forked from luck/tmp_suning_uos_patched
mm: Convert collapse_shmem to XArray
I found another victim of the radix tree being hard to use. Because there was no call to radix_tree_preload(), khugepaged was allocating radix_tree_nodes using GFP_ATOMIC. I also converted a local_irq_save()/restore() pair to disable()/enable(). Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox
parent
aa5dc07f70
commit
77da9389b9
159
mm/khugepaged.c
159
mm/khugepaged.c
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@ -1288,17 +1288,17 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
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*
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* Basic scheme is simple, details are more complex:
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* - allocate and freeze a new huge page;
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* - scan over radix tree replacing old pages the new one
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* - scan page cache replacing old pages with the new one
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* + swap in pages if necessary;
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* + fill in gaps;
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* + keep old pages around in case if rollback is required;
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* - if replacing succeed:
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* + keep old pages around in case rollback is required;
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* - if replacing succeeds:
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* + copy data over;
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* + free old pages;
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* + unfreeze huge page;
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* - if replacing failed;
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* + put all pages back and unfreeze them;
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* + restore gaps in the radix-tree;
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* + restore gaps in the page cache;
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* + free huge page;
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*/
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static void collapse_shmem(struct mm_struct *mm,
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@ -1306,12 +1306,11 @@ static void collapse_shmem(struct mm_struct *mm,
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struct page **hpage, int node)
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{
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gfp_t gfp;
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struct page *page, *new_page, *tmp;
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struct page *new_page;
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struct mem_cgroup *memcg;
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pgoff_t index, end = start + HPAGE_PMD_NR;
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LIST_HEAD(pagelist);
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struct radix_tree_iter iter;
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void **slot;
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XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
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int nr_none = 0, result = SCAN_SUCCEED;
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VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
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@ -1336,48 +1335,49 @@ static void collapse_shmem(struct mm_struct *mm,
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__SetPageLocked(new_page);
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BUG_ON(!page_ref_freeze(new_page, 1));
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/*
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* At this point the new_page is 'frozen' (page_count() is zero), locked
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* and not up-to-date. It's safe to insert it into radix tree, because
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* nobody would be able to map it or use it in other way until we
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* unfreeze it.
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* At this point the new_page is 'frozen' (page_count() is zero),
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* locked and not up-to-date. It's safe to insert it into the page
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* cache, because nobody would be able to map it or use it in other
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* way until we unfreeze it.
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*/
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index = start;
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xa_lock_irq(&mapping->i_pages);
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radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
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int n = min(iter.index, end) - index;
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/*
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* Handle holes in the radix tree: charge it from shmem and
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* insert relevant subpage of new_page into the radix-tree.
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*/
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if (n && !shmem_charge(mapping->host, n)) {
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result = SCAN_FAIL;
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/* This will be less messy when we use multi-index entries */
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do {
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xas_lock_irq(&xas);
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xas_create_range(&xas);
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if (!xas_error(&xas))
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break;
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}
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nr_none += n;
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for (; index < min(iter.index, end); index++) {
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radix_tree_insert(&mapping->i_pages, index,
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new_page + (index % HPAGE_PMD_NR));
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xas_unlock_irq(&xas);
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if (!xas_nomem(&xas, GFP_KERNEL))
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goto out;
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} while (1);
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xas_set(&xas, start);
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for (index = start; index < end; index++) {
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struct page *page = xas_next(&xas);
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VM_BUG_ON(index != xas.xa_index);
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if (!page) {
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if (!shmem_charge(mapping->host, 1)) {
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result = SCAN_FAIL;
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break;
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}
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xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
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nr_none++;
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continue;
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}
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/* We are done. */
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if (index >= end)
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break;
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page = radix_tree_deref_slot_protected(slot,
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&mapping->i_pages.xa_lock);
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if (xa_is_value(page) || !PageUptodate(page)) {
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xa_unlock_irq(&mapping->i_pages);
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xas_unlock_irq(&xas);
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/* swap in or instantiate fallocated page */
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if (shmem_getpage(mapping->host, index, &page,
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SGP_NOHUGE)) {
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result = SCAN_FAIL;
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goto tree_unlocked;
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goto xa_unlocked;
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}
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xa_lock_irq(&mapping->i_pages);
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xas_lock_irq(&xas);
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xas_set(&xas, index);
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} else if (trylock_page(page)) {
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get_page(page);
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} else {
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@ -1397,7 +1397,7 @@ static void collapse_shmem(struct mm_struct *mm,
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result = SCAN_TRUNCATED;
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goto out_unlock;
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}
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xa_unlock_irq(&mapping->i_pages);
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xas_unlock_irq(&xas);
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if (isolate_lru_page(page)) {
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result = SCAN_DEL_PAGE_LRU;
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@ -1407,17 +1407,16 @@ static void collapse_shmem(struct mm_struct *mm,
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if (page_mapped(page))
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unmap_mapping_pages(mapping, index, 1, false);
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xa_lock_irq(&mapping->i_pages);
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xas_lock_irq(&xas);
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xas_set(&xas, index);
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slot = radix_tree_lookup_slot(&mapping->i_pages, index);
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VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
