On Oct 30, 2008, at 6:57 PM, FUJITA Tomonori wrote:
On Thu, 30 Oct 2008 18:38:04 -0700
Seokmann Ju <seokmann.ju@xxxxxxxxxx> wrote:
On Oct 30, 2008, at 6:37 AM, Seokmann Ju wrote:
On Oct 29, 2008, at 9:18 PM, FUJITA Tomonori wrote:
[snip]
+ GFP_KERNEL);
+ sg_init_table(service->payload_dma, req->nr_phys_segments);
+ service->payload_sg_cnt =
+ blk_rq_map_sg(q, req, service->payload_dma);
+ service->payload = (void *) bio_data(req->bio);
You don't need service->payload. We use scatterlist for data
transfer.
Yes. Removed.
I need a step back here.
I understand that modules get involved in handling pass through are
treat
FC service requests as opaque data.
However, there are some case where LLDs need to retrieve the
contents of
the service request and pull out some information - for example,
opcode
of the ELS for the case of qla2xxx.
I guess there might be some other LLDs that need to pull out some
information from the service request for similar reasons.
For that purpose, I think it would be good to keep 'payload' and
'response'
field instead.
Any comment?
Simply, you can't access to the data via bio_data(). You must access
to the scatter gather in a proper way.
For example, try to do the following way to allocate a request buffer
in user space:
struct sg_io_v4 sg_io;
char *p = valloc(8192);
struct fc_els_frame *els = (struct fc_els_frame *)(p + 4086);
sg_io.dout_xferp = (__u64) ⪕
fc_els_frame crosses two page frames. bio_data() can't handle it.
I see..
This is a great tip to know. Thank you for explanation.
If a driver wants the payload in a linear buffer, sg_copy_to_buffer()
is helpful.
OK. Using the sg_copy_to_buffer() is the right way to access the
contents if needed.
I will keep the changes as initially committed.
Thank you,
Seokmann
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