Child groups should have a greater depth than their parents.  Prior to
this change, the parent would incorrectly report zero memory usage for
child cgroups when use_hierarchy is enabled.

test script:
  mount -t cgroup none /cgroups -o memory
  cd /cgroups
  mkdir cg1

  echo 1 > cg1/memory.use_hierarchy
  mkdir cg1/cg11

  echo $$ > cg1/cg11/tasks
  dd if=/dev/zero of=/tmp/foo bs=1M count=1

  echo
  echo CHILD
  grep cache cg1/cg11/memory.stat

  echo
  echo PARENT
  grep cache cg1/memory.stat

  echo $$ > tasks
  rmdir cg1/cg11 cg1
  cd /
  umount /cgroups

Using fae9c791, a recent patch that changed alloc_css_id() depth computation,
the parent incorrectly reports zero usage:
  root@ubuntu:~# ./test
  1+0 records in
  1+0 records out
  1048576 bytes (1.0 MB) copied, 0.0151844 s, 69.1 MB/s

  CHILD
  cache 1048576
  total_cache 1048576

  PARENT
  cache 0
  total_cache 0

With this patch, the parent correctly includes child usage:
  root@ubuntu:~# ./test
  1+0 records in
  1+0 records out
  1048576 bytes (1.0 MB) copied, 0.0136827 s, 76.6 MB/s

  CHILD
  cache 1052672
  total_cache 1052672

  PARENT
  cache 0
  total_cache 1052672
Signed-off-by: NGreg Thelen <gthelen@google.com>
Acked-by: NPaul Menage <menage@google.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: <stable@kernel.org>		[2.6.34.x]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add s390 to list of architectures that have atomic64_dec_if_positive
implemented so we get rid of this warning:

lib/atomic64_test.c:129:2: warning: #warning Please implement
atomic64_dec_if_positive for your architecture, and add it to the IF above
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Luca Barbieri <luca@luca-barbieri.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit f6014419 ("imxfb: add support for
i.MX25:) has inserted the symbol HAVE_FB_IMX, which does not depend on FB
after the menuconfig FB.  This breaks the menu, presenting most of the
drivers outside of it, when using menuconfig.

Moving the symbol to the start of the file, just like HAVE_FB_ATMEL, fixes
the problem without breaking it for iMX25 configurations (tested with
ARCH=arm, no build).
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: NBaruch Siach <baruch@tkos.co.il>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kunmap_atomic() takes a pointer to within the page, not the struct page.
Signed-off-by: NCesar Eduardo Barros <cesarb@cesarb.net>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

task_struct->pesonality is "unsigned int", but sys_personality() paths use
"unsigned long pesonality".  This means that every assignment or
comparison is not right.  In particular, if this argument does not fit
into "unsigned int" __set_personality() changes the caller's personality
and then sys_personality() returns -EINVAL.

Turn this argument into "unsigned int" and avoid overflows.  Obviously,
this is the user-visible change, we just ignore the upper bits.  But this
can't break the sane application.

There is another thing which can confuse the poorly written applications.
User-space thinks that this syscall returns int, not long.  This means
that the returned value can be negative and look like the error code.  But
note that libc won't be confused and thus errno won't be set, and with
this patch the user-space can never get -1 unless sys_personality() really
fails.  And, most importantly, the negative RET != -1 is only possible if
that app previously called personality(RET).
Pointed-out-by: NWenming Zhang <wezhang@redhat.com>
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As pointed by Nick Piggin, ->page_mkwrite provides a way to keep a page
locked until the associated PTE is marked dirty.

Re-implement the fix by using this mechanism.
Signed-off-by: NAlbert Herranz <albert_herranz@yahoo.es>
Acked-by: NJaya Kumar <jayakumar.lkml@gmail.com>
Acked-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit 49bbd815 ("fb_defio:
fix for non-dirty ptes").

Although the fix provided is correct, it's been suggested to avoid the
underlying race in the same way as it is currently done in filesystems
like NFS, for maintainability.

