blk_get_request initializes rq->cmd (rq_init does) so the users don't
need to do that.

The purpose of this patch is to remove sizeof(rq->cmd) and &rq->cmd,
as a preparation for large command support, which changes rq->cmd from
the static array to a pointer. sizeof(rq->cmd) will not make sense and
&rq->cmd won't work.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

The block layer initializes rq->cmd (queue_flush calls rq_init) so
prepare_flush_fn hooks don't need to do that.

The purpose of this patch is to remove sizeof(rq->cmd), as a
preparation for large command support, which changes rq->cmd from the
static array to a pointer. sizeof(rq->cmd) will not make sense.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

As ps3disk is a ppc64-only driver, sector_t equals to unsigned long, and the
cast is not needed.

Reuse in another (possibly 32-bit) driver is protected by the safety net called
`compiler warning' (with the cast, it may silently truncate to 32-bit).
If sector_t ever changes, we will get a compiler warning as well (with the
cast, we won't).
Signed-off-by: NGeert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Alter the block device ->direct_access() API to work with the new
get_xip_mem() API (that requires both kaddr and pfn are returned).

Some architectures will not do the right thing in their virt_to_page() for use
by XIP (to translate from the kernel virtual address returned by
direct_access(), to a user mappable pfn in XIP's page fault handler.

However, we can't switch it to just return the pfn and not the kaddr, because
we have no good way to get a kva from a pfn, and XIP requires the kva for its
read(2) and write(2) handlers.  So we have to return both.
Signed-off-by: NJared Hulbert <jaredeh@gmail.com>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Cc: Carsten Otte <cotte@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-mm@kvack.org
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Before getting merged, xen-blkfront was xenblk and
xen-netfront was xennet.

Temporarily adding compatibility module aliases
eases upgrades from older versions by e.g. allowing
mkinitrd to find the new version of the module.
Signed-off-by: NMark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Add module aliases to support autoprobing modules
for xen frontend devices.
Signed-off-by: NMark McLoughlin <markmc@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

When the xen block frontend driver is built as a module the module load
is only synchronous up to the point where the frontend and the backend
become connected rather than when the disk is added.

This means that there can be a race on boot between loading the module and
loading the dm-* modules and doing the scan for LVM physical volumes (all
in the initrd). In the failure case the disk is not present until after the
scan for physical volumes is complete.

Taken from:

  http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/11483a00c017Signed-off-by: NChristian Limpach <Christian.Limpach@xensource.com>
Signed-off-by: NMark McLoughlin <markmc@redhat.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

info->dev is never initialized to anything, so bdget(info->dev) is
meaningless.  Get rid of info->dev, and use bdget_disk on the gendisk.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Frontends are expected to write their protocol ABI to xenstore.  Since
the protocol ABI defaults to the backend's native ABI, things work
fine without that as long as the frontend's native ABI is identical to
the backend's native ABI.  This is not the case for xen-blkfront
running 32-on-64, because its ABI differs between 32 and 64 bit, and
thus needs this fix.

Based on http://xenbits.xensource.com/xen-unstable.hg?rev/c545932a18f3
and http://xenbits.xensource.com/xen-unstable.hg?rev/ffe52263b430 by
Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NJeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

While looking at the implementation of the Ram backed block device
driver, I stumbled across a write-only local variable, which makes
little sense, so I assume it should actually work like this:
Signed-off-by: NPetr Tesarik <ptesarik@suse.cz>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__FUNCTION__ is gcc-specific, use __func__
Signed-off-by: NHarvey Harrison <harvey.harrison@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

* Fix oops on cciss rmmod due to calling pci_free_consistent with
  irqs disabled.
Signed-off-by: NStephen M. Cameron <scameron@beardog.cca.cpqcorp.net>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Fix race condition between cciss_init_one(), cciss_update_drive_info(),
and cciss_check_queues().
Signed-off-by: NStephen M. Cameron <scameron@beardog.cca.cpqcorp.net>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This patch allows to use loop device with partitionned disk image.

Original behavior of loop is not modified.

A new parameter is introduced to define how many partition we want to be
able to manage per loop device. This parameter is "max_part".

For instance, to manage 63 partitions / loop device, we will do:
# modprobe loop max_part=63
# ls -l /dev/loop?*
brw-rw---- 1 root disk 7,   0 2008-03-05 14:55 /dev/loop0
brw-rw---- 1 root disk 7,  64 2008-03-05 14:55 /dev/loop1
brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2
brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3
brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4
brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5
brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6
brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7

And to attach a raw partitionned disk image, the original losetup is used:

# losetup -f etch.img
# ls -l /dev/loop?*
brw-rw---- 1 root disk 7,   0 2008-03-05 14:55 /dev/loop0
brw-rw---- 1 root disk 7,   1 2008-03-05 14:57 /dev/loop0p1
brw-rw---- 1 root disk 7,   2 2008-03-05 14:57 /dev/loop0p2
brw-rw---- 1 root disk 7,   5 2008-03-05 14:57 /dev/loop0p5
brw-rw---- 1 root disk 7,  64 2008-03-05 14:55 /dev/loop1
brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2
brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3
brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4
brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5
brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6
brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7
# mount /dev/loop0p1 /mnt
# ls /mnt
bench  cdrom  home        lib         mnt   root     srv  usr
bin    dev    initrd      lost+found  opt   sbin     sys  var
boot   etc    initrd.img  media       proc  selinux  tmp  vmlinuz
# umount /mnt
# losetup -d /dev/loop0

Of course, the same behavior can be done using kpartx on a loop device,
but modifying loop avoids to stack several layers of block device (loop +
device mapper), this is a very light modification (40% of modifications
are to manage the new parameter).
Signed-off-by: NLaurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

None of these files use any of the functionality promised by
asm/semaphore.h.  It's possible that they rely on it dragging in some
unrelated header file, but I can't build all these files, so we'll have
fix any build failures as they come up.
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>

This patch adds the missing include directive <linux/scatterlist.h> to the
cciss.c source file.    This was discovered by our release team when building
the kernel for the Alpha architecture.

Errors were found as references to functions 'sg_init_table' and 'sg_page' do
not exist without the include for Alpha.
Signed-off-by: NMike Pagano <mpagano@gentoo.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: <mike.miller@hp.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When __blk_end_request returns nonzero, it means that the request was
not completely processed and some BIOs are still attached. Since we
have dequeued it by that time, it means leaking requests and hanging
processes, which is why BUG() was in there. In ub this happens if
a packet request ends normally, but with residue (e.g. when scsi_id
issues INQUIRY).

The fix is to make sure that arguments passed to __blk_end_request
are correct: the full request length and not just transferred length.
The transferred length is indicated to applications by adjusting
rq->data_len with old, unchanged code outside of this patch.
Signed-off-by: NPete Zaitcev <zaitcev@redhat.com>
Cc: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Cc: Greg KH <greg@kroah.com>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

NBD does not protect the nbd_device's socket from becoming NULL during
receives.

This closes a race with the NBD_CLEAR_SOCK ioctl (nbd-client -d) setting
the nbd_device's socket to NULL right before NBD calls sock_xmit.
Signed-off-by: NMike Snitzer <snitzer@gmail.com>
Cc: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Robert P.J. Day proposed to use the macro FIELD_SIZEOF in replace of code
that matches its definition.

The modification was made using the following semantic patch
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@haskernel@
@@

#include <linux/kernel.h>

@depends on haskernel@
type t;
identifier f;
@@

- (sizeof(((t*)0)->f))
+ FIELD_SIZEOF(t, f)

@depends on haskernel@
type t;
identifier f;
@@

- sizeof(((t*)0)->f)
+ FIELD_SIZEOF(t, f)
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Introduce per-net_device inlines: dev_net(), dev_net_set().
Without CONFIG_NET_NS, no namespace other than &init_net exists.
Let's explicitly define them to help compiler optimizations.
Signed-off-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

Fix up so that the virtio_blk devices in sysfs link correctly to their
block device.  This then allows them to be detected by hal, etc
Signed-off-by: NJeremy Katz <katzj@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

no longer working for some time.

