From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-202.mailbox.org (mout-p-202.mailbox.org [80.241.56.172]) (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 AB4191AC8BC; Thu, 15 Aug 2024 10:04:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723716276; cv=none; b=GUwmGZnSq7Hcotq5+MMp3EGcwjPYeFdUEwR1Omz+DWWvq7IV38bRFHxGJlEZL3B7jju5W5vZtF5vU5E7T6jc5ykA+NdATKLFpKLd0wOao867+a84+tRdudYdiHD6eO0YT+YvAd7CrBRdGti6n49/roRuvUTWA5fYxceQ8rnu2So= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723716276; c=relaxed/simple; bh=LMI9zugfdC8nxqWGFsq56iMeNYCzn8+Pg1VGDx+73zM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Loog+qfUCdOTw91ErYMAI6N5OLXG+ogUjuWNpN9Xs2K3Pme3Je0e45bX6LAl23s4xBHYVMwjYGJ+pQWJ0iYxrO4rF0sm0wKqXUy19SBgfUDnFTnZFJjJMC+qcjrW3z3dT3DW1FKSsE/B0mdmREwZOeVs7vERmTIB+0vTIw6GJ44= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=samsung.com; spf=pass smtp.mailfrom=pankajraghav.com; arc=none smtp.client-ip=80.241.56.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=samsung.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pankajraghav.com Received: from smtp1.mailbox.org (smtp1.mailbox.org [IPv6:2001:67c:2050:b231:465::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-202.mailbox.org (Postfix) with ESMTPS id 4Wl11n6qm7z9sRJ; Thu, 15 Aug 2024 12:04:29 +0200 (CEST) From: Pankaj Raghav To: david@redhat.com Cc: agordeev@linux.ibm.com, akpm@linux-foundation.org, borntraeger@linux.ibm.com, corbet@lwn.net, frankja@linux.ibm.com, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, hca@linux.ibm.com, imbrenda@linux.ibm.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, svens@linux.ibm.com, willy@infradead.org Subject: Re: [PATCH v1 07/11] mm/huge_memory: convert split_huge_pages_pid() from follow_page() to folio_walk Date: Thu, 15 Aug 2024 12:04:23 +0200 Message-ID: <20240815100423.974775-1-p.raghav@samsung.com> In-Reply-To: <20240802155524.517137-8-david@redhat.com> References: <20240802155524.517137-8-david@redhat.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4Wl11n6qm7z9sRJ Hi David, On Fri, Aug 02, 2024 at 05:55:20PM +0200, David Hildenbrand wrote: > continue; > } > > - /* FOLL_DUMP to ignore special (like zero) pages */ > - page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > - > - if (IS_ERR_OR_NULL(page)) > + folio = folio_walk_start(&fw, vma, addr, 0); > + if (!folio) > continue; > > - folio = page_folio(page); > if (!is_transparent_hugepage(folio)) > goto next; > > @@ -3544,13 +3542,19 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start, > > if (!folio_trylock(folio)) > goto next; > + folio_get(folio); Shouldn't we lock the folio after we increase the refcount on the folio? i.e we do folio_get() first and then folio_trylock()? That is how it was done before (through follow_page) and this patch changes that. Maybe it doesn't matter? To me increasing the refcount and then locking sounds more logical but I do see this ordering getting mixed all over the kernel. > + folio_walk_end(&fw, vma); > > if (!split_folio_to_order(folio, new_order)) > split++; > > folio_unlock(folio); > -next: > folio_put(folio); > + > + cond_resched(); > + continue; > +next: > + folio_walk_end(&fw, vma); > cond_resched(); > } > mmap_read_unlock(mm); > -- > 2.45.2 -- Pankaj Raghav