Re: generic_make_request fucntion for scsi_disk

[James Bottomley]

On Sat, 2009-06-20 at 19:35 +0530, Ravish Tayal wrote:
> I am debugging Filesystem code for USB mass storage devices.  I need
> help to figure out after generic_make_request how the request is
> placed to scsi disk (sd) requeset queue and than how sd qeueuecommand
> to usb_storeage thread.  (in which context, is it system call context)

requests out of the lower end of block come from the elevators.  The
elevators can operate in a variety of contexts: user, kernel thread or
softirq depending on state.

The mechanism for queueing to the USB thread is in
scsiglue.c:queuecommand() it's basically a simple single command
consumer model: fill in slot and wake thread.

James


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