mke2fs support for BLKDISCARD

Try calling the BLKDISCARD ioctl at mkfs time to pre-discard all blocks on an ssd, or a thinly-provisioned storage device.

No real error checking; if it fails, it fails, and that's ok - it's just an optimization. Also, it cannot work in conjunction with the undo io manager, for obvious reasons.

Optionally disabled with a "-K" (mnemonic: Keep) option.

---

index b02905b..45a99f8 100644
@@ -45,6 +45,9 @@ mke2fs \- create an ext2/ext3/ext4 filesystem

.I journal-options
]
[
+.B \-K
+]
+[
.B \-N
.I number-of-inodes
]
@@ -366,6 +369,10 @@ and may be no more than 102,400 filesystem blocks. @[email protected] size " or " device
@JDEV@options can be given for a filesystem.
.TP
+.BI \-K
+Keep, do not attempt to discard blocks at mkfs time (discarding blocks initially +is useful on solid state devices and sparse / thin-provisioned storage). +.TP
.BI \-l " filename"
Read the bad blocks list from
.IR filename .

index 2d9107a..9558495 100644
@@ -80,6 +80,7 @@ int	cflag;

int verbose;
int quiet;
int super_only;
+int discard = 1;
int force;
int noaction;
int journal_size;
@@ -112,7 +113,7 @@ static void usage(void)

	"\t[-g blocks-per-group] [-L volume-label] "
	"[-M last-mounted-directory]\n\t[-O feature[,...]] "
	"[-r fs-revision] [-E extended-option[,...]]\n"
-	"\t[-T fs-type] [-U UUID] [-jnqvFSV] device [blocks-count]\n"),
+	"\t[-T fs-type] [-U UUID] [-jnqvFKSV] device [blocks-count]\n"),
		program_name);
	exit(1);
}
@@ -1150,7 +1151,7 @@ static void PRS(int argc, char *argv[])
	}

	while ((c = getopt (argc, argv,
-		    "b:cf:g:G:i:jl:m:no:qr:s:t:vE:FI:J:L:M:N:O:R:ST:U:V")) != EOF) {
+		    "b:cf:g:G:i:jl:m:no:qr:s:t:vE:FI:J:KL:M:N:O:R:ST:U:V")) != EOF) {
		switch (c) {
		case 'b':
			blocksize = strtol(optarg, &tmp, 0);
@@ -1229,6 +1230,9 @@ static void PRS(int argc, char *argv[])
		case 'J':
			parse_journal_opts(optarg);
			break;
+		case 'K':
+			discard = 0;
+			break;
		case 'j':
			if (!journal_size)
				journal_size = -1;
@@ -1854,6 +1858,48 @@ static int mke2fs_setup_tdb(const char *name, io_manager *io_ptr)
	return retval;
}

+#ifdef __linux__
+
+#ifndef BLKDISCARD
+#define BLKDISCARD _IO(0x12,119)
+#endif
+
+static void mke2fs_discard_blocks(ext2_filsys fs) +{
+ int fd;
+ int ret;
+ int blocksize;
+ __u64 blocks;
+ __uint64_t range[2];
+
+ blocks = ext2fs_blocks_count(fs->super);
+ blocksize = EXT2_BLOCK_SIZE(fs->super);
+ range[0] = 0;
+ range[1] = blocks * blocksize;
+
+ fd = open64(fs->device_name, O_RDONLY);
+
+ /*
+ * We don't care about whether the ioctl succeeds; it's only an
+ * optmization for SSDs or sparse storage.
+ */
+ if (fd > 0) {
+ ret = ioctl(fd, BLKDISCARD, &range);
+ if (verbose) {
+ printf(_("Calling BLKDISCARD from %llu to %llu "),
+ range[0], range[1]);
+ if (ret)
+ printf(_("failed.\n"));
+ else
+ printf(_("succeeded.\n"));
+ }
+ close(fd);
+ }
+}
+#else
+#define mke2fs_discard_blocks(fs)
+#endif
+
int main (int argc, char *argv[])

{
	errcode_t	retval = 0;
@@ -1911,6 +1957,10 @@ int main (int argc, char *argv[])
		exit(1);
	}

+ /* Can't undo discard ... */
+ if (discard && (io_ptr != undo_io_manager))
+ mke2fs_discard_blocks(fs);
+

	sprintf(tdb_string, "tdb_data_size=%d", fs->blocksize <= 4096 ?
		32768 : fs->blocksize * 8);
	io_channel_set_options(fs->io, tdb_string);

Added to e2fsprogs's maint branch, thanks.

- Ted