diff options
| -rw-r--r-- | include/linux/rmap.h | 6 | ||||
| -rw-r--r-- | mm/internal.h | 2 | ||||
| -rw-r--r-- | mm/mlock.c | 375 | ||||
| -rw-r--r-- | mm/rmap.c | 80 |
4 files changed, 25 insertions, 438 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index e704b1a4c06c..dc48aa8c2c94 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -237,12 +237,6 @@ unsigned long page_address_in_vma(struct page *, struct vm_area_struct *); */ int folio_mkclean(struct folio *); -/* - * called in munlock()/munmap() path to check for other vmas holding - * the page mlocked. - */ -void page_mlock(struct page *page); - void remove_migration_ptes(struct page *old, struct page *new, bool locked); /* diff --git a/mm/internal.h b/mm/internal.h index d80300392a19..e48c486d5ddf 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -409,7 +409,7 @@ static inline void munlock_vma_pages_all(struct vm_area_struct *vma) * must be called with vma's mmap_lock held for read or write, and page locked. */ extern void mlock_vma_page(struct page *page); -extern unsigned int munlock_vma_page(struct page *page); +extern void munlock_vma_page(struct page *page); extern int mlock_future_check(struct mm_struct *mm, unsigned long flags, unsigned long len); diff --git a/mm/mlock.c b/mm/mlock.c index 8f584eddd305..aec4ce7919da 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -46,12 +46,6 @@ EXPORT_SYMBOL(can_do_mlock); * be placed on the LRU "unevictable" list, rather than the [in]active lists. * The unevictable list is an LRU sibling list to the [in]active lists. * PageUnevictable is set to indicate the unevictable state. - * - * When lazy mlocking via vmscan, it is important to ensure that the - * vma's VM_LOCKED status is not concurrently being modified, otherwise we - * may have mlocked a page that is being munlocked. So lazy mlock must take - * the mmap_lock for read, and verify that the vma really is locked - * (see mm/rmap.c). */ /* @@ -106,299 +100,28 @@ void mlock_vma_page(struct page *page) } } -/* - * Finish munlock after successful page isolation - * - * Page must be locked. This is a wrapper for page_mlock() - * and putback_lru_page() with munlock accounting. - */ -static void __munlock_isolated_page(struct page *page) -{ - /* - * Optimization: if the page was mapped just once, that's our mapping - * and we don't need to check all the other vmas. - */ - if (page_mapcount(page) > 1) - page_mlock(page); - - /* Did try_to_unlock() succeed or punt? */ - if (!PageMlocked(page)) - count_vm_events(UNEVICTABLE_PGMUNLOCKED, thp_nr_pages(page)); - - putback_lru_page(page); -} - -/* - * Accounting for page isolation fail during munlock - * - * Performs accounting when page isolation fails in munlock. There is nothing - * else to do because it means some other task has already removed the page - * from the LRU. putback_lru_page() will take care of removing the page from - * the unevictable list, if necessary. vmscan [page_referenced()] will move - * the page back to the unevictable list if some other vma has it mlocked. - */ -static void __munlock_isolation_failed(struct page *page) -{ - int nr_pages = thp_nr_pages(page); - - if (PageUnevictable(page)) - __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages); - else - __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages); -} - /** * munlock_vma_page - munlock a vma page * @page: page to be unlocked, either a normal page or THP page head - * - * returns the size of the page as a page mask (0 for normal page, - * HPAGE_PMD_NR - 1 for THP head page) - * - * called from munlock()/munmap() path with page supposedly on the LRU. - * When we munlock a page, because the vma where we found the page is being - * munlock()ed or munmap()ed, we want to check whether other vmas hold the - * page locked so that we can leave it on the unevictable lru list and not - * bother vmscan with it. However, to walk the page's rmap list in - * page_mlock() we must isolate the page from the LRU. If some other - * task has removed the page from the LRU, we won't be able to do that. - * So we clear the PageMlocked as we might not get another chance. If we - * can't isolate the page, we leave it for putback_lru_page() and vmscan - * [page_referenced()/try_to_unmap()] to deal with. */ -unsigned int munlock_vma_page(struct page *page) +void