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  1. 07 11月, 2015 8 次提交
  3. 09 9月, 2015 13 次提交
  5. 26 6月, 2015 2 次提交
  7. 11 6月, 2015 1 次提交
  9. 16 4月, 2015 13 次提交
    • S
      zsmalloc: remove extra cond_resched() in __zs_compact · 160a117f
      由 Sergey Senozhatsky 提交于 
      Do not perform cond_resched() before the busy compaction loop in
__zs_compact(), because this loop does it when needed.
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      160a117f
    • H
      zsmalloc: fix fatal corruption due to wrong size class selection · 81da9b13
      由 Heesub Shin 提交于 
      There is no point in overriding the size class below.  It causes fatal
corruption on the next chunk on the 3264-bytes size class, which is the
last size class that is not huge.

For example, if the requested size was exactly 3264 bytes, current
zsmalloc allocates and returns a chunk from the size class of 3264 bytes,
not 4096.  User access to this chunk may overwrite head of the next
adjacent chunk.

Here is the panic log captured when freelist was corrupted due to this:

    Kernel BUG at ffffffc00030659c [verbose debug info unavailable]
    Internal error: Oops - BUG: 96000006 [#1] PREEMPT SMP
    Modules linked in:
    exynos-snapshot: core register saved(CPU:5)
    CPUMERRSR: 0000000000000000, L2MERRSR: 0000000000000000
    exynos-snapshot: context saved(CPU:5)
    exynos-snapshot: item - log_kevents is disabled
    CPU: 5 PID: 898 Comm: kswapd0 Not tainted 3.10.61-4497415-eng #1
    task: ffffffc0b8783d80 ti: ffffffc0b71e8000 task.ti: ffffffc0b71e8000
    PC is at obj_idx_to_offset+0x0/0x1c
    LR is at obj_malloc+0x44/0xe8
    pc : [<ffffffc00030659c>] lr : [<ffffffc000306604>] pstate: a0000045
    sp : ffffffc0b71eb790
    x29: ffffffc0b71eb790 x28: ffffffc00204c000
    x27: 000000000001d96f x26: 0000000000000000
    x25: ffffffc098cc3500 x24: ffffffc0a13f2810
    x23: ffffffc098cc3501 x22: ffffffc0a13f2800
    x21: 000011e1a02006e3 x20: ffffffc0a13f2800
    x19: ffffffbc02a7e000 x18: 0000000000000000
    x17: 0000000000000000 x16: 0000000000000feb
    x15: 0000000000000000 x14: 00000000a01003e3
    x13: 0000000000000020 x12: fffffffffffffff0
    x11: ffffffc08b264000 x10: 00000000e3a01004
    x9 : ffffffc08b263fea x8 : ffffffc0b1e611c0
    x7 : ffffffc000307d24 x6 : 0000000000000000
    x5 : 0000000000000038 x4 : 000000000000011e
    x3 : ffffffbc00003e90 x2 : 0000000000000cc0
    x1 : 00000000d0100371 x0 : ffffffbc00003e90
Reported-by: NSooyong Suk <s.suk@samsung.com>
Signed-off-by: NHeesub Shin <heesub.shin@samsung.com>
Tested-by: NSooyong Suk <s.suk@samsung.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      81da9b13
    • M
      zsmalloc: remove unnecessary insertion/removal of zspage in compaction · 839373e6
      由 Minchan Kim 提交于 
      In putback_zspage, we don't need to insert a zspage into list of zspage
in size_class again to just fix fullness group. We could do directly
without reinsertion so we could save some instuctions.
Reported-by: NHeesub Shin <heesub.shin@samsung.com>
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Juneho Choi <juno.choi@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      839373e6
    • S
      zsmalloc: micro-optimize zs_object_copy() · 495819ea
      由 Sergey Senozhatsky 提交于 
      A micro-optimization.  Avoid additional branching and reduce (a bit)
registry pressure (f.e.  s_off += size; d_off += size; may be calculated
twise: first for >= PAGE_SIZE check and later for offset update in "else"
clause).

