imap/src/osdep/unix/flocklnx.c

   1 /* ========================================================================
   2  * Copyright 2008-2009 Mark Crispin
   3  * ========================================================================
   4  */
   5
   6 /*
   7  * Program:     Safe File Lock for Linux
   8  *
   9  * Author:      Mark Crispin
  10  *
  11  * Date:        20 April 2005
  12  * Last Edited: 18 May 2009
  13  *
  14  * Previous versions of this file were:
  15  *
  16  * Copyright 1988-2006 University of Washington
  17  *
  18  * Licensed under the Apache License, Version 2.0 (the "License");
  19  * you may not use this file except in compliance with the License.
  20  * You may obtain a copy of the License at
  21  *
  22  *     http://www.apache.org/licenses/LICENSE-2.0
  23  *
  24  */
  25 \f
  26 #undef flock
  27
  28 #include <sys/vfs.h>
  29 #ifndef NFS_SUPER_MAGIC
  30 #define NFS_SUPER_MAGIC 0x6969
  31 #endif
  32
  33 int safe_flock (int fd,int op)
  34 {
  35   struct statfs sfbuf;
  36   char tmp[MAILTMPLEN];
  37   int e;
  38   int logged = 0;
  39   /* Check for NFS because Linux 2.6 broke flock() on NFS.  Instead of being
  40    * a no-op, flock() on NFS now returns ENOLCK.  Read
  41    *   https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=123415
  42    * for the gruesome details.
  43    */
  44                                 /* check filesystem type */
  45   while ((e = fstatfs (fd,&sfbuf)) && (errno == EINTR));
  46   if (!e) switch (sfbuf.f_type) {
  47   case NFS_SUPER_MAGIC:         /* always a fast no-op on NFS */
  48     break;
  49   default:                      /* allow on other filesystem types */
  50                                 /* do the lock */
  51     while (flock (fd,op)) switch (errno) {
  52     case EINTR:                 /* interrupt */
  53       break;
  54     case ENOLCK:                /* lock table is full */
  55       sprintf (tmp,"File locking failure: %s",strerror (errno));
  56       mm_log (tmp,WARN);        /* give the user a warning of what happened */
  57       if (!logged++) syslog (LOG_ERR,"%s",tmp);
  58                                 /* return failure if non-blocking lock */
  59       if (op & LOCK_NB) return -1;
  60       sleep (5);                /* slow down in case it loops */
  61       break;
  62     case EWOULDBLOCK:           /* file is locked, LOCK_NB should be set */
  63       if (op & LOCK_NB) return -1;
  64     case EBADF:                 /* not valid open file descriptor */
  65     case EINVAL:                /* invalid operator */
  66     default:                    /* other error code? */
  67       sprintf (tmp,"Unexpected file locking failure: %s",strerror (errno));
  68       fatal (tmp);
  69     }
  70     break;
  71   }
  72   return 0;                     /* success */
  73 }