linux-ext4 - Re: [PATCH 3/5] ext4_zero_range: fix incorect journal credits reservation

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Message-ID: <20140823190835.GB6236@thunk.org>
Date:	Sat, 23 Aug 2014 15:08:35 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
Cc:	linux-ext4@...r.kernel.org, lczerner@...hat.com
Subject: Re: [PATCH 3/5] ext4_zero_range: fix incorect journal credits
 reservation

On Fri, Aug 22, 2014 at 03:32:25PM +0400, Dmitry Monakhov wrote:
> -	handle = ext4_journal_start(inode, EXT4_HT_MISC, 4);
> +	/* In worst case we have to writeout two nonadjacent unwritten blocks */
> +	credits = ext4_chunk_trans_blocks(inode, 1) * 2 -
> +		EXT4_META_TRANS_BLOCKS(inode->i_sb);

This looks like it would be a massive over-estimate, since it includes
the block group allocation bitmaps, which we wouldn't need to update,
no?

Wouldn't

	credts = ext4_index_trans_blocks(inode, 1, 1) * 2;

be sufficient?

					- Ted
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