zram: make compression algorithm selection possible

Add and document `comp_algorithm' device attribute.  This attribute allows
to show supported compression and currently selected compression
algorithms:

	cat /sys/block/zram0/comp_algorithm
	[lzo] lz4

and change selected compression algorithm:
	echo lzo > /sys/block/zram0/comp_algorithm

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 0da9ed6b82ea..70ec992514d0 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -65,6 +65,14 @@ Description:
                 number of backend's zcomp_strm compression streams (number of
                 concurrent compress operations).
 
+What:           /sys/block/zram<id>/comp_algorithm
+Date:           February 2014
+Contact:        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+                The comp_algorithm file is read-write and lets to show
+                available and selected compression algorithms, change
+                compression algorithm selection.
+
 What:           /sys/block/zram<id>/notify_free
 Date:           August 2010
 Contact:        Nitin Gupta <ngupta@vflare.org>