Herbert Poetzl reported a performance regression since 2.6.39.  The test
is a simple dd read, but with big block size.  The reason is:

T1: ra (A, A+128k), (A+128k, A+256k)
T2: lock_page for page A, submit the 256k
T3: hit page A+128K, ra (A+256k, A+384). the range isn't submitted
because of plug and there isn't any lock_page till we hit page A+256k
because all pages from A to A+256k is in memory
T4: hit page A+256k, ra (A+384, A+ 512). Because of plug, the range isn't
submitted again.
T5: lock_page A+256k, so (A+256k, A+512k) will be submitted. The task is
waitting for (A+256k, A+512k) finish.

There is no request to disk in T3 and T4, so readahead pipeline breaks.

We really don't need block plug for generic_file_aio_read() for buffered
I/O.  The readahead already has plug and has fine grained control when I/O
should be submitted.  Deleting plug for buffered I/O fixes the regression.

One side effect is plug makes the request size 256k, the size is 128k
without it.  This is because default ra size is 128k and not a reason we
need plug here.

Vivek said:

: We submit some readahead IO to device request queue but because of nested
: plug, queue never gets unplugged.  When read logic reaches a page which is
: not in page cache, it waits for page to be read from the disk
: (lock_page_killable()) and that time we flush the plug list.
:
: So effectively read ahead logic is kind of broken in parts because of
: nested plugging.  Removing top level plug (generic_file_aio_read()) for
: buffered reads, will allow unplugging queue earlier for readahead.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Reported-by: NHerbert Poetzl <herbert@13thfloor.at>
Tested-by: NEric Dumazet <eric.dumazet@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In function pre_handler_kretprobe(), the allocated kretprobe_instance
object will get leaked if the entry_handler callback returns non-zero.
This may cause all the preallocated kretprobe_instance objects exhausted.

This issue can be reproduced by changing
samples/kprobes/kretprobe_example.c to probe "mutex_unlock".  And the fix
is straightforward: just put the allocated kretprobe_instance object back
onto the free_instances list.

[akpm@linux-foundation.org: use raw_spin_lock/unlock]
Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
Acked-by: NJim Keniston <jkenisto@us.ibm.com>
Acked-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

KDFONTOP(GET) currently fails with EIO when being run in a 32bit userland
with a 64bit kernel if the font width is not 8.

This is because of the setting of the KD_FONT_FLAG_OLD flag, which makes
con_font_get return EIO in such case.

This flag should *not* be set for KDFONTOP, since it's actually the whole
point of this flag (see comment in con_font_set for instance).
Signed-off-by: NSamuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: NArnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Arthur Taylor <art@ified.ca>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lkdtm_do_action() may call sleeping functions like kmalloc(), so do not
call it with spin lock held.
Signed-off-by: NWANG Cong <xiyou.wangcong@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Reviewed-by: NDave Young <dyoung@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix a race condition that shows in conjunction with xip_file_fault() when
two threads of the same user process fault on the same memory page.

In this case, the race winner will install the page table entry and the
unlucky loser will cause an oops: xip_file_fault calls vm_insert_pfn (via
vm_insert_mixed) which drops out at this check:

	retval = -EBUSY;
	if (!pte_none(*pte))
		goto out_unlock;

The resulting -EBUSY return value will trigger a BUG_ON() in
xip_file_fault.

This fix simply considers the fault as fixed in this case, because the
race winner has successfully installed the pte.

[akpm@linux-foundation.org: use conventional (and consistent) comment layout]
Reported-by: NDavid Sadler <dsadler@us.ibm.com>
Signed-off-by: NCarsten Otte <cotte@de.ibm.com>
Reported-by: NLouis Alex Eisner <leisner@cs.ucsd.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c: In function 'memcg_check_events':
mm/memcontrol.c:779: warning: unused variable 'do_numainfo'
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Hiroyuki KAMEZAWA <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: N"Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Enable use of the generic atomic64 implementation on AVR32 platforms.
Without this the kernel fails to build as the architecture does not
provide its version.
Signed-off-by: NFabio Baltieri <fabio.baltieri@gmail.com>
Acked-by: NHans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Postpone resetting page->mapping until the final remove_migration_ptes().
Otherwise the expression PageAnon(migration_entry_to_page(entry)) does not
work.
Signed-off-by: NKonstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Defining memscan() as memchr() is wrong, because the return values of
memscan() and memchr() are different when the character is not found.  So
use the generic memscan() implementation to fix this.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.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>

commit 07fe9977 ("lguest: move the lguest tool to the tools
directory") moved the files, update the patterns.  Sort F: patterns
alphabetically too.
Signed-off-by: NJoe Perches <joe@perches.com>
Cc: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Two commits moved files from staging to drivers/media/

commit d6ce55de ("[media] move cx25821 out of staging")
commit be304970 ("[media] move tm6000 to drivers/media/video")

