Because bios will merge at block-layer,so bios-error may caused by other
bio which be merged into to the same request.
Using this flag,it will find exactly error-sector and not do redundant
operation like re-write and re-read.

V0->V1:Using REQ_FLUSH instead REQ_NOMERGE avoid bio merging at block
layer.
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

For SSD, if request size exceeds specific value (optimal io size), request size
isn't important for bandwidth. In such condition, if making request size bigger
will cause some disks idle, the total throughput will actually drop. A good
example is doing a readahead in a two-disk raid1 setup.

So when should we split big requests? We absolutly don't want to split big
request to very small requests. Even in SSD, big request transfer is more
efficient. This patch only considers request with size above optimal io size.

If all disks are busy, is it worth doing a split? Say optimal io size is 16k,
two requests 32k and two disks. We can let each disk run one 32k request, or
split the requests to 4 16k requests and each disk runs two. It's hard to say
which case is better, depending on hardware.

So only consider case where there are idle disks. For readahead, split is
always better in this case. And in my test, below patch can improve > 30%
thoughput. Hmm, not 100%, because disk isn't 100% busy.

Such case can happen not just in readahead, for example, in directio. But I
suppose directio usually will have bigger IO depth and make all disks busy, so
I ignored it.

Note: if the raid uses any hard disk, we don't prevent merging. That will make
performace worse.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

SSD hasn't spindle, distance between requests means nothing. And the original
distance based algorithm sometimes can cause severe performance issue for SSD
raid.

Considering two thread groups, one accesses file A, the other access file B.
The first group will access one disk and the second will access the other disk,
because requests are near from one group and far between groups. In this case,
read balance might keep one disk very busy but the other relative idle.  For
SSD, we should try best to distribute requests to as many disks as possible.
There isn't spindle move penality anyway.

With below patch, I can see more than 50% throughput improvement sometimes
depending on workloads.

The only exception is small requests can be merged to a big request which
typically can drive higher throughput for SSD too. Such small requests are
sequential reads. Unlike hard disk, sequential read which can't be merged (for
example direct IO, or read without readahead) can be ignored for SSD. Again
there is no spindle move penality. readahead dispatches small requests and such
requests can be merged.

Last patch can help detect sequential read well, at least if concurrent read
number isn't greater than raid disk number. In that case, distance based
algorithm doesn't work well too.

V2: For hard disk and SSD mixed raid, doesn't use distance based algorithm for
random IO too. This makes the algorithm generic for raid with SSD.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

Currently the sequential read detection is global wide. It's natural to make it
per disk based, which can improve the detection for concurrent multiple
sequential reads. And next patch will make SSD read balance not use distance
based algorithm, where this change help detect truly sequential read for SSD.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

md/raid10: Export is_congested test.

In similar fashion to commits
	11d8a6e3
	1ed7242e
we export the RAID10 congestion checking function so that dm-raid.c can
make use of it and make use of the personality.  The 'queue' and 'gendisk'
structures will not be available to the MD code when device-mapper sets
up the device, so we conditionalize access to these fields also.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

MD RAID1/RAID10: Move some macros from .h file to .c file

There are three macros (IO_BLOCKED,IO_MADE_GOOD,BIO_SPECIAL) which are defined
in both raid1.h and raid10.h.  They are only used in there respective .c files.
However, if we wish to make RAID10 accessible to the device-mapper RAID
target (dm-raid.c), then we need to move these macros into the .c files where
they are used so that they do not conflict with each other.

The macros from the two files are identical and could be moved into md.h, but
I chose to leave the duplication and have them remain in the personality
files.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

MD RAID1: Rename the structure 'mirror_info' to 'raid1_info'

The same structure name ('mirror_info') is used by raid10.  Each of these
structures are defined in there respective header files.  If dm-raid is
to support both RAID1 and RAID10, the header files will be included and
the structure names must not collide.  While only one of these structure
names needs to change, this patch adds consistency to the naming of the
structure.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

MD RAID10: Rename the structure 'mirror_info' to 'raid10_info'

The same structure name ('mirror_info') is used by raid1.  Each of these
structures are defined in there respective header files.  If dm-raid is
to support both RAID1 and RAID10, the header files will be included and
the structure names must not collide.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

MD RAID10:  Fix compiler warning.

Initialize variable to prevent compiler warning.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

Add a per-stripe lock to protect stripe specific data. The purpose is to reduce
lock contention of conf->device_lock.

stripe ->toread, ->towrite are protected by per-stripe lock.  Accessing bio
list of the stripe is always serialized by this lock, so adding bio to the
lists (add_stripe_bio()) and removing bio from the lists (like
ops_run_biofill()) not race.

