f2fs: clean up bggc mount option

There are three status for background gc: on, off and sync, it's
a little bit confused to use test_opt(BG_GC) and test_opt(FORCE_FG_GC)
combinations to indicate status of background gc.

So let's remove F2FS_MOUNT_BG_GC and F2FS_MOUNT_FORCE_FG_GC mount
options, and add F2FS_OPTION().bggc_mode with below three status
to clean up codes and enhance bggc mode's scalability.

enum {
	BGGC_MODE_ON,		/* background gc is on */
	BGGC_MODE_OFF,		/* background gc is off */
	BGGC_MODE_SYNC,		/*
				 * background gc is on, migrating blocks
				 * like foreground gc
				 */
};

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e27d30d..ef3ec65 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -74,7 +74,6 @@ extern const char *f2fs_fault_name[FAULT_MAX];
 /*
  * For mount options
  */
-#define F2FS_MOUNT_BG_GC		0x00000001
 #define F2FS_MOUNT_DISABLE_ROLL_FORWARD	0x00000002
 #define F2FS_MOUNT_DISCARD		0x00000004
 #define F2FS_MOUNT_NOHEAP		0x00000008
@@ -88,7 +87,6 @@ extern const char *f2fs_fault_name[FAULT_MAX];
 #define F2FS_MOUNT_NOBARRIER		0x00000800
 #define F2FS_MOUNT_FASTBOOT		0x00001000
 #define F2FS_MOUNT_EXTENT_CACHE		0x00002000
-#define F2FS_MOUNT_FORCE_FG_GC		0x00004000
 #define F2FS_MOUNT_DATA_FLUSH		0x00008000
 #define F2FS_MOUNT_FAULT_INJECTION	0x00010000
 #define F2FS_MOUNT_USRQUOTA		0x00080000
@@ -138,6 +136,7 @@ struct f2fs_mount_info {
 	int alloc_mode;			/* segment allocation policy */
 	int fsync_mode;			/* fsync policy */
 	int fs_mode;			/* fs mode: LFS or ADAPTIVE */
+	int bggc_mode;			/* bggc mode: off, on or sync */
 	bool test_dummy_encryption;	/* test dummy encryption */
 	block_t unusable_cap;		/* Amount of space allowed to be
 					 * unusable when disabling checkpoint
@@ -1173,6 +1172,15 @@ enum {
 };
 
 enum {
+	BGGC_MODE_ON,		/* background gc is on */
+	BGGC_MODE_OFF,		/* background gc is off */
+	BGGC_MODE_SYNC,		/*
+				 * background gc is on, migrating blocks
+				 * like foreground gc
+				 */
+};
+
+enum {
 	FS_MODE_ADAPTIVE,	/* use both lfs/ssr allocation */
 	FS_MODE_LFS,		/* use lfs allocation only */
 };