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sfdisk: add --lock and LOCK_BLOCK_DEVICE 

Addresses: https://github.com/karelzak/util-linux/issues/921
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2020-05-27 16:58:08 +02:00
parent b8671fe763
commit c3ef1268a0
2 changed files with 58 additions and 53 deletions
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23
disk-utils/sfdisk.8
View File

@ -63,17 +63,8 @@ partitions.
uses BLKRRPART (reread partition table) ioctl to make sure that the device is
not used by system or another tools (see also \-\-no-reread). It's possible that
this feature or another sfdisk activity races with \fBudevd\fR. The recommended way
how to avoid possible collisions is to use exclusive flock for the whole-disk
device to serialize device access. The exclusive lock will cause udevd to skip
the event handling on the device. For example:
.RS
.sp
.nf
.B "flock /dev/sdc sfdisk /dev/sdc"
.fi
.sp
.RE
Note, this semantic is not currently supported by udevd for MD and DM devices.
how to avoid possible collisions is to use \fB\-\-lock\fR option.
The exclusive lock will cause udevd to skip the event handling on the device.
.PP
The sfdisk prompt is only a hint for users and a displayed partition number does
not mean that the same partition table entry will be created (if -N not
@ -221,6 +212,14 @@ Disable all consistency checking.
Deprecated and ignored option. Partitioning that is compatible with
Linux (and other modern operating systems) is the default.
.TP
\fB\-\-lock\fR[=\fImode\fR]
Use exclusive BSD lock for device or file it operates. The optional argument
\fImode\fP can be \fByes\fR, \fBno\fR (or 1 and 0) or \fBnonblock\fR. If the \fImode\fR
argument is omitted, it defaults to \fB"yes"\fR. This option overwrites
environment variable \fB$LOCK_BLOCK_DEVICE\fR. The default is not to use any
lock at all, but it's recommended to avoid collisions with udevd or other
tools.
.TP
.BR \-n , " \-\-no\-act"
Do everything except writing to the device.
.TP
@ -610,6 +609,8 @@ enables libfdisk debug output.
enables libblkid debug output.
.IP LIBSMARTCOLS_DEBUG=all
enables libsmartcols debug output.
.IP LOCK_BLOCK_DEVICE=<mode>
use exclusive BSD lock. The mode is "1" or "0". See \fB\-\-lock\fR for more details.
.SH NOTES
Since version 2.26 \fBsfdisk\fR no longer provides the \fB\-R\fR or

88
disk-utils/sfdisk.c
View File

@ -96,6 +96,7 @@ struct sfdisk {
int partno; /* -N <partno>, default -1 */
int wipemode; /* remove foreign signatures from disk */
int pwipemode; /* remove foreign signatures from partitions */
const char *lockmode; /* as specified by --lock */
const char *label; /* --label <label> */
const char *label_nested; /* --label-nested <label> */
const char *backup_file; /* -O <path> */
@ -369,6 +370,25 @@ static void backup_partition_table(struct sfdisk *sf, const char *devname)
free(tpl);
}
static int assign_device(struct sfdisk *sf, const char *devname, int rdonly)
{
struct fdisk_context *cxt = sf->cxt;
if (fdisk_assign_device(cxt, devname, rdonly) != 0)
err(EXIT_FAILURE, _("cannot open %s"), devname);
if (!fdisk_is_readonly(cxt)) {
