From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794389745; b=ZGVIMExjN7NP+uRO8FtL3cF07sEML2sF2IRUOBfM+Oy1VS8vtjfLnyScb5mTbqgWMKiN dgktRHW0YJjc9TjGDXkrc43IvX/XpvQcPrtbZ2KSNfNFYjjSrx6hyokVTFcu6voncd+2v u4OWLj4APYr0lZ9gjp6We/qZMXWnNoDFue5GS7xu37ct8zYCqw8nndqesD7ep+mFTqpDh 8Q6qZ33HppldIxeFkArFJFiUG8tWG8xxvSud4ScC8FFdm0cMsVZvMExDlL3Lu108p9o6s D7Vb+hbtrJMp7I0hjgkcjG3IPU9F6FLwwVZ7P5TpovE9OifufC3cNYcB25J/XjQIC1A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794389745; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:Content-Language:To:Cc:References:From:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=9X8CCswIaiCe2k/d80ea7S7jWAHEKF+u255fg2VFMFw=; b=s4Z6ETJmw4UX80EHJFJpnPUsDyn9HJAXcJjsTukdOdd6NIQHzjvQpUvNwDeayG4D588e XNI4HESmNelZXoAACkywpSn456MU52NxpBVFjrzQiu+aOWbjCx0ihJKdT427+wAHOLmXH +lelFhEryPAWpV+cUJgX13rI2m4bhe/fePPs4VzWIqMRqA4FfQrdqtbzXArShwcgJtgfa LWc5IU0YZtWwl2qluJDitHW/XXXOfeG8gpA+r1ePihQqzK8esF7JX1SpCdzROe5nYKu41 9lLSmcB4QUYx0As/yZifGcfSJo2L2P7wr53fO7zohfWqFEkEfaaivC/7ak6+M0UPm5w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=T2qNYQkE; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7FB2606A321 for ; Wed, 11 Nov 2026 09:35:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=T2qNYQkE Received: by smtp.kernel.org (Postfix) with ESMTPSA id E19881F00A05; Wed, 11 Nov 2026 09:35:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794389745; bh=9X8CCswIaiCe2k/d80ea7S7jWAHEKF+u255fg2VFMFw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=T2qNYQkE61kCIR/UriUiEp2Xe+xDAU4E1joo4LXujXTT1NiLFqQTbEsOAsAo2g5bK hG0PCYjhQ2JRcdXyUEN7VcGwBsupQZ6hAxvCLVilPlRb4MlylhqRGPyxI+BFNutXCt D0PHRPnp4Nz7HgQeYs1joXy4FBbJUpsLYykHZoqr4I+1MwtIetWyqpKOam8RZAV5u2 4ELqRRMIndDcRR4uw8FynIaqqaRRRb04+OVZl2kxVj186R/6T/2+swrwHPsSk235q0 LK/ktYI3fqYgg3oGJ8cVWMbvVzIdCQRYtvjdprwTT78fEBSuTVxMJBHQSIBUMepRuk 7nL0CN6YmKO8Q== Message-ID: Date: Wed, 11 Nov 2026 10:35:42 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] mm: only assert mmap locks if CONFIG_DEBUG_VM or lockdep is set Content-Language: en-US To: "Lorenzo Stoakes (ARM)" , Andrew Morton , Suren Baghdasaryan , "Liam R. Howlett" , Shakeel Butt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261110-tame-vma-asserts-v1-0-be293ff499a7@kernel.org> <20261110-tame-vma-asserts-v1-1-be293ff499a7@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20261110-tame-vma-asserts-v1-1-be293ff499a7@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/10/26 17:57, Lorenzo Stoakes (ARM) wrote: > For a long while we have asserted the mmap lock being held regardless of > whether or not the kernel is a debug build or not. > > In general, given that these have been added as programmatic asserts that > nobody did something stupid, production kernels are simply wasting their > time checking for this. > > It also means there is a two tier system - where some programmatic > asserts (e.g. VM_WARN_ON_ONCE()-checked conditions) are only checked for if > CONFIG_DEBUG_VM is enabled, whereas others are checked unconditionally. > > If we genuinely want to unconditionally check for the mmap lock being held > at runtime, then that should be made clear in the code doing it. > > Regardless, if CONFIG_LOCKDEP is enabled, ensure that the lockdep > assertions are performed. > > Signed-off-by: Lorenzo Stoakes (ARM) Reviewed-by: Vlastimil Babka (SUSE) > --- > include/linux/mmap_lock.h | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > index 9c3a9c6525c1..9367430ee53c 100644 > --- a/include/linux/mmap_lock.h > +++ b/include/linux/mmap_lock.h > @@ -75,12 +75,14 @@ static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write) > > static inline void mmap_assert_locked(const struct mm_struct *mm) > { > - rwsem_assert_held(&mm->mmap_lock); > + if (IS_ENABLED(CONFIG_DEBUG_VM) || IS_ENABLED(CONFIG_LOCKDEP)) > + rwsem_assert_held(&mm->mmap_lock); > } > > static inline void mmap_assert_write_locked(const struct mm_struct *mm) > { > - rwsem_assert_held_write(&mm->mmap_lock); > + if (IS_ENABLED(CONFIG_DEBUG_VM) || IS_ENABLED(CONFIG_LOCKDEP)) > + rwsem_assert_held_write(&mm->mmap_lock); > } > > #ifdef CONFIG_LOCKDEP >