From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 277532BB04; Sun, 30 Mar 2025 12:04:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743336257; cv=none; b=b8hx3XdtnBiyJ6fUkSGar0Jo7L/ZYgn6qWf3Xl3EvUt1NDM8iRWM/0Pf8y5IsD/vJMZrEWRY4qGTzCoJi1xOGHCsyvg3kF8b8x8w4oCRvOiFNNg9+So0FmZDWAthG9/cV4ygAQ1X2JfG9nf4sgzNNoM5VoUw/OSIJXDmPefMxNk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743336257; c=relaxed/simple; bh=j8I7Y4X262Zlf2k8C6vN5Flngo160/1EeL7FXB8cA3s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bQG+XCWLrsZj/rysOdxLnCARvubVWPJd5fhlXd7GH59GFj7BP8A3hP/OjnUOI7+Gd6IDdQ2dTB+uDGD2pm9+MFBBXTBf/ZqB8uePURq3yx/4zEWmz/oPifo2OfEwyNnJIFyVB++PWz10Ga//5HdK8QZpIR01EQd/yoz88BuFQ0k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=q0GkGU+6; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="q0GkGU+6" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=voDv8EMh3wDI8Ol9zgDNGOFRR3qzvAQIM67ZjI3SCz8=; b=q0GkGU+6GJ3rbA/gqQ0Af/LEyg b4UR04DsVRCaisDDpggnecveh2T2HG2hI3FYGxHsV1yK2jwXaHKw8+5hJeqAeB4TBDUiZJBV7sK5/ e4ntTTvaW7srOCXgoxG6mHOKljPVQ2BnECSogx8ttaFZu3ZML+5CIYNQ2a7wgaCcuVvrBcPdVvUYW lbIbWtB2ftNtQf31ZMqCRR3mV8C2Pyrtf6kKqRPN4VOnuGrPyjUuCTvFG6iV5og6xRBvpgwMhFmma Yd1uPj0T2gQ+64/f6JemxhVYWoP36361IdpKdNI+arvw72ypRh9rXc64cLBtR3gNUANvGtPGC4Ot0 4R2A6eUg==; Received: from willy by casper.infradead.org with local (Exim 4.98.1 #2 (Red Hat Linux)) id 1tyrOU-00000004M53-2Dfn; Sun, 30 Mar 2025 12:04:02 +0000 Date: Sun, 30 Mar 2025 13:04:02 +0100 From: Matthew Wilcox To: Luis Chamberlain Cc: brauner@kernel.org, jack@suse.cz, tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, riel@surriel.com, hannes@cmpxchg.org, oliver.sang@intel.com, dave@stgolabs.net, david@redhat.com, axboe@kernel.dk, hare@suse.de, david@fromorbit.com, djwong@kernel.org, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com Subject: Re: [PATCH 1/3] mm/migrate: add might_sleep() on __migrate_folio() Message-ID: References: <20250330064732.3781046-1-mcgrof@kernel.org> <20250330064732.3781046-2-mcgrof@kernel.org> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250330064732.3781046-2-mcgrof@kernel.org> On Sat, Mar 29, 2025 at 11:47:30PM -0700, Luis Chamberlain wrote: > However tracing shows that folio_mc_copy() *isn't* being called > as often as we'd expect from buffer_migrate_folio_norefs() path > as we're likely bailing early now thanks to the check added by commit > 060913999d7a ("mm: migrate: support poisoned recover from migrate > folio"). Umm. You're saying that most folios we try to migrate have extra refs? That seems unexpected; does it indicate a bug in 060913999d7a? > +++ b/mm/migrate.c > @@ -751,6 +751,8 @@ static int __migrate_folio(struct address_space *mapping, struct folio *dst, > { > int rc, expected_count = folio_expected_refs(mapping, src); > > + might_sleep(); 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)); > /* Check whether src does not have extra refs before we do more work */ > if (folio_ref_count(src) != expected_count) > return -EAGAIN; > -- > 2.47.2 >