A following patch "fb_defio: redo fix for non-dirty ptes" will provide
such an alternate fix.
Signed-off-by: NAlbert Herranz <albert_herranz@yahoo.es>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The data chunk is mmaped with 'len' which remains unchanged, so use that
when unmapping in the error path rather than trying to recalculate (and
incorrectly so) the value used originally.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Acked-by: NDavid McCullough <davidm@snapgear.com>
Acked-by: NGreg Ungerer <gerg@uclinux.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The stack and data have different alignment requirements, so don't force
them to wear the same shoe.  Increase the data alignment to match that
which the elf2flt linker script has always been using: 0x20 bytes.  Not
only does this bring the kernel loader in line with the toolchain, but it
also fixes a swath of gcc tests which try to force larger alignment values
but randomly fail when the FLAT loader fails to deliver.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Woodhouse <David.Woodhouse@intel.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: NDavid McCullough <davidm@snapgear.com>
Acked-by: NGreg Ungerer <gerg@uclinux.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Tested-by: NMichal Simek <monstr@monstr.eu>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jie Zhang <jie@codesourcery.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Limit number of accumulated non-balloonable pages during inflation cycle,
otherwise there is a chance we will be spinning and growing the list
forever.  This happens during torture tests when balloon target changes
while we are in the middle of inflation cycle and monitor starts refusing
to lock pages (since they are not needed anymore).
Signed-off-by: NDmitry Torokhov <dtor@vmware.com>
Acked-by: NBhavesh Davda <bhavesh@vmware.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As explained in commit 1c0fe6e3 ("mm: invoke oom-killer from page
fault") , we want to call the architecture independent oom killer when
getting an unexplained OOM from handle_mm_fault, rather than simply
killing current.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As explained in commit 1c0fe6e3 ("mm: invoke oom-killer from page
fault") , we want to call the architecture independent oom killer when
getting an unexplained OOM from handle_mm_fault, rather than simply
killing current.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As explained in commit 1c0fe6e3 ("mm: invoke oom-killer from page
fault") , we want to call the architecture independent oom killer when
getting an unexplained OOM from handle_mm_fault, rather than simply
killing current.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As explained in commit 1c0fe6e3 ("mm: invoke oom-killer from page
fault") , we want to call the architecture independent oom killer when
getting an unexplained OOM from handle_mm_fault, rather than simply
killing current.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Acked-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The driver fails to compile on s390:

drivers/char/ramoops.c: In function 'ramoops_init':
drivers/char/ramoops.c:122: error: implicit declaration of function 'ioremap'

Since we won't make use of the driver anyway on s390 just let it depend on
HAS_IOMEM.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A call to access_ok is missing a compat_ptr conversion.  Introduced with
b8373363 "compat: factor out
compat_rw_copy_check_uvector from compat_do_readv_writev"

fs/compat.c: In function 'compat_rw_copy_check_uvector':
fs/compat.c:629: warning: passing argument 1 of '__access_ok' makes pointer from integer without a cast
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make sure s3c_rtc_cpu_type is initialised _before_ it's used in an if()
check.
Reported-by: NJiri Pinkava <jiri.pinkava@vscht.cz>
Signed-off-by: NMaurus Cuelenaere <mcuelenaere@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Maurus Cuelenaere <mcuelenaere@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

s3c_rtc_setfreq() uses the platform driver data to derive struct rtc_device,
so make sure drvdata is set _before_ s3c_rtc_setfreq() is called.
Signed-off-by: NMaurus Cuelenaere <mcuelenaere@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Maurus Cuelenaere <mcuelenaere@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
  ACPI: Eliminate us to pm ticks conversion in common path
  ACPI: Fix the incorrect calculation about C-state idle time
  ACPI: update feature-removal.txt to reflect deleted acpi=ht option
  ACPI / EC / PM: Fix names of functions that block/unblock EC transactions
  ACPI / EC / PM: Fix race between EC transactions and system suspend

* 'sfi-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-sfi-2.6:
  SFI: do not return freed pointer

acpi_enter_[simple|bm] routines does us to pm tick conversion on every
idle wakeup and the value is only used in /proc/acpi display. We can
store the time in us and convert it into pm ticks before printing instead and
avoid the conversion in the common path.
Signed-off-by: NVenkatesh Pallipadi <venki@google.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

The C-state idle time is not calculated correctly, which will return the wrong
residency time in C-state. It will have the following effects:
   1.  The system can't choose the deeper C-state when it is idle next time.
Of course the system power is increased. E.g. On one server machine about 40W
idle power is increased.
   2.  The powertop shows that it will stay in C0 running state about 95% time
although the system is idle at most time.

