f2fs: speed up gc_urgent mode with SSR

This patch activates SSR in gc_urgent mode.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 273cc64..7fd742f 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -169,6 +169,21 @@ static unsigned long __find_rev_next_zero_bit(const unsigned long *addr,
 	return result - size + __reverse_ffz(tmp);
 }
 
+bool need_SSR(struct f2fs_sb_info *sbi)
+{
+	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
+	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);
+	int imeta_secs = get_blocktype_secs(sbi, F2FS_DIRTY_IMETA);
+
+	if (test_opt(sbi, LFS))
+		return false;
+	if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
+		return true;
+
+	return free_sections(sbi) <= (node_secs + 2 * dent_secs + imeta_secs +
+						2 * reserved_sections(sbi));
+}
+
 void register_inmem_page(struct inode *inode, struct page *page)
 {
 	struct f2fs_inode_info *fi = F2FS_I(inode);