2012/10/17 Dmitry Filippov [off-list ref]:

Hi,

Recently i've started with development of kernel module, which uses
existing block devices/partitions as backend and represents itself as
scsi disk.

i've found good start point - scsi_debug module which is in official
kernel tree under drivers/scsi/
i suppose you are aware about this module. So in fact it is low level
scsi adapter which represents itself as scsi disk /dev/sd? on the
system and uses RAM as backend storage. actually what i need!

It's a adapter, it use RAM represent as scsi disk
snip..

the problem is with response to READ.
scsi_debug just uses sg_copy_from_buffer from RAM storage - where data
is always uptodate.
but in my case i need to read data from block device by submit_bio
first and only after this can use buffer updated to pass it to
sg_copy_from_buffer... I still don't have idea how to accomplish this.

you just need to pass the request to block device and can scsi_done when ready,
I'm not sure submit_io block or not through.

Jack

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