Re: [PATCH] mm/vmstat: add events for ksm cow
From: kernel test robot
Date: Wed Mar 23 2022 - 02:30:28 EST
Hi,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on hnaz-mm/master]
url: https://github.com/0day-ci/linux/commits/cgel-zte-gmail-com/mm-vmstat-add-events-for-ksm-cow/20220323-111932
base: https://github.com/hnaz/linux-mm master
config: nios2-defconfig (https://download.01.org/0day-ci/archive/20220323/202203231454.DszZMI5Y-lkp@xxxxxxxxx/config)
compiler: nios2-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/cc1a5f6c95b38b1bebb673c7fe3a2b64e2362acc
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review cgel-zte-gmail-com/mm-vmstat-add-events-for-ksm-cow/20220323-111932
git checkout cc1a5f6c95b38b1bebb673c7fe3a2b64e2362acc
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=nios2 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
All errors (new ones prefixed by >>):
mm/memory.c: In function 'do_wp_page':
>> mm/memory.c:3341:40: error: 'KSM_COW_FAIL' undeclared (first use in this function)
3341 | count_vm_event(KSM_COW_FAIL);
| ^~~~~~~~~~~~
mm/memory.c:3341:40: note: each undeclared identifier is reported only once for each function it appears in
>> mm/memory.c:3343:40: error: 'KSM_COW_SUCCESS' undeclared (first use in this function)
3343 | count_vm_event(KSM_COW_SUCCESS);
| ^~~~~~~~~~~~~~~
vim +/KSM_COW_FAIL +3341 mm/memory.c
3229
3230 /*
3231 * This routine handles present pages, when users try to write
3232 * to a shared page. It is done by copying the page to a new address
3233 * and decrementing the shared-page counter for the old page.
3234 *
3235 * Note that this routine assumes that the protection checks have been
3236 * done by the caller (the low-level page fault routine in most cases).
3237 * Thus we can safely just mark it writable once we've done any necessary
3238 * COW.
3239 *
3240 * We also mark the page dirty at this point even though the page will
3241 * change only once the write actually happens. This avoids a few races,
3242 * and potentially makes it more efficient.
3243 *
3244 * We enter with non-exclusive mmap_lock (to exclude vma changes,
3245 * but allow concurrent faults), with pte both mapped and locked.
3246 * We return with mmap_lock still held, but pte unmapped and unlocked.
3247 */
3248 static vm_fault_t do_wp_page(struct vm_fault *vmf)
3249 __releases(vmf->ptl)
3250 {
3251 struct vm_area_struct *vma = vmf->vma;
3252 vm_fault_t ret = 0;
3253 bool ksm = 0;
3254
3255 if (userfaultfd_pte_wp(vma, *vmf->pte)) {
3256 pte_unmap_unlock(vmf->pte, vmf->ptl);
3257 return handle_userfault(vmf, VM_UFFD_WP);
3258 }
3259
3260 /*
3261 * Userfaultfd write-protect can defer flushes. Ensure the TLB
3262 * is flushed in this case before copying.
3263 */
3264 if (unlikely(userfaultfd_wp(vmf->vma) &&
3265 mm_tlb_flush_pending(vmf->vma->vm_mm)))
3266 flush_tlb_page(vmf->vma, vmf->address);
3267
3268 vmf->page = vm_normal_page(vma, vmf->address, vmf->orig_pte);
3269 if (!vmf->page) {
3270 /*
3271 * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a
3272 * VM_PFNMAP VMA.
3273 *
3274 * We should not cow pages in a shared writeable mapping.
3275 * Just mark the pages writable and/or call ops->pfn_mkwrite.
3276 */
3277 if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
3278 (VM_WRITE|VM_SHARED))
3279 return wp_pfn_shared(vmf);
3280
3281 pte_unmap_unlock(vmf->pte, vmf->ptl);
3282 return wp_page_copy(vmf);
3283 }
3284
3285 /*
3286 * Take out anonymous pages first, anonymous shared vmas are
3287 * not dirty accountable.
3288 */
3289 if (PageAnon(vmf->page)) {
3290 struct page *page = vmf->page;
3291 ksm = PageKsm(page);
3292
3293 /*
3294 * We have to verify under page lock: these early checks are
3295 * just an optimization to avoid locking the page and freeing
3296 * the swapcache if there is little hope that we can reuse.
3297 *
3298 * PageKsm() doesn't necessarily raise the page refcount.
3299 */
3300 if (ksm || page_count(page) > 3)
3301 goto copy;
3302 if (!PageLRU(page))
3303 /*
3304 * Note: We cannot easily detect+handle references from
3305 * remote LRU pagevecs or references to PageLRU() pages.
3306 */
3307 lru_add_drain();
3308 if (page_count(page) > 1 + PageSwapCache(page))
3309 goto copy;
3310 if (!trylock_page(page))
3311 goto copy;
3312 if (PageSwapCache(page))
3313 try_to_free_swap(page);
3314 if (ksm || page_count(page) != 1) {
3315 unlock_page(page);
3316 goto copy;
3317 }
3318 /*
3319 * Ok, we've got the only page reference from our mapping
3320 * and the page is locked, it's dark out, and we're wearing
3321 * sunglasses. Hit it.
3322 */
3323 unlock_page(page);
3324 wp_page_reuse(vmf);
3325 return VM_FAULT_WRITE;
3326 } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
3327 (VM_WRITE|VM_SHARED))) {
3328 return wp_page_shared(vmf);
3329 }
3330 copy:
3331 /*
3332 * Ok, we need to copy. Oh, well..
3333 */
3334 get_page(vmf->page);
3335
3336 pte_unmap_unlock(vmf->pte, vmf->ptl);
3337 ret = wp_page_copy(vmf);
3338
3339 if (ksm) {
3340 if (unlikely(ret & VM_FAULT_ERROR))
> 3341 count_vm_event(KSM_COW_FAIL);
3342 else
> 3343 count_vm_event(KSM_COW_SUCCESS);
3344 }
3345
3346 return ret;
3347 }
3348
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