fs/ocfs2/locks.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* -*- mode: c; c-basic-offset: 8; -*-
   3  * vim: noexpandtab sw=8 ts=8 sts=0:
   4  *
   5  * locks.c
   6  *
   7  * Userspace file locking support
   8  *
   9  * Copyright (C) 2007 Oracle.  All rights reserved.
  10  */
  11
  12 #include <linux/fs.h>
  13 #include <linux/fcntl.h>
  14
  15 #include <cluster/masklog.h>
  16
  17 #include "ocfs2.h"
  18
  19 #include "dlmglue.h"
  20 #include "file.h"
  21 #include "inode.h"
  22 #include "locks.h"
  23
  24 static int ocfs2_do_flock(struct file *file, struct inode *inode,
  25                           int cmd, struct file_lock *fl)
  26 {
  27         int ret = 0, level = 0, trylock = 0;
  28         struct ocfs2_file_private *fp = file->private_data;
  29         struct ocfs2_lock_res *lockres = &fp->fp_flock;
  30
  31         if (fl->fl_type == F_WRLCK)
  32                 level = 1;
  33         if (!IS_SETLKW(cmd))
  34                 trylock = 1;
  35
  36         mutex_lock(&fp->fp_mutex);
  37
  38         if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
  39             lockres->l_level > LKM_NLMODE) {
  40                 int old_level = 0;
  41                 struct file_lock request;
  42
  43                 if (lockres->l_level == LKM_EXMODE)
  44                         old_level = 1;
  45
  46                 if (level == old_level)
  47                         goto out;
  48
  49                 /*
  50                  * Converting an existing lock is not guaranteed to be
  51                  * atomic, so we can get away with simply unlocking
  52                  * here and allowing the lock code to try at the new
  53                  * level.
  54                  */
  55
  56                 locks_init_lock(&request);
  57                 request.fl_type = F_UNLCK;
  58                 request.fl_flags = FL_FLOCK;
  59                 locks_lock_file_wait(file, &request);
  60
  61                 ocfs2_file_unlock(file);
  62         }
  63
  64         ret = ocfs2_file_lock(file, level, trylock);
  65         if (ret) {
  66                 if (ret == -EAGAIN && trylock)
  67                         ret = -EWOULDBLOCK;
  68                 else
  69                         mlog_errno(ret);
  70                 goto out;
  71         }
  72
  73         ret = locks_lock_file_wait(file, fl);
  74         if (ret)
  75                 ocfs2_file_unlock(file);
  76
  77 out:
  78         mutex_unlock(&fp->fp_mutex);
  79
  80         return ret;
  81 }
  82
  83 static int ocfs2_do_funlock(struct file *file, int cmd, struct file_lock *fl)
  84 {
  85         int ret;
  86         struct ocfs2_file_private *fp = file->private_data;
  87
  88         mutex_lock(&fp->fp_mutex);
  89         ocfs2_file_unlock(file);
  90         ret = locks_lock_file_wait(file, fl);
  91         mutex_unlock(&fp->fp_mutex);
  92
  93         return ret;
  94 }
  95
  96 /*
  97  * Overall flow of ocfs2_flock() was influenced by gfs2_flock().
  98  */
  99 int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl)
 100 {
 101         struct inode *inode = file->f_mapping->host;
 102         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 103
 104         if (!(fl->fl_flags & FL_FLOCK))
 105                 return -ENOLCK;
 106         if (__mandatory_lock(inode))
 107                 return -ENOLCK;
 108
 109         if ((osb->s_mount_opt & OCFS2_MOUNT_LOCALFLOCKS) ||
 110             ocfs2_mount_local(osb))
 111                 return locks_lock_file_wait(file, fl);
 112
 113         if (fl->fl_type == F_UNLCK)
 114                 return ocfs2_do_funlock(file, cmd, fl);
 115         else
 116                 return ocfs2_do_flock(file, inode, cmd, fl);
 117 }
 118
 119 int ocfs2_lock(struct file *file, int cmd, struct file_lock *fl)
 120 {
 121         struct inode *inode = file->f_mapping->host;
 122         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 123
 124         if (!(fl->fl_flags & FL_POSIX))
 125                 return -ENOLCK;
 126         if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
 127                 return -ENOLCK;
 128
 129         return ocfs2_plock(osb->cconn, OCFS2_I(inode)->ip_blkno, file, cmd, fl);
 130 }