munlock_vma_page(struct page *page) { - int nr_pages; - - /* For page_mlock() and to serialize with page migration */ + /* Serialize with page migration */ BUG_ON(!PageLocked(page)); - VM_BUG_ON_PAGE(PageTail(page), page); - - if (!TestClearPageMlocked(page)) { - /* Potentially, PTE-mapped THP: do not skip the rest PTEs */ - return 0; - } - - nr_pages = thp_nr_pages(page); - mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages); - - if (!isolate_lru_page(page)) - __munlock_isolated_page(page); - else - __munlock_isolation_failed(page); - - return nr_pages - 1; -} - -/* - * convert get_user_pages() return value to posix mlock() error - */ -static int __mlock_posix_error_return(long retval) -{ - if (retval == -EFAULT) - retval = -ENOMEM; - else if (retval == -ENOMEM) - retval = -EAGAIN; - return retval; -} - -/* - * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec() - * - * The fast path is available only for evictable pages with single mapping. - * Then we can bypass the per-cpu pvec and get better performance. - * when mapcount > 1 we need page_mlock() which can fail. - * when !page_evictable(), we need the full redo logic of putback_lru_page to - * avoid leaving evictable page in unevictable list. - * - * In case of success, @page is added to @pvec and @pgrescued is incremented - * in case that the page was previously unevictable. @page is also unlocked. - */ -static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec, - int *pgrescued) -{ - VM_BUG_ON_PAGE(PageLRU(page), page); - VM_BUG_ON_PAGE(!PageLocked(page), page); - - if (page_mapcount(page) <= 1 && page_evictable(page)) { - pagevec_add(pvec, page); - if (TestClearPageUnevictable(page)) - (*pgrescued)++; - unlock_page(page); - return true; - } - - return false; -} -/* - * Putback multiple evictable pages to the LRU - * - * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of - * the pages might have meanwhile become unevictable but that is OK. - */ -static void __putback_lru_fast(struct pagevec *pvec, int pgrescued) -{ - count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec)); - /* - *__pagevec_lru_add() calls release_pages() so we don't call - * put_page() explicitly - */ - __pagevec_lru_add(pvec); - count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); -} - -/* - * Munlock a batch of pages from the same zone - * - * The work is split to two main phases. First phase clears the Mlocked flag - * and attempts to isolate the pages, all under a single zone lru lock. - * The second phase finishes the munlock only for pages where isolation - * succeeded. - * - * Note that the pagevec may be modified during the process. - */ -static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) -{ - int i; - int nr = pagevec_count(pvec); - int delta_munlocked = -nr; - struct pagevec pvec_putback; - struct lruvec *lruvec = NULL; - int pgrescued = 0; - - pagevec_init(&pvec_putback); - - /* Phase 1: page isolation */ - for (i = 0; i < nr; i++) { - struct page *page = pvec->pages[i]; - struct folio *folio = page_folio(page); - - if (TestClearPageMlocked(page)) { - /* - * We already have pin from follow_page_mask() - * so we can spare the get_page() here. - */ - if (TestClearPageLRU(page)) { - lruvec = folio_lruvec_relock_irq(folio, lruvec); - del_page_from_lru_list(page, lruvec); - continue; - } else - __munlock_isolation_failed(page); - } else { - delta_munlocked++; - } + VM_BUG_ON_PAGE(PageTail(page), page); - /* - * We won't be munlocking this page in the next phase - * but we still need to release the follow_page_mask() - * pin. We cannot do it under lru_lock however. If it's - * the last pin, __page_cache_release() would deadlock. - */ - pagevec_add(&pvec_putback, pvec->pages[i]); - pvec->pages[i] = NULL; - } - if (lruvec) { - __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked); - unlock_page_lruvec_irq(lruvec); - } else if (delta_munlocked) { - mod_zone_page_state(zone, NR_MLOCK, delta_munlocked); - } + if (TestClearPageMlocked(page)) { + int nr_pages = thp_nr_pages(page); - /* Now we can release pins of pages that we are not munlocking */ - pagevec_release(&pvec_putback); - - /* Phase 2: page munlock */ - for (i = 0; i < nr; i++) { - struct page *page = pvec->pages[i]; - - if (page) { - lock_page(page); - if (!