Commit Graph

55 Commits

Author SHA1 Message Date
Roger Pau Monne ffb1dabd1e xen-blkback: don't store dev_bus_addr
dev_bus_addr returned in the grant ref map operation is the mfn of the
passed page, there's no need to store it in the persistent grant
entry, since we can always get it provided that we have the page.

This reduces the memory overhead of persistent grants in blkback.

While at it, rename the 'seg[i].buf' to be 'seg[i].offset' as
it makes much more sense - as we use that value in bio_add_page
which as the fourth argument expects the offset.

We hadn't used the physical address as part of this at all.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: xen-devel@lists.xen.org
[v1: s/buf/offset/]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-03-19 12:50:00 -04:00
Roger Pau Monne 217fd5e709 xen-blkback: fix foreach_grant_safe to handle empty lists
We may use foreach_grant_safe in the future with empty lists, so make
sure we can handle them.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: xen-devel@lists.xen.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-03-19 08:53:15 -04:00
Jan Beulich 0e5e098ac2 xen-blkback: fix dispatch_rw_block_io() error path
Commit 7708992 ("xen/blkback: Seperate the bio allocation and the bio
submission") consolidated the pendcnt updates to just a single write,
neglecting the fact that the error path relied on it getting set to 1
up front (such that the decrement in __end_block_io_op() would actually
drop the count to zero, triggering the necessary cleanup actions).

Also remove a misleading and a stale (after said commit) comment.

CC: stable@vger.kernel.org
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-03-18 16:31:22 -04:00
Zoltan Kiss 986cacbd26 xen/blkback: Change statistics counter types to unsigned
These values shouldn't be negative, but after an overflow their value
can turn into negative, if they are signed. xentop can show bogus
values in this case.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: Ichiro Ogino <ichiro.ogino@citrix.co.jp>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-03-11 13:56:54 -04:00
David Vrabel 0e367ae465 xen/blkback: correctly respond to unknown, non-native requests
If the frontend is using a non-native protocol (e.g., a 64-bit
frontend with a 32-bit backend) and it sent an unrecognized request,
the request was not translated and the response would have the
incorrect ID.  This may cause the frontend driver to behave
incorrectly or crash.

Since the ID field in the request is always in the same place,
regardless of the request type we can get the correct ID and make a
valid response (which will report BLKIF_RSP_EOPNOTSUPP).

This bug affected 64-bit SLES 11 guests when using a 32-bit backend.
This guest does a BLKIF_OP_RESERVED_1 (BLKIF_OP_PACKET in the SLES
source) and would crash in blkif_int() as the ID in the response would
be invalid.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-03-11 13:54:28 -04:00
Chen Gang a72d9002f8 xen/xen-blkback: preq.dev is used without initialized
If call xen_vbd_translate failed, the preq.dev will be not initialized.
Use blkif->vbd.pdevice instead (still better to print relative info).

Note that before commit 01c681d4c7
(xen/blkback: Don't trust the handle from the frontend.)
the value bogus, as it was the guest provided value from req->u.rw.handle
rather than the actual device.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-03-01 08:41:43 -05:00
Roger Pau Monne 087ffecdaa xen-blkback: use balloon pages for persistent grants
With current persistent grants implementation we are not freeing the
persistent grants after we disconnect the device. Since grant map
operations change the mfn of the allocated page, and we can no longer
pass it to __free_page without setting the mfn to a sane value, use
balloon grant pages instead, as the gntdev device does.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: stable@vger.kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-02-19 15:17:21 -05:00
Konrad Rzeszutek Wilk 01c681d4c7 xen/blkback: Don't trust the handle from the frontend.
The 'handle' is the device that the request is from. For the life-time
of the ring we copy it from a request to a response so that the frontend
is not surprised by it. But we do not need it - when we start processing
I/Os we have our own 'struct phys_req' which has only most essential
information about the request. In fact the 'vbd_translate' ends up
over-writing the preq.dev with a value from the backend.

This assignment of preq.dev with the 'handle' value is superfluous
so lets not do it.

