From a2c4fcd5e9782dc8d2998773380c7171ee53b813 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 29 Aug 2019 14:49:58 +0200
Subject: [PATCH] Don't rely on st_blocks

It doesn't seem very reliable on ZFS.
---
 src/libstore/gc.cc  | 7 +++----
 src/libutil/util.cc | 2 +-
 tests/gc-auto.sh    | 4 ++--
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index f73601679..a166f4ee2 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -690,9 +690,8 @@ void LocalStore::removeUnusedLinks(const GCState & state)
             throw SysError(format("statting '%1%'") % path);
 
         if (st.st_nlink != 1) {
-            unsigned long long size = st.st_blocks * 512ULL;
-            actualSize += size;
-            unsharedSize += (st.st_nlink - 1) * size;
+            actualSize += st.st_size;
+            unsharedSize += (st.st_nlink - 1) * st.st_size;
             continue;
         }
 
@@ -701,7 +700,7 @@ void LocalStore::removeUnusedLinks(const GCState & state)
         if (unlink(path.c_str()) == -1)
             throw SysError(format("deleting '%1%'") % path);
 
-        state.results.bytesFreed += st.st_blocks * 512ULL;
+        state.results.bytesFreed += st.st_size;
     }
 
     struct stat st;
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 44fa72482..1b7449991 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -397,7 +397,7 @@ static void _deletePath(const Path & path, unsigned long long & bytesFreed)
     }
 
     if (!S_ISDIR(st.st_mode) && st.st_nlink == 1)
-        bytesFreed += st.st_blocks * 512;
+        bytesFreed += st.st_size;
 
     if (S_ISDIR(st.st_mode)) {
         /* Make the directory accessible. */
diff --git a/tests/gc-auto.sh b/tests/gc-auto.sh
index 68b7219f2..54ead227e 100644
--- a/tests/gc-auto.sh
+++ b/tests/gc-auto.sh
@@ -22,7 +22,7 @@ with import ./config.nix; mkDerivation {
     echo foo > \$out/bar
     echo 1...
     sleep 2
-    echo 100 > $fake_free
+    echo 200 > $fake_free
     echo 2...
     sleep 2
     echo 3...
@@ -44,7 +44,7 @@ with import ./config.nix; mkDerivation {
     echo foo > \$out/bar
     echo 1...
     sleep 2
-    echo 100 > $fake_free
+    echo 200 > $fake_free
     echo 2...
     sleep 2
     echo 3...