From 3d89bca8b1feefa6b4a574207115de1458711c7f Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Mon, 14 Nov 2016 17:38:35 -0800
Subject: [PATCH] f2fs: avoid BG_GC in f2fs_balance_fs

If many threads hit has_not_enough_free_secs() in f2fs_balance_fs() at the same
time, all the threads would do FG_GC or BG_GC.
In this critical path, we totally don't need to do BG_GC at all.
Let's avoid that.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/f2fs.h    | 2 +-
 fs/f2fs/file.c    | 2 +-
 fs/f2fs/gc.c      | 7 +++++--
 fs/f2fs/segment.c | 2 +-
 4 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8dc378d82f67..687ab43a6cd8 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2235,7 +2235,7 @@ int f2fs_migrate_page(struct address_space *, struct 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, struct inode *);
-int f2fs_gc(struct f2fs_sb_info *, bool);
+int f2fs_gc(struct f2fs_sb_info *, bool, bool);
 void build_gc_manager(struct f2fs_sb_info *);
 
 /*
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index fbfcd809baec..84f4572ae959 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1853,7 +1853,7 @@ static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
 		mutex_lock(&sbi->gc_mutex);
 	}
 
-	ret = f2fs_gc(sbi, sync);
+	ret = f2fs_gc(sbi, sync, true);
 out:
 	mnt_drop_write_file(filp);
 	return ret;
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 744031194934..54d06c21af07 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -82,7 +82,7 @@ static int gc_thread_func(void *data)
 		stat_inc_bggc_count(sbi);
 
 		/* if return value is not zero, no victim was selected */
-		if (f2fs_gc(sbi, test_opt(sbi, FORCE_FG_GC)))
+		if (f2fs_gc(sbi, test_opt(sbi, FORCE_FG_GC), true))
 			wait_ms = gc_th->no_gc_sleep_time;
 
 		trace_f2fs_background_gc(sbi->sb, wait_ms,
@@ -905,7 +905,7 @@ next:
 	return sec_freed;
 }
 
-int f2fs_gc(struct f2fs_sb_info *sbi, bool sync)
+int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool background)
 {
 	unsigned int segno;
 	int gc_type = sync ? FG_GC : BG_GC;
@@ -946,6 +946,9 @@ gc_more:
 			if (ret)
 				goto stop;
 		}
+	} else if (gc_type == BG_GC && !background) {
+		/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
+		goto stop;
 	}
 
 	if (segno == NULL_SEGNO && !__get_victim(sbi, &segno, gc_type))
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 30d0e9a76c62..27e1b7c56e4c 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -364,7 +364,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
 	 */
 	if (has_not_enough_free_secs(sbi, 0, 0)) {
 		mutex_lock(&sbi->gc_mutex);
-		f2fs_gc(sbi, false);
+		f2fs_gc(sbi, false, false);
 	}
 }