This patch adds the af_alg plugin for hash, corresponding to
the ahash kernel operation type.

Keys can optionally be set through the setsockopt interface.

Each sendmsg call will finalise the hash unless sent with a MSG_MORE
flag.

Partial hash states can be cloned using accept(2).

The interface is completely synchronous, all operations will
complete prior to the system call returning.

Both sendmsg(2) and splice(2) support reading the user-space
data directly without copying (except that the Crypto API itself
may copy the data if alignment is off).

For now only the splice(2) interface supports performing digest
instead of init/update/final.  In future the sendmsg(2) interface
will also be modified to use digest/finup where possible so that
hardware that cannot return a partial hash state can still benefit
from this interface.

Thakns to Miloslav Trmac for reviewing this and contributing
fixes and improvements.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Tested-by: NMartin Willi <martin@strongswan.org>

This patch creates the backbone of the user-space interface for
the Crypto API, through a new socket family AF_ALG.

Each session corresponds to one or more connections obtained from
that socket.  The number depends on the number of inputs/outputs
of that particular type of operation.  For most types there will
be a s ingle connection/file descriptor that is used for both input
and output.  AEAD is one of the few that require two inputs.

Each algorithm type will provide its own implementation that plugs
into af_alg.  They're keyed using a string such as "skcipher" or
"hash".

IOW this patch only contains the boring bits that is required
to hold everything together.

Thakns to Miloslav Trmac for reviewing this and contributing
fixes and improvements.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Tested-by: NMartin Willi <martin@strongswan.org>

This patch adds the socket family/level macros for the yet-to-be-born
AF_ALG family.  The AF_ALG family provides the user-space interface
for the kernel crypto API.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: NDavid S. Miller <davem@davemloft.net>

Updated RFC4106 AES-GCM testing. Some test vectors were taken from
http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/
gcm/gcm-test-vectors.tar.gz
Signed-off-by: NAdrian Hoban <adrian.hoban@intel.com>
Signed-off-by: NTadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: NGabriele Paoloni <gabriele.paoloni@intel.com>
Signed-off-by: NAidan O'Mahony <aidan.o.mahony@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch adds an optimized RFC4106 AES-GCM implementation for 64-bit
kernels. It supports 128-bit AES key size. This leverages the crypto
AEAD interface type to facilitate a combined AES & GCM operation to
be implemented in assembly code. The assembly code leverages Intel(R)
AES New Instructions and the PCLMULQDQ instruction.
Signed-off-by: NAdrian Hoban <adrian.hoban@intel.com>
Signed-off-by: NTadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: NGabriele Paoloni <gabriele.paoloni@intel.com>
Signed-off-by: NAidan O'Mahony <aidan.o.mahony@intel.com>
Signed-off-by: NErdinc Ozturk <erdinc.ozturk@intel.com>
Signed-off-by: NJames Guilford <james.guilford@intel.com>
Signed-off-by: NWajdi Feghali <wajdi.k.feghali@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

I noticed that by factoring out common rounds from the
branches of the if-statements in the encryption and
decryption functions, the executable file size goes down
significantly, for crypto/cast5.ko from 26688 bytes
to 24336 bytes (amd64).

On my test system, I saw a slight speedup. This is the
first time I'm doing such a benchmark - I found a similar
one on the crypto mailing list, and I hope I did it right?

Before:
# cryptsetup create dm-test /dev/hda2 -c cast5-cbc-plain -s 128
Passsatz eingeben: 
# dd if=/dev/zero of=/dev/mapper/dm-test bs=1M count=50
52428800 Bytes (52 MB) kopiert, 2,43484 s, 21,5 MB/s
# dd if=/dev/zero of=/dev/mapper/dm-test bs=1M count=50
52428800 Bytes (52 MB) kopiert, 2,4089 s, 21,8 MB/s
# dd if=/dev/zero of=/dev/mapper/dm-test bs=1M count=50
52428800 Bytes (52 MB) kopiert, 2,41091 s, 21,7 MB/s

After:
# cryptsetup create dm-test /dev/hda2 -c cast5-cbc-plain -s 128
Passsatz eingeben: 
# dd if=/dev/zero of=/dev/mapper/dm-test bs=1M count=50
52428800 Bytes (52 MB) kopiert, 2,38128 s, 22,0 MB/s
# dd if=/dev/zero of=/dev/mapper/dm-test bs=1M count=50
52428800 Bytes (52 MB) kopiert, 2,29486 s, 22,8 MB/s
# dd if=/dev/zero of=/dev/mapper/dm-test bs=1M count=50
52428800 Bytes (52 MB) kopiert, 2,37162 s, 22,1 MB/s
Signed-off-by: NNicolas Kaiser <nikai@nikai.net>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The function shash_async_import did not initialise the descriptor
correctly prior to calling the underlying shash import function.

This patch adds the required initialisation.
Reported-by: NMiloslav Trmac <mitr@redhat.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

* 'upstream-merge' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (50 commits)
  ext4,jbd2: convert tracepoints to use major/minor numbers
  ext4: optimize orphan_list handling for ext4_setattr
  ext4: fix unbalanced mutex unlock in error path of ext4_li_request_new
  ext4: fix compile error in ext4_fallocate()
  ext4: move ext4_mb_{get,put}_buddy_cache_lock and make them static
  ext4: rename mark_bitmap_end() to ext4_mark_bitmap_end()
  ext4: move flush_completed_IO to fs/ext4/fsync.c and make it static
  ext4: rename {ext,idx}_pblock and inline small extent functions
  ext4: make various ext4 functions be static
  ext4: rename {exit,init}_ext4_*() to ext4_{exit,init}_*()
  ext4: fix kernel oops if the journal superblock has a non-zero j_errno
  ext4: update writeback_index based on last page scanned
  ext4: implement writeback livelock avoidance using page tagging
  ext4: tidy up a void argument in inode.c
  ext4: add batched_discard into ext4 feature list
  ext4: Add batched discard support for ext4
  fs: Add FITRIM ioctl
  ext4: Use return value from sb_issue_discard()
  ext4: Check return value of sb_getblk() and friends
  ext4: use bio layer instead of buffer layer in mpage_da_submit_io
  ...

Conflicts:
	fs/ext4/inode.c
	fs/ext4/mballoc.c
	include/trace/events/ext4.h

* 'drm-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6:
  drm/radeon/kms: enable unmappable vram for evergreen
  drm/radeon/kms: fix tiled db height calculation on 6xx/7xx
  drm/radeon/kms: fix handling of tex lookup disable in cs checker on r2xx

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6: (24 commits)
  quota: Fix possible oops in __dquot_initialize()
  ext3: Update kernel-doc comments
  jbd/2: fixed typos
  ext2: fixed typo.
  ext3: Fix debug messages in ext3_group_extend()
  jbd: Convert atomic_inc() to get_bh()
  ext3: Remove misplaced BUFFER_TRACE() in ext3_truncate()
  jbd: Fix debug message in do_get_write_access()
  jbd: Check return value of __getblk()
  ext3: Use DIV_ROUND_UP() on group desc block counting
  ext3: Return proper error code on ext3_fill_super()
  ext3: Remove unnecessary casts on bh->b_data
  ext3: Cleanup ext3_setup_super()
  quota: Fix issuing of warnings from dquot_transfer
  quota: fix dquot_disable vs dquot_transfer race v2
  jbd: Convert bitops to buffer fns
  ext3/jbd: Avoid WARN() messages when failing to write the superblock
  jbd: Use offset_in_page() instead of manual calculation
  jbd: Remove unnecessary goto statement
  jbd: Use printk_ratelimited() in journal_alloc_journal_head()
  ...

Unfortunately perf can't deal with anything other than direct structure
accesses in the TP_printk() section.  It will drop dead when it sees
jbd2_dev_to_name() in the "print fmt" section of the tracepoint.

Addresses-Google-Bug: 3138508
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Surprisingly chown() on ext4 is not SMP scalable operation. 
Due to unconditional orphan_del(NULL, inode) in ext4_setattr()
result in significant performance overhead because of global orphan
mutex, especially in no-journal mode (where orphan_add() is noop).
It is possible to skip explicit orphan_del if possible.
Results of fchown() micro-benchmark in no-journal mode
while (1) {
   iteration++;
   fchown(fd, uid, gid);
   fchown(fd, uid + 1, gid + 1)
}
measured: iterations per millisecond
| nr_tasks | w/o patch | with patch |
|        1 |       142 |        185 |
|        4 |       109 |        642 |
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Signed-off-by: NNicolas Kaiser <nikai@nikai.net>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx: (48 commits)
  DMAENGINE: move COH901318 to arch_initcall
  dma: imx-dma: fix signedness bug
  dma/timberdale: simplify conditional
  ste_dma40: remove channel_type
  ste_dma40: remove enum for endianess
  ste_dma40: remove TIM_FOR_LINK option
  ste_dma40: move mode_opt to separate config
  ste_dma40: move channel mode to a separate field
  ste_dma40: move priority to separate field
  ste_dma40: add variable to indicate valid dma_cfg
  async_tx: make async_tx channel switching opt-in
  move async raid6 test to lib/Kconfig.debug
  dmaengine: Add Freescale i.MX1/21/27 DMA driver
  intel_mid_dma: change the slave interface
  intel_mid_dma: fix the WARN_ONs
  intel_mid_dma: Add sg list support to DMA driver
  intel_mid_dma: Allow DMAC2 to share interrupt
  intel_mid_dma: Allow IRQ sharing
  intel_mid_dma: Add runtime PM support
  DMAENGINE: define a dummy filter function for ste_dma40
  ...

* 'viafb-next' of git://github.com/schandinat/linux-2.6: (29 commits)
  viafb: add initial VX900 support
  viafb: fix hardware acceleration for suspend & resume
  viafb: make suspend and resume work (on all machines?)
  viafb: restore display on resume
  Minimal support for viafb suspend/resume
  viafb: use proper register for colour when doing fill ops
  viafb: add documentation for proc interface
  viafb: rename output devices
  viafb: add a mapping of supported output devices
  viafb: set sync polarity for all output devices
  viafb: add function to change sync polarity per device
  viafb: reduce I2C timeout and delay
  viafb: enable I2C for CRT
  viafb: fix i2c_transfer error handling
  viafb: vt1636 cleanup
  viafb: introduce per output device power management
  viafb: limit LCD code impact
  viafb: add interface for output device configuration
  viafb: merge the remaining output path with enable functions
  viafb: use new device routing
  ...

* git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-2.6-mn10300: (44 commits)
  MN10300: Save frame pointer in thread_info struct rather than global var
  MN10300: Change "Matsushita" to "Panasonic".
  MN10300: Create a defconfig for the ASB2364 board
  MN10300: Update the ASB2303 defconfig
  MN10300: ASB2364: Add support for SMSC911X and SMC911X
  MN10300: ASB2364: Handle the IRQ multiplexer in the FPGA
  MN10300: Generic time support
  MN10300: Specify an ELF HWCAP flag for MN10300 Atomic Operations Unit support
  MN10300: Map userspace atomic op regs as a vmalloc page
  MN10300: And Panasonic AM34 subarch and implement SMP
  MN10300: Delete idle_timestamp from irq_cpustat_t
  MN10300: Make various interrupt priority settings configurable
  MN10300: Optimise do_csum()
  MN10300: Implement atomic ops using atomic ops unit
  MN10300: Make the FPU operate in non-lazy mode under SMP
  MN10300: SMP TLB flushing
  MN10300: Use the [ID]PTEL2 registers rather than [ID]PTEL for TLB control
  MN10300: Make the use of PIDR to mark TLB entries controllable
  MN10300: Rename __flush_tlb*() to local_flush_tlb*()
  MN10300: AM34 erratum requires MMUCTR read and write on exception entry
  ...

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6:
  ALSA: usb-audio: automatically detect feedback format
  ASoC: sound/wm9090: add missing __devexit marker
  ASoC: sound/max98088: add missing __devexit marker
  ASoC: sound/ad73311: add missing __devexit marker
  ASoC: fsl - fix build error in pcm030-audio-fabric.c
  sound/oss/sb_ess.c: delete double assignment
  ALSA: hda - Change BTL amp level on some HP notebooks

