linux-ext4 - [PATCH 4/7] mke2fs: create a regular file if necessary

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Date:	Sat, 26 Apr 2014 20:00:31 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:	Theodore Ts'o <tytso@....edu>
Subject: [PATCH 4/7] mke2fs: create a regular file if necessary

This is useful when creating a filesystem for use with a VM, for
example.

Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
 misc/mke2fs.c |  3 ++-
 misc/util.c   | 20 ++++++++++++++++----
 misc/util.h   |  1 +
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index fa61e7b..a2b1f65 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1749,7 +1749,8 @@ profile_error:
 	if (optind < argc)
 		usage();
 
-	if (!check_plausibility(device_name, 0, &is_device) && !force)
+	if (!check_plausibility(device_name, CREATE_FILE,
+				&is_device) && !force)
 		proceed_question();
 
 	check_mount(device_name, force, _("filesystem"));
diff --git a/misc/util.c b/misc/util.c
index 08ec761..f85942e 100644
--- a/misc/util.c
+++ b/misc/util.c
@@ -13,6 +13,7 @@
 #define _LARGEFILE64_SOURCE
 
 #include "config.h"
+#include <fcntl.h>
 #include <stdio.h>
 #include <string.h>
 #ifdef HAVE_ERRNO_H
@@ -21,6 +22,7 @@
 #ifdef HAVE_LINUX_MAJOR_H
 #include <linux/major.h>
 #endif
+#include <sys/types.h>
 #ifdef HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
@@ -85,19 +87,29 @@ void proceed_question(void)
  */
 int check_plausibility(const char *device, int flags, int *ret_is_dev)
 {
-	int val, is_dev = 0;
+	int fd, is_dev = 0;
 	ext2fs_struct_stat s;
+	int fl = O_RDONLY;
 
-	val = ext2fs_stat(device, &s);
+	if (flags & CREATE_FILE)
+		fl |= O_CREAT;
 
-	if(val == -1) {
-		fprintf(stderr, _("Could not stat %s --- %s\n"),
+	fd = open(device, fl, 0666);
+	if (fd < 0) {
+		fprintf(stderr, _("Could not open %s: %s\n"),
 			device, error_message(errno));
 		if (errno == ENOENT)
 			fputs(_("\nThe device apparently does not exist; "
 				"did you specify it correctly?\n"), stderr);
 		exit(1);
 	}
+
+	if (ext2fs_fstat(fd, &s) < 0) {
+		perror("stat");
+		exit(1);
+	}
+	close(fd);
+
 	if (S_ISBLK(s.st_mode))
 		is_dev = 1;
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
diff --git a/misc/util.h b/misc/util.h
index 867f4b0..b80d489 100644
--- a/misc/util.h
+++ b/misc/util.h
@@ -19,6 +19,7 @@ extern char	*journal_location_string;
  * Flags for check_plausibility()
  */
 #define CHECK_BLOCK_DEV	0x0001
+#define CREATE_FILE	0x0002
 
 #ifndef HAVE_STRCASECMP
 extern int strcasecmp (char *s1, char *s2);
-- 
1.9.0

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