linux-kernel - Re: [PATCH v6 06/11] filemap: cap PTE range to be created to allowed zero fill in folio_map

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Date: Mon, 3 Jun 2024 08:35:54 +0200
From: Hannes Reinecke <hare@...e.de>
To: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>, david@...morbit.com,
 chandan.babu@...cle.com, akpm@...ux-foundation.org, brauner@...nel.org,
 willy@...radead.org, djwong@...nel.org
Cc: linux-kernel@...r.kernel.org, john.g.garry@...cle.com,
 gost.dev@...sung.com, yang@...amperecomputing.com, p.raghav@...sung.com,
 cl@...amperecomputing.com, linux-xfs@...r.kernel.org, hch@....de,
 mcgrof@...nel.org, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 06/11] filemap: cap PTE range to be created to allowed
 zero fill in folio_map_range()

On 5/29/24 15:45, Pankaj Raghav (Samsung) wrote:
> From: Pankaj Raghav <p.raghav@...sung.com>
> 
> Usually the page cache does not extend beyond the size of the inode,
> therefore, no PTEs are created for folios that extend beyond the size.
> 
> But with LBS support, we might extend page cache beyond the size of the
> inode as we need to guarantee folios of minimum order. Cap the PTE range
> to be created for the page cache up to the max allowed zero-fill file
> end, which is aligned to the PAGE_SIZE.
> 
> An fstests test has been created to trigger this edge case [0].
> 
> [0] https://lore.kernel.org/fstests/20240415081054.1782715-1-mcgrof@kernel.org/
> 
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> ---
>   mm/filemap.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich