linux-kernel - Re: [PATCH mmotm] mm: warn on deleting redirtied only if accounted

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Message-ID: <YiGX2prSQEFoFOdL@casper.infradead.org>
Date:   Fri, 4 Mar 2022 04:38:50 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.de>,
        Christoph Hellwig <hch@....de>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH mmotm] mm: warn on deleting redirtied only if accounted

On Thu, Mar 03, 2022 at 08:25:50PM -0800, Hugh Dickins wrote:
> filemap_unaccount_folio() has a WARN_ON_ONCE(folio_test_dirty(folio)).
> It is good to warn of late dirtying on a persistent filesystem, but late
> dirtying on tmpfs can only lose data which is expected to be thrown away;
> and it's a pity if that warning comes ONCE on tmpfs, then hides others
> which really matter.  Make it conditional on mapping_cap_writeback().
> 
> Cleanup: then folio_account_cleaned() no longer needs to check that
> for itself, and so no longer needs to know the mapping.

At first blush, I like this a lot.  Will look more in the morning.