zram: promote zram from staging

Zram has lived in staging for a LONG LONG time and have been
fixed/improved by many contributors so code is clean and stable now.  Of
course, there are lots of product using zram in real practice.

The major TV companys have used zram as swap since two years ago and
recently our production team released android smart phone with zram
which is used as swap, too and recently Android Kitkat start to use zram
for small memory smart phone.  And there was a report Google released
their ChromeOS with zram, too and cyanogenmod have been used zram long
time ago.  And I heard some disto have used zram block device for tmpfs.
In addition, I saw many report from many other peoples.  For example,
Lubuntu start to use it.

The benefit of zram is very clear.  With my experience, one of the
benefit was to remove jitter of video application with backgroud memory
pressure.  It would be effect of efficient memory usage by compression
but more issue is whether swap is there or not in the system.  Recent
mobile platforms have used JAVA so there are many anonymous pages.  But
embedded system normally are reluctant to use eMMC or SDCard as swap
because there is wear-leveling and latency issues so if we do not use
swap, it means we can't reclaim anoymous pages and at last, we could
encounter OOM kill.  :(

Although we have real storage as swap, it was a problem, too.  Because
it sometime ends up making system very unresponsible caused by slow swap
storage performance.

Quote from Luigi on Google
 "Since Chrome OS was mentioned: the main reason why we don't use swap
  to a disk (rotating or SSD) is because it doesn't degrade gracefully
  and leads to a bad interactive experience.  Generally we prefer to
  manage RAM at a higher level, by transparently killing and restarting
  processes.  But we noticed that zram is fast enough to be competitive
  with the latter, and it lets us make more efficient use of the
  available RAM.  " and he announced.
http://www.spinics.net/lists/linux-mm/msg57717.html

Other uses case is to use zram for block device.  Zram is block device
so anyone can format the block device and mount on it so some guys on
the internet start zram as /var/tmp.
http://forums.gentoo.org/viewtopic-t-838198-start-0.html

Let's promote zram and enhance/maintain it instead of removing.

Change-Id: Ie8f4e47eb9b74f4269da921eb6c709964fb6753e
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Conflicts:

	drivers/block/Kconfig
	drivers/staging/Kconfig
	drivers/staging/Makefile

9 files changed, 3 insertions, 3 deletions

diff --git a/drivers/staging/zram/zram.txt b/Documentation/blockdev/zram.txt
index 765d790..765d790 100644
--- a/drivers/staging/zram/zram.txt
+++ b/Documentation/blockdev/zram.txt
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 717d6e4..b7ac932 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -116,6 +116,8 @@ config PARIDE
 
 source "drivers/block/paride/Kconfig"
 
+source "drivers/block/zram/Kconfig"
+
 config BLK_CPQ_DA
 	tristate "Compaq SMART2 support"
 	depends on PCI && VIRT_TO_BUS
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index 76646e9..edc9543 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -40,4 +40,5 @@ obj-$(CONFIG_XEN_BLKDEV_BACKEND)	+= xen-blkback/
 obj-$(CONFIG_BLK_DEV_DRBD)     += drbd/
 obj-$(CONFIG_BLK_DEV_RBD)     += rbd.o
 
+obj-$(CONFIG_ZRAM) += zram/
 swim_mod-y	:= swim.o swim_asm.o
diff --git a/drivers/staging/zram/Kconfig b/drivers/block/zram/Kconfig
index 983314c..983314c 100644
--- a/drivers/staging/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
diff --git a/drivers/staging/zram/Makefile b/drivers/block/zram/Makefile
index cb0f9ce..cb0f9ce 100644
--- a/drivers/staging/zram/Makefile
+++ b/drivers/block/zram/Makefile
diff --git a/drivers/staging/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index d22e5ad..d22e5ad 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
diff --git a/drivers/staging/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 1c39fed..1c39fed 100644
--- a/drivers/staging/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index 11a4b5b..d0f6718 100644
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -104,8 +104,6 @@ source "drivers/staging/iio/Kconfig"
 
 source "drivers/staging/cs5535_gpio/Kconfig"
 
-source "drivers/staging/zram/Kconfig"
-
 source "drivers/staging/zcache/Kconfig"
 
 source "drivers/staging/wlags49_h2/Kconfig"
diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
index c7d5f89..9400eb7 100644
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -43,7 +43,6 @@ obj-$(CONFIG_VME_BUS)		+= vme/
 obj-$(CONFIG_DX_SEP)            += sep/
 obj-$(CONFIG_IIO)		+= iio/
 obj-$(CONFIG_CS5535_GPIO)	+= cs5535_gpio/
-obj-$(CONFIG_ZRAM)		+= zram/
 obj-$(CONFIG_ZCACHE)		+= zcache/
 obj-$(CONFIG_WLAGS49_H2)	+= wlags49_h2/
 obj-$(CONFIG_WLAGS49_H25)	+= wlags49_h25/