A driver that had been marked as BROKEN for such a long time seems to be
unlikely to be revived in the forseeable future.

But if anyone wants to ever revive this driver, the code is still present in
the older kernel releases.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Acked-by: NAlan Cox <alan@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Floppy rmmod locks up when no such hardware was initialized, since there is
nobody to wake the remove code up.  Remove the completion, because release is
called during platform_unregister anyway.
Signed-off-by: NJiri Slaby <jirislaby@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The iSeries viodasd drivers does some very strange things with
scatterlists, one of these causing a BUG_ON to trigger when
scatterlist debugging is enabled due to initializing the
scatterlist with memset instead of sg_init_table().

This fixes it by using sg_init_table().  The rest of the stuff
it does to that poor list is still pretty awful but it will work.

I may look into fixing things in a nicer way some other time.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

On my system, pkt_open() consumes 584 bytes because the compiler decides to
inline lots of functions that would not normally be part of long call chains.
The following patch fixes that problem on my system.
Signed-off-by: NPeter Osterlund <petero2@telia.com>
Cc: Nix <nix@esperi.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch removes the #define READ_AHEAD 1024 from the driver and uses the
block layer defaults, instead. We have found that under certain workloads
the setting can cause a disk connected to the e200 controller to go offline.
If the disk hiccups the link may try to downshift but the controller is
never notified that the link successfully completed the renegotiation.
We've also found that performance using the block layer default of 32 pages
was on par with the 1024 setting. We tried setting it to zero at one time
based on info from our firmware guys but that killed performance. Turns out
we were talking about 2 different read ahead settings.
Please consider this for inclusion.
Signed-off-by: NMike Miller <mike.miller@hp.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

volumes

This patch allows us to display information about all of the logical volumes
configured on a particular controller without stepping on memory even when
there are many volumes (128 or more) configured.
Please consider this for inclusion.
Signed-off-by: NMike Miller <mike.miller@hp.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

NBD doesn't work well with CFQ (or AS) schedulers, so let's default to
something else.

The two problems I have experienced with nbd and cfq are:

1) nbd hangs with cfq on RHEL 5 (2.6.18) -- this may well have been
   fixed

   There's a similar debian bug that has been filed as well:

   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=447638

   There have been posts to nbd-general mailing list about problems with
   cfq and nbd also.

2) nbd performs about 10% better (the last time I tested) with deadline
   vs.  cfq (the overhead of cfq doesn't provide much advantage to nbd [not
   being a real disk], and you end up going through the I/O scheduler on
   the nbd server anyway, so it makes sense that deadline is better with
   nbd)
Signed-off-by: NPaul Clements <paul.clements@steeleye.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The below implements the getgeo hook for Xen block devices. Extracted
from the xen-unstable tree where it has been used for ages.

It is useful to have because it allows things like grub2 (used by the
Debian installer images) to work in a guest domain without having to
sprinkle Xen specific hacks around the place.
Signed-off-by: NIan Campbell <ijc@hellion.org.uk>
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The current pmac32_defconfig fails to build with the following error:

  Building modules, stage 2.
ERROR: "check_media_bay" [drivers/block/swim3.ko] undefined!
WARNING: modpost: Found 23 section mismatch(es).
To see full details build your kernel with:
'make CONFIG_DEBUG_SECTION_MISMATCH=y'
make[2]: *** [__modpost] Error 1

This patch fixes that.
Signed-off-by: NTony Breeds <tony@bakeyournoodle.com>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NPete Zaitcev <zaitcev@redhat.com>
Cc: "Oliver Pinter" <oliver.pntr@gmail.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove the arbitrary 128 device limit for NBD.  nbds_max can now be set to
any number.  In certain scenarios where devices are used sparsely we have
run into the 128 device limit.
Signed-off-by: NPaul Clements <paul.clements@steeleye.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

I guess aoedev_init() can go away now.

Cc: Greg KH <greg@kroah.com>
Cc: "Ed L. Cashin" <ecashin@coraid.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Update the year in the copyright notices.
Signed-off-by: NEd L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Andrew Morton pointed out that the "too many targets" message in patch 2 could
be printed for failing GFP_ATOMIC allocations.  This patch makes the messages
more specific.
Signed-off-by: NEd L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The aoedev aoeminor member doesn't need a long format.
Signed-off-by: NEd L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

An AoE target provides an estimate of the number of outstanding commands that
the AoE initiator can send before getting a response.  The aoe_maxout
parameter provides a way to set an even lower limit.  It will not allow a user
to use more outstanding commands than the target permits.  If a user discovers
a problem with a large setting, this parameter provides a way for us to work
with them to debug the problem.  We expect to improve the dynamic window
sizing algorithm and drop this parameter.  For the time being, it is a
debugging aid.
Signed-off-by: NEd L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

An aoe driver user who had about 70 AoE targets found that he was hitting a
BUG in sysfs_create_file because the aoe driver was trying to tell the kernel
about an AoE device more than once.  Each AoE device was reachable by several
local network interfaces, and multiple ATA device indentify responses were
returning from that single device.

This patch eliminates a race condition so that aoe always informs the block
layer of a new AoE device once in the presence of multiple incoming ATA device
identify responses.
Signed-off-by: NEd L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

What this Patch Does

  Even before this recent series of 12 patches to 2.6.22-rc4, the aoe
  driver was reusing a small set of skbs that were allocated once and
  were only used for outbound AoE commands.

  The network layer cannot be allowed to put_page on the data that is
  still associated with a bio we haven't returned to the block layer,
  so the aoe driver (even before the patch under discussion) is still
  the owner of skbs that have been handed to the network layer for
  transmission.  We need to keep track of these skbs so that we can
  free them, but by tracking them, we can also easily re-use them.

  The new patch was a response to the behavior of certain network
  drivers.  We cannot reuse an skb that the network driver still has
  in its transmit ring.  Network drivers can defer transmit ring
  cleanup and then use the state in the skb to determine how many data
  segments to clean up in its transmit ring.  The tg3 driver is one
  driver that behaves in this way.

  When the network driver defers cleanup of its transmit ring, the aoe
  driver can find itself in a situation where it would like to send an
  AoE command, and the AoE target is ready for more work, but the
  network driver still has all of the pre-allocated skbs.  In that
  case, the new patch just calls alloc_skb, as you'd expect.

  We don't want to get carried away, though.  We try not to do
  excessive allocation in the write path, so we cap the number of skbs
  we dynamically allocate.

  Probably calling it a "dynamic pool" is misleading.  We were already
  trying to use a small fixed-size set of pre-allocated skbs before
  this patch, and this patch just provides a little headroom (with a
  ceiling, though) to accomodate network drivers that hang onto skbs,
  by allocating when needed.  The d->skbpool_hd list of allocated skbs
  is necessary so that we can free them later.

  We didn't notice the need for this headroom until AoE targets got
  fast enough.

Alternatives

  If the network layer never did a put_page on the pages in the bio's
  we get from the block layer, then it would be possible for us to
  hand skbs to the network layer and forget about them, allowing the
  network layer to free skbs itself (and thereby calling our own
  skb->destructor callback function if we needed that).  In that case
  we could get rid of the pre-allocated skbs and also the
  d->skbpool_hd, instead just calling alloc_skb every time we wanted
  to transmit a packet.  The slab allocator would effectively maintain
  the list of skbs.

  Besides a loss of CPU cache locality, the main concern with that
  approach the danger that it would increase the likelihood of
  deadlock when VM is trying to free pages by writing dirty data from
  the page cache through the aoe driver out to persistent storage on
  an AoE device.  Right now we have a situation where we have
  pre-allocation that corresponds to how much we use, which seems
  ideal.

  Of course, there's still the separate issue of receiving the packets
  that tell us that a write has successfully completed on the AoE
  target.  When memory is low and VM is using AoE to flush dirty data
  to free up pages, it would be perfect if there were a way for us to
  register a fast callback that could recognize write command
  completion responses.  But I don't think the current problems with
  the receive side of the situation are a justification for
  exacerbating the problem on the transmit side.
Signed-off-by: NEd L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>