If bio in ->read, ->written ... list are not shared by multiple stripes, we
don't need any lock to protect ->read, ->written, because STRIPE_ACTIVE will
protect them. If the bio are shared,  there are two protections:
1. bi_phys_segments acts as a reference count
2. traverse the list uses r5_next_bio, which makes traverse never access bio
not belonging to the stripe

Let's have an example:
|  stripe1 |  stripe2    |  stripe3  |
...bio1......|bio2|bio3|....bio4.....

stripe2 has 4 bios, when it's finished, it will decrement bi_phys_segments for
all bios, but only end_bio for bio2 and bio3. bio1->bi_next still points to
bio2, but this doesn't matter. When stripe1 is finished, it will not touch bio2
because of r5_next_bio check. Next time stripe1 will end_bio for bio1 and
stripe3 will end_bio bio4.

before add_stripe_bio() addes a bio to a stripe, we already increament the bio
bi_phys_segments, so don't worry other stripes release the bio.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

Neil pointed out the bitmap write optimization in handle_stripe_clean_event()
is unnecessary, because the chance one stripe gets written twice in the mean
time is rare. We can always do a bitmap_startwrite when a write request is
added to a stripe and bitmap_endwrite after write request is done.  Delete the
optimization. With it, we can delete some cases of device_lock.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

Raid5 overrides bio->bi_phys_segments, accessing it is with device_lock hold,
which is unnecessary, We can make it lockless actually.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

release_stripe() is a place conf->device_lock is heavily contended. We take the
lock even stripe count isn't 1, which isn't required.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

commit 4367af55
   md/raid1: clear bad-block record when write succeeds.

Added a 'reschedule_retry' call possibility at the end of
end_sync_write, but didn't add matching code at the end of
sync_request_write.  So if the writes complete very quickly, or
scheduling makes it seem that way, then we can miss rescheduling
the request and the resync could hang.

Also commit 73d5c38a
    md: avoid races when stopping resync.

Fix a race condition in this same code in end_sync_write but didn't
make the change in sync_request_write.

This patch updates sync_request_write to fix both of those.
Patch is suitable for 3.1 and later kernels.
Reported-by: Alexander Lyakas <alex.bolshoy@gmail.com>
Original-version-by: Alexander Lyakas <alex.bolshoy@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>

md will refuse to stop an array if any other fd (or mounted fs) is
using it.
When any fs is unmounted of when the last open fd is closed all
pending IO will be flushed (e.g. sync_blockdev call in __blkdev_put)
so there will be no pending IO to worry about when the array is
stopped.

However in order to send the STOP_ARRAY ioctl to stop the array one
must first get and open fd on the block device.
If some fd is being used to write to the block device and it is closed
after mdadm open the block device, but before mdadm issues the
STOP_ARRAY ioctl, then there will be no last-close on the md device so
__blkdev_put will not call sync_blockdev.

If this happens, then IO can still be in-flight while md tears down
the array and bad things can happen (use-after-free and subsequent
havoc).

So in the case where do_md_stop is being called from an open file
descriptor, call sync_block after taking the mutex to ensure there
will be no new openers.

This is needed when setting a read-write device to read-only too.

Cc: stable@vger.kernel.org
Reported-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

commit c6563a8c
    md: add possibility to change data-offset for devices.

introduced a 'new_data_offset' attribute which should normally
be the same as 'data_offset', but can be explicitly set to a different
value to allow a reshape operation to move the data.

Unfortunately when the 'data_offset' is explicitly set through
sysfs, the new_data_offset is not also set, so the two would become
out-of-sync incorrectly.

One result of this is that trying to set the 'size' after the
'data_offset' would fail because it is not permitted to set the size
when the 'data_offset' and 'new_data_offset' are different - as that
can be confusing.
Consequently when mdadm tried to do this while assembling an IMSM
array it would fail.

This bug was introduced in 3.5-rc1.
Reported-by: Brian Downing <bdowning@lavos.net>
Bisected-by: Brian Downing <bdowning@lavos.net>
Tested-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: NeilBrown <neilb@suse.de>

The idr_pre_get() function never returns a value < 0.  It returns 0 (no
memory) or 1 (OK).
Reported-by: Silva Paulo <psdasilva@yahoo.com>
[ Rewrote Silva's patch, but attributing it to Silva anyway  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull sound fixes from Takashi Iwai:
 "Containing the regression fixes for USB-audio due to the transition to
  the new streaming logic, mostly found on Logitech webcams."

