sfx2 store: avoid rename() for files with >1 hard link count

Rename would break the hard link; in practice e.g. Online's 'make run'
debug feature depends on not breaking hardlinks.

Change-Id: Id3ac19493b6b473274b7ed53a4ca06fc34bc1668
Reviewed-on: https://gerrit.libreoffice.org/51858
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

2 files changed, 59 insertions, 1 deletions

diff --git a/sfx2/qa/cppunit/test_misc.cxx b/sfx2/qa/cppunit/test_misc.cxx
index a1ecc01a7c61..72f21fc66c3a 100644
--- a/sfx2/qa/cppunit/test_misc.cxx
+++ b/sfx2/qa/cppunit/test_misc.cxx
@@ -11,6 +11,7 @@
 
 #ifndef _WIN32
 #include <sys/stat.h>
+#include <unistd.h>
 #endif
 #include <memory>
 
@@ -51,6 +52,7 @@ public:
     virtual void setUp() override;
     void testODFCustomMetadata();
     void testNoThumbnail();
+    void testHardLinks();
 
     virtual void registerNamespaces(xmlXPathContextPtr& pXmlXpathCtx) override
     {
@@ -66,6 +68,7 @@ public:
     CPPUNIT_TEST_SUITE(MiscTest);
     CPPUNIT_TEST(testODFCustomMetadata);
     CPPUNIT_TEST(testNoThumbnail);
+    CPPUNIT_TEST(testHardLinks);
     CPPUNIT_TEST_SUITE_END();
 
 private:
@@ -147,6 +150,35 @@ void MiscTest::testNoThumbnail()
     xComponent->dispose();
 }
 
+void MiscTest::testHardLinks()
+{
+#ifndef _WIN32
+    OUString aSourceDir = m_directories.getURLFromSrc("/sfx2/qa/cppunit/misc/");
+    OUString aTargetDir = m_directories.getURLFromWorkdir("/CppunitTest/sfx2_misc.test.user/");
+    const OUString aURL(aTargetDir + "hello.odt");
+    osl::File::copy(aSourceDir + "hello.odt", aURL);
+    OUString aTargetPath;
+    osl::FileBase::getSystemPathFromFileURL(aURL, aTargetPath);
+    OString aOld = aTargetPath.toUtf8();
+    aTargetPath += ".2";
+    OString aNew = aTargetPath.toUtf8();
+    link(aOld.getStr(), aNew.getStr());
+
+    uno::Reference<lang::XComponent> xComponent = loadFromDesktop(aURL, "com.sun.star.text.TextDocument");
+    CPPUNIT_ASSERT(xComponent.is());
+
+    uno::Reference<frame::XStorable> xStorable(xComponent, uno::UNO_QUERY);
+    xStorable->store();
+
+    struct stat buf;
+    stat(aOld.getStr(), &buf);
+    // This failed: hard link count was 1, the hard link broke on store.
+    CPPUNIT_ASSERT(buf.st_nlink > 1);
+
+    xComponent->dispose();
+#endif
+}
+
 CPPUNIT_TEST_SUITE_REGISTRATION(MiscTest);
 
 }
diff --git a/sfx2/source/doc/docfile.cxx b/sfx2/source/doc/docfile.cxx
index 63ce058f0a47..d3f78d2d6078 100644
--- a/sfx2/source/doc/docfile.cxx
+++ b/sfx2/source/doc/docfile.cxx
@@ -19,6 +19,10 @@
 
 #include <config_features.h>
 
+#ifdef UNX
+#include <sys/stat.h>
+#endif
+
 #include <sfx2/docfile.hxx>
 #include <sfx2/signaturestate.hxx>
 
@@ -190,6 +194,28 @@ sal_uInt64 GetDefaultFileAttributes(const OUString& rURL)
     return nRet;
 }
 
+/// Determines if rURL is a non-hard-linked file:// URL.
+bool IsNotHardLinkedFile(const OUString& rURL)
+{
+    if (!comphelper::isFileUrl(rURL))
+        return false;
+
+#ifdef UNX
+    OUString rPath;
+    if (osl::FileBase::getSystemPathFromFileURL(rURL, rPath) != osl::FileBase::E_None)
+        return false;
+
+    struct stat buf;
+    if (stat(rPath.toUtf8().getStr(), &buf) != 0)
+        return false;
+
+    if (buf.st_nlink > 1)
+        return false;
+#endif
+
+    return true;
+}
+
 } // anonymous namespace
 
 class SfxMedium_Impl
@@ -1812,7 +1838,7 @@ void SfxMedium::TransactedTransferForFS_Impl( const INetURLObject& aSource,
                 OUString aDestMainURL = aDest.GetMainURL(INetURLObject::DecodeMechanism::NONE);
 
                 sal_uInt64 nAttributes = GetDefaultFileAttributes(aDestMainURL);
-                if (comphelper::isFileUrl(aDestMainURL) && osl::File::move(aSourceMainURL, aDestMainURL) == osl::FileBase::E_None)
+                if (IsNotHardLinkedFile(aDestMainURL) && osl::File::move(aSourceMainURL, aDestMainURL) == osl::FileBase::E_None)
                 {
                     if (nAttributes)
                         // Adjust attributes, source might be created with