fix: incorrect O_DIRECT behavior for reads (#12811)

O_DIRECT behavior was broken and it was still
caching all the reads, this change properly fixes
this behavior.

cmd/xl-storage.go

@@ -43,7 +43,6 @@ import (
 	"github.com/minio/minio/internal/bucket/lifecycle"
 	"github.com/minio/minio/internal/color"
 	"github.com/minio/minio/internal/config"
-	"github.com/minio/minio/internal/config/storageclass"
 	"github.com/minio/minio/internal/disk"
 	xioutil "github.com/minio/minio/internal/ioutil"
 	"github.com/minio/minio/internal/logger"
@@ -1109,11 +1108,12 @@ func (s *xlStorage) ReadVersion(ctx context.Context, volume, path, versionID str
 		// - object has not yet transitioned
 		// - object size lesser than 128KiB
 		// - object has maximum of 1 parts
-		if fi.TransitionStatus == "" && fi.DataDir != "" && fi.Size <= smallFileThreshold && len(fi.Parts) == 1 {
-			// Enable O_DIRECT optionally only if drive supports it.
-			requireDirectIO := globalStorageClass.GetDMA() == storageclass.DMAReadWrite
+		if fi.TransitionStatus == "" &&
+			fi.DataDir != "" && fi.Size <= smallFileThreshold &&
+			len(fi.Parts) == 1 {
 			partPath := fmt.Sprintf("part.%d", fi.Parts[0].Number)
-			fi.Data, err = s.readAllData(volumeDir, pathJoin(volumeDir, path, fi.DataDir, partPath), requireDirectIO)
+			dataPath := pathJoin(volumeDir, path, fi.DataDir, partPath)
+			fi.Data, err = s.readAllData(volumeDir, dataPath)
 			if err != nil {
 				return FileInfo{}, err
 			}
@@ -1123,15 +1123,8 @@ func (s *xlStorage) ReadVersion(ctx context.Context, volume, path, versionID str
 	return fi, nil
 }
 
-func (s *xlStorage) readAllData(volumeDir string, filePath string, requireDirectIO bool) (buf []byte, err error) {
-	var r io.ReadCloser
-	if requireDirectIO {
-		var f *os.File
-		f, err = OpenFileDirectIO(filePath, readMode, 0666)
-		r = &odirectReader{f, nil, nil, true, true, s, nil}
-	} else {
-		r, err = OpenFile(filePath, readMode, 0)
-	}
+func (s *xlStorage) readAllData(volumeDir string, filePath string) (buf []byte, err error) {
+	f, err := OpenFileDirectIO(filePath, readMode, 0666)
 	if err != nil {
 		if osIsNotExist(err) {
 			// Check if the object doesn't exist because its bucket
@@ -1163,7 +1156,7 @@ func (s *xlStorage) readAllData(volumeDir string, filePath string, requireDirect
 		}
 		return nil, err
 	}
-
+	r := &odirectReader{f, nil, nil, true, true, s, nil}
 	defer r.Close()
 	buf, err = ioutil.ReadAll(r)
 	if err != nil {
@@ -1191,8 +1184,7 @@ func (s *xlStorage) ReadAll(ctx context.Context, volume string, path string) (bu
 		return nil, err
 	}
 
-	requireDirectIO := globalStorageClass.GetDMA() == storageclass.DMAReadWrite
-	return s.readAllData(volumeDir, filePath, requireDirectIO)
+	return s.readAllData(volumeDir, filePath)
 }
 
 // ReadFile reads exactly len(buf) bytes into buf. It returns the
@@ -1415,7 +1407,7 @@ func (s *xlStorage) ReadFileStream(ctx context.Context, volume, path string, off
 
 	var file *os.File
 	// O_DIRECT only supported if offset is zero
-	if offset == 0 && globalStorageClass.GetDMA() == storageclass.DMAReadWrite {
+	if offset == 0 {
 		file, err = OpenFileDirectIO(filePath, readMode, 0666)
 	} else {
 		// Open the file for reading.
@@ -1456,7 +1448,7 @@ func (s *xlStorage) ReadFileStream(ctx context.Context, volume, path string, off
 		return nil, errIsNotRegular
 	}
 
-	if offset == 0 && globalStorageClass.GetDMA() == storageclass.DMAReadWrite {
+	if offset == 0 {
 		or := &odirectReader{file, nil, nil, true, false, s, nil}
 		if length <= smallFileThreshold {
 			or = &odirectReader{file, nil, nil, true, true, s, nil}

cmd/xl-storage_test.go

@@ -30,8 +30,6 @@ import (
 	"strings"
 	"syscall"
 	"testing"
-
-	"github.com/minio/minio/internal/config/storageclass"
 )
 
 func TestCheckPathLength(t *testing.T) {
@@ -1152,10 +1150,6 @@ func TestXLStorageReadFile(t *testing.T) {
 	}
 
 	for l := 0; l < 2; l++ {
-		// 1st loop tests with dma=write, 2nd loop tests with dma=read-write.
-		if l == 1 {
-			globalStorageClass.DMA = storageclass.DMAReadWrite
-		}
 		// Following block validates all ReadFile test cases.
 		for i, testCase := range testCases {
 			var n int64
@@ -1213,9 +1207,6 @@ func TestXLStorageReadFile(t *testing.T) {
 		}
 	}
 