Cc: stable@vger.kernel.org
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-02-19 15:17:03 -05:00
Roger Pau Monne 7dc341175a xen-blkback: implement safe iterator for the list of persistent grants
Change foreach_grant iterator to a safe version, that allows freeing
the element while iterating. Also move the free code in
free_persistent_gnts to prevent freeing the element before the rb_next
call.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: xen-devel@lists.xen.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-12-07 15:13:09 -05:00
Roger Pau Monne 4d4f270f18 xen-blkback: move free persistent grants code
Move the code that frees persistent grants from the red-black tree
to a function. This will make it easier for other consumers to move
this to a common place.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-11-26 14:58:11 -05:00
Roger Pau Monne cb5bd4d19b xen/blkback: persistent-grants fixes
This patch contains fixes for persistent grants implementation v2:

 * handle == 0 is a valid handle, so initialize grants in blkback
   setting the handle to BLKBACK_INVALID_HANDLE instead of 0. Reported
   by Konrad Rzeszutek Wilk.

 * new_map is a boolean, use "true" or "false" instead of 1 and 0.
   Reported by Konrad Rzeszutek Wilk.

 * blkfront announces the persistent-grants feature as
   feature-persistent-grants, use feature-persistent instead which is
   consistent with blkback and the public Xen headers.

 * Add a consistency check in blkfront to make sure we don't try to
   access segments that have not been set.

Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
[v1: The new_map int->bool had already been changed]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-11-04 10:35:40 -05:00
Roger Pau Monne 0a8704a51f xen/blkback: Persistent grant maps for xen blk drivers
This patch implements persistent grants for the xen-blk{front,back}
mechanism. The effect of this change is to reduce the number of unmap
operations performed, since they cause a (costly) TLB shootdown. This
allows the I/O performance to scale better when a large number of VMs
are performing I/O.

Previously, the blkfront driver was supplied a bvec[] from the request
queue. This was granted to dom0; dom0 performed the I/O and wrote
directly into the grant-mapped memory and unmapped it; blkfront then
removed foreign access for that grant. The cost of unmapping scales
badly with the number of CPUs in Dom0. An experiment showed that when
Dom0 has 24 VCPUs, and guests are performing parallel I/O to a
ramdisk, the IPIs from performing unmap's is a bottleneck at 5 guests
(at which point 650,000 IOPS are being performed in total). If more
than 5 guests are used, the performance declines. By 10 guests, only
400,000 IOPS are being performed.

This patch improves performance by only unmapping when the connection
between blkfront and back is broken.

On startup blkfront notifies blkback that it is using persistent
grants, and blkback will do the same. If blkback is not capable of
persistent mapping, blkfront will still use the same grants, since it
is compatible with the previous protocol, and simplifies the code
complexity in blkfront.

To perform a read, in persistent mode, blkfront uses a separate pool
of pages that it maps to dom0. When a request comes in, blkfront
transmutes the request so that blkback will write into one of these
free pages. Blkback keeps note of which grefs it has already
mapped. When a new ring request comes to blkback, it looks to see if
it has already mapped that page. If so, it will not map it again. If
the page hasn't been previously mapped, it is mapped now, and a record
is kept of this mapping. Blkback proceeds as usual. When blkfront is
notified that blkback has completed a request, it memcpy's from the
shared memory, into the bvec supplied. A record that the {gref, page}
tuple is mapped, and not inflight is kept.

Writes are similar, except that the memcpy is peformed from the
supplied bvecs, into the shared pages, before the request is put onto
the ring.

Blkback stores a mapping of grefs=>{page mapped to by gref} in
a red-black tree. As the grefs are not known apriori, and provide no
guarantees on their ordering, we have to perform a search
through this tree to find the page, for every gref we receive. This
operation takes O(log n) time in the worst case. In blkfront grants
are stored using a single linked list.

The maximum number of grants that blkback will persistenly map is
currently set to RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST, to
prevent a malicios guest from attempting a DoS, by supplying fresh
grefs, causing the Dom0 kernel to map excessively. If a guest
is using persistent grants and exceeds the maximum number of grants to
map persistenly the newly passed grefs will be mapped and unmaped.
Using this approach, we can have requests that mix persistent and
non-persistent grants, and we need to handle them correctly.
This allows us to set the maximum number of persistent grants to a
lower value than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST, although
setting it will lead to unpredictable performance.

In writing this patch, the question arrises as to if the additional
cost of performing memcpys in the guest (to/from the pool of granted
pages) outweigh the gains of not performing TLB shootdowns. The answer
to that question is `no'. There appears to be very little, if any
additional cost to the guest of using persistent grants. There is
perhaps a small saving, from the reduced number of hypercalls
performed in granting, and ending foreign access.

