[kbuild-all] Re: [PATCH v2 4/6] mm/mremap: Use mmu gather interface instead of flush_tlb_range

Hi "Aneesh, I love your patch! Yet something to improve: [auto build test ERROR on powerpc/next] [also build test ERROR on kselftest/next v5.12-rc3 next-20210317] [cannot apply to hnaz-linux-mm/master] [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] url: https://github.com/0day-ci/linux/commits/Aneesh-Kumar-K-V/Speedup-mremap-... base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next config: x86_64-rhel-8.3 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://github.com/0day-ci/linux/commit/d3b9a3e6f414413d8f822185158b937d9... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Aneesh-Kumar-K-V/Speedup-mremap-on-ppc64/20210315-194324 git checkout d3b9a3e6f414413d8f822185158b937d9f19b7a6 # save the attached .config to linux build tree make W=1 ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; Note: the linux-review/Aneesh-Kumar-K-V/Speedup-mremap-on-ppc64/20210315-194324 HEAD 79633714ff2b990b3e4972873457678bb34d029f builds fine. It only hurts bisectibility. All errors (new ones prefixed by >>): mm/mremap.c: In function 'move_normal_pmd': 219 | struct mmu_gather tlb; | ^~~ 267 | tlb_flush_pte_range(&tlb, old_addr, PMD_SIZE); | ^~~~~~~~~~~~~~~~~~~ mm/mremap.c:219:20: warning: unused variable 'tlb' [-Wunused-variable] 219 | struct mmu_gather tlb; | ^~~ mm/mremap.c: In function 'move_normal_pud': mm/mremap.c:297:20: error: storage size of 'tlb' isn't known 297 | struct mmu_gather tlb; | ^~~ mm/mremap.c:297:20: warning: unused variable 'tlb' [-Wunused-variable] cc1: some warnings being treated as errors vim +219 mm/mremap.c 212 213 #ifdef CONFIG_HAVE_MOVE_PMD 214 static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, 215 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) 216 { 217 spinlock_t *old_ptl, *new_ptl; 218 struct mm_struct *mm = vma->vm_mm; 220 pmd_t pmd; 221 222 /* 223 * The destination pmd shouldn't be established, free_pgtables() 224 * should have released it. 225 * 226 * However, there's a case during execve() where we use mremap 227 * to move the initial stack, and in that case the target area 228 * may overlap the source area (always moving down). 229 * 230 * If everything is PMD-aligned, that works fine, as moving 231 * each pmd down will clear the source pmd. But if we first 232 * have a few 4kB-only pages that get moved down, and then 233 * hit the "now the rest is PMD-aligned, let's do everything 234 * one pmd at a time", we will still have the old (now empty 235 * of any 4kB pages, but still there) PMD in the page table 236 * tree. 237 * 238 * Warn on it once - because we really should try to figure 239 * out how to do this better - but then say "I won't move 240 * this pmd". 241 * 242 * One alternative might be to just unmap the target pmd at 243 * this point, and verify that it really is empty. We'll see. 244 */ 245 if (WARN_ON_ONCE(!pmd_none(*new_pmd))) 246 return false; 247 248 tlb_gather_mmu(&tlb, mm); 249 /* 250 * We don't have to worry about the ordering of src and dst 251 * ptlocks because exclusive mmap_lock prevents deadlock. 252 */ 253 old_ptl = pmd_lock(mm, old_pmd); 254 new_ptl = pmd_lockptr(mm, new_pmd); 255 if (new_ptl != old_ptl) 256 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 257 258 /* Clear the pmd */ 259 pmd = *old_pmd; 260 pmd_clear(old_pmd); 261 262 /* 263 * Mark the range. We are not freeing page table pages nor 264 * regular pages. Hence we don't need to call tlb_remove_table() 265 * or tlb_remove_page(). 266 */ 268 tlb.freed_tables = 1; 269 VM_BUG_ON(!pmd_none(*new_pmd)); 270 pmd_populate(mm, new_pmd, (pgtable_t)pmd_page_vaddr(pmd)); 271 272 if (new_ptl != old_ptl) 273 spin_unlock(new_ptl); 274 spin_unlock(old_ptl); 275 /* 276 * This will invalidate both the old TLB and page table walk caches. 277 */ 278 tlb_finish_mmu(&tlb); 279 280 return true; 281 } 282 #else 283 static inline bool move_normal_pmd(struct vm_area_struct *vma, 284 unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd, 285 pmd_t *new_pmd) 286 { 287 return false; 288 } 289 #endif 290 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org