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Thu, 1 Jun 2023 13:19:03 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 330772004F; Thu, 1 Jun 2023 13:19:03 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7D8E420040; Thu, 1 Jun 2023 13:19:02 +0000 (GMT) Received: from thinkpad-T15 (unknown [9.152.212.238]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 1 Jun 2023 13:19:02 +0000 (GMT) Date: Thu, 1 Jun 2023 15:19:00 +0200 From: Gerald Schaefer To: "Vishal Moola (Oracle)" Cc: Andrew Morton , Matthew Wilcox , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, David Hildenbrand , Claudio Imbrenda , Alexander Gordeev , Vasily Gorbik , Heiko Carstens , Hugh Dickins , Christian Borntraeger Subject: Re: [PATCH v3 03/34] s390: Use pt_frag_refcount for pagetables Message-ID: <20230601151900.6f184e8c@thinkpad-T15> In-Reply-To: <20230531213032.25338-4-vishal.moola@gmail.com> References: <20230531213032.25338-1-vishal.moola@gmail.com> <20230531213032.25338-4-vishal.moola@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.37; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org On Wed, 31 May 2023 14:30:01 -0700 "Vishal Moola (Oracle)" wrote: > s390 currently uses _refcount to identify fragmented page tables. > The page table struct already has a member pt_frag_refcount used by > powerpc, so have s390 use that instead of the _refcount field as well. > This improves the safety for _refcount and the page table tracking. > > This also allows us to simplify the tracking since we can once again use > the lower byte of pt_frag_refcount instead of the upper byte of _refcount. This would conflict with s390 impact of pte_free_defer() work from Hugh Dickins https://lore.kernel.org/lkml/35e983f5-7ed3-b310-d949-9ae8b130cdab@google.com/ https://lore.kernel.org/lkml/6dd63b39-e71f-2e8b-7e0-83e02f3bcb39@google.com/ There he uses pt_frag_refcount, or rather pt_mm in the same union, to save the mm_struct for deferred pte_free(). I still need to look closer into both of your patch series, but so far it seems that you have no hard functional requirement to switch from _refcount to pt_frag_refcount here, for s390. If this is correct, and you do not e.g. need this to make some other use of _refcount, I would suggest to drop this patch. _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um