With this patch, blk_rq_map_user_iov uses bio_copy_user_iov when a low
level driver needs padding or a buffer in sg_iovec isn't aligned. That
is, it uses temporary kernel buffers instead of mapping user pages
directly.

When a LLD needs padding, later blk_rq_map_sg needs to extend the last
entry of a scatter list. bio_copy_user_iov guarantees that there is
enough space for padding by using temporary kernel buffers instead of
user pages.

blk_rq_map_user_iov needs buffers in sg_iovec to be aligned. The
comment in blk_rq_map_user_iov indicates that drivers/scsi/sg.c also
needs buffers in sg_iovec to be aligned. Actually, drivers/scsi/sg.c
works with unaligned buffers in sg_iovec (it always uses temporary
kernel buffers).
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Introduced between 2.6.25-rc2 and -rc3
block/blk-map.c:154:14: warning: symbol 'bio' shadows an earlier one
block/blk-map.c:110:13: originally declared here
Signed-off-by: NHarvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This patch removes the unused export of blk_rq_map_user_iov.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Block layer alignment was used for two different purposes - memory
alignment and padding.  This causes problems in lower layers because
drivers which only require memory alignment ends up with adjusted
rq->data_len.  Separate out padding such that padding occurs iff
driver explicitly requests it.

Tomo: restorethe code to update bio in blk_rq_map_user
      introduced by the commit 40b01b9b
      according to padding alignment.
Signed-off-by: NTejun Heo <htejun@gmail.com>
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

The meaning of rq->data_len was changed to the length of an allocated
buffer from the true data length. It breaks SG_IO friends and
bsg. This patch restores the meaning of rq->data_len to the true data
length and adds rq->extra_len to store an extended length (due to
drain buffer and padding).

This patch also removes the code to update bio in blk_rq_map_user
introduced by the commit 40b01b9b.
The commit adjusts bio according to memory alignment
(queue_dma_alignment). However, memory alignment is NOT padding
alignment. This adjustment also breaks SG_IO friends and bsg. Padding
alignment needs to be fixed in a proper way (by a separate patch).
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <axboe@carl.home.kernel.dk>

With padding and draining moved into it, block layer now may extend
requests as directed by queue parameters, so now a request has two
sizes - the original request size and the extended size which matches
the size of area pointed to by bios and later by sgs.  The latter size
is what lower layers are primarily interested in when allocating,
filling up DMA tables and setting up the controller.

Both padding and draining extend the data area to accomodate
controller characteristics.  As any controller which speaks SCSI can
handle underflows, feeding larger data area is safe.

So, this patch makes the primary data length field, request->data_len,
indicate the size of full data area and add a separate length field,
request->raw_data_len, for the unmodified request size.  The latter is
used to report to higher layer (userland) and where the original
request size should be fed to the controller or device.
Signed-off-by: NTejun Heo <htejun@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

DMA start address and transfer size alignment for PC requests are
achieved using bio_copy_user() instead of bio_map_user().  This works
because bio_copy_user() always uses full pages and block DMA alignment
isn't allowed to go over PAGE_SIZE.

However, the implementation didn't update the last bio of the request
to make this padding visible to lower layers.  This patch makes
blk_rq_map_user() extend the last bio such that it includes the
padding area and the size of area pointed to by the request is
properly aligned.
Signed-off-by: NTejun Heo <htejun@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

That way the interface is symmetric, and calling blk_rq_unmap_user()
on the request wont oops.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Adds files for barrier handling, rq execution, io context handling,
mapping data to requests, and queue settings.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>