f2fs: add sysfs entries to select the gc policy

Add sysfs entry gc_idle to control the gc policy. Where
gc_idle = 1 corresponds to selecting a cost benefit approach,
while gc_idle = 2 corresponds to selecting a greedy approach
to garbage collection. The selection is mutually exclusive one
approach will work at any point. If gc_idle = 0, then this
option is disabled.

Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Pankaj Kumar <pankaj.km@samsung.com>
Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
[Jaegeuk Kim: change the select_gc_type() flow slightly]
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 98e53a09530a..31942efcaf0e 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -18,3 +18,9 @@ Contact:	"Namjae Jeon" <namjae.jeon@samsung.com>
 Description:
                  Controls the default sleep time for gc_thread. Time
                  is in milliseconds.
+
+What:           /sys/fs/f2fs/<disk>/gc_idle
+Date:           July 2013
+Contact:        "Namjae Jeon" <namjae.jeon@samsung.com>
+Description:
+                 Controls the victim selection policy for garbage collection.
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 5daf3bb2eef9..3cd27bed6349 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -158,6 +158,12 @@ Files in /sys/fs/f2fs/<devname>
                               time for the garbage collection thread. Time is
                               in milliseconds.
 
+ gc_idle                      This parameter controls the selection of victim
+                              policy for garbage collection. Setting gc_idle = 0
+                              (default) will disable this option. Setting
+                              gc_idle = 1 will select the Cost Benefit approach
+                              & setting gc_idle = 2 will select the greedy aproach.
+
 ================================================================================
 USAGE
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