with more details.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

From the blkif.h header, which was exposed to the frontend.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

It is not really used for anything.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

To make it easier to read.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

And also make them uniform and prefix the message with 'xen-blkback'.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Suggested-by: NIan Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

They had the wrong data or were in the wrong spot.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We do a check for the operations right before calling dispatch_rw_block_io.
And then we do the same check in dispatch_rw_block_io. This patch
squashes those checks into the 'dispatch_rw_block_io' function.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We drop the support for 'feature-barrier' and add in the support
for the 'feature-flush-cache' if the real backend storage supports
flushing.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The operation BLKIF_OP_WRITE_FLUSH_CACHE has existed in the Xen
tree header file for years but it was never present in the Linux tree
because the frontend (nor the backend) supported this interface.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This reverts commit 97961ef4 b/c
we lose about 15% performance if we do the unplugging and the
end of the reading the ring buffer.

If one runs a simple fio request with random read/write with a
20%/80% ratio, the numbers are incredibly bad when using the CFQ scheduler.

IOmeter       |       |      |          |
64K, randrw   |  NOOP | CFQ  | deadline |
randrwmix=80  |       |      |          |
--------------+-------+------+----------+
blkback       |103/27 |32/10 | 102/27   |
--------------+-------+------+----------+
QEMU qdisk    |103/27 |102/27| 102/27   |

The problem as explained by Vivek Goyal was:

".. that difference is that sync vs async requests. In the case of
a kernel thread submitting IO, [..] all the WRITES might be being
considered as async and will go in a different queue. If you mix those
with some READS, they are always sync and will go in differnet queue.
In presence of sync queue, CFQ will idle and choke up WRITES in
an attempt to improve latencies of READs.

In case of AIO [note: this is what QEMU qdisk is doing] , [..]
it is direct IO and both READS and WRITES will be considered SYNC
and will go in a single queue and no choking of WRITES will take place."

The solution is quite simple, tack on REQ_SYNC (which is
what the WRITE_ODIRECT macro points to) and the numbers go
back up.

Suggested-by: Vivek Goyal <vgoyal@redhat.com
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We used to the plug/unplug on the submit_bio. But that means
if within a stream of WRITE, WRITE, WRITE,...,WRITE we have
one READ, it could stall the pipeline (as the 'submio_bio'
could trigger the unplug_fnc to be called and stall/sync
when doing the READ). Instead we want to move the unplugging
when the whole (or as a much as possible) ring buffer has been
processed. This also eliminates us doing plug/unplug for
each request.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

And also shorten the name if it has blkback to blkbk.

This results in the symbol table (if compiled in the kernel)
to be much shorter, prettier,  and also easier to search for.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Shuffling code around.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

There is no need for it, as the address is updated constatly
in the root of the Linux kernel.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Daniel Stodden suggested to eliminate vbd.c and interface.c, inlining the
critical bits where they belong, respectively.

Leaving only blkback.c for the data- and xenbus.c for the control path.
Suggested-by: NDaniel Stodden <daniel.stodden@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

.. and modify the Makefile and Kconfig files appropriately.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

They were used to check if the queue does not have QUEUE_FLAG_DEAD
set. That is not necessary anymore as the 'submit_io' call
ends up doing that for us.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

After the commit 0faa8cca
("    xen/blkback: remove per-queue plugging") we forgot
to retrieve the 'struct request_queue' from the block device.

This puts the functionality back in and fixes a NULL pointer
bug.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The commit 976222e0

    xen/blkback: Move the check for misaligned I/O higher.

moved it a bit to high. The preq->vbdev was not set, so the
check for misaligned I/O would cause a NULL pointer derefence.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The previous name ('fast_flush_area') had nothing to do with what it
does right now. Changing the names so that the code dealing with
mapping pages in and out of the guest is called xen_blkbk_[map|unmap].
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We move it up higher to be in same loop that actually computes
the sector number.

This way, all of the code that deals with verifying that the
request is correct is all done before we do any of the
page mapping, I/O submission, etc.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We take out the chunk of code dealing with mapping to the guest
of pages into the xen_blk_map_buf code. And we also move the
vbd_translate to be done much earlier.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Moving it so that the code that 'fast_flush_area' code is
close to the code that deals with it so that the reader
won't lose focus.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We seperate the bio allocation (bio_alloc) from the bio submission so
that the error paths are much easier, and also so that the bio
submission can be done in one tight loop. It also makes the
plug/unplug calls much much easier.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

commit 7eaceacc ("block: remove per-queue plugging")
added two new interfaces to plug and unplug: blk_start_plug
and blk_finish_plug. Lets use those.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

+               sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;

WARNING: line over 80 characters
+               BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);

as breaking them up really does not help that much.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

checkpatch.pl suggested that we don't use the typdef in common.h
and this triggered this avalanche of patches.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The WRITE_BARRIER was missing the REQ_WRITE option. This
was causing the blktap to die.
Signed-off-by: NTom Goetz <tom.goetz@virtualcomputer.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The patch titled:"xen/blkback: Use 'vzalloc' for page arrays and pre-allocate pages."
allocates the structures and its member variables using the 'vzalloc'.

Daniel Stodden pointed out that vzalloc is good when we use
big number of pages - while these are at the max two pages.

We can do this using kzalloc. Also the GFP_HIGHMEM does not
work properly with Xen, so take that out.

We will have to revisit this when a "get_empty_pages_and_pagevec"
type API shows up to leverage that.

BugLink: http://mid.gmane.org/1299898639.11681.227.camel@agari.van.xensource.com

CC: Daniel Stodden <daniel.stodden@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Instead of doing copy grants lets do mapping grants using
the M2P(and P2M) override mechanism.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Conflicts:

	drivers/xen/blkback/blkback.c

Previously we would allocate the array for page using 'kmalloc' which
we can as easily do with 'vzalloc'. The pre-allocation of pages
was done a bit differently in the past - it used to be that
the balloon driver would export "alloc_empty_pages_and_pagevec"
which would have in one function created an array, allocated
the pages, balloned the pages out (so the memory behind those
pages would be non-present), and provide us those pages.

This was OK as those pages were shared between other guest and
the only thing we needed was to "swizzel" the MFN of those pages
to point to the other guest MFN. We can still "swizzel" the MFNs
using the M2P (and P2M) override API calls, but for the sake of
simplicity we are dropping the balloon API calls. We can return
to those later on.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Following in the steps of patch:
"xen: Union the blkif_request request specific fields" this patch
changes the blkback. Per the original patch:

"Prepare for extending the block device ring to allow request
specific fields, by moving the request specific fields for
reads, writes and barrier requests to a union member."

Cc: Owen Smith <owen.smith@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>