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Message-ID: <202601071005.oEsmtf0J-lkp@intel.com>
Date: Wed, 7 Jan 2026 10:46:12 +0100
From: kernel test robot <lkp@...el.com>
To: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org
Cc: oe-kbuild-all@...ts.linux.dev, david@...nel.org, dave.hansen@...el.com,
dave.hansen@...ux.intel.com, will@...nel.org,
aneesh.kumar@...nel.org, npiggin@...il.com, peterz@...radead.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
hpa@...or.com, arnd@...db.de, lorenzo.stoakes@...cle.com,
ziy@...dia.com, baolin.wang@...ux.alibaba.com,
Liam.Howlett@...cle.com, npache@...hat.com, ryan.roberts@....com,
dev.jain@....com, baohua@...nel.org, shy828301@...il.com,
riel@...riel.com, jannh@...gle.com, linux-arch@...r.kernel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
ioworker0@...il.com, Lance Yang <lance.yang@...ux.dev>
Subject: Re: [PATCH RESEND v3 2/2] mm: introduce pmdp_collapse_flush_sync()
to skip redundant IPI
Hi Lance,
kernel test robot noticed the following build errors:
[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on next-20260107]
[cannot apply to tip/x86/core tip/x86/mm arnd-asm-generic/master linus/master v6.19-rc4]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Lance-Yang/mm-tlb-skip-redundant-IPI-when-TLB-flush-already-synchronized/20260106-200505
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20260106120303.38124-3-lance.yang%40linux.dev
patch subject: [PATCH RESEND v3 2/2] mm: introduce pmdp_collapse_flush_sync() to skip redundant IPI
config: s390-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260107/202601071005.oEsmtf0J-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260107/202601071005.oEsmtf0J-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601071005.oEsmtf0J-lkp@intel.com/
All errors (new ones prefixed by >>):
mm/khugepaged.c: In function 'collapse_huge_page':
>> mm/khugepaged.c:1180:16: error: implicit declaration of function 'pmdp_collapse_flush_sync'; did you mean 'pmdp_collapse_flush'? [-Wimplicit-function-declaration]
1180 | _pmd = pmdp_collapse_flush_sync(vma, address, pmd);
| ^~~~~~~~~~~~~~~~~~~~~~~~
| pmdp_collapse_flush
vim +1180 mm/khugepaged.c
1092
1093 static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long address,
1094 int referenced, int unmapped,
1095 struct collapse_control *cc)
1096 {
1097 LIST_HEAD(compound_pagelist);
1098 pmd_t *pmd, _pmd;
1099 pte_t *pte;
1100 pgtable_t pgtable;
1101 struct folio *folio;
1102 spinlock_t *pmd_ptl, *pte_ptl;
1103 enum scan_result result = SCAN_FAIL;
1104 struct vm_area_struct *vma;
1105 struct mmu_notifier_range range;
1106
1107 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1108
1109 /*
1110 * Before allocating the hugepage, release the mmap_lock read lock.
1111 * The allocation can take potentially a long time if it involves
1112 * sync compaction, and we do not need to hold the mmap_lock during
1113 * that. We will recheck the vma after taking it again in write mode.
1114 */
1115 mmap_read_unlock(mm);
1116
1117 result = alloc_charge_folio(&folio, mm, cc);
1118 if (result != SCAN_SUCCEED)
1119 goto out_nolock;
1120
1121 mmap_read_lock(mm);
1122 result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
1123 if (result != SCAN_SUCCEED) {
1124 mmap_read_unlock(mm);
1125 goto out_nolock;
1126 }
1127
1128 result = find_pmd_or_thp_or_none(mm, address, &pmd);
1129 if (result != SCAN_SUCCEED) {
1130 mmap_read_unlock(mm);
1131 goto out_nolock;
1132 }
1133
1134 if (unmapped) {
1135 /*
1136 * __collapse_huge_page_swapin will return with mmap_lock
1137 * released when it fails. So we jump out_nolock directly in
1138 * that case. Continuing to collapse causes inconsistency.
