linux-kernel - Re: [PATCH v12 00/10] enable bs

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Message-ID: <3427742.1724076489@warthog.procyon.org.uk>
Date: Mon, 19 Aug 2024 15:08:09 +0100
From: David Howells <dhowells@...hat.com>
To: Hannes Reinecke <hare@...e.de>
Cc: dhowells@...hat.com,
    "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>,
    brauner@...nel.org, akpm@...ux-foundation.org,
    chandan.babu@...cle.com, linux-fsdevel@...r.kernel.org,
    djwong@...nel.org, gost.dev@...sung.com, linux-xfs@...r.kernel.org,
    hch@....de, david@...morbit.com, Zi Yan <ziy@...dia.com>,
    yang@...amperecomputing.com, linux-kernel@...r.kernel.org,
    linux-mm@...ck.org, willy@...radead.org, john.g.garry@...cle.com,
    cl@...amperecomputing.com, p.raghav@...sung.com, mcgrof@...nel.org,
    ryan.roberts@....com
Subject: Re: [PATCH v12 00/10] enable bs > ps in XFS

Hannes Reinecke <hare@...e.de> wrote:

> Wouldn't the second truncate end up with a 4k file, and not an 8k?
> IE the resulting file will be:
> After step 1: 8k
> After step 2: 4
> After step 3: 4k

Yes, but the folio should still be an 8K folio, and it is:

>   pankaj-5833: netfs_folio: pfn=116fec i=0009e ix=00000-00001 inval-part

as indicated by the inclusive folio index range ix=00000-00001.

The problem is that the bottom four bytes of the file are getting cleared
somewhere.  They *should* be "XXXX", but they're all zeros.

David