linux-kernel - Re: [PATCH] mm/truncate: reset xa_has

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Message-ID: <xqpohu2prms6cdhasdwup7dgkj6jsnnal7rx4t4i2qddownomf@gtx42zkp2n7t>
Date: Thu, 3 Oct 2024 13:11:14 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, 
	Matthew Wilcox <willy@...radead.org>, Yu Zhao <yuzhao@...gle.com>, linux-fsdevel@...r.kernel.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH] mm/truncate: reset xa_has_values flag on each iteration

On Thu, Oct 03, 2024 at 01:01:33PM GMT, Andrew Morton wrote:
> On Wed, 2 Oct 2024 16:09:11 -0700 Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> 
> > On Wed, Oct 02, 2024 at 03:55:55PM GMT, Andrew Morton wrote:
> > > On Wed,  2 Oct 2024 15:51:50 -0700 Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> > > 
> > > > Currently mapping_try_invalidate() and invalidate_inode_pages2_range()
> > > > traverses the xarray in batches and then for each batch, maintains and
> > > > set the flag named xa_has_values if the batch has a shadow entry to
> > > > clear the entries at the end of the iteration. However they forgot to
> > > > reset the flag at the end of the iteration which cause them to always
> > > > try to clear the shadow entries in the subsequent iterations where
> > > > there might not be any shadow entries. Fixing it.
> > > > 
> > > 
> > > So this is an efficiency thing, no other effects expected?
> > > 
> > 
> > Correct, just an efficiency thing.
> 
> Thanks.  I'm assuming the benfits are sufficiently small that a
> backport is inappropriate.

I agree.