From f13cfcb83e931ed6cabdabee588bbaf308e7952b Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Sat, 29 Jul 2023 15:17:56 -0700
Subject: [PATCH] allow disabling O_DIRECT for write ops (#17751)

on really slow systems, O_DIRECT simply kills the drives
allow for a way to disable them.
---
 cmd/xl-storage.go           | 23 +++++++++++++----------
 internal/config/api/help.go |  2 +-
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/cmd/xl-storage.go b/cmd/xl-storage.go
index f81b560d3..85634eef4 100644
--- a/cmd/xl-storage.go
+++ b/cmd/xl-storage.go
@@ -284,16 +284,18 @@ func newXLStorage(ep Endpoint, cleanUp bool) (s *xlStorage, err error) {
 		s.formatLegacy = format.Erasure.DistributionAlgo == formatErasureVersionV2DistributionAlgoV1
 	}
 
-	// Return an error if ODirect is not supported
-	// unless it is a single erasure disk mode
-	if err := s.checkODirectDiskSupport(); err == nil {
-		s.oDirect = true
-	} else {
-		// Allow if unsupported platform or single disk.
-		if errors.Is(err, errUnsupportedDisk) && globalIsErasureSD || !disk.ODirectPlatform {
-			s.oDirect = false
+	if !globalAPIConfig.isDisableODirect() {
+		// Return an error if ODirect is not supported
+		// unless it is a single erasure disk mode
+		if err := s.checkODirectDiskSupport(); err == nil {
+			s.oDirect = true
 		} else {
-			return s, err
+			// Allow if unsupported platform or single disk.
+			if errors.Is(err, errUnsupportedDisk) && globalIsErasureSD || !disk.ODirectPlatform {
+				s.oDirect = false
+			} else {
+				return s, err
+			}
 		}
 	}
 
@@ -1896,7 +1898,8 @@ func (s *xlStorage) writeAllDirect(ctx context.Context, filePath string, fileSiz
 		return osErrToFileErr(err)
 	}
 
-	odirectEnabled := s.oDirect
+	odirectEnabled := !globalAPIConfig.isDisableODirect() && s.oDirect
+
 	var w *os.File
 	if odirectEnabled {
 		w, err = OpenFileDirectIO(filePath, flags, 0o666)
diff --git a/internal/config/api/help.go b/internal/config/api/help.go
index ea4a408cb..c347884cc 100644
--- a/internal/config/api/help.go
+++ b/internal/config/api/help.go
@@ -94,7 +94,7 @@ var (
 		},
 		config.HelpKV{
 			Key:         apiDisableODirect,
-			Description: "set to disable O_DIRECT for reads under special conditions. NOTE: it is not recommended to disable O_DIRECT without prior testing" + defaultHelpPostfix(apiDisableODirect),
+			Description: "set to disable O_DIRECT for read and writes under special conditions. NOTE: it is not recommended to disable O_DIRECT without prior testing" + defaultHelpPostfix(apiDisableODirect),
 			Optional:    true,
 			Type:        "boolean",
 		},