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Wed, 13 Aug 2025 17:29:44 +0000 (GMT) Received: from tuxmaker.lnxne.boe (unknown [9.152.85.9]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 13 Aug 2025 17:29:44 +0000 (GMT) From: Gerald Schaefer To: stable@vger.kernel.org Cc: Gerald Schaefer , Alexander Gordeev , Claudio Imbrenda Subject: [PATCH 6.6.y] s390/mm: Remove possible false-positive warning in pte_free_defer() Date: Wed, 13 Aug 2025 19:29:17 +0200 Message-ID: <20250813172917.1693059-1-gerald.schaefer@linux.ibm.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <2025081255-shabby-impound-4a47@gregkh> References: <2025081255-shabby-impound-4a47@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Ae7Ow31aKZo9fmwFJEGK20dMz865Csfl X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODEyMDIyNCBTYWx0ZWRfX3QzHA+Of3l3b 9MoZpB/8QxoPg2bQzzrlHWixLlmRY3aADZglgLBuvpHhoSLLJkMjGH3Z456MdG7PUGSaiids8Fx f97//ricebLCsm0lZTVRGXoym/BmqglxUtLPvp89QHOHk6rFdmtdc7A9UiS69Gt9nuMZRfeUj8I usKcU1gYzwedB6i6KQWCUbOXKwhB2tqU/LJyQRpY+JXQ/BGBJhO1oB3wD12vHogPN2dL1R4BV9x nPX844aQpcAW7ruyRaI+OoZMW+ZJAXzQDohbYighqX4r0aNSvku0Ym04yP2Vb73XyHMVtnZ4PK4 LBMBbgCnK16255b+CqK3zwCXY3ZlV/Li7wpEAZH1Y3UbhG+UmOvSOQ5SEQWMn2jU8UzE9nUT0Zd UxzlOrbr X-Proofpoint-GUID: Ae7Ow31aKZo9fmwFJEGK20dMz865Csfl X-Authority-Analysis: v=2.4 cv=fLg53Yae c=1 sm=1 tr=0 ts=689ccb8e cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=2OwXVqhp2XgA:10 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=sPEAky355RQtuwAHJkYA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-13_01,2025-08-11_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1011 spamscore=0 priorityscore=1501 impostorscore=0 phishscore=0 malwarescore=0 bulkscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508120224 Commit 8211dad627981 ("s390: add pte_free_defer() for pgtables sharing page") added a warning to pte_free_defer(), on our request. It was meant to warn if this would ever be reached for KVM guest mappings, because the page table would be freed w/o a gmap_unlink(). THP mappings are not allowed for KVM guests on s390, so this should never happen. However, it is possible that the warning is triggered in a valid case as false-positive. s390_enable_sie() takes the mmap_lock, marks all VMAs as VM_NOHUGEPAGE and splits possibly existing THP guest mappings. mm->context.has_pgste is set to 1 before that, to prevent races with the mm_has_pgste() check in MADV_HUGEPAGE. khugepaged drops the mmap_lock for file mappings and might run in parallel, before a vma is marked VM_NOHUGEPAGE, but after mm->context.has_pgste was set to 1. If it finds file mappings to collapse, it will eventually call pte_free_defer(). This will trigger the warning, but it is a valid case because gmap is not yet set up, and the THP mappings will be split again. Therefore, remove the warning and the comment. Fixes: 8211dad627981 ("s390: add pte_free_defer() for pgtables sharing page") Cc: # 6.6+ Reviewed-by: Alexander Gordeev Reviewed-by: Claudio Imbrenda Signed-off-by: Gerald Schaefer Signed-off-by: Alexander Gordeev (cherry picked from commit 5647f61ad9171e8f025558ed6dc5702c56a33ba3) --- arch/s390/mm/pgalloc.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c index 9355fbe5f51e..2f534b26fda6 100644 --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -456,11 +456,6 @@ void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable) page = virt_to_page(pgtable); SetPageActive(page); page_table_free(mm, (unsigned long *)pgtable); - /* - * page_table_free() does not do the pgste gmap_unlink() which - * page_table_free_rcu() does: warn us if pgste ever reaches here. - */ - WARN_ON_ONCE(mm_has_pgste(mm)); } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ -- 2.48.1