Remove the sections.
Signed-off-by: NJoe Perches <joe@perches.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

commit 784a90c0 ("ARM i.MX: Merge i.MX5 support into mach-imx")
merged the files, remove the iMX5 section.
Signed-off-by: NJoe Perches <joe@perches.com>
Cc: Amit Kucheria <amit.kucheria@canonical.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 9be96f3f ("move fs/partitions to block/") moved the files,
update the patterns.
Signed-off-by: NJoe Perches <joe@perches.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
  rbd: fix safety of rbd_put_client()
  rbd: fix a memory leak in rbd_get_client()
  ceph: create a new session lock to avoid lock inversion
  ceph: fix length validation in parse_reply_info()
  ceph: initialize client debugfs outside of monc->mutex
  ceph: change "ceph.layout" xattr to be "ceph.file.layout"

Signed-off-by: NJosh Triplett <josh@joshtriplett.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The rbd_client structure uses a kref to arrange for cleaning up and
freeing an instance when its last reference is dropped.  The cleanup
routine is rbd_client_release(), and one of the things it does is
delete the rbd_client from rbd_client_list.  It acquires node_lock
to do so, but the way it is done is still not safe.

The problem is that when attempting to reuse an existing rbd_client,
the structure found might already be in the process of getting
destroyed and cleaned up.

Here's the scenario, with "CLIENT" representing an existing
rbd_client that's involved in the race:

 Thread on CPU A                | Thread on CPU B
 ---------------                | ---------------
 rbd_put_client(CLIENT)         | rbd_get_client()
   kref_put()                   |   (acquires node_lock)
     kref->refcount becomes 0   |   __rbd_client_find() returns CLIENT
     calls rbd_client_release() |   kref_get(&CLIENT->kref);
                                |   (releases node_lock)
       (acquires node_lock)     |
       deletes CLIENT from list | ...and starts using CLIENT...
       (releases node_lock)     |
       and frees CLIENT         | <-- but CLIENT gets freed here

Fix this by having rbd_put_client() acquire node_lock.  The result
could still be improved, but at least it avoids this problem.
Signed-off-by: NAlex Elder <elder@dreamhost.com>
Signed-off-by: NSage Weil <sage@newdream.net>

This fixes the race in process_vm_core found by Oleg (see

  http://article.gmane.org/gmane.linux.kernel/1235667/

for details).

This has been updated since I last sent it as the creation of the new
mm_access() function did almost exactly the same thing as parts of the
previous version of this patch did.

In order to use mm_access() even when /proc isn't enabled, we move it to
kernel/fork.c where other related process mm access functions already
are.
Signed-off-by: NChris Yeoh <yeohc@au1.ibm.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If an existing rbd client is found to be suitable for use in
rbd_get_client(), the rbd_options structure is not being
freed as it should.  Fix that.
Signed-off-by: NAlex Elder <elder@dreamhost.com>
Signed-off-by: NSage Weil <sage@newdream.net>

Lockdep was reporting a possible circular lock dependency in
dentry_lease_is_valid().  That function needs to sample the
session's s_cap_gen and and s_cap_ttl fields coherently, but needs
to do so while holding a dentry lock.  The s_cap_lock field was
being used to protect the two fields, but that can't be taken while
holding a lock on a dentry within the session.

In most cases, the s_cap_gen and s_cap_ttl fields only get operated
on separately.  But in three cases they need to be updated together.
Implement a new lock to protect the spots updating both fields
atomically is required.
Signed-off-by: NAlex Elder <elder@dreamhost.com>
Reviewed-by: NSage Weil <sage@newdream.net>

"len" is read from network and thus needs validation.  Otherwise, given
a bogus "len" value, p+len could be an out-of-bounds pointer, which is
used in further parsing.
Signed-off-by: NXi Wang <xi.wang@gmail.com>
Signed-off-by: NSage Weil <sage@newdream.net>

Initializing debufs under monc->mutex introduces a lock dependency for
sb->s_type->i_mutex_key, which (combined with several other dependencies)
leads to an annoying lockdep warning.  There's no particular reason to do
the debugfs setup under this lock, so move it out.

It used to be the case that our first monmap could come from the OSD; that
is no longer the case with recent servers, so we will reliably set up the
client entry during the initial authentication.

We don't have to worry about racing with debugfs teardown by
ceph_debugfs_client_cleanup() because ceph_destroy_client() calls
ceph_msgr_flush() first, which will wait for the message dispatch work
to complete (and the debugfs init to complete).

