fs/ocfs2/locks.c

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