linux-kernel - Re: [PATCH 3/7] mm: Add an 'end' parameter to find_get

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Message-ID: <20200821163306.GW17456@casper.infradead.org>
Date:   Fri, 21 Aug 2020 17:33:06 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] mm: Add an 'end' parameter to find_get_entries

On Fri, Aug 21, 2020 at 06:07:59PM +0200, Jan Kara wrote:
> On Wed 19-08-20 16:05:51, Matthew Wilcox (Oracle) wrote:
> > This simplifies the callers and leads to a more efficient implementation
> > since the XArray has this functionality already.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> 
> The patch looks good to me. Just I'd note that you could drop some:
> 
> 	if (index >= end)
> 		break;
> 
> checks in shmem_undo_range() as well.

Oh yes, missed a couple ;-)  Thanks, I'll add.

> In the past I was considering moving find_get_entries() to the same API as
> find_get_pages_range() has (which is essentially what you do now, but I
> also had 'start' to be a pgoff_t * so that we can return there where the
> iteration ended in the range). But in the end I've decided the churn is not
> worth the few removed lines and didn't push the patch in the end. What you
> did in this patch seems to be a reasonable middle-ground :)

I did look at that, but since we're returning the indices, we don't _need_
to update the index here.

I have some other ideas for this family of interfaces, but I'm trying
to get the THP work off my plate before getting distracted by that ;-)