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

* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (50 commits)
  perf python scripting: Add futex-contention script
  perf python scripting: Fixup cut'n'paste error in sctop script
  perf scripting: Shut up 'perf record' final status
  perf record: Remove newline character from perror() argument
  perf python scripting: Support fedora 11 (audit 1.7.17)
  perf python scripting: Improve the syscalls-by-pid script
  perf python scripting: print the syscall name on sctop
  perf python scripting: Improve the syscalls-counts script
  perf python scripting: Improve the failed-syscalls-by-pid script
  kprobes: Remove redundant text_mutex lock in optimize
  x86/oprofile: Fix uninitialized variable use in debug printk
  tracing: Fix 'faild' -> 'failed' typo
  perf probe: Fix format specified for Dwarf_Off parameter
  perf trace: Fix detection of script extension
  perf trace: Use $PERF_EXEC_PATH in canned report scripts
  perf tools: Document event modifiers
  perf tools: Remove direct slang.h include
  perf_events: Fix for transaction recovery in group_sched_in()
  perf_events: Revert: Fix transaction recovery in group_sched_in()
  perf, x86: Use NUMA aware allocations for PEBS/BTS/DS allocations
  ...

* 'module' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  NULL-terminate all pci_device_id tables
  (trivial) Fix compiler warning in kernel/modules.c

* akpm-incoming-2: (139 commits)
  epoll: make epoll_wait() use the hrtimer range feature
  select: rename estimate_accuracy() to select_estimate_accuracy()
  Remove duplicate includes from many files
  ramoops: use the platform data structure instead of module params
  kernel/resource.c: handle reinsertion of an already-inserted resource
  kfifo: fix kfifo_alloc() to return a signed int value
  w1: don't allow arbitrary users to remove w1 devices
  alpha: remove dma64_addr_t usage
  mips: remove dma64_addr_t usage
  sparc: remove dma64_addr_t usage
  fuse: use release_pages()
  taskstats: use real microsecond granularity for CPU times
  taskstats: split fill_pid function
  taskstats: separate taskstats commands
  delayacct: align to 8 byte boundary on 64-bit systems
  delay-accounting: reimplement -c for getdelays.c to report information on a target command
  namespaces Kconfig: move namespace menu location after the cgroup
  namespaces Kconfig: remove the cgroup device whitelist experimental tag
  namespaces Kconfig: remove pointless cgroup dependency
  namespaces Kconfig: make namespace a submenu
  ...

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:
  percpu: Remove the multi-page alignment facility
  x86-32: Allocate irq stacks seperate from percpu area
  x86-32, mm: Remove duplicated #include
  x86, printk: Get rid of <0> from stack output
  x86, kexec: Make sure to stop all CPUs before exiting the kernel
  x86/vsmp: Eliminate kconfig dependency warning

The BKL was pushed into this function when it was converted to use the
unlocked_ioctl interface, but nothing that the function touches is
actually protected by the BKL.  So just remove the BKL entirely, so that
we finally can get a realistic system build without the BKL being
enabled at all.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When I compiled 2.6.36-rc3 kernel with EXT4FS_DEBUG definition, I got
the following compile error.

  CC [M]  fs/ext4/extents.o
fs/ext4/extents.c: In function 'ext4_fallocate':
fs/ext4/extents.c:3772: error: 'block' undeclared (first use in this function)
fs/ext4/extents.c:3772: error: (Each undeclared identifier is reported only once
fs/ext4/extents.c:3772: error: for each function it appears in.)
make[2]: *** [fs/ext4/extents.o] Error 1

The patch fixes this problem.
Signed-off-by: NKazuya Mio <k-mio@sx.jp.nec.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

These functions are only used within fs/ext4/mballoc.c, so move them
so they are used after they are defined, and then make them be static.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Fix a namespace leak from fs/ext4
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Fix a namespace leak by moving the function to the file where it is
used and making it static.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Cleanup namespace leaks from fs/ext4 and the inline trivial functions
ext4_{ext,idx}_pblock() and ext4_{ext,idx}_store_pblock() since the
code size actually shrinks when we make these functions inline,
they're so trivial.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

These functions have no need to be exported beyond file context.

No functions needed to be moved for this commit; just some function
declarations changed to be static and removed from header files.

(A similar patch was submitted by Eric Sandeen, but I wanted to handle
code movement in separate patches to make sure code changes didn't
accidentally get dropped.)
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This is a cleanup to avoid namespace leaks out of fs/ext4
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Commit 84061e07 fixed an accounting bug only to introduce the
possibility of a kernel OOPS if the journal has a non-zero j_errno
field indicating that the file system had detected a fs inconsistency.
After the journal replay, if the journal superblock indicates that the
file system has an error, this indication is transfered to the file
system and then ext4_commit_super() is called to write this to the
disk.

