linux-ext4 - Re: [PATCH 2/3] Add batched discard support for ext3

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Date:	Thu, 5 Aug 2010 16:00:20 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Andreas Dilger <adilger@...ger.ca>
cc:	Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org,
	jmoyer@...hat.com, rwheeler@...hat.com, eshishki@...hat.com,
	sandeen@...hat.com, jack@...e.cz, tytso@....edu
Subject: Re: [PATCH 2/3] Add batched discard support for ext3

On Wed, 4 Aug 2010, Andreas Dilger wrote:

> On 2010-08-04, at 07:44, Lukas Czerner wrote:
> > +		/*
> > +		 * Clear bits in the bitmap
> > +		 */
> > +		for (bit = start; bit < next; bit++) {
> > +			BUFFER_TRACE(bitmap_bh, "clear bit");
> > +			if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, group),
> > +						bit, bitmap_bh->b_data)) {
> > +				ext3_error(sb, __func__,
> > +					"bit already cleared for block "E3FSBLK,
> > +					 (unsigned long)bit);
> > +				BUFFER_TRACE(bitmap_bh, "bit already cleared");
> > +			} else {
> > +				freed++;
> > +			}
> > +		}
> > +
> > +		/* Update couters */
> > +		spin_lock(sb_bgl_lock(sbi, group));
> > +		le16_add_cpu(&gdp->bg_free_blocks_count, freed);
> > +		spin_unlock(sb_bgl_lock(sbi, group));
> > +		percpu_counter_add(&sbi->s_freeblocks_counter, next - start);
> 
> It wouldn't be a terrible idea to put this code into a helper function that is shared with ext3_free_blocks_sb() so that it is kept in sync.  There are a lot of places that need to be kept coordinated (disk bitmap, memory bitmap, group descriptor, percpu counter) so I'd like that to be localized to one part of the code.
> 
> 
> Cheers, Andreas
> 

Ok, I will see what I can do with that.

Thanks.

-Lukas
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