From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerald Schaefer Subject: Re: [PATCH v3 03/34] s390: Use pt_frag_refcount for pagetables Date: Thu, 1 Jun 2023 15:19:00 +0200 Message-ID: <20230601151900.6f184e8c@thinkpad-T15> References: <20230531213032.25338-1-vishal.moola@gmail.com> <20230531213032.25338-4-vishal.moola@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : in-reply-to : references : content-type : content-transfer-encoding : mime-version; s=pp1; bh=tTBWxMHAGeJlpPAzqjw4yCDaupaYk6+WOuZ0r7RHXlQ=; b=S/K5bR2wzWD8jF0s2LtK3vF/J1ec5Pw9lqbPdCL6ZXZARzxk77m6XthOAVrzcENBYS/e ov9SEtmnnKsZTXa99Jk5hlMimhCPtmwo+YCJttdvMRkZI8Kj3tec3MJCAkANML7vJgEN mm82HHoVVpteTT1109f2h3OEi5Dtya1+qWK/izBLKcrhp4adRtqmgRrMH7o6BtITpGsV XQajjlwcskrHiNYJ0m2IzKlfajqLyEOsVlAvnpMojNTW61NI6Y/l6FXM9CcrwKrRoiRU 5yYyiViugHG/GJk6Dj84G7GFPGbzxZudOaESQkF8/B03VEx03rqx3lIPkJn/GXcV7VmA dQ== In-Reply-To: <20230531213032.25338-4-vishal.moola@gmail.com> List-ID: Content-Type: text/plain; charset="us-ascii" 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 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.