Signed-off-by: Oliver Chick <oliver.chick@citrix.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v1: Fixed up the misuse of bool as int]
2012-10-30 09:50:04 -04:00
Linus Torvalds f1c6872e49 Features:
* Allow a Linux guest to boot as initial domain and as normal guests
    on Xen on ARM (specifically ARMv7 with virtualized extensions).
    PV console, block and network frontend/backends are working.
 Bug-fixes:
  * Fix compile linux-next fallout.
  * Fix PVHVM bootup crashing.
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Merge tag 'stable/for-linus-3.7-arm-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull ADM Xen support from Konrad Rzeszutek Wilk:

  Features:
   * Allow a Linux guest to boot as initial domain and as normal guests
     on Xen on ARM (specifically ARMv7 with virtualized extensions).  PV
     console, block and network frontend/backends are working.
  Bug-fixes:
   * Fix compile linux-next fallout.
   * Fix PVHVM bootup crashing.

  The Xen-unstable hypervisor (so will be 4.3 in a ~6 months), supports
  ARMv7 platforms.

  The goal in implementing this architecture is to exploit the hardware
  as much as possible.  That means use as little as possible of PV
  operations (so no PV MMU) - and use existing PV drivers for I/Os
  (network, block, console, etc).  This is similar to how PVHVM guests
  operate in X86 platform nowadays - except that on ARM there is no need
  for QEMU.  The end result is that we share a lot of the generic Xen
  drivers and infrastructure.

  Details on how to compile/boot/etc are available at this Wiki:

    http://wiki.xen.org/wiki/Xen_ARMv7_with_Virtualization_Extensions

  and this blog has links to a technical discussion/presentations on the
  overall architecture:

    http://blog.xen.org/index.php/2012/09/21/xensummit-sessions-new-pvh-virtualisation-mode-for-arm-cortex-a15arm-servers-and-x86/

* tag 'stable/for-linus-3.7-arm-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen: (21 commits)
  xen/xen_initial_domain: check that xen_start_info is initialized
  xen: mark xen_init_IRQ __init
  xen/Makefile: fix dom-y build
  arm: introduce a DTS for Xen unprivileged virtual machines
  MAINTAINERS: add myself as Xen ARM maintainer
  xen/arm: compile netback
  xen/arm: compile blkfront and blkback
  xen/arm: implement alloc/free_xenballooned_pages with alloc_pages/kfree
  xen/arm: receive Xen events on ARM
  xen/arm: initialize grant_table on ARM
  xen/arm: get privilege status
  xen/arm: introduce CONFIG_XEN on ARM
  xen: do not compile manage, balloon, pci, acpi, pcpu and cpu_hotplug on ARM
  xen/arm: Introduce xen_ulong_t for unsigned long
  xen/arm: Xen detection and shared_info page mapping
  docs: Xen ARM DT bindings
  xen/arm: empty implementation of grant_table arch specific functions
  xen/arm: sync_bitops
  xen/arm: page.h definitions
  xen/arm: hypercalls
  ...
2012-10-07 07:13:01 +09:00
Stefano Stabellini 2fc136eecd xen/m2p: do not reuse kmap_op->dev_bus_addr
If the caller passes a valid kmap_op to m2p_add_override, we use
kmap_op->dev_bus_addr to store the original mfn, but dev_bus_addr is
part of the interface with Xen and if we are batching the hypercalls it
might not have been written by the hypervisor yet. That means that later
on Xen will write to it and we'll think that the original mfn is
actually what Xen has written to it.

Rather than "stealing" struct members from kmap_op, keep using
page->index to store the original mfn and add another parameter to
m2p_remove_override to get the corresponding kmap_op instead.
It is now responsibility of the caller to keep track of which kmap_op
corresponds to a particular page in the m2p_override (gntdev, the only
user of this interface that passes a valid kmap_op, is already doing that).

CC: stable@kernel.org
Reported-and-Tested-By: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-09-12 11:21:40 -04:00
Stefano Stabellini e79affc3f2 xen/arm: compile blkfront and blkback
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-08-08 17:21:14 +00:00
Konrad Rzeszutek Wilk 4dae76705f xen/blkback: Squash the discard support for 'file' and 'phy' type.
The only reason for the distinction was for the special case of
'file' (which is assumed to be loopback device), was to reach inside
the loopback device, find the underlaying file, and call fallocate on it.
Fortunately "xen-blkback: convert hole punching to discard request on
loop devices" removes that use-case and we now based the discard
support based on blk_queue_discard(q) and extract all appropriate
parameters from the 'struct request_queue'.

