linux-ext4 - Re: e2fsprogs-1.41.0 - error opening fs with badblocks.

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Message-ID: <20080902123050.GN13069@mit.edu>
Date:	Tue, 2 Sep 2008 08:30:50 -0400
From:	Theodore Tso <tytso@....edu>
To:	Manish Katiyar <mkatiyar@...il.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: e2fsprogs-1.41.0 - error opening fs with badblocks.

On Tue, Sep 02, 2008 at 05:38:25PM +0530, Manish Katiyar wrote:
> 
> I have created a test ext4 FS of 2.3GB. While running badblocks on it,
> I get the below error.
> 
> /home/mkatiyar/e2fs-git/e2fsprogs_work/sbin> ./badblocks myfs
> ./badblocks: Value too large for defined data type while trying to open myfs
> 
> /home/mkatiyar/e2fs-git/e2fsprogs_work/sbin> ls -lh myfs
> -rw-r--r-- 1 mkatiyar mkatiyar 2.3G 2008-09-02 10:13 myfs
> 
> This is due to open returning EOVERFLOW , but as per man page it
> should happen if the size of the file cannot be represented correctly
> in off_t which I don't think
> is the case here.

That's the problem, actually.  off_t is a signed type (it has to be,
because lseek needs to be able to represent negative offsets), so if
you open files greater than 2GB, you have to use the Large File
Support ABI extensions (also known as LFS)[1].  Specifically, this
means you have to either open the file using open64(), or if you use
open, you need to pass in the O_LARGEFILE flag.  

[1] http://www.suse.de/~aj/linux_lfs.html

Linux doesn't enforce this for block devices (only files), and no one
I know has ever tried to run badblocks on a local file (since there's
generally not much point), and so that's why you're the first person
to report this.

The attached patch should address your problem (although I'm not sure
why you would want to run badblocks on a normal file.  :-)

    	      	      	  	       	 - Ted

commit 22301afb01f3059a2b1baf68abff26aaf6db7c9e
Author: Theodore Ts'o <tytso@....edu>
Date:   Tue Sep 2 08:29:20 2008 -0400

    badblocks: Open the device with O_LARGEFILE

    Linux doesn't enforce the Large File Support API requirements on block
    devices, but in case someone wants to run badblocks on a normal file,
    open the device file with O_LARGEFILE.

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

diff --git a/misc/badblocks.c b/misc/badblocks.c
index 6261cbe..1d0f95a 100644
--- a/misc/badblocks.c
+++ b/misc/badblocks.c
@@ -31,6 +31,10 @@

 #define _GNU_SOURCE /* for O_DIRECT */

+#ifndef O_LARGEFILE
+#define O_LARGEFILE 0
+#endif
+
 #include <errno.h>
 #include <fcntl.h>
 #ifdef HAVE_GETOPT_H
@@ -933,7 +937,7 @@ int main (int argc, char ** argv)
 	unsigned int (*test_func)(int, blk_t,
 				  int, blk_t,
 				  unsigned int);
-	int open_flag = 0;
+	int open_flag;
 	long sysval;

 	setbuf(stdout, NULL);
@@ -1096,7 +1100,7 @@ int main (int argc, char ** argv)
 	if (w_flag)
 		check_mount(device_name);

-	open_flag = w_flag ? O_RDWR : O_RDONLY;
+	open_flag = O_LARGEFILE | (w_flag ? O_RDWR : O_RDONLY);
 	dev = open (device_name, open_flag);
 	if (dev == -1) {
 		com_err (program_name, errno, _("while trying to open %s"),

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