Fixes: #1940
Signed-off-by: NSage Weil <sage@newdream.net>

The virtual extended attribute named "ceph.layout" is meaningful
only for regular files.  Change its name to be "ceph.file.layout" to
more directly reflect that in the ceph xattr namespace.  Preserve
the old "ceph.layout" name for the time being (until we decide it's
safe to get rid of it entirely).

Add a missing initializer for "readonly" in the terminating entry.
Signed-off-by: NAlex Elder <elder@dreamhost.com>
Reviewed-by: NSage Weil <sage@newdream.net>

* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux:
  drm/radeon/kms/blit: fix blit copy for very large buffers
  drm/radeon/kms: fix TRAVIS panel setup
  drm/radeon: fix use after free in ATRM bios reading code.
  drm/radeon/kms: Fix device tree linkage of DP i2c buses too
  drm/radeon: Set DESKTOP_HEIGHT register to the framebuffer (not mode) height.
  drm/radeon/kms: disable output polling when suspended
  drm/nv50/pm: signedness bug in nv50_pm_clocks_pre()
  drm/nouveau/gem: fix fence_sync race / oops
  drm/nouveau: fix typo on mxmdcb option
  drm/nouveau/mxm: pretend to succeed, even if we can't shadow the MXM-SIS
  drm/nouveau/disp: check that panel power gpio is enabled at init time

* 'next' of git://git.monstr.eu/linux-2.6-microblaze:
  Revert "microblaze: Add topology init"

Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus', 'sched-urgent-for-linus' and 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  bugs, x86: Fix printk levels for panic, softlockups and stack dumps

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf top: Fix number of samples displayed
  perf tools: Fix strlen() bug in perf_event__synthesize_event_type()
  perf tools: Fix broken build by defining _GNU_SOURCE in Makefile
  x86/dumpstack: Remove unneeded check in dump_trace()
  perf: Fix broken interrupt rate throttling

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/rt: Fix task stack corruption under __ARCH_WANT_INTERRUPTS_ON_CTXSW
  sched: Fix ancient race in do_exit()
  sched/nohz: Fix nohz cpu idle load balancing state with cpu hotplug
  sched/s390: Fix compile error in sched/core.c
  sched: Fix rq->nr_uninterruptible update race

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/reboot: Remove VersaLogic Menlow reboot quirk
  x86/reboot: Skip DMI checks if reboot set by user
  x86: Properly parenthesize cmpxchg() macro arguments

Evergreen and NI blit copy was broken if the buffer maps to a rectangle
whose one dimension is 16384 (max dimension allowed by these chips).
In the mainline kernel, the problem is exposed only when buffers are
very large (1G), but it's still a problem. The problem could be exposed
for smaller buffers if anyone modifies the algorithm for rectangle
construction in r600_blit_create_rect() (the reason why someone would
modify that algorithm is to tune the performance of buffer moves).

The root cause was in i2f() function which only operated on range between
0 and 16383. Fix this by extending the range of i2f() function to 0 to
32767.

While at it improve the function so that the range can be easily
extended in the future (if it becomes necessary), cleanup lines
over 80 characters, and replace in-line comments with one strategic
comment that explains the crux of the function.

Credits to michel@daenzer.net for pointing out the root cause of
the bug.

v2: Fix I2F_MAX_INPUT constant definition goof and warn only once
    if input argument is out of range. Edit the comment a little
    bit to avoid some linguistic confusion and make it look better
    in general.
Signed-off-by: NIlija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NMichel Dänzer <michel@daenzer.net>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Different versions of the DP to LVDS bridge chip
need different panel mode settings depending on
the chip version used.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=41569Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=45503

Reported-and-Debugged-by: mlambda@gmail.com
Signed-off-by: NDave Airlie <airlied@redhat.com>

firewire fixes post v3.3-rc1

Add workarounds table entries for hardware bugs in
  - FireWire part of Sound Blaster Audigy cards,
  - Ricoh PCIe 1394 controllers.
Without these, several protocols, e.g. AV/C, do not work on the
Audigy, and the Ricoh PCIe controllers wouldn't work at all.
This does not concern the older Ricoh PCI controllers.