* tag 'sound-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: snd-usb: move calls to usb_set_interface
  ALSA: usb-audio: Fix the first PCM interface assignment

Pull ACPI patch from Len Brown.

* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
  ACPICA: Fix possible fault in return package object repair code

vsyscall_seccomp introduced a dependency on __secure_computing.  On
configurations with CONFIG_SECCOMP disabled, compilation will fail.
Reported-by: feng xiangjun <fengxj325@gmail.com>
Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull cpufreq fix from Rafael Wysocki:
 "This fixes a regression preventing the ACPI cpufreq driver from
  loading on some systems where it worked previously without any
  problems."

* tag 'cpufreq-for-3.5-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  cpufreq / ACPI: Fix not loading acpi-cpufreq driver regression

Pull ARM Samsung SoC fixes from Arnd Bergmann.

* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  ARM: S3C24XX: Correct CAMIF interrupt definitions
  ARM: S3C24XX: Correct AC97 clock control bit for S3C2440
  ARM: SAMSUNG: fix race in s3c_adc_start for ADC
  ARM: SAMSUNG: Update default rate for xusbxti clock
  ARM: EXYNOS: register devices in 'need_restore' state for pm_domains
  ARM: EXYNOS: read initial state of power domain from hw registers

Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus' and 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU, perf, and scheduler fixes from Ingo Molnar.

The RCU fix is a revert for an optimization that could cause deadlocks.

One of the scheduler commits (164c33c6 "sched: Fix fork() error path
to not crash") is correct but not complete (some architectures like Tile
are not covered yet) - the resulting additional fixes are still WIP and
Ingo did not want to delay these pending fixes.  See this thread on
lkml:

  [PATCH] fork: fix error handling in dup_task()

The perf fixes are just trivial oneliners.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix segfault with report and mixed guestmount use
  perf kvm: Fix regression with guest machine creation
  perf script: Fix format regression due to libtraceevent merge
  ring-buffer: Fix accounting of entries when removing pages
  ring-buffer: Fix crash due to uninitialized new_pages list head

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  MAINTAINERS/sched: Update scheduler file pattern
  sched/nohz: Rewrite and fix load-avg computation -- again
  sched: Fix fork() error path to not crash

Fixes a problem that can occur when a lone package object is
wrapped with an outer package object in order to conform to
the ACPI specification. Can affect these predefined names:
_ALR,_MLS,_PSS,_TRT,_TSS,_PRT,_HPX,_DLM,_CSD,_PSD,_TSD

https://bugzilla.kernel.org/show_bug.cgi?id=44171

This problem was introduced in 3.4-rc1 by commit
6a99b1c9
(ACPICA: Object repair code: Support to add Package wrappers)
Reported-by: Vlastimil Babka <caster@gentoo.org>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Cc: <stable@vger.kernel.org> # 3.4
Signed-off-by: Len Brown <len.brown@intel.com>

Merge branch 'v3.5-samsung-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung into fixes

From Kukjin Kim <kgene.kim@samsung.com>:

* 'v3.5-samsung-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung:
  ARM: S3C24XX: Correct CAMIF interrupt definitions
  ARM: S3C24XX: Correct AC97 clock control bit for S3C2440
  ARM: SAMSUNG: fix race in s3c_adc_start for ADC
  ARM: SAMSUNG: Update default rate for xusbxti clock
  ARM: EXYNOS: register devices in 'need_restore' state for pm_domains
  ARM: EXYNOS: read initial state of power domain from hw registers
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Pull use-after-free RAID1 bugfix from NeilBrown.

* tag 'md-3.5-fixes' of git://neil.brown.name/md:
  md/raid1: fix use-after-free bug in RAID1 data-check code.

Pull the leap second fixes from Thomas Gleixner:
 "It's a rather large series, but well discussed, refined and reviewed.
  It got a massive testing by John, Prarit and tip.

  In theory we could split it into two parts.  The first two patches

    f55a6faa: hrtimer: Provide clock_was_set_delayed()
    4873fa07: timekeeping: Fix leapsecond triggered load spike issue

  are merely preventing the stuff loops forever issues, which people
  have observed.

  But there is no point in delaying the other 4 commits which achieve
  full correctness into 3.6 as they are tagged for stable anyway.  And I
  rather prefer to have the full fixes merged in bulk than a "prevent
  the observable wreckage and deal with the hidden fallout later"
  approach."

