Progress due to tests with test/open-cd-excl
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@ -3,6 +3,23 @@
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Implementation of Delicate Device Locking Protocol level A.
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Copyright (C) 2007 Thomas Schmitt <scdbackup@gmx.net>
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Provided under any of the following licenses: GPL, LGPL, BSD. Choose one.
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Compile as test program:
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cc -g -Wall \
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-D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE=1 -D_LARGEFILE64_SOURCE \
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-DDDLPA_C_STANDALONE -o ddlpa ddlpa.c
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The system macros are needed for 8-bit off_t and for open flag O_LARGEFILE
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which are not absolutely necessary but explicitely take into respect that
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our devices can offer more than 2 GB of addressable data.
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Run test program:
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./ddlpa /dev/sr0 15
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./ddlpa 0,0,0 15
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*/
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#include <stdio.h>
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@ -91,7 +108,7 @@ static int ddlpa_std_by_rdev(struct ddlpa_lock *o)
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if (ddlpa_debug_mode)
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fprintf(stderr,
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"DDLPA_DEBUG: ddlpa_std_by_rdev(\"%s\") = \"%s\"\n",
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"DDLPA_DEBUG: ddlpa_std_by_rdev(\"%s\") = \"%s\"\n",
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o->path, o->std_path);
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return 0;
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@ -143,20 +160,32 @@ static int ddlpa_fcntl_lock(struct ddlpa_lock *o, int fd, int l_type)
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static int ddlpa_occupy(struct ddlpa_lock *o, char *path, int *fd,
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int no_o_excl)
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{
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int ret, o_flags = O_RDWR | O_NDELAY;
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int ret, o_flags, o_rw, l_type;
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char *o_rwtext;
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o_flags = o->o_flags | O_NDELAY;
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if(!no_o_excl)
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o_flags |= O_EXCL;
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o_rw = (o_flags) & (O_RDONLY | O_WRONLY | O_RDWR);
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o_rwtext = (o_rw == O_RDONLY ? "O_RDONLY" :
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(o_rw == O_WRONLY ? "O_WRONLY" :
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(o_rw == O_RDWR ? "O_RDWR " : "O_?rw-mode?")));
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*fd = open(path, o_flags);
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if (*fd == -1) {
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o->errmsg = malloc(strlen(path)+160);
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if (o->errmsg)
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sprintf(o->errmsg,
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"Failed to open O_RDWR | O_NDELAY %s: '%s'",
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(no_o_excl ? "" : "| O_EXCL "), path);
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"Failed to open %s | O_NDELAY %s: '%s'",
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o_rwtext,
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(o_flags & O_EXCL ? "| O_EXCL " : ""), path);
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return (errno ? errno : EBUSY);
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}
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ret = ddlpa_fcntl_lock(o, *fd, F_WRLCK);
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if (o_rw == O_RDWR || o_rw == O_WRONLY)
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l_type = F_WRLCK;
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else
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l_type = F_RDLCK;
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ret = ddlpa_fcntl_lock(o, *fd, l_type);
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if (ret) {
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o->errmsg = malloc(strlen(path)+160);
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if (o->errmsg)
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@ -167,7 +196,8 @@ static int ddlpa_occupy(struct ddlpa_lock *o, char *path, int *fd,
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return ret;
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}
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if (ddlpa_debug_mode)
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fprintf(stderr, "DDLPA_DEBUG: ddlpa_occupy() %s: '%s'\n",
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fprintf(stderr, "DDLPA_DEBUG: ddlpa_occupy() %s %s: '%s'\n",
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o_rwtext,
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(no_o_excl ? " " : "O_EXCL "), path);
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return 0;
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}
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@ -270,7 +300,7 @@ static int ddlpa_collect_siblings(struct ddlpa_lock *o)
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if (ddlpa_debug_mode)
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fprintf(stderr,
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"DDLPA_DEBUG: ddlpa_collect_siblings() found \"%s\"\n",
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"DDLPA_DEBUG: ddlpa_collect_siblings() found \"%s\"\n",
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try_path);
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(o->num_siblings)++;
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@ -315,7 +345,7 @@ static int ddlpa_std_by_btl(struct ddlpa_lock *o)
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if (ddlpa_debug_mode)
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fprintf(stderr,
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"DDLPA_DEBUG: ddlpa_std_by_rdev(%d,%d,%d) = \"%s\"\n",
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"DDLPA_DEBUG: ddlpa_std_by_btl(%d,%d,%d) = \"%s\"\n",
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t_bus, t_id, t_lun, o->std_path);
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return 0;
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@ -490,6 +520,14 @@ usage:;
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if (duration < 0)
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goto usage;
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/* For our purpose, only O_RDWR is a suitable access mode.
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But in order to allow experiments, o_flags are freely adjustable.
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Warning: Do _not_ set an own O_EXCL flag with the following calls !
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(This freedom to fail may get removed in a final version.)
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*/
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if (my_path[0] != '/' && my_path[0] != '.' &&
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strchr(my_path, ',') != NULL) {
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/*
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@ -497,15 +535,17 @@ usage:;
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*/
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sscanf(my_path, "%d,%d,%d", &bus, &target, &lun);
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ret = ddlpa_lock_btl(bus, target, lun, O_RDWR, 0, &lck,
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&errmsg);
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ret = ddlpa_lock_btl(bus, target, lun, O_RDWR | O_LARGEFILE,
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0, &lck, &errmsg);
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} else {
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/*
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This substitutes for:
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fd = open(my_path, O_RDWR | O_EXCL);
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fd = open(my_path, O_RDWR | O_EXCL | O_LARGEFILE);
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*/
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ret = ddlpa_lock_path(my_path, O_RDWR, 0, &lck, &errmsg);
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ret = ddlpa_lock_path(my_path, O_RDWR | O_LARGEFILE,
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0, &lck, &errmsg);
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}
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if (ret) {
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fprintf(stderr, "Cannot exclusively open '%s'\n", my_path);
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@ -51,7 +51,9 @@ struct ddlpa_lock {
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/** Lock a recorder by naming a device file path. Allocate a new container.
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@param path Gives the file system path of the recorder
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as known to the calling program.
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@param o_flags flags for open(2)
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@param o_flags flags for open(2). Do not use O_EXCL here because this
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is done automatically whenever appropriate.
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Advised is O_RDWR | O_LARGEFILE, eventually | O_NDELAY.
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@param ddlpa_flags 0 = default behavior: the standard path will be opened
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and treated by fcntl(F_SETLK)
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DDLPA_OPEN_GIVEN_PATH causes the input parameter "path"
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@ -75,7 +77,7 @@ int ddlpa_lock_path(char *path, int o_flags, int ddlpa_flags,
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@param bus parameter to match ioctl(SCSI_IOCTL_GET_BUS_NUMBER)
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@param target parameter to match ioctl(SCSI_IOCTL_GET_IDLUN) &0xff
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@param lun parameter to match ioctl(SCSI_IOCTL_GET_IDLUN) &0xff00
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@param o_flags flags for open(2)
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@param o_flags see ddlpa_lock_path().
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@param ddlpa_flags see ddlpa_lock_path(). Flag DDLPA_OPEN_GIVEN_PATH
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will be ignored.
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@param lockbundle see ddlpa_lock_path().
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