linux-kernel - Re: [PATCH mm-unstable v1] mm/truncate: batch-clear shadow entries

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Message-ID: <ZoxqAW5_GjbesrW5@casper.infradead.org>
Date: Mon, 8 Jul 2024 23:36:49 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Yu Zhao <yuzhao@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Bharata B Rao <bharata@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH mm-unstable v1] mm/truncate: batch-clear shadow entries

On Mon, Jul 08, 2024 at 03:27:53PM -0600, Yu Zhao wrote:
> Make clear_shadow_entry() clear shadow entries in `struct folio_batch`
> so that it can reduce contention on i_lock and i_pages locks, e.g.,

I think it needs to be renamed, perhaps to clear_shadow_entries().

> @@ -503,8 +486,8 @@ unsigned long mapping_try_invalidate(struct address_space *mapping,
>  			/* We rely upon deletion not changing folio->index */
>  
>  			if (xa_is_value(folio)) {
> -				count += invalidate_exceptional_entry(mapping,
> -							     indices[i], folio);
> +				xa_has_values = true;
> +				count++;

Mmm.  This is awkward.  It's supposed to return the number of pages,
not the number of folios (or shadow entries) invalidated.