linux-ext4 - Re: [PATCH 2/3] fs/buffer: avoid races with folio migrations on __find_get_block

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Message-ID: <Z-yZxMVJgqOOpjHn@casper.infradead.org>
Date: Wed, 2 Apr 2025 02:58:28 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Jan Kara <jack@...e.cz>, Luis Chamberlain <mcgrof@...nel.org>,
	brauner@...nel.org, tytso@....edu, adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org, riel@...riel.com, hannes@...xchg.org,
	oliver.sang@...el.com, david@...hat.com, axboe@...nel.dk,
	hare@...e.de, david@...morbit.com, djwong@...nel.org,
	ritesh.list@...il.com, linux-fsdevel@...r.kernel.org,
	linux-block@...r.kernel.org, linux-mm@...ck.org,
	gost.dev@...sung.com, p.raghav@...sung.com, da.gomez@...sung.com
Subject: Re: [PATCH 2/3] fs/buffer: avoid races with folio migrations on
 __find_get_block_slow()

On Tue, Apr 01, 2025 at 02:49:51PM -0700, Davidlohr Bueso wrote:
> So the below could be tucked in for norefs only (because this is about the addr
> space i_private_lock), but this also shortens the hold time; if that matters
> at all, of course, vs changing the migration semantics.

I like this approach a lot better.  One wrinkle is that it doesn't seem
that we need to set the BH_Migrate bit on every buffer; we could define
that it's only set on the head BH, right?