diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 4ac1099..584612b 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -589,7 +589,7 @@ static void __z_erofs_vle_work_release(struct z_erofs_vle_workgroup *grp,
 	erofs_workgroup_put(&grp->obj);
 }
 
-void z_erofs_vle_work_release(struct z_erofs_vle_work *work)
+static void z_erofs_vle_work_release(struct z_erofs_vle_work *work)
 {
 	struct z_erofs_vle_workgroup *grp =
 		z_erofs_vle_work_workgroup(work, true);
diff --git a/drivers/staging/erofs/unzip_vle_lz4.c b/drivers/staging/erofs/unzip_vle_lz4.c
index 52797bd..8e8d705 100644
--- a/drivers/staging/erofs/unzip_vle_lz4.c
+++ b/drivers/staging/erofs/unzip_vle_lz4.c
@@ -13,7 +13,7 @@
 #include "unzip_vle.h"
 #include <linux/lz4.h>
 
-int z_erofs_unzip_lz4(void *in, void *out, size_t inlen, size_t outlen)
+static int z_erofs_unzip_lz4(void *in, void *out, size_t inlen, size_t outlen)
 {
 	int ret = LZ4_decompress_safe_partial(in, out, inlen, outlen, outlen);
 
diff --git a/drivers/staging/erofs/utils.c b/drivers/staging/erofs/utils.c
index b535898..fc30025 100644
--- a/drivers/staging/erofs/utils.c
+++ b/drivers/staging/erofs/utils.c
@@ -131,9 +131,9 @@ static void erofs_workgroup_unfreeze_final(struct erofs_workgroup *grp)
 	__erofs_workgroup_free(grp);
 }
 
-bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
-				    struct erofs_workgroup *grp,
-				    bool cleanup)
+static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
+					   struct erofs_workgroup *grp,
+					   bool cleanup)
 {
 	/*
 	 * for managed cache enabled, the refcount of workgroups
@@ -172,9 +172,9 @@ bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
 
 #else
 /* for nocache case, no customized reclaim path at all */
-bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
-				    struct erofs_workgroup *grp,
-				    bool cleanup)
+static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
+					   struct erofs_workgroup *grp,
+					   bool cleanup)
 {
 	int cnt = atomic_read(&grp->refcount);