From: Theodore Ts'o <tytso@mit.edu>
Date: Thu, 22 Mar 2012 20:00:49 +0000 (-0400)
Subject: mke2fs: add option to use direct I/O (mke2fs -D)
X-Git-Tag: v1.42.2~19
X-Git-Url: https://git.whamcloud.com/?a=commitdiff_plain;h=37c8db7b2078d0310e5676404e21cc143d8e4d56;p=tools%2Fe2fsprogs.git

mke2fs: add option to use direct I/O (mke2fs -D)

This can be useful when using mke2fs on loaded servers, since
otherwise mke2fs can dirty a huge amount of memory very quickly,
leading to other applications not being happy at all.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---

diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
index a63ea18..b06371c 100644
--- a/lib/ext2fs/initialize.c
+++ b/lib/ext2fs/initialize.c
@@ -119,6 +119,8 @@ errcode_t ext2fs_initialize(const char *name, int flags,
 	io_flags = IO_FLAG_RW;
 	if (flags & EXT2_FLAG_EXCLUSIVE)
 		io_flags |= IO_FLAG_EXCLUSIVE;
+	if (flags & EXT2_FLAG_DIRECT_IO)
+		io_flags |= IO_FLAG_DIRECT_IO;
 	retval = manager->open(name, io_flags, &fs->io);
 	if (retval)
 		goto cleanup;
diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index 8e78249..6d443a2 100644
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -18,6 +18,9 @@ mke2fs \- create an ext2/ext3/ext4 filesystem
 .I block-size
 ]
 [
+.B \-D
+]
+[
 .B \-f
 .I fragment-size
 ]
@@ -184,6 +187,12 @@ Check the device for bad blocks before creating the file system.  If
 this option is specified twice, then a slower read-write
 test is used instead of a fast read-only test.
 .TP
+.B \-D
+Use direct I/O when writing to the disk.  This avoids mke2fs dirtying a
+lot of buffer cache memory, which may impact other applications running
+on a busy server.  This option will cause mke2fs to run much more
+slowly, however, so there is a tradeoff to using direct I/O.
+.TP
 .BI \-E " extended-options"
 Set extended options for the filesystem.  Extended options are comma
 separated, and may take an argument using the equals ('=') sign.  The
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 51435d2..0d793f7 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -88,6 +88,7 @@ int	verbose;
 int	quiet;
 int	super_only;
 int	discard = 1;	/* attempt to discard device before fs creation */
+int	direct_io;
 int	force;
 int	noaction;
 int	journal_size;
@@ -122,7 +123,7 @@ static void usage(void)
 	"[-M last-mounted-directory]\n\t[-O feature[,...]] "
 	"[-r fs-revision] [-E extended-option[,...]]\n"
 	"\t[-t fs-type] [-T usage-type ] [-U UUID] "
-	"[-jnqvFKSV] device [blocks-count]\n"),
+	"[-jnqvDFKSV] device [blocks-count]\n"),
 		program_name);
 	exit(1);
 }
@@ -1321,7 +1322,7 @@ profile_error:
 	}
 
 	while ((c = getopt (argc, argv,
-		    "b:cg:i:jl:m:no:qr:s:t:vC:E:FG:I:J:KL:M:N:O:R:ST:U:V")) != EOF) {
+		    "b:cg:i:jl:m:no:qr:s:t:vC:DE:FG:I:J:KL:M:N:O:R:ST:U:V")) != EOF) {
 		switch (c) {
 		case 'b':
 			blocksize = strtol(optarg, &tmp, 0);
@@ -1354,6 +1355,9 @@ profile_error:
 				exit(1);
 			}
 			break;
+		case 'D':
+			direct_io = 1;
+			break;
 		case 'g':
 			fs_param.s_blocks_per_group = strtoul(optarg, &tmp, 0);
 			if (*tmp) {
@@ -2257,6 +2261,8 @@ int main (int argc, char *argv[])
 	 * Initialize the superblock....
 	 */
 	flags = EXT2_FLAG_EXCLUSIVE;
+	if (direct_io)
+		flags |= EXT2_FLAG_DIRECT_IO;
 	profile_get_boolean(profile, "options", "old_bitmaps", 0, 0,
 			    &old_bitmaps);
 	if (!old_bitmaps)