From: Akira Fujita <a-fujita@rs.jp.nec.com>
Subject: Re: [PATCH 1/3] ext4: Fix insertion point of extent in mext_insert_across_blocks()
Date: Mon, 08 Mar 2010 17:40:29 +0900
Message-ID: <4B94B7FD.4050202@rs.jp.nec.com>
References: <4B8E0679.8060706@rs.jp.nec.com> <20100304012508.GD3530@thunk.org> <4B90BEA9.9020208@rs.jp.nec.com> <20100305161008.GB6000@thunk.org>
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Cc: ext4 development <linux-ext4@vger.kernel.org>
To: tytso@mit.edu
In-Reply-To: <20100305161008.GB6000@thunk.org>
Sender: linux-ext4-owner@vger.kernel.org

Hi Ted,

(2010/03/06 1:10), tytso@mit.edu wrote:
> On Fri, Mar 05, 2010 at 05:19:53PM +0900, Akira Fujita wrote:
>>
>> Sounds interesting.
>> It seems to be able to try easily except (2).
>> I think that we can mark block bitmap as in use with debugfs (do_setb).
>> Do you have another better idea for the tool you mentioned at (2)?
> 
> The libext2fs library is very powerful.  :-)
> 
> Here's a quicky program I whipped up fairly quickly.  The code that
> actually messes with the block bitmap is in the for loop; the rest is
> just generic setup.  Feel free to reuse this program as a framework
> for other times when you want to quickly create a program to do
> something programmatic where debugfs isn't quite powerful enough for
> your needs.
> 
> I have considered trying to integrate tcl into debugfs, so that you
> could do this in thing more easily in debugfs directly, but it's so
> easy to write throwaway C programs that I've never bothered.
> 

Thank you.
This program will be great help for my work.
I will give it a shot.

Regards,
Akria Fujita.


> /*
>   * fill-bitmap.c --- Program which writes marks roughly half of the
>   *     blocks in the filesystem as being in use.
>   *
>   * Compile via: cc -o fill-bitmap fill-bitmap.c -lext2fs -lcom_err
>   *
>   * Copyright 2010 by Theodore Ts'o.
>   *
>   * %Begin-Header%
>   * This file may be redistributed under the terms of the GNU Public
>   * License.
>   * %End-Header%
>   */
> 
> #include<ext2fs/ext2_fs.h>
> #include<ext2fs/ext2fs.h>
> #include<et/com_err.h>
> #include<stdlib.h>
> 
> char *program_name;
> 
> static void usage(void)
> {
> 	fprintf(stderr, "Usage: %s device\n", program_name);
> 	exit (1);
> }
> 
> int main (int argc, char ** argv)
> {
> 	errcode_t retval;
> 	ext2_filsys fs;
> 	char *device_name;
> 	blk_t blk;
> 
> 	add_error_table(&et_ext2_error_table);
> 	if (argc != 2)
> 		usage();
> 	program_name = argv[0];
> 	device_name = argv[1];
> 
> 	retval = ext2fs_open (device_name, EXT2_FLAG_RW, 0, 0,
> 			      unix_io_manager,&fs);
>          if (retval) {
> 		com_err(program_name, retval, "while trying to open %s",
> 			device_name);
> 		exit(1);
> 	}
> 
> 	retval = ext2fs_read_bitmaps(fs);
> 	if (retval) {
> 		com_err(program_name, retval, "while reading bitmaps");
> 		exit(1);
> 	}
> 
> 	for (blk = fs->super->s_first_data_block;
> 	     blk<  fs->super->s_blocks_count; blk++) {
> 		if (ext2fs_test_block_bitmap(fs->block_map, blk))
> 			continue;
> 
> 		if (random()&  1)
> 			continue;
> 
> 		ext2fs_mark_block_bitmap(fs->block_map, blk);
> 		ext2fs_block_alloc_stats(fs, blk, 1);
> 	}
> 
> 	ext2fs_close(fs);
> 	remove_error_table(&et_ext2_error_table);
> 	exit (0);
> }
>