From 612d531dae3b878af8d2e110a805df6fff147695 Mon Sep 17 00:00:00 2001
From: localhorst <localhorst@mosad.xyz>
Date: Fri, 12 Dec 2025 23:16:57 +0100
Subject: [PATCH] use O_DIRECT

---
 include/shred.h |  5 +++--
 src/shred.cpp   | 34 +++++++++++++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/include/shred.h b/include/shred.h
index 635f265..044166e 100644
--- a/include/shred.h
+++ b/include/shred.h
@@ -19,6 +19,7 @@
 
 #define CHUNK_SIZE 1024 * 1024 * 32 // amount of bytes that are overwritten at once --> 32MB
 #define TFNG_DATA_SIZE CHUNK_SIZE   // amount of bytes used by tfng
+#define O_DIRECT_PAGE_SIZE 4096     // needed page size for O_DIRECT
 
 // #define DEMO_DRIVE_SIZE 1024*1024*256L // 256MB
 // #define DEMO_DRIVE_SIZE 1024*1024*1024L // 1GB
@@ -38,8 +39,8 @@ public:
 private:
     fileDescriptor randomSrcFileDiscr;
     fileDescriptor driveFileDiscr;
-    unsigned char caTfngData[TFNG_DATA_SIZE];
-    unsigned char caReadBuffer[CHUNK_SIZE];
+    unsigned char *caTfngData;
+    unsigned char *caReadBuffer;
     unsigned long ulDriveByteSize;
     unsigned long ulDriveByteOverallCount = 0; // all bytes shredded in all iterations + checking -> used for progress calculation
     double d32Percent = 0.0;
diff --git a/src/shred.cpp b/src/shred.cpp
index 6cddd6c..abff03d 100644
--- a/src/shred.cpp
+++ b/src/shred.cpp
@@ -21,10 +21,30 @@ const static char *randomsrc = (char *)"/dev/urandom";
 
 Shred::Shred()
 {
+    // Allocate aligned buffers for O_DIRECT
+    if (posix_memalign((void **)&caTfngData, O_DIRECT_PAGE_SIZE, TFNG_DATA_SIZE) != 0)
+    {
+        Logger::logThis()->error("Failed to allocate aligned buffer for tfng data");
+        caTfngData = nullptr;
+    }
+
+    if (posix_memalign((void **)&caReadBuffer, O_DIRECT_PAGE_SIZE, CHUNK_SIZE) != 0)
+    {
+        Logger::logThis()->error("Failed to allocate aligned buffer for read buffer");
+        caReadBuffer = nullptr;
+    }
 }
 
 Shred::~Shred()
 {
+    if (caTfngData != nullptr)
+    {
+        free(caTfngData);
+    }
+    if (caReadBuffer != nullptr)
+    {
+        free(caReadBuffer);
+    }
 }
 
 /**
@@ -43,6 +63,12 @@ int Shred::shredDrive(Drive *drive, int *ipSignalFd)
     drive->u32DriveChecksumAfterShredding = UINT32_MAX;
     drive->state = Drive::TaskState::SHRED_ACTIVE;
 
+    if ((caTfngData == nullptr) || (caReadBuffer == nullptr))
+    {
+        Logger::logThis()->error("Shred-Task: Aligned memory not available! - Drive: " + drive->getSerial());
+        return -1;
+    }
+
 #ifdef DRYRUN
     for (int i = 0; i <= 100; i++)
     {
@@ -69,7 +95,13 @@ int Shred::shredDrive(Drive *drive, int *ipSignalFd)
     }
 
     // open disk
-    driveFileDiscr = open(cpDrivePath, O_RDWR | O_LARGEFILE);
+    driveFileDiscr = open(cpDrivePath, O_RDWR | O_LARGEFILE | O_DIRECT);
+    if (driveFileDiscr == -1 && errno == EINVAL)
+    {
+        driveFileDiscr = open(cpDrivePath, O_RDWR | O_LARGEFILE);
+        Logger::logThis()->warning("O_DIRECT not supported, using standard I/O - Drive: " + drive->getSerial());
+    }
+
     if (driveFileDiscr == -1)
     {
         std::string errorMsg(strerror(errno));