From dbea68ddd21cb3132dedb20892a4259057454d5e Mon Sep 17 00:00:00 2001
From: Tom Marshall <tdm.code@gmail.com>
Date: Sat, 9 Nov 2019 17:07:38 +0100
Subject: [PATCH] Do not vmap singe pages, just use page_address

---
 dm-compress/pbat.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/dm-compress/pbat.c b/dm-compress/pbat.c
index eaa5510..2c067c2 100644
--- a/dm-compress/pbat.c
+++ b/dm-compress/pbat.c
@@ -65,9 +65,14 @@ pbat_ctr(struct pbat* pbat,
     if (!cbd_alloc_pagev(pbat->pagev, nr_pages)) {
         return false;
     }
-    pbat->buf = vmap(pbat->pagev, nr_pages, VM_MAP, PAGE_KERNEL);
-    if (!pbat->buf) {
-        return false;
+    if (nr_pages == 1) {
+        pbat->buf = page_address(pbat->pagev[0]);
+    }
+    else {
+        pbat->buf = vmap(pbat->pagev, nr_pages, VM_MAP, PAGE_KERNEL);
+        if (!pbat->buf) {
+            return false;
+        }
     }
 
     return true;
@@ -82,7 +87,9 @@ pbat_dtr(struct pbat* pbat)
     for (n = 0; n < nr_pages; ++n) {
         lock_page(pbat->pagev[n]);
     }
-    vunmap(pbat->buf);
+    if (nr_pages != 1) {
+        vunmap(pbat->buf);
+    }
     pbat->buf = NULL;
     cbd_free_pagev(pbat->pagev, nr_pages);
     kfree(pbat->pagev);