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimer: Update hrtimer base offsets each hrtimer_interrupt
  timekeeping: Provide hrtimer update function
  hrtimers: Move lock held region in hrtimer_interrupt()
  timekeeping: Maintain ktime_t based offsets for hrtimers
  timekeeping: Fix leapsecond triggered load spike issue
  hrtimer: Provide clock_was_set_delayed()

If a seccomp filter program is installed, older static binaries and
distributions with older libc implementations (glibc 2.13 and earlier)
that rely on vsyscall use will be terminated regardless of the filter
program policy when executing time, gettimeofday, or getcpu.  This is
only the case when vsyscall emulation is in use (vsyscall=emulate is the
default).

This patch emulates system call entry inside a vsyscall=emulate by
populating regs->ax and regs->orig_ax with the system call number prior
to calling into seccomp such that all seccomp-dependencies function
normally.  Additionally, system call return behavior is emulated in line
with other vsyscall entrypoints for the trace/trap cases.

[ v2: fixed ip and sp on SECCOMP_RET_TRAP/TRACE (thanks to luto@mit.edu) ]
Reported-and-tested-by: Owen Kibel <qmewlo@gmail.com>
Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Please pull one hwmon subsystem fix from Jean Delvare.

* 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging:
  hwmon: (it87) Preserve configuration register bits on init

Pull NFS client bugfixes from Trond Myklebust:
 - Fix an NFSv4 mount regression
 - Fix O_DIRECT list manipulation snafus

* tag 'nfs-for-3.5-4' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFSv4: Fix an NFSv4 mount regression
  NFS: Fix list manipulation snafus in fs/nfs/direct.c

This can be trivially triggered from userspace by passing in something unexpected.

    kernel BUG at fs/locks.c:1468!
    invalid opcode: 0000 [#1] SMP
    RIP: 0010:generic_setlease+0xc2/0x100
    Call Trace:
      __vfs_setlease+0x35/0x40
      fcntl_setlease+0x76/0x150
      sys_fcntl+0x1c6/0x810
      system_call_fastpath+0x1a/0x1f
Signed-off-by: Dave Jones <davej@redhat.com>
Cc: stable@kernel.org # 3.2+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull input layer fixes from Dmitry Torokhov:
 "The changes are limited to adding new VID/PID combinations to drivers
  to enable support for new versions of hardware, most notably hardware
  found in new MacBook Pro Retina boxes."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: xpad - add Andamiro Pump It Up pad
  Input: xpad - add signature for Razer Onza Tournament Edition
  Input: xpad - handle all variations of Mad Catz Beat Pad
  Input: bcm5974 - Add support for 2012 MacBook Pro Retina
  HID: add support for 2012 MacBook Pro Retina

Pull media fixes from Mauro Carvalho Chehab:
 - Some regression fixes at the audio part for devices with
   cx23885/cx25840
 - A DMA corruption fix at cx231xx
 - two fixes at the winbond IR driver
 - Several fixes for the EXYNOS media driver (s5p)
 - two fixes at the OMAP3 preview driver
 - one fix at the dvb core failure path
 - an include missing (slab.h) at smiapp-core causing compilation
   breakage
 - em28xx was not loading the IR driver driver anymore.

* 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (31 commits)
  [media] Revert "[media] V4L: JPEG class documentation corrections"
  [media] s5p-fimc: Add missing FIMC-LITE file operations locking
  [media] omap3isp: preview: Fix contrast and brightness handling
  [media] omap3isp: preview: Fix output size computation depending on input format
  [media] winbond-cir: Initialise timeout, driver_type and allowed_protos
  [media] winbond-cir: Fix txandrx module info
  [media] cx23885: Silence unknown command warnings
  [media] cx23885: add support for HVR-1255 analog (cx23888 variant)
  [media] cx23885: make analog support work for HVR_1250 (cx23885 variant)
  [media] cx25840: fix vsrc/hsrc usage on cx23888 designs
  [media] cx25840: fix regression in HVR-1800 analog audio
  [media] cx25840: fix regression in analog support hue/saturation controls
  [media] cx25840: fix regression in HVR-1800 analog support
  [media] s5p-mfc: Fixed setup of custom controls in decoder and encoder
  [media] cx231xx: don't DMA to random addresses
  [media] em28xx: fix em28xx-rc load
  [media] dvb-core: Release semaphore on error path dvb_register_device()
  [media] s5p-fimc: Stop media entity pipeline if fimc_pipeline_validate fails
  [media] s5p-fimc: Fix compiler warning in fimc-lite.c
  [media] s5p-fimc: media_entity_pipeline_start() may fail
  ...

