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

     1  //go:build !windows && !plan9 && !solaris
     2  // +build !windows,!plan9,!solaris
     3  
     4  // Copyright (c) 2015-2021 MinIO, Inc.
     5  //
     6  // This file is part of MinIO Object Storage stack
     7  //
     8  // This program is free software: you can redistribute it and/or modify
     9  // it under the terms of the GNU Affero General Public License as published by
    10  // the Free Software Foundation, either version 3 of the License, or
    11  // (at your option) any later version.
    12  //
    13  // This program is distributed in the hope that it will be useful
    14  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    15  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    16  // GNU Affero General Public License for more details.
    17  //
    18  // You should have received a copy of the GNU Affero General Public License
    19  // along with this program.  If not, see <http://www.gnu.org/licenses/>.
    20  
    21  package lock
    22  
    23  import (
    24  	"os"
    25  	"syscall"
    26  )
    27  
    28  // Internal function implements support for both
    29  // blocking and non blocking lock type.
    30  func lockedOpenFile(path string, flag int, perm os.FileMode, lockType int) (*LockedFile, error) {
    31  	switch flag {
    32  	case syscall.O_RDONLY:
    33  		lockType |= syscall.LOCK_SH
    34  	case syscall.O_WRONLY:
    35  		fallthrough
    36  	case syscall.O_RDWR:
    37  		fallthrough
    38  	case syscall.O_WRONLY | syscall.O_CREAT:
    39  		fallthrough
    40  	case syscall.O_RDWR | syscall.O_CREAT:
    41  		lockType |= syscall.LOCK_EX
    42  	default:
    43  		return nil, &os.PathError{
    44  			Op:   "open",
    45  			Path: path,
    46  			Err:  syscall.EINVAL,
    47  		}
    48  	}
    49  
    50  	f, err := os.OpenFile(path, flag|syscall.O_SYNC, perm)
    51  	if err != nil {
    52  		return nil, err
    53  	}
    54  
    55  	if err = syscall.Flock(int(f.Fd()), lockType); err != nil {
    56  		f.Close()
    57  		if err == syscall.EWOULDBLOCK {
    58  			err = ErrAlreadyLocked
    59  		}
    60  		return nil, err
    61  	}
    62  
    63  	st, err := os.Stat(path)
    64  	if err != nil {
    65  		f.Close()
    66  		return nil, err
    67  	}
    68  
    69  	if st.IsDir() {
    70  		f.Close()
    71  		return nil, &os.PathError{
    72  			Op:   "open",
    73  			Path: path,
    74  			Err:  syscall.EISDIR,
    75  		}
    76  	}
    77  
    78  	return &LockedFile{File: f}, nil
    79  }
    80  
    81  // TryLockedOpenFile - tries a new write lock, functionality
    82  // it is similar to LockedOpenFile with with syscall.LOCK_EX
    83  // mode but along with syscall.LOCK_NB such that the function
    84  // doesn't wait forever but instead returns if it cannot
    85  // acquire a write lock.
    86  func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
    87  	return lockedOpenFile(path, flag, perm, syscall.LOCK_NB)
    88  }
    89  
    90  // LockedOpenFile - initializes a new lock and protects
    91  // the file from concurrent access across mount points.
    92  // This implementation doesn't support all the open
    93  // flags and shouldn't be considered as replacement
    94  // for os.OpenFile().
    95  func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
    96  	return lockedOpenFile(path, flag, perm, 0)
    97  }
    98  
    99  // Open - Call os.OpenFile
   100  func Open(path string, flag int, perm os.FileMode) (*os.File, error) {
   101  	return os.OpenFile(path, flag, perm)
   102  }