zed_file.c

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    1 /*
    2  * This file is part of the ZFS Event Daemon (ZED).
    3  *
    4  * Developed at Lawrence Livermore National Laboratory (LLNL-CODE-403049).
    5  * Copyright (C) 2013-2014 Lawrence Livermore National Security, LLC.
    6  * Refer to the OpenZFS git commit log for authoritative copyright attribution.
    7  *
    8  * The contents of this file are subject to the terms of the
    9  * Common Development and Distribution License Version 1.0 (CDDL-1.0).
   10  * You can obtain a copy of the license from the top-level file
   11  * "OPENSOLARIS.LICENSE" or at <http://opensource.org/licenses/CDDL-1.0>.
   12  * You may not use this file except in compliance with the license.
   13  */
   14 
   15 #include <dirent.h>
   16 #include <errno.h>
   17 #include <fcntl.h>
   18 #include <limits.h>
   19 #include <string.h>
   20 #include <sys/stat.h>
   21 #include <sys/types.h>
   22 #include <unistd.h>
   23 #include "zed_file.h"
   24 #include "zed_log.h"
   25 
   26 /*
   27  * Set an exclusive advisory lock on the open file descriptor [fd].
   28  * Return 0 on success, 1 if a conflicting lock is held by another process,
   29  * or -1 on error (with errno set).
   30  */
   31 int
   32 zed_file_lock(int fd)
   33 {
   34         struct flock lock;
   35 
   36         if (fd < 0) {
   37                 errno = EBADF;
   38                 return (-1);
   39         }
   40         lock.l_type = F_WRLCK;
   41         lock.l_whence = SEEK_SET;
   42         lock.l_start = 0;
   43         lock.l_len = 0;
   44 
   45         if (fcntl(fd, F_SETLK, &lock) < 0) {
   46                 if ((errno == EACCES) || (errno == EAGAIN))
   47                         return (1);
   48 
   49                 return (-1);
   50         }
   51         return (0);
   52 }
   53 
   54 /*
   55  * Release an advisory lock held on the open file descriptor [fd].
   56  * Return 0 on success, or -1 on error (with errno set).
   57  */
   58 int
   59 zed_file_unlock(int fd)
   60 {
   61         struct flock lock;
   62 
   63         if (fd < 0) {
   64                 errno = EBADF;
   65                 return (-1);
   66         }
   67         lock.l_type = F_UNLCK;
   68         lock.l_whence = SEEK_SET;
   69         lock.l_start = 0;
   70         lock.l_len = 0;
   71 
   72         if (fcntl(fd, F_SETLK, &lock) < 0)
   73                 return (-1);
   74 
   75         return (0);
   76 }
   77 
   78 /*
   79  * Test whether an exclusive advisory lock could be obtained for the open
   80  * file descriptor [fd].
   81  * Return 0 if the file is not locked, >0 for the PID of another process
   82  * holding a conflicting lock, or -1 on error (with errno set).
   83  */
   84 pid_t
   85 zed_file_is_locked(int fd)
   86 {
   87         struct flock lock;
   88 
   89         if (fd < 0) {
   90                 errno = EBADF;
   91                 return (-1);
   92         }
   93         lock.l_type = F_WRLCK;
   94         lock.l_whence = SEEK_SET;
   95         lock.l_start = 0;
   96         lock.l_len = 0;
   97 
   98         if (fcntl(fd, F_GETLK, &lock) < 0)
   99                 return (-1);
  100 
  101         if (lock.l_type == F_UNLCK)
  102                 return (0);
  103 
  104         return (lock.l_pid);
  105 }
  106 
  107 
  108 #if __APPLE__
  109 #define PROC_SELF_FD "/dev/fd"
  110 #else /* Linux-compatible layout */
  111 #define PROC_SELF_FD "/proc/self/fd"
  112 #endif
  113 
  114 /*
  115  * Close all open file descriptors greater than or equal to [lowfd].
  116  * Any errors encountered while closing file descriptors are ignored.
  117  */
  118 void
  119 zed_file_close_from(int lowfd)
  120 {
  121         int errno_bak = errno;
  122         int maxfd = 0;
  123         int fd;
  124         DIR *fddir;
  125         struct dirent *fdent;
  126 
  127         if ((fddir = opendir(PROC_SELF_FD)) != NULL) {
  128                 while ((fdent = readdir(fddir)) != NULL) {
  129                         fd = atoi(fdent->d_name);
  130                         if (fd > maxfd && fd != dirfd(fddir))
  131                                 maxfd = fd;
  132                 }
  133                 (void) closedir(fddir);
  134         } else {
  135                 maxfd = sysconf(_SC_OPEN_MAX);
  136         }
  137         for (fd = lowfd; fd < maxfd; fd++)
  138                 (void) close(fd);
  139 
  140         errno = errno_bak;
  141 }

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FreeBSD/Linux Kernel Cross Reference sys/contrib/openzfs/cmd/zed/zed_file.c

FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/cmd/zed/zed_file.c