linux-ext4 - Re: [PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect block files

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Message-ID: <alpine.LFD.2.00.1406191737150.2182@localhost.localdomain>
Date:	Thu, 19 Jun 2014 17:38:12 +0200 (CEST)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	Jan Kara <jack@...e.cz>
cc:	Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] ext4: Fix block zeroing when punching holes in
 indirect block files

On Wed, 18 Jun 2014, Jan Kara wrote:

> Date: Wed, 18 Jun 2014 21:33:03 +0200
> From: Jan Kara <jack@...e.cz>
> To: Ted Tso <tytso@....edu>
> Cc: linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
> Subject: [PATCH 1/2] ext4: Fix block zeroing when punching holes in indirect
>     block files
> 
> free_holes_block() passed local variable as a block pointer
> to ext4_clear_blocks(). Thus ext4_clear_blocks() zeroed out this local
> variable instead of proper place in inode / indirect block. We later
> zero out proper place in inode / indirect block but don't dirty the
> inode / buffer again which can lead to subtle issues (some changes e.g.
> to inode can be lost).

Please see my patch

[PATCH] ext4: Fix punch hole on files with indirect mapping

which fixes those issues in a different way while also make this
operation faster.

Thanks!
-Lukas

> 
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/indirect.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 8a57e9fcd1b9..9d381707a6fc 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -1329,8 +1329,8 @@ static int free_hole_blocks(handle_t *handle, struct inode *inode,
>  		if (level == 0 ||
>  		    (bh && all_zeroes((__le32 *)bh->b_data,
>  				      (__le32 *)bh->b_data + addr_per_block))) {
> -			ext4_free_data(handle, inode, parent_bh, &blk, &blk+1);
> -			*i_data = 0;
> +			ext4_free_data(handle, inode, parent_bh,
> +				       i_data, i_data + 1);
>  		}
>  		brelse(bh);
>  		bh = NULL;
> 
--
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