But since the percpu counters are now initialized after the journal
replay, the call to ext4_commit_super() will cause a kernel oops since
it needs to use the percpu counters the ext4 superblock structure.

The fix is to skip setting the ext4 free block and free inode fields
if the percpu counter has not been set.

Thanks to Ken Sumrall for reporting and analyzing the root causes of
this bug.

Addresses-Google-Bug: #3054080
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

As pointed out in a prior patch, updating the mapping's
writeback_index based on pages written isn't quite right;
what the writeback index is really supposed to reflect is
the next page which should be scanned for writeback during
periodic flush.

As in write_cache_pages(), write_cache_pages_da() does
this scanning for us as we assemble the mpd for later
writeout.  If we keep track of the next page after the
current scan, we can easily update writeback_index without
worrying about pages written vs. pages skipped, etc.

Without this, an fsync will reset writeback_index to
0 (its starting index) + however many pages it wrote, which
can mess up the progress of periodic flush.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This is analogous to Jan Kara's commit,
f446daae
mm: implement writeback livelock avoidance using page tagging

but since we forked write_cache_pages, we need to reimplement
it there (and in ext4_da_writepages, since range_cyclic handling
was moved to there)

If you start a large buffered IO to a file, and then set
fsync after it, you'll find that fsync does not complete
until the other IO stops.

If you continue re-dirtying the file (say, putting dd
with conv=notrunc in a loop), when fsync finally completes
(after all IO is done), it reports via tracing that
it has written many more pages than the file contains;
in other words it has synced and re-synced pages in
the file multiple times.

This then leads to problems with our writeback_index
update, since it advances it by pages written, and
essentially sets writeback_index off the end of the
file...

With the following patch, we only sync as much as was
dirty at the time of the sync.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

This doesn't fix anything at all, it just removes a vestige
of prior use from __mpage_da_writepage()

__mpage_da_writepage() had a *void argument leftover from
its previous life as a callback; make it reflect the actual type.

Fixing this up makes it slightly more obvious to read, and 
enables proper typechecking.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Should be applied on the top of "lazy inode table initialization"
and "batched discard support" patch-sets.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Walk through allocation groups and trim all free extents. It can be
invoked through FITRIM ioctl on the file system. The main idea is to
provide a way to trim the whole file system if needed, since some SSD's
may suffer from performance loss after the whole device was filled (it
does not mean that fs is full!).

It search for free extents in allocation groups specified by Byte range
start -> start+len. When the free extent is within this range, blocks
are marked as used and then trimmed. Afterwards these blocks are marked
as free in per-group bitmap.

Since fstrim is a long operation it is good to have an ability to
interrupt it by a signal. This was added by Dmitry Monakhov.
Thanks Dimitry.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Adds an filesystem independent ioctl to allow implementation of file
system batched discard support. I takes fstrim_range structure as an
argument. fstrim_range is definec in the include/fs.h and its
definition is as follows.

struct fstrim_range {
	start;
	len;
	minlen;
}

start	- first Byte to trim
len	- number of Bytes to trim from start
minlen	- minimum extent length to trim, free extents shorter than this
	  number of Bytes will be ignored. This will be rounded up to fs
	  block size.

It is also possible to specify NULL as an argument. In this case the
arguments will set itself as follows:

start = 0;
len = ULLONG_MAX;
minlen = 0;

So it will trim the whole file system at one run.

After the FITRIM is done, the number of actually discarded Bytes is stored
in fstrim_range.len to give the user better insight on how much storage
space has been really released for wear-leveling.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Reviewed-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Use return value from sb_issue_discard() as return value in
ext4_issue_discard(). Since sb_issue_discard() may result in more
serious errors than just -EOPNOTSUPP it is worth to inform user of this
function about them to handle error cases properly.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Fail block allocation if sb_getblk() returns NULL. In that case,
sb_find_get_block() also likely to fail so that it should skip
calling ext4_forget().
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Call the block I/O layer directly instad of going through the buffer
layer.  This should give us much better performance and scalability,
as well as lowering our CPU utilization when doing buffered writeback.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>