-	// Reset the flag.
-	globalStorageClass.DMA = storageclass.DMAWrite
-
 	// TestXLStorage for permission denied.
 	if runtime.GOOS != globalWindowsOSName {
 		permDeniedDir := createPermDeniedFile(t)

internal/config/storageclass/help.go

@@ -34,12 +34,6 @@ var (
 			Optional:    true,
 			Type:        "string",
 		},
-		config.HelpKV{
-			Key:         ClassDMA,
-			Description: `enable O_DIRECT for both read and write, defaults to "write" e.g. "read+write"`,
-			Optional:    true,
-			Type:        "string",
-		},
 		config.HelpKV{
 			Key:         config.Comment,
 			Description: config.DefaultComment,

internal/config/storageclass/storage-class.go

@@ -19,7 +19,6 @@ package storageclass
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"strconv"
 	"strings"
@@ -35,26 +34,17 @@ const (
 	RRS = "REDUCED_REDUNDANCY"
 	// Standard storage class
 	STANDARD = "STANDARD"
-	// DMA storage class
-	DMA = "DMA"
-
-	// Valid values are "write" and "read+write"
-	DMAWrite     = "write"
-	DMAReadWrite = "read+write"
 )
 
 // Standard constats for config info storage class
 const (
 	ClassStandard = "standard"
 	ClassRRS      = "rrs"
-	ClassDMA      = "dma"
 
 	// Reduced redundancy storage class environment variable
 	RRSEnv = "MINIO_STORAGE_CLASS_RRS"
 	// Standard storage class environment variable
 	StandardEnv = "MINIO_STORAGE_CLASS_STANDARD"
-	// DMA storage class environment variable
-	DMAEnv = "MINIO_STORAGE_CLASS_DMA"
 
 	// Supported storage class scheme is EC
 	schemePrefix = "EC"
@@ -64,9 +54,6 @@ const (
 
 	// Default RRS parity is always minimum parity.
 	defaultRRSParity = minParityDisks
-
-	// Default DMA value
-	defaultDMA = DMAReadWrite
 )
 
 // DefaultKVS - default storage class config
@@ -80,10 +67,6 @@ var (
 			Key:   ClassRRS,
 			Value: "EC:2",
 		},
-		config.KV{
-			Key:   ClassDMA,
-			Value: defaultDMA,
-		},
 	}
 )
 
@@ -99,7 +82,6 @@ var ConfigLock = sync.RWMutex{}
 type Config struct {
 	Standard StorageClass `json:"standard"`
 	RRS      StorageClass `json:"rrs"`
-	DMA      string       `json:"dma"`
 }
 
 // UnmarshalJSON - Validate SS and RRS parity when unmarshalling JSON.
@@ -256,17 +238,9 @@ func (sCfg Config) Update(newCfg Config) {
 	ConfigLock.Lock()
 	defer ConfigLock.Unlock()
 	sCfg.RRS = newCfg.RRS
-	sCfg.DMA = newCfg.DMA
 	sCfg.Standard = newCfg.Standard
 }
 
-// GetDMA - returns DMA configuration.
-func (sCfg Config) GetDMA() string {
-	ConfigLock.RLock()
-	defer ConfigLock.RUnlock()
-	return sCfg.DMA
-}
-
 // Enabled returns if etcd is enabled.
 func Enabled(kvs config.KVS) bool {
 	ssc := kvs.Get(ClassStandard)
@@ -278,13 +252,14 @@ func Enabled(kvs config.KVS) bool {
 func LookupConfig(kvs config.KVS, setDriveCount int) (cfg Config, err error) {
 	cfg = Config{}
 
+	kvs.Delete("dma")
+
 	if err = config.CheckValidKeys(config.StorageClassSubSys, kvs, DefaultKVS); err != nil {
 		return Config{}, err
 	}
 
 	ssc := env.Get(StandardEnv, kvs.Get(ClassStandard))
 	rrsc := env.Get(RRSEnv, kvs.Get(ClassRRS))
-	dma := env.Get(DMAEnv, kvs.Get(ClassDMA))
 	// Check for environment variables and parse into storageClass struct
 	if ssc != "" {
 		cfg.Standard, err = parseStorageClass(ssc)
@@ -303,14 +278,6 @@ func LookupConfig(kvs config.KVS, setDriveCount int) (cfg Config, err error) {
 		cfg.RRS.Parity = defaultRRSParity
 	}
 
-	if dma == "" {
-		dma = defaultDMA
-	}
-	if dma != DMAReadWrite && dma != DMAWrite {
-		return Config{}, errors.New(`valid dma values are "read-write" and "write"`)
-	}
-	cfg.DMA = dma
-
 	// Validation is done after parsing both the storage classes. This is needed because we need one
 	// storage class value to deduce the correct value of the other storage class.
 	if err = validateParity(cfg.Standard.Parity, cfg.RRS.Parity, setDriveCount); err != nil {