1139 */
1140 result = __collapse_huge_page_swapin(mm, vma, address, pmd,
1141 referenced);
1142 if (result != SCAN_SUCCEED)
1143 goto out_nolock;
1144 }
1145
1146 mmap_read_unlock(mm);
1147 /*
1148 * Prevent all access to pagetables with the exception of
1149 * gup_fast later handled by the ptep_clear_flush and the VM
1150 * handled by the anon_vma lock + PG_lock.
1151 *
1152 * UFFDIO_MOVE is prevented to race as well thanks to the
1153 * mmap_lock.
1154 */
1155 mmap_write_lock(mm);
1156 result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
1157 if (result != SCAN_SUCCEED)
1158 goto out_up_write;
1159 /* check if the pmd is still valid */
1160 vma_start_write(vma);
1161 result = check_pmd_still_valid(mm, address, pmd);
1162 if (result != SCAN_SUCCEED)
1163 goto out_up_write;
1164
1165 anon_vma_lock_write(vma->anon_vma);
1166
1167 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address,
1168 address + HPAGE_PMD_SIZE);
1169 mmu_notifier_invalidate_range_start(&range);
1170
1171 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1172 /*
1173 * This removes any huge TLB entry from the CPU so we won't allow
1174 * huge and small TLB entries for the same virtual address to
1175 * avoid the risk of CPU bugs in that area.
1176 *
1177 * Parallel GUP-fast is fine since GUP-fast will back off when
1178 * it detects PMD is changed.
1179 */
> 1180 _pmd = pmdp_collapse_flush_sync(vma, address, pmd);
1181 spin_unlock(pmd_ptl);
1182 mmu_notifier_invalidate_range_end(&range);
1183
1184 pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);
1185 if (pte) {
1186 result = __collapse_huge_page_isolate(vma, address, pte, cc,
1187 &compound_pagelist);
1188 spin_unlock(pte_ptl);
1189 } else {
1190 result = SCAN_NO_PTE_TABLE;
1191 }
1192
1193 if (unlikely(result != SCAN_SUCCEED)) {
1194 if (pte)
1195 pte_unmap(pte);
1196 spin_lock(pmd_ptl);
1197 BUG_ON(!pmd_none(*pmd));
1198 /*
1199 * We can only use set_pmd_at when establishing
1200 * hugepmds and never for establishing regular pmds that
1201 * points to regular pagetables. Use pmd_populate for that
1202 */
1203 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1204 spin_unlock(pmd_ptl);
1205 anon_vma_unlock_write(vma->anon_vma);
1206 goto out_up_write;
1207 }
1208
1209 /*
1210 * All pages are isolated and locked so anon_vma rmap
1211 * can't run anymore.
1212 */
1213 anon_vma_unlock_write(vma->anon_vma);
1214
1215 result = __collapse_huge_page_copy(pte, folio, pmd, _pmd,
1216 vma, address, pte_ptl,
1217 &compound_pagelist);
1218 pte_unmap(pte);
1219 if (unlikely(result != SCAN_SUCCEED))
1220 goto out_up_write;
1221
1222 /*
1223 * The smp_wmb() inside __folio_mark_uptodate() ensures the
1224 * copy_huge_page writes become visible before the set_pmd_at()
1225 * write.
1226 */
1227 __folio_mark_uptodate(folio);
1228 pgtable = pmd_pgtable(_pmd);
1229
1230 spin_lock(pmd_ptl);
1231 BUG_ON(!pmd_none(*pmd));
1232 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1233 map_anon_folio_pmd_nopf(folio, pmd, vma, address);
1234 spin_unlock(pmd_ptl);
1235
1236 folio = NULL;
1237
1238 result = SCAN_SUCCEED;
1239 out_up_write:
1240 mmap_write_unlock(mm);
1241 out_nolock:
1242 if (folio)
1243 folio_put(folio);
1244 trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
1245 return result;
1246 }
1247
--
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https://github.com/intel/lkp-tests/wiki
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