CC: Li Dongyang <lidongyang@novell.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
[v1: Dropping pointless initializer and keeping blank line]
[v2: Remove the kfree as it is not used anymore]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-03-24 10:04:35 -04:00
Daniel De Graaf b2167ba6dd xen/blkback: Enable blkback on HVM guests
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-03-20 12:52:41 +01:00
Daniel De Graaf 4f14faaab4 xen/blkback: use grant-table.c hypercall wrappers
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-03-20 12:52:41 +01:00
Li Dongyang ae18be11b5 xen-blkback: convert hole punching to discard request on loop devices
As of dfaa2ef68e, loop devices support
discard request now. We could just issue a discard request, and
the loop driver will punch the hole for us, so we don't need to touch
the internals of loop device and punch the hole ourselves, Thanks.

V0->V1: rebased on devel/for-jens-3.3

Signed-off-by: Li Dongyang <lidongyang@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-11-18 13:28:05 -05:00
Konrad Rzeszutek Wilk 421463526f xen/blkback: Move processing of BLKIF_OP_DISCARD from dispatch_rw_block_io
.. and move it to its own function that will deal with the
discard operation.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-11-18 13:28:03 -05:00
Konrad Rzeszutek Wilk 5ea4298669 xen/blk[front|back]: Enhance discard support with secure erasing support.
Part of the blkdev_issue_discard(xx) operation is that it can also
issue a secure discard operation that will permanantly remove the
sectors in question. We advertise that we can support that via the
'discard-secure' attribute and on the request, if the 'secure' bit
is set, we will attempt to pass in REQ_DISCARD | REQ_SECURE.

CC: Li Dongyang <lidongyang@novell.com>
[v1: Used 'flag' instead of 'secure:1' bit]
[v2: Use 'reserved' uint8_t instead of adding a new value]
[v3: Check for nseg when mapping instead of operation]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-11-18 13:28:01 -05:00
Konrad Rzeszutek Wilk 97e36834f5 xen/blk[front|back]: Squash blkif_request_rw and blkif_request_discard together
In a union type structure to deal with the overlapping
attributes in a easier manner.

Suggested-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-11-18 13:27:59 -05:00
Linus Torvalds 3d0a8d10cf Merge branch 'for-3.2/drivers' of git://git.kernel.dk/linux-block
* 'for-3.2/drivers' of git://git.kernel.dk/linux-block: (30 commits)
  virtio-blk: use ida to allocate disk index
  hpsa: add small delay when using PCI Power Management to reset for kump
  cciss: add small delay when using PCI Power Management to reset for kump
  xen/blkback: Fix two races in the handling of barrier requests.
  xen/blkback: Check for proper operation.
  xen/blkback: Fix the inhibition to map pages when discarding sector ranges.
  xen/blkback: Report VBD_WSECT (wr_sect) properly.
  xen/blkback: Support 'feature-barrier' aka old-style BARRIER requests.
  xen-blkfront: plug device number leak in xlblk_init() error path
  xen-blkfront: If no barrier or flush is supported, use invalid operation.
  xen-blkback: use kzalloc() in favor of kmalloc()+memset()
  xen-blkback: fixed indentation and comments
  xen-blkfront: fix a deadlock while handling discard response
  xen-blkfront: Handle discard requests.
  xen-blkback: Implement discard requests ('feature-discard')
  xen-blkfront: add BLKIF_OP_DISCARD and discard request struct
  drivers/block/loop.c: remove unnecessary bdev argument from loop_clr_fd()
  drivers/block/loop.c: emit uevent on auto release
  drivers/block/cpqarray.c: use pci_dev->revision
  loop: always allow userspace partitions and optionally support automatic scanning
  ...

Fic up trivial header file includsion conflict in drivers/block/loop.c
2011-11-04 17:22:14 -07:00
Konrad Rzeszutek Wilk 6927d92091 xen/blkback: Fix two races in the handling of barrier requests.
There are two windows of opportunity to cause a race when
processing a barrier request. This patch fixes this.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-17 14:28:57 -04:00
Konrad Rzeszutek Wilk dda1852802 xen/blkback: Check for proper operation.
The patch titled: "xen/blkback: Fix the inhibition to map pages
when discarding sector ranges." had the right idea except that
it used the wrong comparison operator. It had == instead of !=.