scripts/bloat-o-meter shows some improvement

add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10)
function                          old     new   delta
zs_object_copy                    550     540     -10
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      495819ea
    • S
      zsmalloc: remove synchronize_rcu from zs_compact() · 1ec7cfb1
      由 Sergey Senozhatsky 提交于 
      Do not synchronize rcu in zs_compact(). Neither zsmalloc not
zram use rcu.
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1ec7cfb1
    • Y
      mm/zsmalloc.c: fix comment for get_pages_per_zspage · 888fa374
      由 Yinghao Xie 提交于 
      Signed-off-by: NYinghao Xie <yinghao.xie@sumsung.com>
Suggested-by: NMinchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      888fa374
    • M
      zsmalloc: zsmalloc documentation · d02be50d
      由 Minchan Kim 提交于 
      Create zsmalloc doc which explains design concept and stat information.
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d02be50d
    • M
      zsmalloc: add fullness into stat · 248ca1b0
      由 Minchan Kim 提交于 
      During investigating compaction, fullness information of each class is
helpful for investigating how the compaction works well.  With that, we
could know how compaction works well more clear on each size class.
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      248ca1b0
    • M
      zsmalloc: record handle in page->private for huge object · 7b60a685
      由 Minchan Kim 提交于 
      We store handle on header of each allocated object so it increases the
size of each object by sizeof(unsigned long).

If zram stores 4096 bytes to zsmalloc(ie, bad compression), zsmalloc needs
4104B-class to add handle.

However, 4104B-class has 1-pages_per_zspage so wasted size by internal
fragment is 8192 - 4104, which is terrible.

So this patch records the handle in page->private on such huge object(ie,
pages_per_zspage == 1 && maxobj_per_zspage == 1) instead of header of each
object so we could use 4096B-class, not 4104B-class.
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      7b60a685
    • M
      zsmalloc: adjust ZS_ALMOST_FULL · d3d07c92
      由 Minchan Kim 提交于 
      Curretly, zsmalloc regards a zspage as ZS_ALMOST_EMPTY if the zspage has
under 1/4 used objects(ie, fullness_threshold_frac).  It could make result
in loose packing since zsmalloc migrates only ZS_ALMOST_EMPTY zspage out.

This patch changes the rule so that zsmalloc makes zspage which has above
3/4 used object ZS_ALMOST_FULL so it could make tight packing.
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d3d07c92
    • M
      zsmalloc: support compaction · 312fcae2
      由 Minchan Kim 提交于 
      This patch provides core functions for migration of zsmalloc.  Migraion
policy is simple as follows.

for each size class {
        while {
                src_page = get zs_page from ZS_ALMOST_EMPTY
                if (!src_page)
                        break;
                dst_page = get zs_page from ZS_ALMOST_FULL
                if (!dst_page)
                        dst_page = get zs_page from ZS_ALMOST_EMPTY
                if (!dst_page)
                        break;
                migrate(from src_page, to dst_page);
        }
}

For migration, we need to identify which objects in zspage are allocated
to migrate them out.  We could know it by iterating of freed objects in a
zspage because first_page of zspage keeps free objects singly-linked list
but it's not efficient.  Instead, this patch adds a tag(ie,
OBJ_ALLOCATED_TAG) in header of each object(ie, handle) so we could check
whether the object is allocated easily.

This patch adds another status bit in handle to synchronize between user
access through zs_map_object and migration.  During migration, we cannot
move objects user are using due to data coherency between old object and
new object.

[akpm@linux-foundation.org: zsmalloc.c needs sched.h for cond_resched()]
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      312fcae2
    • M
      zsmalloc: factor out obj_[malloc|free] · c7806261
      由 Minchan Kim 提交于 
      In later patch, migration needs some part of functions in zs_malloc and
zs_free so this patch factor out them.
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c7806261
    • M
      zsmalloc: decouple handle and object · 2e40e163
      由 Minchan Kim 提交于 
      Recently, we started to use zram heavily and some of issues
popped.

1) external fragmentation

I got a report from Juneho Choi that fork failed although there are plenty
of free pages in the system.  His investigation revealed zram is one of
the culprit to make heavy fragmentation so there was no more contiguous
16K page for pgd to fork in the ARM.

2) non-movable pages

Other problem of zram now is that inherently, user want to use zram as
swap in small memory system so they use zRAM with CMA to use memory
efficiently.  However, unfortunately, it doesn't work well because zRAM
cannot use CMA's movable pages unless it doesn't support compaction.  I
got several reports about that OOM happened with zram although there are
lots of swap space and free space in CMA area.

