From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) (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 0FF271EA84 for ; Wed, 3 Jun 2026 12:20:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780489213; cv=none; b=aq05l1tS8/Mi838I3e0ZMcTPAGhe58Kn2X46Ef3TQsiBl2+c4z8uM/0oATj/6I5kd1adEBycD3lVigoazoPmomp30JVqk3L88me6LYA3IUTSUud6tO+j5PynQUL3OritWwPA1WTKTz0vUEJaoMBuekSWVeIy7nXF7xG6QoZUkp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780489213; c=relaxed/simple; bh=tn8mvKpksfdjgnNmAj7SbS2Rs6s6zpvS0Gvz7YNElc4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bKSxRyDbjDfiIF9NC6Y8l+24uHmcaq6mrWnU8n2Wu9HW19A5/FhCPlvTsGDlfaAdg1ospO5XwD0N30E85mRo+SoMEJ9ng1OEpZuZCl8LPdkx/KKZqbvqobpj5sYUL8XyS+/QJWxEnTdqX7BrnUF1iekScimZWn/84H04XCIfGn8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=MkxB/4IX; arc=none smtp.client-ip=95.215.58.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="MkxB/4IX" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780489210; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JVPf2HxnOSeDo+U9qlfy4aat8ZJ692PaW/P5vPj0roc=; b=MkxB/4IXntiepknr2HPty4AE/U6fUgJTQXWGd/DQzxZkMcFotDK0S4I1PROFNjE83/wgaY fOzGvdJSZVKI4IPaZKPvt9cMJaUNvGT/c24R8FMu0qsaXcvxvrVZs4D0ceLlN05uSOga8E 5eGLLSIMksIxNpQw4dGLg9m/HWOR6m0= Date: Wed, 3 Jun 2026 13:20:00 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] mm/mincore: handle non-swap entries before !CONFIG_SWAP guard To: Lorenzo Stoakes Cc: Andrew Morton , jannh@google.com, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pfalcato@suse.de, vbabka@kernel.org, chrisl@kernel.org, kasong@tencent.com, baoquan.he@linux.dev, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, kas@kernel.org, kernel-team@meta.com References: <20260602172247.279421-1-usama.arif@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 03/06/2026 13:08, Lorenzo Stoakes wrote: > On Tue, Jun 02, 2026 at 10:22:47AM -0700, Usama Arif wrote: >> mincore_swap() also fields migration/hwpoison entries (and shmem >> swapin-error entries), which can exist on !CONFIG_SWAP builds when >> CONFIG_MIGRATION or CONFIG_MEMORY_FAILURE is enabled. The >> !IS_ENABLED(CONFIG_SWAP) guard ran before the non-swap-entry early >> return, so mincore_pte_range() can spuriously WARN and report these >> pages nonresident on !CONFIG_SWAP kernels. >> >> Move the guard below the non-swap-entry check so only true swap >> entries trip the WARN, and migration/hwpoison entries take the >> existing "uptodate / non-shmem" path. >> >> Fixes: 1f2052755c15 ("mm/mincore: use a helper for checking the swap cache") >> Signed-off-by: Usama Arif > > Logic LGTM so: > > Reviewed-by: Lorenzo Stoakes > > Small note below but I think not a problem. > > Thanks, Lorenzo > >> --- >> This was discovered when working on PMD swap entry series >> (https://lore.kernel.org/all/20260602142537.198755-1-usama.arif@linux.dev/) >> --- >> mm/mincore.c | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/mm/mincore.c b/mm/mincore.c >> index e5d13eea9234..296f2e3922b5 100644 >> --- a/mm/mincore.c >> +++ b/mm/mincore.c >> @@ -64,11 +64,6 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem) >> struct folio *folio = NULL; >> unsigned char present = 0; >> >> - if (!IS_ENABLED(CONFIG_SWAP)) { >> - WARN_ON(1); >> - return 0; >> - } >> - >> /* >> * Shmem mapping may contain swapin error entries, which are >> * absent. Page table may contain migration or hwpoison >> @@ -77,6 +72,11 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem) >> if (!softleaf_is_swap(entry)) >> return !shmem; >> > > I guess fine to do this after software_is_swap() because for !CONFIG_SWAP this > will always evaluate false? Yes, thats right. In softleaf_is_swap(), softleaf_type() returns SOFTLEAF_SWAP iff type_num < MAX_SWAPFILES. MAX_SWAPFILES is a compile-time constant independent of CONFIG_SWAP, so softleaf_is_swap() isn't structurally gated, but every producer of real swap entries lives under CONFIG_SWAP. With !CONFIG_SWAP none of those run, so softleaf_is_swap() is always false. > > Not a big deal therefore I think. > >> + if (!IS_ENABLED(CONFIG_SWAP)) { >> + WARN_ON(1); >> + return 0; >> + } >> + >> /* >> * Shmem mapping lookup is lockless, so we need to grab the swap >> * device. mincore page table walk locks the PTL, and the swap >> -- >> 2.52.0 >>