This fixes the bug where all (except discard) operations would
have been ignored.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-14 12:29:55 -04:00
Konrad Rzeszutek Wilk 64391b2536 xen/blkback: Fix the inhibition to map pages when discarding sector ranges.
The 'operation' parameters are the ones provided to the bio layer while
the req->operation are the ones passed in between the backend and
frontend. We used the wrong 'operation' value to squash the
call to map pages when processing the discard operation resulting
in an hypercall that did nothing. Lets guard against going in the
mapping function by checking for the proper operation type.

CC: Li Dongyang <lidongyang@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-13 09:48:38 -04:00
Konrad Rzeszutek Wilk 5c62cb4860 xen/blkback: Report VBD_WSECT (wr_sect) properly.
We did not increment the amount of sectors written to disk
b/c we tested for the == WRITE which is incorrect - as the
operations are more of WRITE_FLUSH, WRITE_ODIRECT. This patch
fixes it by doing a & WRITE check.

CC: stable@kernel.org
Reported-by: Andy Burns <xen.lists@burns.me.uk>
Suggested-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-13 09:48:37 -04:00
Konrad Rzeszutek Wilk 29bde09378 xen/blkback: Support 'feature-barrier' aka old-style BARRIER requests.
We emulate the barrier requests by draining the outstanding bio's
and then sending the WRITE_FLUSH command. To drain the I/Os
we use the refcnt that is used during disconnect to wait for all
the I/Os before disconnecting from the frontend. We latch on its
value and if it reaches either the threshold for disconnect or when
there are no more outstanding I/Os, then we have drained all I/Os.

Suggested-by: Christopher Hellwig <hch@infradead.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-13 09:48:36 -04:00
Jan Beulich 8e6dc6fe51 xen-blkback: use kzalloc() in favor of kmalloc()+memset()
This fixes the problem of three of those four memset()-s having
improper size arguments passed: Sizeof a pointer-typed expression
returns the size of the pointer, not that of the pointed to data.

It also reverts using kmalloc() instead of kzalloc() for the allocation
of the pending grant handles array, as that array gets fully
initialized in a subsequent loop.

Reported-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-13 09:48:34 -04:00
Li Dongyang b3cb0d6adc xen-blkback: Implement discard requests ('feature-discard')
..aka ATA TRIM/SCSI UNMAP command to be passed through the frontend
and used as appropiately by the backend. We also advertise
certain granulity parameters to the frontend so it can plug them in.
If the backend is a realy device - we just end up using
'blkdev_issue_discard' while for loopback devices - we just punch
a hole in the image file.

Signed-off-by: Li Dongyang <lidongyang@novell.com>
[v1: Fixed up pr_debug and commit description]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-13 09:48:30 -04:00
Stefano Stabellini 0930bba674 xen: modify kernel mappings corresponding to granted pages
If we want to use granted pages for AIO, changing the mappings of a user
vma and the corresponding p2m is not enough, we also need to update the
kernel mappings accordingly.
Currently this is only needed for pages that are created for user usages
through /dev/xen/gntdev. As in, pages that have been in use by the
kernel and use the P2M will not need this special mapping.
However there are no guarantees that in the future the kernel won't
start accessing pages through the 1:1 even for internal usage.

In order to avoid the complexity of dealing with highmem, we allocated
the pages lowmem.
We issue a HYPERVISOR_grant_table_op right away in
m2p_add_override and we remove the mappings using another
HYPERVISOR_grant_table_op in m2p_remove_override.
Considering that m2p_add_override and m2p_remove_override are called
once per page we use multicalls and hypercall batching.

Use the kmap_op pointer directly as argument to do the mapping as it is
guaranteed to be present up until the unmapping is done.
Before issuing any unmapping multicalls, we need to make sure that the
mapping has already being done, because we need the kmap->handle to be
set correctly.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
[v1: Removed GRANT_FRAME_BIT usage]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-09-29 10:32:58 -04:00
Bastian Blank a7e9357f10 xen/blkback: Add module alias for autoloading
Add xen-backend:vbd module alias to the xen-blkback module. This allows
automatic loading of the module.