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&mapping->i_pages.xa_lock), page);
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VM_BUG_ON_PAGE(page != xas_load(&xas), page);
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VM_BUG_ON_PAGE(page_mapped(page), page);
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/*
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* The page is expected to have page_count() == 3:
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* - we hold a pin on it;
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* - one reference from radix tree;
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* - one reference from page cache;
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* - one from isolate_lru_page;
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*/
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if (!page_ref_freeze(page, 3)) {
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@ -1432,56 +1431,30 @@ static void collapse_shmem(struct mm_struct *mm,
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list_add_tail(&page->lru, &pagelist);
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/* Finally, replace with the new page. */
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radix_tree_replace_slot(&mapping->i_pages, slot,
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new_page + (index % HPAGE_PMD_NR));
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slot = radix_tree_iter_resume(slot, &iter);
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index++;
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xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
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continue;
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out_lru:
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xa_unlock_irq(&mapping->i_pages);
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xas_unlock_irq(&xas);
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putback_lru_page(page);
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out_isolate_failed:
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unlock_page(page);
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put_page(page);
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goto tree_unlocked;
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goto xa_unlocked;
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out_unlock:
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unlock_page(page);
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put_page(page);
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break;
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}
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xas_unlock_irq(&xas);
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/*
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* Handle hole in radix tree at the end of the range.
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* This code only triggers if there's nothing in radix tree
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* beyond 'end'.
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*/
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if (result == SCAN_SUCCEED && index < end) {
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int n = end - index;
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if (!shmem_charge(mapping->host, n)) {
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result = SCAN_FAIL;
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goto tree_locked;
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}
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for (; index < end; index++) {
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radix_tree_insert(&mapping->i_pages, index,
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new_page + (index % HPAGE_PMD_NR));
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}
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nr_none += n;
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}
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tree_locked:
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xa_unlock_irq(&mapping->i_pages);
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tree_unlocked:
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xa_unlocked:
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if (result == SCAN_SUCCEED) {
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unsigned long flags;
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struct page *page, *tmp;
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struct zone *zone = page_zone(new_page);
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/*
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* Replacing old pages with new one has succeed, now we need to
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* copy the content and free old pages.
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* Replacing old pages with new one has succeeded, now we
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* need to copy the content and free the old pages.
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*/
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list_for_each_entry_safe(page, tmp, &pagelist, lru) {
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copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
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@ -1495,16 +1468,16 @@ static void collapse_shmem(struct mm_struct *mm,
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put_page(page);
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}
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local_irq_save(flags);
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local_irq_disable();
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__inc_node_page_state(new_page, NR_SHMEM_THPS);
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if (nr_none) {
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__mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
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__mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
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}
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local_irq_restore(flags);
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local_irq_enable();
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/*
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* Remove pte page tables, so we can re-faulti
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* Remove pte page tables, so we can re-fault
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* the page as huge.
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*/
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retract_page_tables(mapping, start);
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@ -1521,37 +1494,37 @@ static void collapse_shmem(struct mm_struct *mm,
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khugepaged_pages_collapsed++;
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} else {
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/* Something went wrong: rollback changes to the radix-tree */
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struct page *page;
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/* Something went wrong: roll back page cache changes */
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shmem_uncharge(mapping->host, nr_none);
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xa_lock_irq(&mapping->i_pages);
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radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
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if (iter.index >= end)
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break;
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xas_lock_irq(&xas);
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xas_set(&xas, start);
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xas_for_each(&xas, page, end - 1) {
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page = list_first_entry_or_null(&pagelist,
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struct page, lru);
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if (!page || iter.index < page->index) {
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if (!page || xas.xa_index < page->index) {
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if (!nr_none)
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break;
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nr_none--;
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/* Put holes back where they were */
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radix_tree_delete(&mapping->i_pages, iter.index);
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xas_store(&xas, NULL);
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continue;
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}
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VM_BUG_ON_PAGE(page->index != iter.index, page);
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VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
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/* Unfreeze the page. */
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list_del(&page->lru);
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page_ref_unfreeze(page, 2);
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radix_tree_replace_slot(&mapping->i_pages, slot, page);
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slot = radix_tree_iter_resume(slot, &iter);
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xa_unlock_irq(&mapping->i_pages);
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xas_store(&xas, page);
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xas_pause(&xas);
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xas_unlock_irq(&xas);
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putback_lru_page(page);
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unlock_page(page);
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xa_lock_irq(&mapping->i_pages);
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xas_lock_irq(&xas);
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}
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VM_BUG_ON(nr_none);
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xa_unlock_irq(&mapping->i_pages);
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xas_unlock_irq(&xas);
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/* Unfreeze new_page, caller would take care about freeing it */
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page_ref_unfreeze(new_page, 1);
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