Re: Fw: 2.6.6-rc3 ia64 smp_call_function() called with interrupts disabled

From: Patrick Mansfield
Date: Fri May 14 2004 - 15:02:20 EST

Christopoh -

On Tue, May 04, 2004 at 10:41:43AM +0100, Christoph Hellwig wrote:

> Better than what was there, but I still don't like it. A global array
> of devices is just utter crap. Every entry point from scsi already has
> struct scsi_device from which we can derive the sg-specific portion easily,
> and for anything else (from a quick look that seems to be only procfs
> stuff which should fade out anyway) a linear search on a linked list
> is okay.
> btw, why are we vmalloc()ing Sg_device?

With Doug's latest version of the patch, and changing the vmalloc of
Sg_device to a kmalloc, I was able to get sg to attach to 16k devices.
(I'm still debugging major/minor issues, hopefully just userspace stuff.)

I was trying to get rid of the sg_dev_arr, but there is no connection from
a scsi_device to a Sg_device, there is only the pointer from Sg_device to
scsi_device. The sg simple class class_data is set but never used
(class_set_devdata is used but not class_get_devdata).

We have a scsi_device class_data that could store the Sg_device, that is a
bit of a hack, since it is supposed hold scsi core data, and in theory we
could have multiple scsi_device class interfaces (st and any other upper
level character drivers would not use this).

There is no cdev private_data, similiar to the block_device gendisk
private data, so we can't use that in sg_open. The other upper level char
devices (st) could also use this, as well as other char drivers. I am told
this is a 2.7 item.

Do you think we should do anything else (besides losing the one vmalloc)
here for sg in 2.6?

Specifically -

Do you think we should try for a cdev private_data? With only this added,
we could have a global list of all Sg_devices, and not have to do a linear
search on open (I don't know how bad that would be for large numbers of
devices). We would still need a linear search of the list on removal (not
that bad).

Should we hack the scsi_device class_data to hold a Sg_device?

-- Patrick Mansfield
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