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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)" 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; x86_64-redhat-linux-gnu) Content-Type: text/plain; charset=US-ASCII X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: NZnx_8FojkhNAEEWitWpik8jaNZSNqYi X-Proofpoint-GUID: URInLnYnsG8BZV2VGVY1OnfgESTv3EvD Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.176.26 definitions=2023-06-01_08,2023-05-31_03,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 spamscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 suspectscore=0 impostorscore=0 bulkscore=0 mlxscore=0 phishscore=0 mlxlogscore=692 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2304280000 definitions=main-2306010115 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, linux-sh@vger.kernel.org, linux-openrisc@vger.kernel.org, Matthew Wilcox , sparclinux@vger.kernel.org, Alexander Gordeev , Claudio Imbrenda , linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, linux-hexagon@vger.kernel.org, David Hildenbrand , Hugh Dickins , linux-csky@vger.kernel.org, xen-devel@lists.xenproject.org, Christian Borntraeger , Vasily Gorbik , Heiko Carstens , linux-um@lists.infradead.org, linux-m68k@lists.linux-m68k.org, loongarch@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-mips@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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.