3) internal fragmentation

zRAM has started support memory limitation feature to limit memory usage
and I sent a patchset(https://lkml.org/lkml/2014/9/21/148) for VM to be
harmonized with zram-swap to stop anonymous page reclaim if zram consumed
memory up to the limit although there are free space on the swap.  One
problem for that direction is zram has no way to know any hole in memory
space zsmalloc allocated by internal fragmentation so zram would regard
swap is full although there are free space in zsmalloc.  For solving the
issue, zram want to trigger compaction of zsmalloc before it decides full
or not.

This patchset is first step to support above issues.  For that, it adds
indirect layer between handle and object location and supports manual
compaction to solve 3th problem first of all.

After this patchset got merged, next step is to make VM aware of zsmalloc
compaction so that generic compaction will move zsmalloced-pages
automatically in runtime.

In my imaginary experiment(ie, high compress ratio data with heavy swap
in/out on 8G zram-swap), data is as follows,

Before =
zram allocated object :      60212066 bytes
zram total used:     140103680 bytes
ratio:         42.98 percent
MemFree:          840192 kB

Compaction

After =
frag ratio after compaction
zram allocated object :      60212066 bytes
zram total used:      76185600 bytes
ratio:         79.03 percent
MemFree:          901932 kB

Juneho reported below in his real platform with small aging.
So, I think the benefit would be bigger in real aging system
for a long time.

- frag_ratio increased 3% (ie, higher is better)
- memfree increased about 6MB
- In buddy info, Normal 2^3: 4, 2^2: 1: 2^1 increased, Highmem: 2^1 21 increased

frag ratio after swap fragment
used :        156677 kbytes
total:        166092 kbytes
frag_ratio :  94
meminfo before compaction
MemFree:           83724 kB
Node 0, zone   Normal  13642   1364     57     10     61     17      9      5      4      0      0
Node 0, zone  HighMem    425     29      1      0      0      0      0      0      0      0      0

num_migrated :  23630
compaction done

frag ratio after compaction
used :        156673 kbytes
total:        160564 kbytes
frag_ratio :  97
meminfo after compaction
MemFree:           89060 kB
Node 0, zone   Normal  14076   1544     67     14     61     17      9      5      4      0      0
Node 0, zone  HighMem    863     50      1      0      0      0      0      0      0      0      0

This patchset adds more logics(about 480 lines) in zsmalloc but when I
tested heavy swapin/out program, the regression for swapin/out speed is
marginal because most of overheads were caused by compress/decompress and
other MM reclaim stuff.

This patch (of 7):

Currently, handle of zsmalloc encodes object's location directly so it
makes support of migration hard.

This patch decouples handle and object via adding indirect layer.  For
that, it allocates handle dynamically and returns it to user.  The handle
is the address allocated by slab allocation so it's unique and we could
keep object's location in the memory space allocated for handle.

With it, we can change object's position without changing handle itself.
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2e40e163
  11. 13 2月, 2015 2 次提交
    • G
      mm/zsmalloc: add statistics support · 0f050d99
      由 Ganesh Mahendran 提交于 
      Keeping fragmentation of zsmalloc in a low level is our target.  But now
we still need to add the debug code in zsmalloc to get the quantitative
data.

This patch adds a new configuration CONFIG_ZSMALLOC_STAT to enable the
statistics collection for developers.  Currently only the objects
statatitics in each class are collected.  User can get the information via
debugfs.

     cat /sys/kernel/debug/zsmalloc/zram0/...

