:31 UTC (permalink / raw) To: James Bottomley Cc: Patrick Mansfield, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List On 6 Jan 2004, James Bottomley wrote: > > The simplest way to export max_sectors to user processes is as a sysfs > > attribute. We have code that will do this for USB devices, but perhaps it > > would be better as a general feature available for all SCSI devices. > > > > What's your feeling? Should max_sectors be exported for all SCSI devices > > or only for USB mass storage devices? > > The value is useful to know for all drivers, so exporting it in sysfs > should be fine. If you want to do an attribute override in usb-storage, > you can...but I'd be very careful not to let the user set it to an > obviously wrong value (like larger than the sg array or something). I was going to have a store() routine that would accept any value greater than 0 and <= the value in the host template (or SCSI_DEFAULT_MAX_SECTORS if the host template value is 0 -- that's what scsi_host_alloc() does). If this is writeable only by root, would that be acceptable for all SCSI devices? Alan Stern ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Sysfs attribute file for max_sectors 2004-01-06 19:31 ` Alan Stern @ 2004-01-06 19:47 ` James Bottomley 2004-01-07 16:16 ` PATCH: (as168) " Alan Stern 2004-01-06 21:11 ` Patrick Mansfield 1 sibling, 1 reply; 19+ messages in thread From: James Bottomley @ 2004-01-06 19:47 UTC (permalink / raw) To: Alan Stern Cc: Patrick Mansfield, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List On Tue, 2004-01-06 at 13:31, Alan Stern wrote: > I was going to have a store() routine that would accept any value greater > than 0 and <= the value in the host template (or SCSI_DEFAULT_MAX_SECTORS > if the host template value is 0 -- that's what scsi_host_alloc() does). > If this is writeable only by root, would that be acceptable for all SCSI > devices? Not really. For most drivers, the max_sectors is a driver table parameter and the user shouldn't be changing it. The value can be acceptably exported read only in scsi_sysfs.c; then, you could use the attribute overriding code to make this read/write for usb-storage only. James ^ permalink raw reply [flat|nested] 19+ messages in thread
* PATCH: (as168) Sysfs attribute file for max_sectors 2004-01-06 19:47 ` James Bottomley @ 2004-01-07 16:16 ` Alan Stern 0 siblings, 0 replies; 19+ messages in thread From: Alan Stern @ 2004-01-07 16:16 UTC (permalink / raw) To: James Bottomley Cc: Patrick Mansfield, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List On 6 Jan 2004, James Bottomley wrote: > Not really. For most drivers, the max_sectors is a driver table > parameter and the user shouldn't be changing it. > > The value can be acceptably exported read only in scsi_sysfs.c; then, > you could use the attribute overriding code to make this read/write for > usb-storage only. Is this patch okay? (Along with exporting max_sectors read-only, it fixes two small typos.) Alan Stern ===== scsi_sysfs.c 1.24 vs edited ===== --- 1.24/drivers/scsi/scsi_sysfs.c Wed Nov 26 18:52:56 2003 +++ edited/drivers/scsi/scsi_sysfs.c Wed Jan 7 11:11:44 2004 @@ -200,7 +200,7 @@ /* - * sdev_rd_attr: create a function and attribute variable for a + * sdev_rw_attr: create a function and attribute variable for a * read/write field. */ #define sdev_rw_attr(field, format_string) \ @@ -217,7 +217,7 @@ static DEVICE_ATTR(field, S_IRUGO | S_IWUSR, sdev_show_##field, sdev_store_##field) /* - * sdev_rd_attr: create a function and attribute variable for a + * sdev_rw_attr: create a function and attribute variable for a * read/write bit field. */ #define sdev_rw_attr_bit(field) \ @@ -283,6 +283,16 @@ }; static DEVICE_ATTR(delete, S_IWUSR, NULL, sdev_store_delete); +static ssize_t +sdev_show_max_sectors(struct device *dev, char *buf) +{ + struct scsi_device *sdev; + sdev = to_scsi_device(dev); + return snprintf (buf, 20, "%d\n", sdev->request_queue->max_sectors); +} +static DEVICE_ATTR(max_sectors, S_IRUGO, sdev_show_max_sectors, NULL); + + /* Default template for device attributes. May NOT be modified */ static struct device_attribute *scsi_sysfs_sdev_attrs[] = { &dev_attr_device_blocked, @@ -295,6 +305,7 @@ &dev_attr_online, &dev_attr_rescan, &dev_attr_delete, + &dev_attr_max_sectors, NULL }; ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Sysfs attribute file for max_sectors 2004-01-06 19:31 ` Alan Stern 2004-01-06 19:47 ` James Bottomley @ 2004-01-06 21:11 ` Patrick Mansfield 2004-01-06 21:14 ` Jens Axboe 2004-01-06 22:00 ` Alan Stern 1 sibling, 2 replies; 19+ messages in thread From: Patrick Mansfield @ 2004-01-06 21:11 UTC (permalink / raw) To: Alan Stern Cc: James Bottomley, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List Alan - Given that we currently don't have any user level intitiated scanning, how can you modify max_sectors in user space prior to the scsi_alloc_queue() call done during scan? Is there a block interface to modify max_sectors? -- Patrick Mansfield ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Sysfs attribute file for max_sectors 2004-01-06 21:11 ` Patrick Mansfield @ 2004-01-06 21:14 ` Jens Axboe 2004-01-06 22:00 ` Alan Stern 1 sibling, 0 replies; 19+ messages in thread From: Jens Axboe @ 2004-01-06 21:14 UTC (permalink / raw) To: Patrick Mansfield Cc: Alan Stern, James Bottomley, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List On Tue, Jan 06 2004, Patrick Mansfield wrote: > Alan - > > Given that we currently don't have any user level intitiated scanning, how > can you modify max_sectors in user space prior to the scsi_alloc_queue() > call done during scan? > > Is there a block interface to modify max_sectors? No. As James very clearly stated (and that I back 100%), max_sectors is a driver template setting. It doesn't make sense to expose it, it's not a configurable item. -- Jens Axboe ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: Sysfs attribute file for max_sectors 2004-01-06 21:11 ` Patrick Mansfield 2004-01-06 21:14 ` Jens Axboe @ 2004-01-06 22:00 ` Alan Stern 1 sibling, 0 replies; 19+ messages in thread From: Alan Stern @ 2004-01-06 22:00 UTC (permalink / raw) To: Patrick Mansfield Cc: James Bottomley, Christoph Hellwig, Matthew Dharm, SCSI development list, USB Storage List On Tue, 6 Jan 2004, Patrick Mansfield wrote: > Alan - > > Given that we currently don't have any user level intitiated scanning, how > can you modify max_sectors in user space prior to the scsi_alloc_queue() > call done during scan? We can't. But scan doesn't put much of a load on a device, and all sd initially does is read partition table entries from single sectors scattered around a disk. Even mount doesn't seem to transfer very large buffers. It's only when people start using the devices and doing large contiguous data transfers that we begin running against limitations. So for us it would be enough to have scsi_slave_configure() set max_sectors to 128, insuring that this default value is workable on every device. Then user space tools could increase that value for more capable devices at any time and reap the benefits of decreased overhead. Making the store() method a USB-specific override is okay with me. Alan Stern ^ permalink raw reply [flat|nested] 19+ messages in thread
end of thread, other threads:[~2004-01-07 16:16 UTC | newest] Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <20031207051634.GB21951@one-eyed-alien.net> 2003-12-08 16:15 ` Notify about errors during initialization Alan Stern 2004-01-05 2:10 ` Matthew Dharm 2004-01-05 22:04 ` Alan Stern 2004-01-05 22:13 ` Christoph Hellwig 2004-01-05 23:32 ` Mike Anderson 2004-01-06 16:17 ` Christoph Hellwig 2004-01-06 17:15 ` Patrick Mansfield 2004-01-06 17:18 ` Christoph Hellwig 2004-01-06 18:08 ` Mike Anderson 2004-01-06 18:08 ` Christoph Hellwig 2004-01-06 19:04 ` Mike Anderson 2004-01-06 18:07 ` Sysfs attribute file for max_sectors Alan Stern 2004-01-06 18:23 ` James Bottomley 2004-01-06 19:31 ` Alan Stern 2004-01-06 19:47 ` James Bottomley 2004-01-07 16:16 ` PATCH: (as168) " Alan Stern 2004-01-06 21:11 ` Patrick Mansfield 2004-01-06 21:14 ` Jens Axboe 2004-01-06 22:00 ` Alan Stern
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.