* tag 'firewire-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394:
  firewire: ohci: disable MSI on Ricoh controllers
  firewire: ohci: add reset packet quirk for SB Audigy

Add MODULE_LICENSE() as per the license in the comment at the top of the
file for this source module to fix build warning:

  WARNING: modpost: missing MODULE_LICENSE() in drivers/staging/media/go7007/go7007-usb.o
  see include/linux/module.h for more information
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Cc: Ross Cohen <rcohen@snurgle.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix 2 fatal errors in the device-drivers docbook.
Also add some missing files from drivers/base/; since several
of these are DMA-related, add a section for DMA Management.

docproc: drivers/base/sys.c: No such file or directory
docproc: drivers/tty/serial/8250.c: No such file or directory
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

* 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  lib: Fix 32-bit sparc udiv_qrnnd() definition in mpilib's longlong.h
  lib: Fix multiple definitions of clz_tab
  lib/digsig: checks for NULL return value
  lib/mpi: added missing NULL check
  lib/mpi: added comment on divide by 0 case
  lib/mpi: check for possible zero length
  lib/digsig: pkcs_1_v1_5_decode_emsa cleanup
  lib/digsig: additional sanity checks against badly formated key payload
  lib/mpi: removed unused functions
  lib/mpi: checks for zero divisor length
  lib/mpi: return error code on dividing by zero
  lib/mpi: replaced MPI_NULL with normal NULL
  lib/mpi: added missing NULL check

This copy of longlong.h is extremely dated and results in compile
errors on sparc32 when MPILIB is enabled, copy over the more uptodate
implementation from arch/sparc/math/sfp-util_32.h
Reported-by: NAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NJames Morris <jmorris@namei.org>

Both sparc 32-bit's software divide assembler and MPILIB provide
clz_tab[] with identical contents.

Break it out into a seperate object file and select it when
SPARC32 or MPILIB is set.
Reported-by: NAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NJames Morris <jmorris@namei.org>

InfiniBand/RDMA fixes for 3.3:

 - Fix a crash due to a regression (uninitialized refcnt) introduced in
   3.2 with XRC support.
 - Close race in how ucma reports events when connect fails.
 - Process vendor-specific MADs in mlx4 so that eg FDR-10 data rate works.
 - Fix regression in qib caused by over-aggressive PCIe tuning.
 - Other small fixes for hardware drivers (ipath, nes, qib).

* tag 'rdma-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband:
  RDMA/nes: Copyright update
  IB/mlx4: pass SMP vendor-specific attribute MADs to firmware
  RDMA/nes: Fix fast memory registration opcode
  RDMA/nes: Fix fast memory registration length
  RDMA/ucma: Discard all events for new connections until accepted
  IB/qib: Roll back PCIe tuning change
  IB/qib: Use GFP_ATOMIC when locks are held
  RDMA/nes: Add missing rcu_read_unlock() in nes_addr_resolve_neigh()
  RDMA/nes: Fix for sending MPA reject frame
  IB/ipath: Calling PTR_ERR() on right variable in create_file()
  RDMA/core: Fix kernel panic by always initializing qp->usecnt

Once /proc/pid/mem is opened, the memory can't be released until
mem_release() even if its owner exits.

Change mem_open() to do atomic_inc(mm_count) + mmput(), this only
pins mm_struct. Change mem_rw() to do atomic_inc_not_zero(mm_count)
before access_remote_vm(), this verifies that this mm is still alive.

I am not sure what should mem_rw() return if atomic_inc_not_zero()
fails. With this patch it returns zero to match the "mm == NULL" case,
may be it should return -EINVAL like it did before e268337d.

Perhaps it makes sense to add the additional fatal_signal_pending()
check into the main loop, to ensure we do not hold this memory if
the target task was oom-killed.

Cc: stable@kernel.org
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

No functional changes, cleanup and preparation.

mem_read() and mem_write() are very similar. Move this code into the
new common helper, mem_rw(), which takes the additional "int write"
argument.

Cc: stable@kernel.org
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_release() can hit mm == NULL, add the necessary check.

Cc: stable@kernel.org
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

My email address has changed, the suse.de one is now dead, so update all
of my MAINTAINER entries with the correct one so that patches don't get
lost.

Also change the status of some of my entries as I'm supposed to be doing
this stuff now for real.
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes merge conflict resolution breakage introduced by merge
d3712b9d ("Merge tag 'for-linus' of git://github.com/prasad-joshi/logfs_upstream").

The commit changed 'mtd_can_have_bb()' function and made it always
return zero, which is incorrect.  Instead, we need it to return whether
the underlying flash device can have bad eraseblocks or not.  UBI needs
this information because it affects how it handles the underlying flash.
E.g., if the underlying flash is NOR, it cannot have bad blocks and any
write or erase error is fatal, and all we can do is to switch to R/O
mode.  We do not need to reserve a pool of good eraseblocks for bad
eraseblocks handling, and so on.

This patch also removes 'mtd_can_have_bb()' invocations from Logfs to
ensure correct Logfs behavior.

I've tested that with this patch UBI works on top of NOR and NAND
flashes emulated by mtdram and nandsim correspondingly.

This patch is based on patch from Linus Torvalds.
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Acked-by: NJörn Engel <joern@logfs.org>
Acked-by: NPrasad Joshi <prasadjoshi.linux@gmail.com>
Acked-by: NBrian Norris <computersforpeace@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>