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blkdiscard: use O_EXCL, add --force 

Let's make it more robust and safe. O_EXCL is an elegant way how to avoid
unwanted discard on mounted device.

Addresses: https://github.com/karelzak/util-linux/issues/915
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2020-01-09 11:03:51 +01:00
parent e3e7cd659e
commit 34fed3ff17
2 changed files with 13 additions and 3 deletions
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5
sys-utils/blkdiscard.8
View File

@ -36,6 +36,11 @@ MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is
optional, e.g., "K" has the same meaning as "KiB") or the suffixes
KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
.TP
.BR \-f , " \-\-force"
Disable all checking. Since v2.36 the block device is open in exclusive mode (O_EXCL)
by default to avoid collision with mounted filesystem or another kernel subsystem.
The force option disables the exclusive access mode.
.TP
.BR \-o , " \-\-offset \fIoffset"
Byte offset into the device from which to start discarding. The provided value
will be aligned to the device sector size. The default value is zero.

11
sys-utils/blkdiscard.c
View File

@ -88,6 +88,7 @@ static void __attribute__((__noreturn__)) usage(void)
fputs(_("Discard the content of sectors on a device.\n"), out);
fputs(USAGE_OPTIONS, out);
fputs(_(" -f, --force disable all checking\n"), out);
fputs(_(" -o, --offset <num> offset in bytes to discard from\n"), out);
fputs(_(" -l, --length <num> length of bytes to discard from the offset\n"), out);
fputs(_(" -p, --step <num> size of the discard iterations within the offset\n"), out);
@ -106,7 +107,7 @@ static void __attribute__((__noreturn__)) usage(void)
int main(int argc, char **argv)
{
char *path;
int c, fd, verbose = 0, secsize;
int c, fd, verbose = 0, secsize, force = 0;
uint64_t end, blksize, step, range[2], stats[2];
struct stat sb;
struct timeval now, last;
@ -116,6 +117,7 @@ int main(int argc, char **argv)
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V' },
{ "offset", required_argument, NULL, 'o' },
{ "force", no_argument, NULL, 'f' },
{ "length", required_argument, NULL, 'l' },
{ "step", required_argument, NULL, 'p' },
{ "secure", no_argument, NULL, 's' },
@ -133,8 +135,11 @@ int main(int argc, char **argv)
range[1] = ULLONG_MAX;
step = 0;
while ((c = getopt_long(argc, argv, "hVsvo:l:p:z", longopts, NULL)) != -1) {
while ((c = getopt_long(argc, argv, "hfVsvo:l:p:z", longopts, NULL)) != -1) {
switch(c) {
case 'f':
force = 1;
break;
case 'l':
range[1] = strtosize_or_err(optarg,
_("failed to parse length"));
@ -176,7 +181,7 @@ int main(int argc, char **argv)
errtryhelp(EXIT_FAILURE);
}
fd = open(path, O_WRONLY);
fd = open(path, O_WRONLY | (force ? 0 : O_EXCL));
if (fd < 0)
err(EXIT_FAILURE, _("cannot open %s"), path);