github.com/minio/minio@v0.0.0-20240328213742-3f72439b8a27/internal/disk/directio_unsupported.go (about)

     1  //go:build windows || openbsd || plan9
     2  
     3  // Copyright (c) 2015-2023 MinIO, Inc.
     4  //
     5  // This file is part of MinIO Object Storage stack
     6  //
     7  // This program is free software: you can redistribute it and/or modify
     8  // it under the terms of the GNU Affero General Public License as published by
     9  // the Free Software Foundation, either version 3 of the License, or
    10  // (at your option) any later version.
    11  //
    12  // This program is distributed in the hope that it will be useful
    13  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    14  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    15  // GNU Affero General Public License for more details.
    16  //
    17  // You should have received a copy of the GNU Affero General Public License
    18  // along with this program.  If not, see <http://www.gnu.org/licenses/>.
    19  
    20  package disk
    21  
    22  import (
    23  	"os"
    24  )
    25  
    26  // ODirectPlatform indicates if the platform supports O_DIRECT
    27  const ODirectPlatform = false
    28  
    29  // OpenBSD, Windows, and illumos do not support O_DIRECT.
    30  // On Windows there is no documentation on disabling O_DIRECT.
    31  // For these systems we do not attempt to build the 'directio' dependency since
    32  // the O_DIRECT symbol may not be exposed resulting in a failed build.
    33  //
    34  //
    35  // On illumos an explicit O_DIRECT flag is not necessary for two primary
    36  // reasons. Note that ZFS is effectively the default filesystem on illumos
    37  // systems.
    38  //
    39  // One benefit of using DirectIO on Linux is that the page cache will not be
    40  // polluted with single-access data. The ZFS read cache (ARC) is scan-resistant
    41  // so there is no risk of polluting the entire cache with data accessed once.
    42  // Another goal of DirectIO is to minimize the mutation of data by the kernel
    43  // before issuing IO to underlying devices. ZFS users often enable features like
    44  // compression and checksumming which currently necessitates mutating data in
    45  // the kernel.
    46  //
    47  // DirectIO semantics for a filesystem like ZFS would be quite different than
    48  // the semantics on filesystems like XFS, and these semantics are not
    49  // implemented at this time.
    50  // For more information on why typical DirectIO semantics do not apply to ZFS
    51  // see this ZFS-on-Linux commit message:
    52  // https://github.com/openzfs/zfs/commit/a584ef26053065f486d46a7335bea222cb03eeea
    53  
    54  // OpenFileDirectIO wrapper around os.OpenFile nothing special
    55  func OpenFileDirectIO(filePath string, flag int, perm os.FileMode) (*os.File, error) {
    56  	return os.OpenFile(filePath, flag, perm)
    57  }
    58  
    59  // DisableDirectIO is a no-op
    60  func DisableDirectIO(f *os.File) error {
    61  	return nil
    62  }
    63  
    64  // AlignedBlock simply returns an unaligned buffer
    65  // for systems that do not support DirectIO.
    66  func AlignedBlock(blockSize int) []byte {
    67  	return make([]byte, blockSize)
    68  }