linux-ext4 - Re: [PATCH] debugfs: properly set up extent header in do

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Date:	Thu, 25 Jul 2013 14:18:33 +0800
From:	Robert Yang <liezhi.yang@...driver.com>
To:	Eric Sandeen <sandeen@...hat.com>
CC:	"Darrick J. Wong" <darrick.wong@...cle.com>,
	<linux-ext4@...r.kernel.org>, "Theodore Ts'o" <tytso@....edu>,
	Darren Hart <dvhart@...ux.intel.com>
Subject: Re: [PATCH] debugfs: properly set up extent header in do_write


Hi Eric,

Thank you very much, it worked well with your patch, I've tested it on
Fedora 18 x86_64, the kernel is 3.6.10-4.fc18.x86_64.

Tested-by: Robert Yang <liezhi.yang@...driver.com>

// Robert

On 07/24/2013 11:11 PM, Eric Sandeen wrote:
> do_write doesn't fully set up the first extent header on a new
> inode, so if we write a 0-length file, and don't write any data
> to the new file, we end up creating something that looks corrupt
> to kernelspace:
>
> EXT4-fs error (device loop0): ext4_ext_check_inode:464: inode #12: comm ls: bad header/extent: invalid magic - magic 0, entries 0, max 0(0), depth 0(0)
>
> Do something similar to ext4_ext_tree_init() here, and
> fill out the first extent header upon creation to avoid this.
>
> Reported-by: Robert Yang <liezhi.yang@...driver.com>
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
> ---
>
> diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
> index dcf16e2..2660218 100644
> --- a/debugfs/debugfs.c
> +++ b/debugfs/debugfs.c
> @@ -1677,8 +1677,19 @@ void do_write(int argc, char *argv[])
>   	inode.i_links_count = 1;
>   	inode.i_size = statbuf.st_size;
>   	if (current_fs->super->s_feature_incompat &
> -	    EXT3_FEATURE_INCOMPAT_EXTENTS)
> +	    EXT3_FEATURE_INCOMPAT_EXTENTS) {
> +		int i;
> +		struct ext3_extent_header *eh;
> +
> +		eh = (struct ext3_extent_header *) &inode.i_block[0];
> +		eh->eh_depth = 0;
> +		eh->eh_entries = 0;
> +		eh->eh_magic = EXT3_EXT_MAGIC;
> +		i = (sizeof(inode.i_block) - sizeof(*eh)) /
> +			sizeof(struct ext3_extent);
> +		eh->eh_max = ext2fs_cpu_to_le16(i);
>   		inode.i_flags |= EXT4_EXTENTS_FL;
> +	}
>   	if (debugfs_write_new_inode(newfile, &inode, argv[0])) {
>   		close(fd);
>   		return;
>
>
>
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