if (blkdev_lock(fdisk_get_devfd(cxt), devname, sf->lockmode) != 0) {
fdisk_deassign_device(cxt, 1);
exit(EXIT_FAILURE);
}
if (sf->backup)
backup_partition_table(sf, devname);
}
return 0;
}
static int move_partition_data(struct sfdisk *sf, size_t partno, struct fdisk_partition *orig_pa)
{
struct fdisk_partition *pa = get_partition(sf->cxt, partno);
@ -724,10 +744,7 @@ static int verify_device(struct sfdisk *sf, const char *devname)
fdisk_enable_listonly(sf->cxt, 1);
if (fdisk_assign_device(sf->cxt, devname, 1)) {
warn(_("cannot open %s"), devname);
return 1;
}
assign_device(sf, devname, 1);
color_scheme_enable("header", UL_COLOR_BOLD);
fdisk_info(sf->cxt, "%s:", devname);
@ -834,10 +851,7 @@ static int print_geom(struct sfdisk *sf, const char *devname)
{
fdisk_enable_listonly(sf->cxt, 1);
if (fdisk_assign_device(sf->cxt, devname, 1)) {
warn(_("cannot open %s"), devname);
return 1;
}
assign_device(sf, devname, 1);
fdisk_info(sf->cxt, "%s: %ju cylinders, %ju heads, %ju sectors/track",
devname,
@ -892,9 +906,7 @@ static int command_activate(struct sfdisk *sf, int argc, char **argv)
/* --activate <device> */
listonly = argc == 1;
rc = fdisk_assign_device(sf->cxt, devname, listonly);
if (rc)
err(EXIT_FAILURE, _("cannot open %s"), devname);
assign_device(sf, devname, listonly);
if (fdisk_is_label(sf->cxt, GPT)) {
if (fdisk_gpt_is_hybrid(sf->cxt))
@ -909,9 +921,6 @@ static int command_activate(struct sfdisk *sf, int argc, char **argv)
} else if (!fdisk_is_label(sf->cxt, DOS))
errx(EXIT_FAILURE, _("toggle boot flags is supported for MBR or PMBR only"));
if (!listonly && sf->backup)
backup_partition_table(sf, devname);
nparts = fdisk_get_npartitions(sf->cxt);
for (i = 0; i < nparts; i++) {
char *data = NULL;
@ -972,11 +981,7 @@ static int command_delete(struct sfdisk *sf, int argc, char **argv)
errx(EXIT_FAILURE, _("no disk device specified"));
devname = argv[0];
if (fdisk_assign_device(sf->cxt, devname, 0) != 0)
err(EXIT_FAILURE, _("cannot open %s"), devname);
if (sf->backup)
backup_partition_table(sf, devname);
assign_device(sf, devname, 0);
/* delete all */
if (argc == 1) {
@ -1012,12 +1017,7 @@ static int command_reorder(struct sfdisk *sf, int argc, char **argv)
if (!devname)
errx(EXIT_FAILURE, _("no disk device specified"));
rc = fdisk_assign_device(sf->cxt, devname, 0); /* read-write */
if (rc)
err(EXIT_FAILURE, _("cannot open %s"), devname);
if (sf->backup)
backup_partition_table(sf, devname);
assign_device(sf, devname, 0); /* read-write */
if (fdisk_reorder_partitions(sf->cxt) == 1) /* unchanged */
rc = fdisk_deassign_device(sf->cxt, 1);
@ -1042,9 +1042,7 @@ static int command_dump(struct sfdisk *sf, int argc, char **argv)
if (!devname)
errx(EXIT_FAILURE, _("no disk device specified"));
rc = fdisk_assign_device(sf->cxt, devname, 1); /* read-only */
if (rc)
err(EXIT_FAILURE, _("cannot open %s"), devname);
assign_device(sf, devname, 1); /* read-only */
if (!fdisk_has_label(sf->cxt))
errx(EXIT_FAILURE, _("%s: does not contain a recognized partition table"), devname);
@ -1083,6 +1081,11 @@ static void assign_device_partition(struct sfdisk *sf,
if (rc)
err(EXIT_FAILURE, _("cannot open %s"), devname);