__putback_lru_fast_prepare(page, &pvec_putback, - &pgrescued)) { - /* - * Slow path. We don't want to lose the last - * pin before unlock_page() - */ - get_page(page); /* for putback_lru_page() */ - __munlock_isolated_page(page); - unlock_page(page); - put_page(page); /* from follow_page_mask() */ - } + mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages); + if (!isolate_lru_page(page)) { + putback_lru_page(page); + count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages); + } else if (PageUnevictable(page)) { + count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages); } } - - /* - * Phase 3: page putback for pages that qualified for the fast path - * This will also call put_page() to return pin from follow_page_mask() - */ - if (pagevec_count(&pvec_putback)) - __putback_lru_fast(&pvec_putback, pgrescued); -} - -/* - * Fill up pagevec for __munlock_pagevec using pte walk - * - * The function expects that the struct page corresponding to @start address is - * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone. - * - * The rest of @pvec is filled by subsequent pages within the same pmd and same - * zone, as long as the pte's are present and vm_normal_page() succeeds. These - * pages also get pinned. - * - * Returns the address of the next page that should be scanned. This equals - * @start + PAGE_SIZE when no page could be added by the pte walk. - */ -static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, - struct vm_area_struct *vma, struct zone *zone, - unsigned long start, unsigned long end) -{ - pte_t *pte; - spinlock_t *ptl; - - /* - * Initialize pte walk starting at the already pinned page where we - * are sure that there is a pte, as it was pinned under the same - * mmap_lock write op. - */ - pte = get_locked_pte(vma->vm_mm, start, &ptl); - /* Make sure we do not cross the page table boundary */ - end = pgd_addr_end(start, end); - end = p4d_addr_end(start, end); - end = pud_addr_end(start, end); - end = pmd_addr_end(start, end); - - /* The page next to the pinned page is the first we will try to get */ - start += PAGE_SIZE; - while (start < end) { - struct page *page = NULL; - pte++; - if (pte_present(*pte)) - page = vm_normal_page(vma, start, *pte); - /* - * Break if page could not be obtained or the page's node+zone does not - * match - */ - if (!page || page_zone(page) != zone) - break; - - /* - * Do not use pagevec for PTE-mapped THP, - * munlock_vma_pages_range() will handle them. - */ - if (PageTransCompound(page)) - break; - - get_page(page); - /* - * Increase the address that will be returned *before* the - * eventual break due to pvec becoming full by adding the page - */ - start += PAGE_SIZE; - if (pagevec_add(pvec, page) == 0) - break; - } - pte_unmap_unlock(pte, ptl); - return start; } /* @@ -413,75 +136,13 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, * * Returns with VM_LOCKED cleared. Callers must be prepared to * deal with this. - * - * We don't save and restore VM_LOCKED here because pages are - * still on lru. In unmap path, pages might be scanned by reclaim - * and re-mlocked by page_mlock/try_to_unmap before we unmap and - * free them. This will result in freeing mlocked pages. */ void munlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end) { vma->vm_flags &= VM_LOCKED_CLEAR_MASK; - while (start < end) { - struct page *page; - unsigned int page_mask = 0; - unsigned long page_increm; - struct pagevec pvec; - struct zone *zone; - - pagevec_init(&pvec); - /* - * Although FOLL_DUMP is intended for get_dump_page(), - * it just so happens that its special treatment of the - * ZERO_PAGE (returning an error instead of doing get_page) - * suits munlock very well (and if somehow an abnormal page - * has sneaked into the range, we won't oops here: great). - */ - page = follow_page(vma, start, FOLL_GET | FOLL_DUMP); - - if (page && !IS_ERR(page)) { - if (PageTransTail(page)) { - VM_BUG_ON_PAGE(PageMlocked(page), page); - put_page(page); /* follow_page_mask() */ - } else if (PageTransHuge(page)) { - lock_page(page); - /* - * Any THP page found by follow_page_mask() may - * have gotten split before reaching - * munlock_vma_page(), so we need to compute - * the page_mask here instead. - */ - page_mask = munlock_vma_page(page); - unlock_page(page); - put_page(page); /* follow_page_mask() */ - } else { - /* - * Non-huge pages