Re: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-25 Thread Jeff Garzik
Ed Lin wrote: There may possibly be some other errors. So we need a lock here. I think the simple but reliable way to do it is just to replace queue lock with a host lock. James pointed out that there may be performance slow down when many devices are accessed at the same time. But I think the ma

RE: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-25 Thread Ed Lin
PROTECTED] > > > > Sent: Wednesday, January 24, 2007 5:03 PM > > > > To: Ed Lin; Michael Reed > > > > Cc: linux-scsi; linux-kernel; james.Bottomley; jeff; > > > > Promise_Linux; Jens Axboe > > > > Subject: RE: [patch] scsi: use lock per ho

Re: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-25 Thread Jens Axboe
in; Michael Reed > > > Cc: linux-scsi; linux-kernel; james.Bottomley; jeff; > > > Promise_Linux; Jens Axboe > > > Subject: RE: [patch] scsi: use lock per host instead of per > > > device for shared queue tag host > > > > > > > > > >

Re: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-25 Thread Jens Axboe
jeff; > > Promise_Linux; Jens Axboe > > Subject: RE: [patch] scsi: use lock per host instead of per > > device for shared queue tag host > > > > > > > It seems another driver(qla4xxx) is also using shared queue tag. > > > It is natural to imagine there

RE: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-24 Thread Ed Lin
> -Original Message- > From: David Somayajulu [mailto:[EMAIL PROTECTED] > Sent: Wednesday, January 24, 2007 5:03 PM > To: Ed Lin; Michael Reed > Cc: linux-scsi; linux-kernel; james.Bottomley; jeff; > Promise_Linux; Jens Axboe > Subject: RE: [patch] scsi: use loc

RE: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-24 Thread David Somayajulu
> It seems another driver(qla4xxx) is also using shared queue tag. > It is natural to imagine there might be same symptom in that > driver. But I don't know the driver and have no hardware so I > can not say anything certain about it. qla4xxx implements slightly differently, in the sense we don't

RE: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-24 Thread Ed Lin
> -Original Message- > From: Michael Reed [mailto:[EMAIL PROTECTED] > Sent: Wednesday, January 24, 2007 7:59 AM > To: Ed Lin > Cc: linux-scsi; linux-kernel; james.Bottomley; jeff; Promise_Linux > Subject: Re: [patch] scsi: use lock per host instead of per > device

Re: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-24 Thread James Bottomley
On Tue, 2007-01-23 at 16:53 -0800, Ed Lin wrote: > The block layer uses lock to protect request queue. Every scsi device > has a unique request queue, and queue lock is the default lock in struct > request_queue. This is good for normal cases. But for a host with > shared queue tag (e.g. stex cont

Re: [patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-24 Thread Michael Reed
How 'bout a comment in scsh_host.h indicating that the pointer will be NULL unless initialized by the driver? "Protect shared block queue tag" is unique to stex. Perhaps have no comment on the variable declaration in scsi_host.h and explain why you use it in stex. Mike Ed Lin wrote: > The blo

[patch] scsi: use lock per host instead of per device for shared queue tag host

2007-01-23 Thread Ed Lin
The block layer uses lock to protect request queue. Every scsi device has a unique request queue, and queue lock is the default lock in struct request_queue. This is good for normal cases. But for a host with shared queue tag (e.g. stex controllers), a queue lock per device means the shared queue