f2fs: make sure f2fs_gc returns consistent errno

By default, f2fs_gc returns -EINVAL in general error cases, e.g., no victim
was selected. However, the default errno may be overwritten in two cases:
gc_more and BG_GC -> FG_GC. We should return consistent errno in such cases.
Signed-off-by: Weichao Guo <guoweichao@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -955,7 +955,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
 {
 	int gc_type = sync ? FG_GC : BG_GC;
 	int sec_freed = 0;
-	int ret = -EINVAL;
+	int ret;
 	struct cp_control cpc;
 	unsigned int init_segno = segno;
 	struct gc_inode_list gc_list = {
@@ -965,8 +965,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
 
 	cpc.reason = __get_cp_reason(sbi);
 gc_more:
-	if (unlikely(!(sbi->sb->s_flags & MS_ACTIVE)))
+	if (unlikely(!(sbi->sb->s_flags & MS_ACTIVE))) {
+		ret = -EINVAL;
 		goto stop;
+	}
 	if (unlikely(f2fs_cp_error(sbi))) {
 		ret = -EIO;
 		goto stop;
@@ -987,6 +989,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
 			gc_type = FG_GC;
 	}
 
+	ret = -EINVAL;
 	/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
 	if (gc_type == BG_GC && !background)
 		goto stop;