if (!fdisk_is_readonly(sf->cxt)
&& blkdev_lock(fdisk_get_devfd(sf->cxt), devname, sf->lockmode) != 0) {
fdisk_deassign_device(sf->cxt, 1);
return;
}
lb = fdisk_get_label(sf->cxt, NULL);
if (!lb)
errx(EXIT_FAILURE, _("%s: no partition table found"), devname);
@ -1346,8 +1349,7 @@ static int command_diskid(struct sfdisk *sf, int argc, char **argv)
else if (argc > 2)
errx(EXIT_FAILURE, _("unexpected arguments"));
if (fdisk_assign_device(sf->cxt, devname, !str) != 0)
err(EXIT_FAILURE, _("cannot open %s"), devname);
assign_device(sf, devname, !str);
/* print */
if (!str) {
@ -1359,10 +1361,6 @@ static int command_diskid(struct sfdisk *sf, int argc, char **argv)
return 0;
}
/* change */
if (sf->backup)
backup_partition_table(sf, devname);
if (fdisk_set_disklabel_id_from_string(sf->cxt, str) != 0)
errx(EXIT_FAILURE, _("%s: failed to set disklabel ID"), devname);
@ -1395,8 +1393,7 @@ static int command_relocate(struct sfdisk *sf, int argc, char **argv)
else if (strcmp(oper, "gpt-bak-std") != 0)
errx(EXIT_FAILURE, _("unsupported relocation operation"));
if (fdisk_assign_device(sf->cxt, devname, 0) != 0)
err(EXIT_FAILURE, _("cannot open %s"), devname);
assign_device(sf, devname, 0);
fdisk_label_set_changed(lb, 1);
@ -1720,9 +1717,7 @@ static int command_fdisk(struct sfdisk *sf, int argc, char **argv)
if (!devname)
errx(EXIT_FAILURE, _("no disk device specified"));
rc = fdisk_assign_device(sf->cxt, devname, 0);
if (rc)
err(EXIT_FAILURE, _("cannot open %s"), devname);
assign_device(sf, devname, 0);
dp = fdisk_new_script(sf->cxt);
if (!dp)
@ -1798,9 +1793,6 @@ static int command_fdisk(struct sfdisk *sf, int argc, char **argv)
if (fdisk_get_collision(sf->cxt))
follow_wipe_mode(sf);
if (sf->backup)
backup_partition_table(sf, devname);
if (!sf->quiet) {
list_disk_geometry(sf->cxt);
if (fdisk_has_label(sf->cxt)) {
@ -2052,6 +2044,8 @@ static void __attribute__((__noreturn__)) usage(void)
_(" --color[=<when>] colorize output (%s, %s or %s)\n"), "auto", "always", "never");
fprintf(out,
" %s\n", USAGE_COLORS_DEFAULT);
fprintf(out,
_(" --lock[=<mode>] use exclusive device lock (%s, %s or %s)\n"), "yes", "no", "nonblock");
fputs(_(" -N, --partno <num> specify partition number\n"), out);
fputs(_(" -n, --no-act do everything except write to device\n"), out);
fputs(_(" --no-reread do not check whether the device is in use\n"), out);
@ -2110,6 +2104,7 @@ int main(int argc, char *argv[])
OPT_DELETE,
OPT_NOTELL,
OPT_RELOCATE,
OPT_LOCK,
};
static const struct option longopts[] = {
@ -2119,6 +2114,7 @@ int main(int argc, char *argv[])
{ "backup-file", required_argument, NULL, 'O' },
{ "bytes", no_argument, NULL, OPT_BYTES },
{ "color", optional_argument, NULL, OPT_COLOR },
{ "lock", optional_argument, NULL, OPT_LOCK },
{ "delete", no_argument, NULL, OPT_DELETE },
{ "dump", no_argument, NULL, 'd' },
{ "help", no_argument, NULL, 'h' },
@ -2324,6 +2320,14 @@ int main(int argc, char *argv[])
case OPT_RELOCATE:
sf->act = ACT_RELOCATE;
break;
case OPT_LOCK:
sf->lockmode = "1";
if (optarg) {
if (*optarg == '=')
optarg++;
sf->lockmode = optarg;
}
break;
default:
errtryhelp(EXIT_FAILURE);
}