are handled in batches via - * pagevec. The pin from follow_page_mask() - * prevents them from collapsing by THP. - */ - pagevec_add(&pvec, page); - zone = page_zone(page); - - /* - * Try to fill the rest of pagevec using fast - * pte walk. This will also update start to - * the next page to process. Then munlock the - * pagevec. - */ - start = __munlock_pagevec_fill(&pvec, vma, - zone, start, end); - __munlock_pagevec(&pvec, zone); - goto next; - } - } - page_increm = 1 + page_mask; - start += page_increm * PAGE_SIZE; -next: - cond_resched(); - } + /* Reimplementation to follow in later commit */ } /* @@ -645,6 +306,18 @@ static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm, return count >> PAGE_SHIFT; } +/* + * convert get_user_pages() return value to posix mlock() error + */ +static int __mlock_posix_error_return(long retval) +{ + if (retval == -EFAULT) + retval = -ENOMEM; + else if (retval == -ENOMEM) + retval = -EAGAIN; + return retval; +} + static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags) { unsigned long locked; diff --git a/mm/rmap.c b/mm/rmap.c index 6a1e8c7f6213..7ce7f1946cff 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1996,76 +1996,6 @@ void try_to_migrate(struct page *page, enum ttu_flags flags) rmap_walk(page, &rwc); } -/* - * Walks the vma's mapping a page and mlocks the page if any locked vma's are - * found. Once one is found the page is locked and the scan can be terminated. - */ -static bool page_mlock_one(struct page *page, struct vm_area_struct *vma, - unsigned long address, void *unused) -{ - struct page_vma_mapped_walk pvmw = { - .page = page, - .vma = vma, - .address = address, - }; - - /* An un-locked vma doesn't have any pages to lock, continue the scan */ - if (!(vma->vm_flags & VM_LOCKED)) - return true; - - while (page_vma_mapped_walk(&pvmw)) { - /* - * Need to recheck under the ptl to serialise with - * __munlock_pagevec_fill() after VM_LOCKED is cleared in - * munlock_vma_pages_range(). - */ - if (vma->vm_flags & VM_LOCKED) { - /* - * PTE-mapped THP are never marked as mlocked; but - * this function is never called on a DoubleMap THP, - * nor on an Anon THP (which may still be PTE-mapped - * after DoubleMap was cleared). - */ - mlock_vma_page(page); - /* - * No need to scan further once the page is marked - * as mlocked. - */ - page_vma_mapped_walk_done(&pvmw); - return false; - } - } - - return true; -} - -/** - * page_mlock - try to mlock a page - * @page: the page to be mlocked - * - * Called from munlock code. Checks all of the VMAs mapping the page and mlocks - * the page if any are found. The page will be returned with PG_mlocked cleared - * if it is not mapped by any locked vmas. - */ -void page_mlock(struct page *page) -{ - struct rmap_walk_control rwc = { - .rmap_one = page_mlock_one, - .done = page_not_mapped, - .anon_lock = page_lock_anon_vma_read, - - }; - - VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); - VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page); - - /* Anon THP are only marked as mlocked when singly mapped */ - if (PageTransCompound(page) && PageAnon(page)) - return; - - rmap_walk(page, &rwc); -} - #ifdef CONFIG_DEVICE_PRIVATE struct make_exclusive_args { struct mm_struct *mm; @@ -2291,11 +2221,6 @@ static struct anon_vma *rmap_walk_anon_lock(struct page *page, * * Find all the mappings of a page using the mapping pointer and the vma chains * contained in the anon_vma struct it points to. - * - * When called from page_mlock(), the mmap_lock of the mm containing the vma - * where the page was found will be held for write. So, we won't recheck - * vm_flags for that VMA. That should be OK, because that vma shouldn't be - * LOCKED. */ static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc, bool locked) @@ -2344,11 +2269,6 @@ static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc, * * Find all the mappings of a page using the mapping pointer and the vma chains * contained in the address_space struct it points to. - * - * When called from page_mlock(), the mmap_lock of the mm containing the vma - * where the page was found will be held for write. So, we won't recheck - * vm_flags for that VMA. That should be OK, because that vma shouldn't be - * LOCKED. */ static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc, bool locked) |