Add -p flag to create the image as a sparse file.

Submitted by:	Shesha Sreenivasamurthy
PR:		bin/167779

usr.sbin/makefs/ffs.c

@@ -493,13 +493,25 @@ ffs_create_image(const char *image, fsinfo_t *fsopts)
 		bufsize = sfs.f_iosize;
 #endif
 	bufrem = fsopts->size;
-	if (debug & DEBUG_FS_CREATE_IMAGE)
-		printf(
-		    "zero-ing image `%s', %lld sectors, using %d byte chunks\n",
-		    image, (long long)bufrem, bufsize);
-	if ((buf = calloc(1, bufsize)) == NULL) {
-		warn("Can't create buffer for sector");
-		return (-1);
+	if (fsopts->sparse) {
+		if (ftruncate(fsopts->fd, bufrem) == -1) {
+			warn("sparse option disabled.\n");
+			fsopts->sparse = 0;
+		}
+	}
+	if (fsopts->sparse) {
+		/* File truncated at bufrem. Remaining is 0 */
+		bufrem = 0;
+		buf = NULL;
+	} else {
+		if (debug & DEBUG_FS_CREATE_IMAGE)
+			printf("zero-ing image `%s', %lld sectors, "
+			    "using %d byte chunks\n", image, (long long)bufrem,
+			    bufsize);
+		if ((buf = calloc(1, bufsize)) == NULL) {
+			warn("Can't create buffer for sector");
+			return (-1);
+		}
 	}
 	while (bufrem > 0) {
 		i = write(fsopts->fd, buf, MIN(bufsize, bufrem));
@@ -511,7 +523,8 @@ ffs_create_image(const char *image, fsinfo_t *fsopts)
 		}
 		bufrem -= i;
 	}
-	free(buf);
+	if (buf)
+		free(buf);
 
 		/* make the file system */
 	if (debug & DEBUG_FS_CREATE_IMAGE)

usr.sbin/makefs/makefs.8

@@ -35,7 +35,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 30, 2012
+.Dd August 22, 2012
 .Dt MAKEFS 8
 .Os
 .Sh NAME
@@ -43,6 +43,7 @@
 .Nd create a file system image from a directory tree or a mtree manifest
 .Sh SYNOPSIS
 .Nm
+.Op Fl p
 .Op Fl x
 .Op Fl B Ar byte-order
 .Op Fl b Ar free-blocks
@@ -188,6 +189,8 @@ Set file system specific options.
 .Ar fs-options
 is a comma separated list of options.
 Valid file system specific options are detailed below.
+.It Fl p 
+Create the image as a sparse file.
 .It Fl S Ar sector-size
 Set the file system sector size to
 .Ar sector-size .

usr.sbin/makefs/makefs.c

@@ -112,7 +112,7 @@ main(int argc, char *argv[])
 	start_time.tv_sec = start.tv_sec;
 	start_time.tv_nsec = start.tv_usec * 1000;
 
-	while ((ch = getopt(argc, argv, "B:b:d:f:F:M:m:N:o:s:S:t:x")) != -1) {
+	while ((ch = getopt(argc, argv, "B:b:d:f:F:M:m:N:o:ps:S:t:x")) != -1) {
 		switch (ch) {
 
 		case 'B':
@@ -199,6 +199,9 @@ main(int argc, char *argv[])
 			}
 			break;
 		}
+		case 'p':
+			fsoptions.sparse = 1;
+			break;
 
 		case 's':
 			fsoptions.minsize = fsoptions.maxsize =
@@ -346,7 +349,7 @@ usage(void)
 	fprintf(stderr,
 "usage: %s [-t fs-type] [-o fs-options] [-d debug-mask] [-B endian]\n"
 "\t[-S sector-size] [-M minimum-size] [-m maximum-size] [-s image-size]\n"
-"\t[-b free-blocks] [-f free-files] [-F mtree-specfile] [-x]\n"
+"\t[-b free-blocks] [-f free-files] [-F mtree-specfile] [-x] [-p]\n"
 "\t[-N userdb-dir] image-file directory | manifest [extra-directory ...]\n",
 	    prog);
 	exit(1);

usr.sbin/makefs/makefs.h

@@ -129,6 +129,7 @@ typedef struct {
 	int	freeblockpc;	/* free block % */
 	int	needswap;	/* non-zero if byte swapping needed */
 	int	sectorsize;	/* sector size */
+	int	sparse;		/* sparse image, don't fill it with zeros */
 
 	void	*fs_specific;	/* File system specific additions. */
 } fsinfo_t;