Signed-off-by: Bastian Blank <waldi@debian.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-06-30 12:48:25 -04:00
Daniel Stodden b4726a9df2 xen/blkback: Don't let in-flight requests defer pending ones.
Running RING_FINAL_CHECK_FOR_REQUESTS from make_response is a bad
idea. It means that in-flight I/O is essentially blocking continued
batches. This essentially kills throughput on frontends which unplug
(or even just notify) early and rightfully assume addtional requests
will be picked up on time, not synchronously.

Signed-off-by: Daniel Stodden <daniel.stodden@citrix.com>
[v1: Rebased and fixed compile problems]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-06-30 12:48:06 -04:00
Dan Carpenter 9b83c77121 xen/blkback: potential null dereference in error handling
blkbk->pending_pages can be NULL here so I added a check for it.

Signed-off-by: Dan Carpenter <error27@gmail.com>
[v1: Redid the loop a bit]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-06-01 09:28:21 -04:00
Jan Beulich 8ab521506c xen/blkback: don't fail empty barrier requests
The sector number on empty barrier requests may (will?) be -1, which,
given that it's being treated as unsigned 64-bit quantity, will almost
always exceed the actual (virtual) disk's size.

Inspired by Konrad's "When writting barriers set the sector number to
zero...".

While at it also add overflow checking to the math in vbd_translate().

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-18 11:28:16 -04:00
Laszlo Ersek 496b318eb6 xen/blkback: fix xenbus_transaction_start() hang caused by double xenbus_transaction_end()
vbd_resize() up_read()'s xs_state.suspend_mutex twice in a row via double
xenbus_transaction_end() calls. The next down_read() in
xenbus_transaction_start() (at eg. the next resize attempt) hangs.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=618317

Acked-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-13 09:45:40 -04:00
Konrad Rzeszutek Wilk cca537af7d xen/blkback: if log_stats is enabled print out the data.
And not depend on the driver being built with -DDEBUG flag.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:54 -04:00
Konrad Rzeszutek Wilk 3d814731ba xen/blkback: Prefix 'vbd' with 'xen' in structs and functions.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:52 -04:00
Konrad Rzeszutek Wilk 30fd150202 xen/blkback: Change structure name blkif_st to xen_blkif.
No need for that '_st' and xen_blkif is more apt.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:51 -04:00
Konrad Rzeszutek Wilk b0f801273f xen/blkback: Fixing some more of the cleanpatch.pl warnings.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:48 -04:00
Konrad Rzeszutek Wilk 03e0edf946 xen/blkback: Checkpatch.pl recommend against multiple assigments.
CHECK: multiple assignments should be avoided

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:47 -04:00
Konrad Rzeszutek Wilk 72468bfcb8 xen/blkback: Removing the debug_lvl option.
It is not really used for anything.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 16:43:20 -04:00
Konrad Rzeszutek Wilk 22b20f2dff xen/blkback: Use the DRV_PFX in the pr_.. macros.
To make it easier to read.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 16:43:12 -04:00
Konrad Rzeszutek Wilk ebe8190659 xen/blkback: Change printk/DPRINTK to pr_.. type variant.
And also make them uniform and prefix the message with 'xen-blkback'.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 16:42:31 -04:00
Konrad Rzeszutek Wilk 01f37f2d53 xen/blkback: Fixed up comments and converted spaces to tabs.
Suggested-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-11 15:57:09 -04:00
Konrad Rzeszutek Wilk 3d68b39926 xen/blkback: Fix up some of the comments.
They had the wrong data or were in the wrong spot.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-05 13:43:26 -04:00
Konrad Rzeszutek Wilk fc53bf757e xen/blkback: Squash the checking for operation into dispatch_rw_block_io
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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-05 13:43:25 -04:00
Konrad Rzeszutek Wilk 24f567f952 xen/blkback: Add support for BLKIF_OP_FLUSH_DISKCACHE and drop BLKIF_OP_WRITE_BARRIER.
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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-05 13:43:24 -04:00
Konrad Rzeszutek Wilk a19be5f0f0 Revert "xen/blkback: Move the plugging/unplugging to a higher level."
This reverts commit 97961ef46b b/c
we lose about 15% performance if we do the unplugging and the
end of the reading the ring buffer.
2011-04-27 12:40:11 -04:00
Konrad Rzeszutek Wilk 013c3ca184 xen/blkback: Stick REQ_SYNC on WRITEs to deal with CFQ I/O scheduler.
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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-04-26 16:24:18 -04:00