linux-ext4 - [PATCH 5/7] mke2fs: Change -K option to discard/nodiscard

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Date:	Tue, 26 Oct 2010 19:54:16 +0200
From:	Lukas Czerner <lczerner@...hat.com>
To:	linux-ext4@...r.kernel.org
Cc:	tytso@....edu, sandeen@...hat.com, adilger@...ger.ca,
	lczerner@...hat.com
Subject: [PATCH 5/7] mke2fs: Change -K option to discard/nodiscard

It would be nice to have consistent "discard" options in every system
tool (mount, fsck, mkfs) taking advantage of discards. Also "discard"
and "nodiscard" is more descriptive instead of just "-K" and can be
easily defaulted and it is something we can not do with "-K".

With this commit you need to specify extended option like this:

./mke2fs -T <fstype> -E nodiscard <device>

in order make a filesystem without discarding the device first. And

./mke2fs -T <fstype> -E discard <device>

respectively.

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
---
 misc/mke2fs.8.in |   18 +++++++++++-------
 misc/mke2fs.c    |   13 ++++++++-----
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index b46e7e2..6b437bc 100644
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -45,9 +45,6 @@ mke2fs \- create an ext2/ext3/ext4 filesystem
 .I journal-options
 ]
 [
-.B \-K
-]
-[
 .B \-N
 .I number-of-inodes
 ]
@@ -240,6 +237,17 @@ enable lazy inode table initialization.
 .B test_fs
 Set a flag in the filesystem superblock indicating that it may be
 mounted using experimental kernel code, such as the ext4dev filesystem.
+.TP
+.BI discard
+Attempt to discard blocks at mkfs time (discarding blocks initially is useful
+on solid state devices and sparse / thin-provisioned storage). When the device
+advertise that discard also zeroes data (any subsequent read after the discard
+and before write returns zero), then mark all not-yet-zeroed inode table as
+zeroed. This significantly speeds up filesystem initialization. This is set
+as default.
+.TP
+.BI nodiscard
+Do not attempt to discard blocks at mkfs time.
 .RE
 .TP
 .BI \-f " fragment-size"
@@ -369,10 +377,6 @@ and may be no more than 102,400 filesystem blocks.
 @JDEV@.BR size " or " device
 @JDEV@...ions 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 .
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 0980045..32e3a2b 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -753,6 +753,10 @@ static void parse_extended_opts(struct ext2_super_block *param,
 				lazy_itable_init = strtoul(arg, &p, 0);
 			else
 				lazy_itable_init = 1;
+		} else if (!strcmp(token, "discard")) {
+			discard = 1;
+		} else if (!strcmp(token, "nodiscard")) {
+			discard = 0;
 		} else {
 			r_usage++;
 			badopt = token;
@@ -768,7 +772,9 @@ static void parse_extended_opts(struct ext2_super_block *param,
 			"\tstripe-width=<RAID stride * data disks in blocks>\n"
 			"\tresize=<resize maximum size in blocks>\n"
 			"\tlazy_itable_init=<0 to disable, 1 to enable>\n"
-			"\ttest_fs\n\n"),
+			"\ttest_fs\n"
+			"\tdiscard\n"
+			"\tnodiscard\n\n"),
 			badopt ? badopt : "");
 		free(buf);
 		exit(1);
@@ -1168,7 +1174,7 @@ 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:KL:M:N:O:R:ST:U:V")) != EOF) {
+		    "b:cf:g:G:i:jl:m:no:qr:s:t:vE:FI:J:L:M:N:O:R:ST:U:V")) != EOF) {
 		switch (c) {
 		case 'b':
 			blocksize = strtol(optarg, &tmp, 0);
@@ -1247,9 +1253,6 @@ 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;
-- 
1.7.2.3

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