f2fs: revisit the f2fs_gc flow

I'd like to revisit the f2fs_gc flow and rewrite as follows.

1. In practical, the nGC parameter of f2fs_gc is meaningless. So, let's
  remove it.
2. Background GC marks victim blocks as dirty one at a time.
3. Foreground GC should do cleaning job until acquiring enough free
  sections. Afterwards, it needs to do checkpoint.

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

3 files changed, 23 insertions, 41 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 280713289d8c..285e43d602f3 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -986,7 +986,7 @@ int do_write_data_page(struct page *);
 int start_gc_thread(struct f2fs_sb_info *);
 void stop_gc_thread(struct f2fs_sb_info *);
 block_t start_bidx_of_node(unsigned int);
-int f2fs_gc(struct f2fs_sb_info *, int);
+int f2fs_gc(struct f2fs_sb_info *);
 void build_gc_manager(struct f2fs_sb_info *);
 int create_gc_caches(void);
 void destroy_gc_caches(void);
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index b0ec721e984a..b4dd90cf1f18 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -78,7 +78,7 @@ static int gc_thread_func(void *data)
 
                 sbi->bg_gc++;
 
-                if (f2fs_gc(sbi, 1) == GC_NONE)
+                if (f2fs_gc(sbi) == GC_NONE)
                         wait_ms = GC_THREAD_NOGC_SLEEP_TIME;
                 else if (wait_ms == GC_THREAD_NOGC_SLEEP_TIME)
                         wait_ms = GC_THREAD_MAX_SLEEP_TIME;
@@ -651,62 +651,44 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
         return ret;
 }
 
-int f2fs_gc(struct f2fs_sb_info *sbi, int nGC)
+int f2fs_gc(struct f2fs_sb_info *sbi)
 {
-        unsigned int segno;
-        int old_free_secs, cur_free_secs;
-        int gc_status, nfree;
         struct list_head ilist;
+        unsigned int segno, i;
         int gc_type = BG_GC;
+        int gc_status = GC_NONE;
 
         INIT_LIST_HEAD(&ilist);
 gc_more:
-        nfree = 0;
-        gc_status = GC_NONE;
+        if (!(sbi->sb->s_flags & MS_ACTIVE))
+                goto stop;
 
         if (has_not_enough_free_secs(sbi))
-                old_free_secs = reserved_sections(sbi);
-        else
-                old_free_secs = free_sections(sbi);
-
-        while (sbi->sb->s_flags & MS_ACTIVE) {
-                int i;
-                if (has_not_enough_free_secs(sbi))
-                        gc_type = FG_GC;
+                gc_type = FG_GC;
 
-                cur_free_secs = free_sections(sbi) + nfree;
+        if (!__get_victim(sbi, &segno, gc_type, NO_CHECK_TYPE))
+                goto stop;
 
-                /* We got free space successfully. */
-                if (nGC < cur_free_secs - old_free_secs)
-                        break;
-
-                if (!__get_victim(sbi, &segno, gc_type, NO_CHECK_TYPE))
+        for (i = 0; i < sbi->segs_per_sec; i++) {
+                /*
+                 * do_garbage_collect will give us three gc_status:
+                 * GC_ERROR, GC_DONE, and GC_BLOCKED.
+                 * If GC is finished uncleanly, we have to return
+                 * the victim to dirty segment list.
+                 */
+                gc_status = do_garbage_collect(sbi, segno + i, &ilist, gc_type);
+                if (gc_status != GC_DONE)
                         break;
-
-                for (i = 0; i < sbi->segs_per_sec; i++) {
-                        /*
-                         * do_garbage_collect will give us three gc_status:
-                         * GC_ERROR, GC_DONE, and GC_BLOCKED.
-                         * If GC is finished uncleanly, we have to return
-                         * the victim to dirty segment list.
-                         */
-                        gc_status = do_garbage_collect(sbi, segno + i,
-                                        &ilist, gc_type);
-                        if (gc_status != GC_DONE)
-                                goto stop;
-                        nfree++;
-                }
         }
-stop:
-        if (has_not_enough_free_secs(sbi) || gc_status == GC_BLOCKED) {
+        if (has_not_enough_free_secs(sbi)) {
                 write_checkpoint(sbi, (gc_status == GC_BLOCKED), false);
-                if (nfree)
+                if (has_not_enough_free_secs(sbi))
                         goto gc_more;
         }
+stop:
         mutex_unlock(&sbi->gc_mutex);
 
         put_gc_inode(&ilist);
-        BUG_ON(!list_empty(&ilist));
         return gc_status;
 }
 
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index de6240922b0a..4b0099066582 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -31,7 +31,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
          */
         if (has_not_enough_free_secs(sbi)) {
                 mutex_lock(&sbi->gc_mutex);
-                f2fs_gc(sbi, 1);
+                f2fs_gc(sbi);
         }
 }