Commit Graph

53 Commits

Author SHA1 Message Date
Linus Torvalds 06d381484f Merge branch 'stable/vmalloc-3.2' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen
* 'stable/vmalloc-3.2' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  net: xen-netback: use API provided by xenbus module to map rings
  block: xen-blkback: use API provided by xenbus module to map rings
  xen: use generic functions instead of xen_{alloc, free}_vm_area()
2011-11-06 18:31:36 -08:00
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
David Vrabel 2d073846b8 block: xen-blkback: use API provided by xenbus module to map rings
The xenbus module provides xenbus_map_ring_valloc() and
xenbus_map_ring_vfree().  Use these to map the ring pages granted by
the frontend.

Acked-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-26 10:02:35 -04:00
Linus Torvalds 59e5253417 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (59 commits)
  MAINTAINERS: linux-m32r is moderated for non-subscribers
  linux@lists.openrisc.net is moderated for non-subscribers
  Drop default from "DM365 codec select" choice
  parisc: Kconfig: cleanup Kernel page size default
  Kconfig: remove redundant CONFIG_ prefix on two symbols
  cris: remove arch/cris/arch-v32/lib/nand_init.S
  microblaze: add missing CONFIG_ prefixes
  h8300: drop puzzling Kconfig dependencies
  MAINTAINERS: microblaze-uclinux@itee.uq.edu.au is moderated for non-subscribers
  tty: drop superfluous dependency in Kconfig
  ARM: mxc: fix Kconfig typo 'i.MX51'
  Fix file references in Kconfig files
  aic7xxx: fix Kconfig references to READMEs
  Fix file references in drivers/ide/
  thinkpad_acpi: Fix printk typo 'bluestooth'
  bcmring: drop commented out line in Kconfig
  btmrvl_sdio: fix typo 'btmrvl_sdio_sd6888'
  doc: raw1394: Trivial typo fix
  CIFS: Don't free volume_info->UNC until we are entirely done with it.
  treewide: Correct spelling of successfully in comments
  ...
2011-10-25 12:11:02 +02:00
Linus Torvalds 31018acd4c Merge branches 'stable/bug.fixes-3.2' and 'stable/mmu.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen
* 'stable/bug.fixes-3.2' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/p2m/debugfs: Make type_name more obvious.
  xen/p2m/debugfs: Fix potential pointer exception.
  xen/enlighten: Fix compile warnings and set cx to known value.
  xen/xenbus: Remove the unnecessary check.
  xen/irq: If we fail during msi_capability_init return proper error code.
  xen/events: Don't check the info for NULL as it is already done.
  xen/events: BUG() when we can't allocate our event->irq array.

* 'stable/mmu.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen: Fix selfballooning and ensure it doesn't go too far
  xen/gntdev: Fix sleep-inside-spinlock
  xen: modify kernel mappings corresponding to granted pages
  xen: add an "highmem" parameter to alloc_xenballooned_pages
  xen/p2m: Use SetPagePrivate and its friends for M2P overrides.
  xen/p2m: Make debug/xen/mmu/p2m visible again.
  Revert "xen/debug: WARN_ON when identity PFN has no _PAGE_IOMAP flag set."
2011-10-25 09:17:47 +02:00
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
Joe Jin c555aab97d xen-blkback: fixed indentation and comments
This patch fixes belows:

1. Fix code style issue.
2. Fix incorrect functions name in comments.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-10-13 09:48:33 -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
Jesper Juhl e5de063016 Remove unneeded version.h includes from drivers/block/
It was pointed out by 'make versioncheck' that some includes of
linux/version.h are not needed in drivers/block/.
This patch removes them.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2011-09-15 14:57:06 +02:00
Jens Axboe 89c63a8ef3 Merge branch 'stable/for-jens' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen into for-linus 2011-08-23 15:09:13 +02:00
Joe Jin 1bc05b0ae6 xen-blkback: fixed indentation and comments
This patch fixes belows:

1. Fix code style issue.
2. Fix incorrect functions name in comments.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-08-22 11:35:36 -04:00
Joe Jin 6f5986bce5 xen-blkback: Don't disconnect backend until state switched to XenbusStateClosed.
When do block-attach/block-detach test with below steps, umount hangs
in the guest. Furthermore shutdown ends up being stuck when umounting file-systems.

