f2fs: clarify and enhance the f2fs_gc flow

This patch makes clearer the ambiguous f2fs_gc flow as follows.

1. Remove intermediate checkpoint condition during f2fs_gc
 (i.e., should_do_checkpoint() and GC_BLOCKED)

2. Remove unnecessary return values of f2fs_gc because of #1.
 (i.e., GC_NODE, GC_OK, etc)

3. Simplify write_checkpoint() because of #2.

4. Clarify the main f2fs_gc flow.
 o monitor how many freed sections during one iteration of do_garbage_collect().
 o do GC more without checkpoints if we can't get enough free sections.
 o do checkpoint once we've got enough free sections through forground GCs.

5. Adopt thread-logging (Slack-Space-Recycle) scheme more aggressively on data
  log types. See. get_ssr_segement()

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 7aa270f3538a..777f17e496e6 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -29,7 +29,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
          * We should do GC or end up with checkpoint, if there are so many dirty
          * dir/node pages without enough free segments.
          */
-        if (has_not_enough_free_secs(sbi)) {
+        if (has_not_enough_free_secs(sbi, 0)) {
                 mutex_lock(&sbi->gc_mutex);
                 f2fs_gc(sbi);
         }
@@ -308,7 +308,7 @@ static unsigned int check_prefree_segments(struct f2fs_sb_info *sbi,
          * If there is not enough reserved sections,
          * we should not reuse prefree segments.
          */
-        if (has_not_enough_free_secs(sbi))
+        if (has_not_enough_free_secs(sbi, 0))
                 return NULL_SEGNO;
 
         /*
@@ -536,6 +536,23 @@ static void change_curseg(struct f2fs_sb_info *sbi, int type, bool reuse)
         }
 }
 
+static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
+{
+        struct curseg_info *curseg = CURSEG_I(sbi, type);
+        const struct victim_selection *v_ops = DIRTY_I(sbi)->v_ops;
+
+        if (IS_NODESEG(type) || !has_not_enough_free_secs(sbi, 0))
+                return v_ops->get_victim(sbi,
+                                &(curseg)->next_segno, BG_GC, type, SSR);
+
+        /* For data segments, let's do SSR more intensively */
+        for (; type >= CURSEG_HOT_DATA; type--)
+                if (v_ops->get_victim(sbi, &(curseg)->next_segno,
+                                                BG_GC, type, SSR))
+                        return 1;
+        return 0;
+}
+
 /*
  * flush out current segment and replace it with new segment
  * This function should be returned with success, otherwise BUG