linux-ext4 - Re: [PATCH] e2image: Add image consistency information and -f option to manpage

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Message-ID: <20131012024905.GA30680@thunk.org>
Date:	Fri, 11 Oct 2013 22:49:05 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Carlos Maiolino <cmaiolino@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2image: Add image consistency information and -f option
 to manpage

On Mon, Sep 30, 2013 at 06:19:25PM -0300, Carlos Maiolino wrote:
> Adds information regarding image consistency when using e2image on a read-write
> filesystem and about -f option used now to force the image creation of a
> read-write filesystem
> 
> Signed-off-by: Carlos Maiolino <cmaiolino@...hat.com>

Here is the combined commit which I've just added to my tree in the
maint branch.  It includes the man page with some clarifications in
the wording.  Also I've changed things so that we only print the error
message for e2image -r and e2image -Q.

						- Ted

commit 6c327e9ca47fa4e51efe3a6601ad661b8c1a3964
Author: Carlos Maiolino <cmaiolino@...hat.com>
Date:   Fri Oct 11 21:38:53 2013 -0400

    e2image: complain if running e2image -r or -Q on a mounted filesystem
    
    Several users have used e2image on a mounted RW filesystem, resulting in
    inconsistent, useless e2images for debugging purposes.
    
    This commit will forbid this and print an error message, although the
    user can override this using a new force option.
    
    Signed-off-by: Carlos Maiolino <cmaiolino@...hat.com>
    Signed-off-by: Theodore Ts'o <tytso@....edu>

diff --git a/misc/e2image.8.in b/misc/e2image.8.in
index 84b9729..78f0682 100644
--- a/misc/e2image.8.in
+++ b/misc/e2image.8.in
@@ -30,6 +30,16 @@ recovering catastrophically corrupted filesystems.  In the future,
 e2fsck will be enhanced to be able to use the image file to help
 recover a badly damaged filesystem.
 .PP
+When saving an e2image for debugging purposes, using either the
+.B \-r
+or
+.B \-Q
+options, the filesystem must be unmounted or be mounted read/only, in order
+for the image file to be in a consistent state.  This requirement can be
+overriden using the
+.B -f
+option, but the resulting image file is very likely not going to be useful.
+.PP
 If
 .I image-file
 is \-, then the output of
diff --git a/misc/e2image.c b/misc/e2image.c
index 885a794..4a5bb22 100644
--- a/misc/e2image.c
+++ b/misc/e2image.c
@@ -87,7 +87,7 @@ static int get_bits_from_size(size_t size)
 
 static void usage(void)
 {
-	fprintf(stderr, _("Usage: %s [-rsIQa] device image_file\n"),
+	fprintf(stderr, _("Usage: %s [-rsIQaf] device image_file\n"),
 		program_name);
 	exit (1);
 }
@@ -1252,9 +1252,11 @@ int main (int argc, char ** argv)
 	int open_flag = EXT2_FLAG_64BITS;
 	int img_type = 0;
 	int flags = 0;
+	int mount_flags = 0;
 	int qcow2_fd = 0;
 	int fd = 0;
 	int ret = 0;
+	int ignore_rw_mount = 0;
 	struct stat st;
 
 #ifdef ENABLE_NLS
@@ -1269,7 +1271,7 @@ int main (int argc, char ** argv)
 	if (argc && *argv)
 		program_name = *argv;
 	add_error_table(&et_ext2_error_table);
-	while ((c = getopt(argc, argv, "rsIQa")) != EOF)
+	while ((c = getopt(argc, argv, "rsIQaf")) != EOF)
 		switch (c) {
 		case 'I':
 			flags |= E2IMAGE_INSTALL_FLAG;
@@ -1290,6 +1292,9 @@ int main (int argc, char ** argv)
 		case 'a':
 			all_data = 1;
 			break;
+		case 'f':
+			ignore_rw_mount = 1;
+			break;
 		default:
 			usage();
 		}
@@ -1305,6 +1310,19 @@ int main (int argc, char ** argv)
 	device_name = argv[optind];
 	image_fn = argv[optind+1];
 
+	ext2fs_check_if_mounted(device_name, &mount_flags);
+
+	if (img_type && !ignore_rw_mount &&
+	    (mount_flags & EXT2_MF_MOUNTED) &&
+	   !(mount_flags & EXT2_MF_READONLY)) {
+		fprintf(stderr, "\nRunning e2image on a R/W mounted "
+			"filesystem can result in an\n"
+			"inconsistent image which will not be useful "
+			"for debugging purposes.\n"
+			"Use -f option if you really want to do that.\n");
+		exit(1);
+	}
+
 	if (flags & E2IMAGE_INSTALL_FLAG) {
 		install_image(device_name, image_fn, img_type);
 		exit (0);
--
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