Pull MMC fixes from Chris Ball:
 - Revert a patch that made failing to select power class fatal;
   it turns out that it fails non-fatally on Tegra boards.
   Regression against 3.5-rc1.
 - Add the IRQF_ONESHOT flag to the cd-gpio driver, which turned
   into a regression in 3.5-rc1 when IRQF_ONESHOT became required
   for threaded IRQs with no handler.

* tag 'mmc-fixes-for-3.5-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/cjb/mmc:
  mmc: cd-gpio: pass IRQF_ONESHOT to request_threaded_irq()
  mmc: core: Revert "skip card initialization if power class selection fails"

Pull late MTD fixes from David Woodhouse:
 - fix 'sparse warning fix' regression which totally breaks MXC NAND
 - fix GPMI NAND regression when used with UBI
 - update/correct sysfs documentation for new 'bitflip_threshold' field
 - fix nandsim build failure

* tag 'for-linus-20120712' of git://git.infradead.org/linux-mtd:
  mtd: nandsim: don't open code a do_div helper
  mtd: ABI documentation: clarification of bitflip_threshold
  mtd: gpmi-nand: fix read page when reading to vmalloced area
  mtd: mxc_nand: use 32bit copy functions

Pull MFD Fixes from Samuel Ortiz:
 - Three Palmas fixes, One of them being a build error fix.
 - Two mc13xx fixes.  One for fixing an SPI regmap configuration and
   another one for working around an i.Mx hardware bug.
 - One omap-usb regression fix.
 - One twl6040 build breakage fix.
 - One file deletion (ab5500-core.h) that was overlooked during the last
   merge window.

* tag 'mfd-for-linus-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/sameo/mfd-2.6:
  mfd: Add missing hunk to change palmas irq to clear on read
  mfd: Fix palmas regulator pdata missing
  mfd: USB: Fix the omap-usb EHCI ULPI PHY reset fix issues.
  mfd: Update twl6040 Kconfig to avoid build breakage
  mfd: Delete ab5500-core.h
  mfd: mc13xxx workaround SPI hardware bug on i.Mx
  mfd: Fix mc13xxx SPI regmap
  mfd: Add terminating entry for i2c_device_id palmas table

Pull SuperH fixes from Paul Mundt.

* tag 'sh-for-linus' of git://github.com/pmundt/linux-sh:
  SH: Convert out[bwl] macros to inline functions
  sh: Fix up se7721 GPIOLIB=y build warnings.

Pull a couple of KVM fixes from Avi Kivity:
 "One is an adjustment for an irq layer change that affected device
  assignment, the other a one-liner ppc fix."

* git://git.kernel.org/pub/scm/virt/kvm/kvm:
  powerpc/kvm: Fix "PR" KVM implementation of H_CEDE
  KVM: Fix device assignment threaded irq handler

Commit 080399aa ("block: don't mark buffers beyond end of disk as
mapped") exposed a bug in __getblk_slow that causes mount to hang as it
loops infinitely waiting for a buffer that lies beyond the end of the
disk to become uptodate.

The problem was initially reported by Torsten Hilbrich here:

    https://lkml.org/lkml/2012/6/18/54

and also reported independently here:

    http://www.sysresccd.org/forums/viewtopic.php?f=13&t=4511

and then Richard W.M.  Jones and Marcos Mello noted a few separate
bugzillas also associated with the same issue.  This patch has been
confirmed to fix:

    https://bugzilla.redhat.com/show_bug.cgi?id=835019

The main problem is here, in __getblk_slow:

        for (;;) {
                struct buffer_head * bh;
                int ret;

                bh = __find_get_block(bdev, block, size);
                if (bh)
                        return bh;

                ret = grow_buffers(bdev, block, size);
                if (ret < 0)
                        return NULL;
                if (ret == 0)
                        free_more_memory();
        }

__find_get_block does not find the block, since it will not be marked as
mapped, and so grow_buffers is called to fill in the buffers for the
associated page.  I believe the for (;;) loop is there primarily to
retry in the case of memory pressure keeping grow_buffers from
succeeding.  However, we also continue to loop for other cases, like the
block lying beond the end of the disk.  So, the fix I came up with is to
only loop when grow_buffers fails due to memory allocation issues
(return value of 0).

The attached patch was tested by myself, Torsten, and Rich, and was
found to resolve the problem in call cases.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Reported-and-Tested-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Josh Boyer <jwboyer@redhat.com>
Cc: Stable <stable@vger.kernel.org>  # 3.0+
[ Jens is on vacation, taking this directly  - Linus ]
--
Stable Notes: this patch requires backport to 3.0, 3.2 and 3.3.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>