linux-ext4 - Re: [PATCH 1/3] mm/migrate: add might_sleep() on __migrate

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Message-ID: <20250401225320.uee5as2bmw4p6ygl@offworld>
Date: Tue, 1 Apr 2025 15:53:20 -0700
From: Davidlohr Bueso <dave@...olabs.net>
To: Matthew Wilcox <willy@...radead.org>
Cc: Luis Chamberlain <mcgrof@...nel.org>, brauner@...nel.org, jack@...e.cz,
	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 1/3] mm/migrate: add might_sleep() on __migrate_folio()

On Sun, 30 Mar 2025, Matthew Wilcox wrote:

>We deliberately don't sleep when the folio is only a single page.
>So this needs to be:
>
>	might_sleep_if(folio_test_large(folio));

Along with willy's suggestion:

Acked-by: Davidlohr Bueso <dave@...olabs.net>

... and the same rules apply for copy_folio():

fs/aio.c: atomic context but no large folio: safe

fs/fuse/file.c: no large folio: safe

fs/nilfs2/page.c: blocking safe, has large folio: safe

mm/migrate_device.c: no large folio: safe

mm/shmem.c: blocking safe, has large folio: safe
shmem_replace_folio() could use a might_sleep() I guess.

Thanks,
Davidlohr