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Fri, 13 Nov 2026 11:31:49 +0000 (GMT) Received: from osiris (unknown [9.111.48.15]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 13 Nov 2026 11:31:49 +0000 (GMT) Date: Fri, 13 Nov 2026 12:31:48 +0100 From: Heiko Carstens To: Alexander Gordeev Cc: Gerald Schaefer , linux-s390 , Christian Borntraeger , Ilya Leoshkevich Subject: Re: [PATCH v2] s390/mm: Allow hugepage migration for s390 Message-ID: <20261113113148.28437A08-hca@linux.ibm.com> References: <20261111182944.4154805-1-gerald.schaefer@linux.ibm.com> <76c9d6b0-77d3-46df-9c64-e4489b5a92c7-agordeev@linux.ibm.com> X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <76c9d6b0-77d3-46df-9c64-e4489b5a92c7-agordeev@linux.ibm.com> X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=POqaavqC c=1 sm=1 tr=0 ts=6af6f52a cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=kj9zAlcOel0A:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=iZIUybvRM2fWnCdp4i8A:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTEzMDA0NCBTYWx0ZWRfXxkkUYn8hpIIu ZClQ7T/dngimK/jzz03ckXRDh6XwDORZFBeS0qZnnDJEP96kMq658dJmXSZqM45bwr716U8HPkO RMKWwUbO2sC5SxgUM4L8ccIcl79I4z62ONmHiAqoSf/NwbfuOGcYIv/s1aOmlWvQsxitaAxSyeq 0sdcsUVT1stPZUy0UCoczE0KGPgUY07mSboMbBjYDwGZJyIPDHomcxi5eLbqjfX5Y+ViigVQho5 yGXmg6rE+fxsfr/FTooMolz1/FkQ89GVljTUa8qNfi5j1XxoPOvFSy2KNcY57chQvYu+5IYcV4f thgslvtivU/d3qHoeDfu0cGtjPIk1n42b9/Tg4J2hF2kfk6eF/iaSSNePazfipJCrdMqj9pznSZ qam9KwTpvOkkaPusdaglMrd4X/vpcg+CnA05bY+X7wr07OZgISs6EXCoiBKxg8O9wSbmrcpd1f6 Xbsk55uaL85hsUcufEg== X-Proofpoint-Spam-Info: AW1haW4tMjYxMTEzMDA0NCBTYWx0ZWRfX4S/I1vQ+eej2 46gNqvfyoz7V3+7RV2j+q/Hh19456vA/pMWi4jfxPZbmLf8nqOi25IH6ufxEUC6/k+gGjxu5SNq b9rnk/erxQARQ4q2lz7JGvyar3e3qP8= X-Proofpoint-ORIG-GUID: 9-h0mEZTzBvFiMVytqM2A1IVrnHV_7G1 X-Proofpoint-GUID: 9-h0mEZTzBvFiMVytqM2A1IVrnHV_7G1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-13_03,2026-11-11_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 impostorscore=0 malwarescore=0 phishscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 spamscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611130044 On Thu, Nov 12, 2026 at 08:54:51AM +0100, Alexander Gordeev wrote: > On Wed, Nov 11, 2026 at 07:29:44PM +0100, Gerald Schaefer wrote: > > > +#if IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION) > > +bool arch_hugetlb_migration_supported(struct hstate *h) > > +{ > > Oh, would you agree to such one? ;) > > return IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION) && > __hugetlb_valid_size(huge_page_size(h)); > > > + return __hugetlb_valid_size(huge_page_size(h)); > > +} > > +#endif Out of curiosity: why? All other architectures do ifdef, instead if IS_ENABLED to make sure the function exists only if the config option is enabled (IS_ENABLED would also make sense if "m" would be a possible option, but that is not the case here). Then if this is only inline within the function, like suggested above, the prototype in the header does not exist (rightfully), leading to compile time warnings. The arch_hugetlb_migration_supported define also indicates the availability of the feature. So I'm wondering what the point of this exercise is and what the deviation compared to other architectures would buy us.