1. start guest.
2. attach new block device by xm block-attach in Dom0.
3. mount new disk in guest.
4. execute xm block-detach to detach the block device in dom0 until timeout
5. Any request to the disk will hung.

Root cause:
This issue is caused when setting backend device's state to
'XenbusStateClosing', which sends to the frontend the XenbusStateClosing
notification. When frontend receives the notification it tries to release
the disk in blkfront_closing(), but at that moment the disk is still in use
by guest, so frontend refuses to close. Specifically it sets the disk state to
XenbusStateClosing and sends the notification to backend - when backend receives the
event, it disconnects the vbd from real device, and sets the vbd device state to
XenbusStateClosing. The backend disconnects the real device/file, and any IO
requests to the disk in guest will end up in ether, leaving disk DEAD and set to
XenbusStateClosing. When the guest wants to disconnect the disk, umount will
hang on blkif_release()->xlvbd_release_gendisk() as it is unable to send any IO
to the disk, which prevents clean system shutdown.

Solution:
Don't disconnect backend until frontend state switched to XenbusStateClosed.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Cc: Daniel Stodden <daniel.stodden@citrix.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Cc: Annie Li <annie.li@oracle.com>
Cc: Ian Campbell <Ian.Campbell@eu.citrix.com>
[v1: Modified description a bit]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-08-22 11:35:35 -04:00
Linus Torvalds 8ded371f81 Merge branch 'for-3.1/drivers' of git://git.kernel.dk/linux-block
* 'for-3.1/drivers' of git://git.kernel.dk/linux-block:
  cciss: do not attempt to read from a write-only register
  xen/blkback: Add module alias for autoloading
  xen/blkback: Don't let in-flight requests defer pending ones.
  bsg: fix address space warning from sparse
  bsg: remove unnecessary conditional expressions
  bsg: fix bsg_poll() to return POLLOUT properly
2011-07-25 10:38:18 -07:00
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
Joe Perches 08b8bfc1c6 xen: Add __attribute__((format(printf... where appropriate
Use the compiler to verify printf formats and arguments.

Fix fallout.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-06-30 12:14:40 -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
Laszlo Ersek 6464920a6e xen/blkback: don't call vbd_size() if bd_disk is NULL
...because vbd_size() dereferences bd_disk if bd_part is NULL.

Signed-off-by: Laszlo Ersek<lersek@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-06-01 09:28:20 -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 5185432277 xen/blkback: Align the tabs on the structure.
The recent changes caused this field of the structure to be offset a bit.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 18:02:28 -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 5a577e3872 xen/blkback: Add the prefix XEN in the common.h.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:53 -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 325a648604 xen/blkback: Remove the unused typedefs.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:50 -04:00
Konrad Rzeszutek Wilk 452a6b2bb6 xen/blkback: Move include/xen/blkif.h into drivers/block/xen-blkback/common.h
Not point of the blkif.h file. It is not used by the frontend.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 17:55:49 -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 b9fc02968c xen/blkback: Fix spelling mistakes.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 16:43:21 -04:00
Konrad Rzeszutek Wilk 68c88dd7d3 xen/blkback: Move blkif_get_x86_[32|64]_req to common.h in block/xen-blkback dir.
From the blkif.h header, which was exposed to the frontend.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 16:43:20 -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 1afbd730a3 xen/blkback: Make the DPRINTK uniform.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-05-12 16:42:51 -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
Konrad Rzeszutek Wilk 97961ef46b xen/blkback: Move the plugging/unplugging to a higher level.
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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-04-26 13:01:32 -04:00
Konrad Rzeszutek Wilk 8b6bf747d7 xen/blkback: Prefix exposed functions with xen_
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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-04-20 11:58:03 -04:00
Konrad Rzeszutek Wilk 42c7841d17 xen-blkback: Inline some of the functions that were moved from vbd/interface.c
Shuffling code around.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-04-20 11:58:02 -04:00