For example:

After I copied "jdk-8u25-linux-x64.tar.gz" to zram with ext4 filesystem:
 class  size obj_allocated   obj_used pages_used
     0    32             0          0          0
     1    48           256         12          3
     2    64            64         14          1
     3    80            51          7          1
     4    96           128          5          3
     5   112            73          5          2
     6   128            32          4          1
     7   144             0          0          0
     8   160             0          0          0
     9   176             0          0          0
    10   192             0          0          0
    11   208             0          0          0
    12   224             0          0          0
    13   240             0          0          0
    14   256            16          1          1
    15   272            15          9          1
    16   288             0          0          0
    17   304             0          0          0
    18   320             0          0          0
    19   336             0          0          0
    20   352             0          0          0
    21   368             0          0          0
    22   384             0          0          0
    23   400             0          0          0
    24   416             0          0          0
    25   432             0          0          0
    26   448             0          0          0
    27   464             0          0          0
    28   480             0          0          0
    29   496            33          1          4
    30   512             0          0          0
    31   528             0          0          0
    32   544             0          0          0
    33   560             0          0          0
    34   576             0          0          0
    35   592             0          0          0
    36   608             0          0          0
    37   624             0          0          0
    38   640             0          0          0
    40   672             0          0          0
    42   704             0          0          0
    43   720            17          1          3
    44   736             0          0          0
    46   768             0          0          0
    49   816             0          0          0
    51   848             0          0          0
    52   864            14          1          3
    54   896             0          0          0
    57   944            13          1          3
    58   960             0          0          0
    62  1024             4          1          1
    66  1088            15          2          4
    67  1104             0          0          0
    71  1168             0          0          0
    74  1216             0          0          0
    76  1248             0          0          0
    83  1360             3          1          1
    91  1488            11          1          4
    94  1536             0          0          0
   100  1632             5          1          2
   107  1744             0          0          0
   111  1808             9          1          4
   126  2048             4          4          2
   144  2336             7          3          4
   151  2448             0          0          0
   168  2720            15         15         10
   190  3072            28         27         21
   202  3264             0          0          0
   254  4096         36209      36209      36209

 Total               37022      36326      36288

We can calculate the overall fragentation by the last line:
    Total               37022      36326      36288
    (37022 - 36326) / 37022 = 1.87%

Also by analysing objects alocated in every class we know why we got so
low fragmentation: Most of the allocated objects is in <class 254>.  And
there is only 1 page in class 254 zspage.  So, No fragmentation will be
introduced by allocating objs in class 254.

And in future, we can collect other zsmalloc statistics as we need and
analyse them.
Signed-off-by: NGanesh Mahendran <opensource.ganesh@gmail.com>
Suggested-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0f050d99
    • G
      mm/zpool: add name argument to create zpool · 3eba0c6a
      由 Ganesh Mahendran 提交于 
      Currently the underlay of zpool: zsmalloc/zbud, do not know who creates
them.  There is not a method to let zsmalloc/zbud find which caller they
belong to.

Now we want to add statistics collection in zsmalloc.  We need to name the
debugfs dir for each pool created.  The way suggested by Minchan Kim is to
use a name passed by caller(such as zram) to create the zsmalloc pool.

    /sys/kernel/debug/zsmalloc/zram0

This patch adds an argument `name' to zs_create_pool() and other related
functions.
Signed-off-by: NGanesh Mahendran <opensource.ganesh@gmail.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3eba0c6a
  13. 19 12月, 2014 1 次提交
    • G
      mm/zsmalloc: adjust order of functions · 66cdef66
      由 Ganesh Mahendran 提交于 
      Currently functions in zsmalloc.c does not arranged in a readable and
reasonable sequence.  With the more and more functions added, we may
meet below inconvenience.  For example:

Current functions:

    void zs_init()
    {
    }

    static void get_maxobj_per_zspage()
    {
    }

Then I want to add a func_1() which is called from zs_init(), and this
new added function func_1() will used get_maxobj_per_zspage() which is
defined below zs_init().

    void func_1()
    {
        get_maxobj_per_zspage()
    }

    void zs_init()
    {
        func_1()
    }

    static void get_maxobj_per_zspage()
    {
    }

This will cause compiling issue. So we must add a declaration:

    static void get_maxobj_per_zspage();

before func_1() if we do not put get_maxobj_per_zspage() before
func_1().

In addition, puting module_[init|exit] functions at the bottom of the
file conforms to our habit.

So, this patch ajusts function sequence as:

    /* helper functions */
    ...
    obj_location_to_handle()
    ...

    /* Some exported functions */
    ...

    zs_map_object()
    zs_unmap_object()

    zs_malloc()
    zs_free()

    zs_init()
    zs_exit()
Signed-off-by: NGanesh Mahendran <opensource.ganesh@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Acked-by: NMinchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      66cdef66