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