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>

3 files changed, 18 insertions, 3 deletions

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 60d4f674efa7..d286d8be8e68 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -106,6 +106,8 @@ int start_gc_thread(struct f2fs_sb_info *sbi)
         gc_th->max_sleep_time = DEF_GC_THREAD_MAX_SLEEP_TIME;
         gc_th->no_gc_sleep_time = DEF_GC_THREAD_NOGC_SLEEP_TIME;
 
+        gc_th->gc_idle = 0;
+
         sbi->gc_thread = gc_th;
         init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
         sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
@@ -130,9 +132,17 @@ void stop_gc_thread(struct f2fs_sb_info *sbi)
         sbi->gc_thread = NULL;
 }
 
-static int select_gc_type(int gc_type)
+static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
 {
-        return (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
+        int gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
+
+        if (gc_th && gc_th->gc_idle) {
+                if (gc_th->gc_idle == 1)
+                        gc_mode = GC_CB;
+                else if (gc_th->gc_idle == 2)
+                        gc_mode = GC_GREEDY;
+        }
+        return gc_mode;
 }
 
 static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
@@ -145,7 +155,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
                 p->dirty_segmap = dirty_i->dirty_segmap[type];
                 p->ofs_unit = 1;
         } else {
-                p->gc_mode = select_gc_type(gc_type);
+                p->gc_mode = select_gc_type(sbi->gc_thread, gc_type);
                 p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
                 p->ofs_unit = sbi->segs_per_sec;
         }
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index f4bf44c9deda..c22dee9f1422 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -30,6 +30,9 @@ struct f2fs_gc_kthread {
         unsigned int min_sleep_time;
         unsigned int max_sleep_time;
         unsigned int no_gc_sleep_time;
+
+        /* for changing gc mode */
+        unsigned int gc_idle;
 };
 
 struct inode_entry {
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index e161a24fbf39..94c0e2049546 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -148,12 +148,14 @@ static struct f2fs_attr f2fs_attr_##_name = {			\
 F2FS_RW_ATTR(gc_min_sleep_time, min_sleep_time);
 F2FS_RW_ATTR(gc_max_sleep_time, max_sleep_time);
 F2FS_RW_ATTR(gc_no_gc_sleep_time, no_gc_sleep_time);
+F2FS_RW_ATTR(gc_idle, gc_idle);
 
 #define ATTR_LIST(name) (&f2fs_attr_##name.attr)
 static struct attribute *f2fs_attrs[] = {
         ATTR_LIST(gc_min_sleep_time),
         ATTR_LIST(gc_max_sleep_time),
         ATTR_LIST(gc_no_gc_sleep_time),
+        ATTR_LIST(gc_idle),
         NULL,
 };