The patch uses 'nr_pages' argument of fuse_readpages() as heuristics for the
number of page pointers to allocate.

This can be improved further by taking in consideration fc->max_read and gaps
between page indices, but it's not clear whether it's worthy or not.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

The patch reworks fuse_retrieve() to allocate only so many page pointers
as needed. The core part of the patch is the following calculation:

	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

(thanks Miklos for formula). All other changes are mostly shuffling lines.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

The patch categorizes all fuse_get_req() invocations into two categories:
 - fuse_get_req_nopages(fc) - when caller doesn't care about req->pages
 - fuse_get_req(fc, n) - when caller need n page pointers (n > 0)

Adding fuse_get_req_nopages() helps to avoid numerous fuse_get_req(fc, 0)
scattered over code. Now it's clear from the first glance when a caller need
fuse_req with page pointers.

The patch doesn't make any logic changes. In multi-page case, it silly
allocates array of FUSE_MAX_PAGES_PER_REQ page pointers. This will be amended
by future patches.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

The patch removes inline array of FUSE_MAX_PAGES_PER_REQ page pointers from
fuse_req. Instead of that, req->pages may now point either to small inline
array or to an array allocated dynamically.

This essentially means that all callers of fuse_request_alloc[_nofs] should
pass the number of pages needed explicitly.

The patch doesn't make any logic changes.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

This patch implements readdirplus support in FUSE, similar to NFS.
The payload returned in the readdirplus call contains
'fuse_entry_out' structure thereby providing all the necessary inputs
for 'faking' a lookup() operation on the spot.

If the dentry and inode already existed (for e.g. in a re-run of ls -l)
then just the inode attributes timeout and dentry timeout are refreshed.

With a simple client->network->server implementation of a FUSE based
filesystem, the following performance observations were made:

Test: Performing a filesystem crawl over 20,000 files with

sh# time ls -lR /mnt

Without readdirplus:
Run 1: 18.1s
Run 2: 16.0s
Run 3: 16.2s

With readdirplus:
Run 1: 4.1s
Run 2: 3.8s
Run 3: 3.8s

The performance improvement is significant as it avoided 20,000 upcalls
calls (lookup). Cache consistency is no worse than what already is.
Signed-off-by: Anand V. Avati <avati@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

Pull more USB fixes from Greg Kroah-Hartman:
 "Here are some more USB fixes for the 3.8-rc4 tree.

  Some gadget driver fixes, and finally resolved the ehci-mxc driver
  build issues (it's just some code moving around and being deleted)."

* tag 'usb-3.8-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  USB: EHCI: fix build error in ehci-mxc
  USB: EHCI: add a name for the platform-private field
  USB: EHCI: fix incorrect configuration test
  USB: EHCI: Move definition of EHCI_STATS to ehci.h
  USB: UHCI: fix IRQ race during initialization
  usb: gadget: FunctionFS: Fix missing braces in parse_opts
  usb: dwc3: gadget: fix ep->maxburst for ep0
  ARM: i.MX clock: Change the connection-id for fsl-usb2-udc
  usb: gadget: fsl_mxc_udc: replace MX35_IO_ADDRESS to ioremap
  usb: gadget: fsl-mxc-udc: replace cpu_is_xxx() with platform_device_id
  usb: musb: cppi_dma: drop '__init' annotation

Pull drivers/misc fix from Greg Kroah-Hartman:
 "Here is a single revert for the ti-st misc driver, fixing problem that
  was introduced in 3.7-rc1 that has been bothering people."

* tag 'char-misc-3.8-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  Revert "drivers/misc/ti-st: remove gpio handling"

Pull a TTY maintainer patch from Greg Kroah-Hartman:
 "Just a MAINTAINERS update, now that Alan has left for a bit, I'll
  continue to watch over the serial drivers."

* tag 'tty-3.8-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  MAINTAINERS: Someone needs to watch over the serial drivers

Pull media fixes from Mauro Carvalho Chehab:
 - gspca: add needed delay for I2C traffic for sonixb/sonixj cameras
 - gspca: add one missing Kinect USB ID
 - usbvideo: some regression fixes
 - omap3isp: fix some build issues
 - videobuf2: fix video output handling
 - exynos s5p/m5mols: a few regression fixes.

* 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  [media] uvcvideo: Set error_idx properly for S_EXT_CTRLS failures
  [media] uvcvideo: Cleanup leftovers of partial revert
  [media] uvcvideo: Return -EACCES when trying to set a read-only control
  [media] omap3isp: Don't include <plat/cpu.h>
  [media] s5p-mfc: Fix interrupt error handling routine
  [media] s5p-fimc: Fix return value of __fimc_md_create_flite_source_links()
  [media] m5mols: Fix typo in get_fmt callback
  [media] v4l: vb2: Set data_offset to 0 for single-plane output buffers
  [media] [FOR,v3.8] omap3isp: Don't include deleted OMAP plat/ header files
  [media] gspca_sonixj: Add a small delay after i2c_w1
  [media] gspca_sonixb: Properly wait between i2c writes
  [media] gspca_kinect: add Kinect for Windows USB id

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull m68k fixes from Geert Uytterhoeven:
 "The asm-generic changeset has been ack'ed by Arnd."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/linux-m68k:
  m68k: Wire up finit_module
  asm-generic/dma-mapping-broken.h: Provide dma_alloc_attrs()/dma_free_attrs()
  m68k: Provide dma_alloc_attrs()/dma_free_attrs()

Pull arm64 fixes from Catalin Marinas:
 - ELF coredump fix (more registers dumped than what user space expects)
 - SUBARCH name generation (s/aarch64/arm64/)

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64:
  arm64: makefile: fix uname munging when setting ARCH on native machine
  arm64: elf: fix core dumping to match what glibc expects

This patch (as1643b) fixes a build error in ehci-hcd when compiling for
ARM with allmodconfig:

drivers/usb/host/ehci-hcd.c:1285:0: warning: "PLATFORM_DRIVER" redefined [enabled by default]
drivers/usb/host/ehci-hcd.c:1255:0: note: this is the location of the previous definition
drivers/usb/host/ehci-mxc.c:280:31: warning: 'ehci_mxc_driver' defined but not used [-Wunused-variable]
drivers/usb/host/ehci-hcd.c:1285:0: warning: "PLATFORM_DRIVER" redefined [enabled by default]
drivers/usb/host/ehci-hcd.c:1255:0: note: this is the location of the previous definition

The fix is to convert ehci-mxc over to the new "ehci-hcd is a library"
scheme so that it can coexist peacefully with the ehci-platform
driver.  As part of the conversion the ehci_mxc_priv data structure,
which was allocated dynamically, is now placed where it belongs: in
the private area at the end of struct ehci_hcd.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull sound fixes from Takashi Iwai:
 "Only a few small HD-audio fixes:
   - Addition of new Conexant codec IDs
   - Two one-liners to add fixups for Realtek codecs
   - A last-minute regression fix for auto-mute with power-saving mode
     (regressed since 3.8-rc1)"

* tag 'sound-3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: hda - Fix inconsistent pin states after resume
  ALSA: hda - Add Conexant CX20755/20756/20757 codec IDs
  ALSA: hda - Add fixup for Acer AO725 laptop
  ALSA: hda - Fix mute led for another HP machine

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The commit [26a6cb6c: ALSA: hda - Implement a poll loop for jacks as a
module parameter] introduced the polling jack detection code, but it
also moved the call of snd_hda_jack_set_dirty_all() in the resume path
after resume/init ops call.  This caused a regression when the jack
state has been changed during power-down (e.g. in the power save
mode).  Since the driver doesn't probe the new jack state but keeps
using the cached value due to no dirty flag, the pin state remains
also as if the jack is still plugged.

The fix is simply moving snd_hda_jack_set_dirty_all() to the original
position.
Reported-by: Manolo Díaz <diaz.manolo@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

This reverts commit eccf2979.

The reason is that it broke TI WiLink shared transport on Panda.
Also, callback functions should not be added to board files anymore,
so revert to implementing the power functions in the driver itself.

Additionally, changed a variable name ('status' to 'err') so that this
revert compiles properly.

Cc: stable <stable@vger.kernel.org> [3.7]
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull PCI updates from Bjorn Helgaas:
 "The most important is a fix for a pciehp deadlock that occurs when
  unplugging a Thunderbolt adapter.  We also applied the same fix to
  shpchp, removed CONFIG_EXPERIMENTAL dependencies, fixed a
  pcie_aspm=force problem, and fixed a refcount leak.

  Details:

   - Hotplug
      PCI: pciehp: Use per-slot workqueues to avoid deadlock
      PCI: shpchp: Make shpchp_wq non-ordered
      PCI: shpchp: Handle push button event asynchronously
      PCI: shpchp: Use per-slot workqueues to avoid deadlock

   - Power management
      PCI: Allow pcie_aspm=force even when FADT indicates it is unsupported

   - Misc
      PCI/AER: pci_get_domain_bus_and_slot() call missing required pci_dev_put()
      PCI: remove depends on CONFIG_EXPERIMENTAL"

* tag '3.8-pci-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  PCI: remove depends on CONFIG_EXPERIMENTAL
  PCI: Allow pcie_aspm=force even when FADT indicates it is unsupported
  PCI: shpchp: Use per-slot workqueues to avoid deadlock
  PCI: shpchp: Handle push button event asynchronously
  PCI: shpchp: Make shpchp_wq non-ordered
  PCI/AER: pci_get_domain_bus_and_slot() call missing required pci_dev_put()
  PCI: pciehp: Use per-slot workqueues to avoid deadlock

Commit 083b804c ("async: use workqueue for worker pool") made it
possible that async jobs are moved from pending to running out-of-order.
While pending async jobs will be queued and dispatched for execution in
the same order, nothing guarantees they'll enter "1) move self to the
running queue" of async_run_entry_fn() in the same order.

Before the conversion, async implemented its own worker pool.  An async
worker, upon being woken up, fetches the first item from the pending
list, which kept the executing lists sorted.  The conversion to
workqueue was done by adding work_struct to each async_entry and async
just schedules the work item.  The queueing and dispatching of such work
items are still in order but now each worker thread is associated with a
specific async_entry and moves that specific async_entry to the
executing list.  So, depending on which worker reaches that point
earlier, which is non-deterministic, we may end up moving an async_entry
with larger cookie before one with smaller one.

This broke __lowest_in_progress().  running->domain may not be properly
sorted and is not guaranteed to contain lower cookies than pending list
when not empty.  Fix it by ensuring sort-inserting to the running list
and always looking at both pending and running when trying to determine
the lowest cookie.

Over time, the async synchronization implementation became quite messy.
We better restructure it such that each async_entry is linked to two
lists - one global and one per domain - and not move it when execution
starts.  There's no reason to distinguish pending and running.  They
behave the same for synchronization purposes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull perf/urgent fixes from Arnaldo Carvalho de Melo:

 . revert 20b279 - require exclude_guest to use PEBS - kernel side, now
   older binaries will continue working for things like cycles:pp
   without needing to pass extra modifiers, from David Ahern.

 . Fix building from 'make perf-*-src-pkg' tarballs, broken by UAPI,
   from Sebastian Andrzej Siewior

[ Pulling directly, Ingo would normally pull but has been unresponsive ]

* tag 'perf-urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux:
  perf tools: Fix building from 'make perf-*-src-pkg' tarballs
  perf x86: revert 20b279 - require exclude_guest to use PEBS - kernel side

Pull parisc fixes from Helge Deller:
 "Improve the stability of the linux kernel on the parisc architecture"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: sigaltstack doesn't round ss.ss_sp as required
  parisc: improve ptrace support for gdb single-step
  parisc: don't claim cpu irqs more than once
  parisc: avoid undefined shift in cnv_float.h

Pull fuse fixes from Miklos Szeredi:
 "This contain a bugfix for CUSE and miscellaneous small fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: remove unused variable in fuse_try_move_page()
  fuse: make fuse_file_fallocate() static
  fuse: Move CUSE Kconfig entry from fs/Kconfig into fs/fuse/Kconfig
  cuse: fix uninitialized variable warnings
  cuse: do not register multiple devices with identical names
  cuse: use mutex as registration lock instead of spinlocks

Pull GPIO fixes from Linus Walleij:
 "Here are some GPIO fixes I stacked up in my GPIO tree:

   - Remove a bad #include from the Samsung driver
   - Some Kconfig hazzle for the Samsungs
   - Skip gpiolib registration on EXYNOS5440
   - Don't free the MVEBU label"

* tag 'fixes-for-v3.8-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio:
  gpio: mvebu: Don't free chip label memory
  gpio: samsung: skip gpio lib registration for EXYNOS5440
  gpio: samsung: silent build warning for EXYNOS5 SoCs
  gpio: samsung: fix pinctrl condition for exynos and exynos5440
  gpio: samsung: remove inclusion <mach/regs-clock.h>

Pull f2fs fixes from Jaegeuk Kim:
 o Support swap file and link generic_file_remap_pages
 o Enhance the bio streaming flow and free section control
 o Major bug fix on recovery routine
 o Minor bug/warning fixes and code cleanups

* tag 'f2fs-for-3.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (22 commits)
  f2fs: use _safe() version of list_for_each
  f2fs: add comments of start_bidx_of_node
  f2fs: avoid issuing small bios due to several dirty node pages
  f2fs: support swapfile
  f2fs: add remap_pages as generic_file_remap_pages
  f2fs: add __init to functions in init_f2fs_fs
  f2fs: fix the debugfs entry creation path
  f2fs: add global mutex_lock to protect f2fs_stat_list
  f2fs: remove the blk_plug usage in f2fs_write_data_pages
  f2fs: avoid redundant time update for parent directory in f2fs_delete_entry
  f2fs: remove redundant call to set_blocksize in f2fs_fill_super
  f2fs: move f2fs_balance_fs to punch_hole
  f2fs: add f2fs_balance_fs in several interfaces
  f2fs: revisit the f2fs_gc flow
  f2fs: check return value during recovery
  f2fs: avoid null dereference in f2fs_acl_from_disk
  f2fs: initialize newly allocated dnode structure
  f2fs: update f2fs partition info about SIT/NAT layout
  f2fs: update f2fs document to reflect SIT/NAT layout correctly
  f2fs: remove unneeded INIT_LIST_HEAD at few places
  ...

Pull vfio fix from Alex Williamson.
 "vfio-pci: Fix buffer overfill"

* tag 'vfio-for-v3.8-rc5' of git://github.com/awilliam/linux-vfio:
  vfio-pci: Fix buffer overfill

Pull ftrace fix from Steven Rostedt:
 "Kprobes now uses the function tracer if it can.  That is, if a probe
  is placed on a function mcount/nop location, and the arch supports it,
  instead of adding a breakpoint, kprobes will register a function
  callback as that is much more efficient.

  The function tracer requires to update modules before they run, and
  uses the module notifier to do so.  But if something else in the
  module notifiers registers a kprobe at one of these locations, before
  ftrace can get to it, then the system could fail.

  The function tracer must be initialized early, otherwise module
  notifiers that probe will only work by chance."

* tag 'trace-3.8-rc4-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  ftrace: Be first to run code modification on modules

Pull libata fixes from Jeff Garzik:

 1) ahci: Fix typo that caused erronenous error handling.

    Thought: I wonder if sparse could have caught this, somehow.

 2) ahci: support a slightly odd Enmotus variant

 3) core: fix a drive detection problem by correcting the logic by which
    the DevSlp timing variables are obtained and used.

* tag 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev:
  [libata] replace sata_settings with devslp_timing
  [libata] ahci: Add support for Enmotus Bobcat device.
  [libata] ahci: Fix lack of command retry after a success error handler.

Pull security subsystem bugfixes from James Morris.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  security/device_cgroup: lock assert fails in dev_exception_clean()
  evm: checking if removexattr is not a NULL

wake_up_process() should never wakeup a TASK_STOPPED/TRACED task.
Change it to use TASK_NORMAL and add the WARN_ON().

