linux-kernel - Re: [PATCH 07/17] writeback: Factor writeback_get_batch() out of write_cache

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Date: Thu, 21 Dec 2023 13:30:28 +0100
From: Jan Kara <jack@...e.cz>
To: Christoph Hellwig <hch@....de>
Cc: Jan Kara <jack@...e.cz>, linux-mm@...ck.org,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Jan Kara <jack@...e.com>, David Howells <dhowells@...hat.com>,
	Brian Foster <bfoster@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/17] writeback: Factor writeback_get_batch() out of
 write_cache_pages()

On Thu 21-12-23 13:22:33, Christoph Hellwig wrote:
> On Thu, Dec 21, 2023 at 12:17:43PM +0100, Jan Kara wrote:
> > > +static void writeback_get_batch(struct address_space *mapping,
> > > +		struct writeback_control *wbc)
> > > +{
> > > +	folio_batch_release(&wbc->fbatch);
> > > +	cond_resched();
> > 
> > I'd prefer to have cond_resched() explicitely in the writeback loop instead
> > of hidden here in writeback_get_batch() where it logically does not make
> > too much sense to me...
> 
> Based on the final state after this series, where would you place it?

I guess writeback_get_folio() would be fine... Which is where it naturally
lands with the inlining I already suggested so probably nothing to do here.

> (That beeing said there is a discussion underway on lkml to maybe
>  kill cond_resched entirely as part of sorting out the preemption
>  model mess, at that point this would become a moot point anyway)
> 
> > >  	} else {
> > > -		index = wbc->range_start >> PAGE_SHIFT;
> > > +		wbc->index = wbc->range_start >> PAGE_SHIFT;
> > >  		end = wbc->range_end >> PAGE_SHIFT;
> > >  	}
> > 
> > Maybe we should have:
> > 	end = wbc_end(wbc);
> > 
> > when we have the helper? But I guess this gets cleaned up in later patches
> > anyway so whatever.
> 
> Yeah, this end just goes away.  I can convert it here, but that feels
> like pointless churn to me.

Agreed. Just leave it alone.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR