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

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Message-Id: <20241003130133.afb8e8bbdfa8f638b0343473@linux-foundation.org>
Date: Thu, 3 Oct 2024 13:01:33 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Shakeel Butt <shakeel.butt@...ux.dev>
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 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.