TASK_ALL has no other users, probably can be killed.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

putreg() assumes that the tracee is not running and pt_regs_access() can
safely play with its stack.  However a killed tracee can return from
ptrace_stop() to the low-level asm code and do RESTORE_REST, this means
that debugger can actually read/modify the kernel stack until the tracee
does SAVE_REST again.

set_task_blockstep() can race with SIGKILL too and in some sense this
race is even worse, the very fact the tracee can be woken up breaks the
logic.

As Linus suggested we can clear TASK_WAKEKILL around the arch_ptrace()
call, this ensures that nobody can ever wakeup the tracee while the
debugger looks at it.  Not only this fixes the mentioned problems, we
can do some cleanups/simplifications in arch_ptrace() paths.

Probably ptrace_unfreeze_traced() needs more callers, for example it
makes sense to make the tracee killable for oom-killer before
access_process_vm().

While at it, add the comment into may_ptrace_stop() to explain why
ptrace_stop() still can't rely on SIGKILL and signal_pending_state().
Reported-by: Salman Qazi <sqazi@google.com>
Reported-by: Suleiman Souhlal <suleiman@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

By popular demand, arch/aarch64 is now known as arch/arm64. However,
uname -m (and indeed the GNU triplet) still use aarch64 as the machine
string.

This patch fixes native builds of both the kernel and perf tools by
updating the relevant Makefiles to munge the output of uname -m and
set the ARCH variable appropriately.

Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

The kernel's internal definition of ELF_NGREG uses struct pt_regs, which
means that we disagree with userspace on the size of coredumps since
glibc correctly uses the user-visible struct user_pt_regs.

This patch fixes our ELF_NGREG definition to use struct user_pt_regs
and introduces our own ELF_CORE_COPY_REGS to convert between the user
and kernel structure definitions.

Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch (as1642) adds an ehci->priv field for private use by EHCI
platform drivers.  The space was provided some time ago, but it didn't
have a name.

Until now none of the platform drivers has used this private space,
but that's about to change in the next patch of this series.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This patch (as1641) fixes a minor bug in ehci-hcd left over from when
the Chipidea driver was converted to the "ehci-hcd is a library"
scheme.  The test for whether the Chipidea platform driver is active
should be IS_ENABLED(), not defined().
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Without this, platform drivers e.g. ehci-omap.c will see a
different version of struct ehci_hcd than ehci-hcd.c and
break reference to 'debug_dir' and 'priv' members when
CONFIG_USB_DEBUG is enabled.
Signed-off-by: Roger Quadros <rogerq@ti.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This patch (as1644) fixes a race that occurs during startup in
uhci-hcd.  If the IRQ line is shared with other devices, it's possible
for the handler routine to be called before the data structures are
fully initialized.

The problem is fixed by adding a check to the IRQ handler routine.  If
the initialization hasn't finished yet, the routine will return
immediately.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Don Zickus <dzickus@redhat.com>
Tested-by: "Huang, Adrian (ISS Linux TW)" <adrian.huang@hp.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Cleanup and preparation for the next change.

signal_wake_up(resume => true) is overused. None of ptrace/jctl callers
actually want to wakeup a TASK_WAKEKILL task, but they can't specify the
necessary mask.

Turn signal_wake_up() into signal_wake_up_state(state), reintroduce
signal_wake_up() as a trivial helper, and add ptrace_signal_wake_up()
which adds __TASK_TRACED.

This way ptrace_signal_wake_up() can work "inside" ptrace_request()
even if the tracee doesn't have the TASK_WAKEKILL bit set.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is calling list_del() inside a loop which is a problem when we try
move to the next item on the list.  I've converted it to use the _safe
version.  And also, as a cleanup, I've converted it to use
list_for_each_entry instead of list_for_each.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

The caller of start_bidx_of_node() should give proper node offsets which
point only direct node blocks. Otherwise, it is a caller's bug.
This patch adds comments to make it clear.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

If some small bios of dirty node pages are supposed to be issued during the
sequential data writes, there-in well-produced consecutive data bios are able
to be split by the small node bios, resulting in performance degradation.
So, let's collect a number of dirty node pages until reaching a threshold.
And, by default, I set the threshold as 2MB, a segment size.

This improves sequential write performance on i5, 512GB SSD (830 w/ SATA2) as
follows.
Before: 231 MB/s -> After: 255 MB/s
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>