2.6.35-rc1 regression caused-by: 2da513f5
(ACPI: Minor cleanup eliminating redundant PMTIMER_TICKS to NS conversion)
Signed-off-by: NZhao Yakui <yakui.zhao@intel.com>
Reported-by: NYu Zhidong <zhidong.yu@intel.com>
Tested-by: NYu Zhidong <zhidong.yu@intel.com>
Acked-by: NVenkatesh Pallipadi <venki@google.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6:
  ALSA: hda-intel - fix wallclk variable update and condition
  ALSA: asihpi - Fix uninitialized variable
  ALSA: hda: Use LPIB for ASUS M2V
  usb/gadget: Replace the old USB audio FU definitions in f_audio.c
  ASoC: MX31ads sound support should depend on MACH_MX31ADS_WM1133_EV1
  ASoC: Add missing Kconfig entry for Phytec boards
  ALSA: usb-audio: export UAC2 clock selectors as mixer controls
  ALSA: usb-audio: clean up find_audio_control_unit()
  ALSA: usb-audio: add UAC2 sepecific Feature Unit controls
  ALSA: usb-audio: unify constants from specification
  ALSA: usb-audio: parse clock topology of UAC2 devices
  ALSA: usb-audio: fix selector unit string index accessor
  include/linux/usb/audio-v2.h: add more UAC2 details
  ALSA: usb-audio: support partially write-protected UAC2 controls
  ALSA: usb-audio: UAC2: clean up parsing of bmaControls
  ALSA: hda: Use LPIB for another mainboard
  ALSA: hda: Use mb31 quirk for an iMac model
  ALSA: hda: Use LPIB for an ASUS device

* 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev:
  libata: implement on-demand HPA unlocking
  libata: use the enlarged capacity after late HPA unlock
  SCSI: implement sd_unlock_native_capacity()
  libata-sff: trivial corrections to Kconfig help text
  sata_nv: don't diddle with nIEN on mcp55
  sata_via: magic vt6421 fix for transmission problems w/ WD drives

Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched, trace: Fix sched_switch() prev_state argument
  sched: Fix wake_affine() vs RT tasks
  sched: Make sure timers have migrated before killing the migration_thread

Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86, smpboot: Fix cores per node printing on boot
  x86/amd-iommu: Fall back to GART if initialization fails
  x86/amd-iommu: Fix crash when request_mem_region fails
  x86/mm: Remove unused DBG() macro
  arch/x86/kernel: Add missing spin_unlock

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc:
  powerpc/macio: Fix probing of macio devices by using the right of match table
  agp/uninorth: Fix oops caused by flushing too much
  powerpc/pasemi: Update MAINTAINERS file
  powerpc/cell: Fix integer constant warning
  powerpc/kprobes: Remove resume_execution() in kprobes
  powerpc/macio: Don't dereference pointer before null check

* 'for-linus/bugfixes' of git://xenbits.xensource.com/people/ianc/linux-2.6:
  xen: avoid allocation causing potential swap activity on the resume path
  xen: ensure timer tick is resumed even on CPU driving the resume

Merge branch 'perf-fixes-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'perf-fixes-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  perf: Fix crash in swevents
  perf buildid-list: Fix --with-hits event processing
  perf scripts python: Give field dict to unhandled callback
  perf hist: fix objdump output parsing
  perf-record: Check correct pid when forking
  perf: Do the comm inheritance per thread in event__process_task
  perf: Use event__process_task from perf sched
  perf: Process comm events by tid
  blktrace: Fix new kernel-doc warnings
  perf_events: Fix unincremented buffer base on partial copy
  perf_events: Fix event scheduling issues introduced by transactional API
  perf_events, trace: Fix perf_trace_destroy(), mutex went missing
  perf_events, trace: Fix probe unregister race
  perf_events: Fix races in group composition
  perf_events: Fix races and clean up perf_event and perf_mmap_data interaction

* 'virtio' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  virtio: console: Fix crash when port is unplugged and blocked for write
  virtio: console: Fix crash when hot-unplugging a port and read is blocked
  virtio-blk: fix minimum number of S/G elements

* 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging:
  i2c: Remove all i2c_set_clientdata(client, NULL) in drivers
  i2c/busses: Move two drivers to embedded section
  i2c: Rename i2c_check_addr to i2c_check_addr_busy
  i2c: Document reserved I2C addresses
  i2c: Check for address validity on client registration
  i2c: Share the I2C device presence detection code
  Documentation/i2c: Checkpatch cleanup

* git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: crypto4xx - Fix build breakage
  n2_crypto: Plumb fallback ahash requests properly.
  n2_crypto: Fix MAU kmem_cache name.
  n2_crypto: Fix build after of_device/of_platform_driver changes.

Frederic reported that because swevents handling doesn't disable IRQs
anymore, we can get a recursion of perf_adjust_period(), once from
overflow handling and once from the tick.

If both call ->disable, we get a double hlist_del_rcu() and trigger
a LIST_POISON2 dereference.

Since we don't actually need to stop/start a swevent to re-programm
the hardware (lack of hardware to program), simply nop out these
callbacks for the swevent pmu.
Reported-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1275557609.27810.35218.camel@twins>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

* git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6:
  cifs: fix page refcount leak

* 'drm-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6: (41 commits)
  drm/radeon/kms: make sure display hw is disabled when suspending
  drm/vmwgfx: Allow userspace to change default layout. Bump minor.
  drm/vmwgfx: Fix framebuffer modesetting
  drm/vmwgfx: Fix vga save / restore with display topology.
  vgaarb: use MIT license
  vgaarb: convert pr_devel() to pr_debug()
  drm: fix typos in Linux DRM Developer's Guide
  drm/radeon/kms/pm: voltage fixes
  drm/radeon/kms/pm: radeon_set_power_state fixes
  drm/radeon/kms/pm: patch default power state with default clocks/voltages on r6xx+
  drm/radeon/kms/pm: enable SetVoltage on r7xx/evergreen
  drm/radeon/kms/pm: add support for SetVoltage cmd table (V2)
  drm/radeon/kms/evergreen: add initial CS parser
  drm/kms: disable/enable poll around switcheroo on/off
  drm/nouveau: fixup confusion over which handle the DSM is hanging off.
  drm/nouveau: attempt to get bios from ACPI v3
  drm/nv50: cast IGP memory location to u64 before shifting
  drm/ttm: Fix ttm_page_alloc.c
  drm/ttm: Fix cached TTM page allocation.
  drm/vmwgfx: Remove some leftover debug messages.
  ...

* 'merge' of git://git.secretlab.ca/git/linux-2.6:
  of/powerpc: fix fsl_msi device node pointer
  of/watchdog: gef_wdt.c: fix build breakage
  of/edac: fix build breakage in drivers
  of/net: fs_enet/mii-bitbang.c: fix build breakage
  of/usb: fsl_qe_udc.c: fix build breakage
  of/crypto: crypto4xx_core.c: fix build breakage
  of/dma: fix build breakage in ppc4xx adma driver
  of/mtd: nand: fix build breakage in drivers
  of/video: fix build breakage in FB drivers
  of/pcmcia: m8xx_pcmcia.c: Fix build failures
  of/rtc: rtc-mpc5121.c: Fix build failures
  of/dma: mpc512x_dma.c: Fix build failures
  of/mtd/nand: mpc5121_nfc.c: Fix build failures
  of/spi: mpc512x_psc_spi.c: Fix build failures
  watchdog: Fix build failure with OF changes
  of/spi: Fix build failure on spi_ppc4xx.c
  of/usb: fix build error due to of_node pointer move
  of/powerpc: fix 85xx RapidIO device node pointer

When a program that has a virtio port opened and blocked for a write
operation, a port hot-unplug event will later led to a crash when
SIGTERM was sent to the program. Fix that.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

When removing a port we don't check if a program was blocked for read.
This leads to a crash when SIGTERM is sent to the program after
hot-unplugging the port.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

We need at least one S/G element to operate properly, as does the block
layer which increments it to one anyway.  We hit this due to a qemu
bug which advertises a sg_elements of 0 under some circumstances.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (tweaked logic)