From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Matthew Wilcox To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Matthew Wilcox , Jan Kara , Jeff Layton , Lukas Czerner , Ross Zwisler , Christoph Hellwig , Goldwyn Rodrigues , Nicholas Piggin , Ryusuke Konishi , linux-nilfs@vger.kernel.org, Jaegeuk Kim , Chao Yu , linux-f2fs-devel@lists.sourceforge.net Subject: [PATCH v14 43/74] mm: Convert collapse_shmem to XArray Date: Sat, 16 Jun 2018 19:00:21 -0700 Message-Id: <20180617020052.4759-44-willy@infradead.org> In-Reply-To: <20180617020052.4759-1-willy@infradead.org> References: <20180617020052.4759-1-willy@infradead.org> Sender: owner-linux-mm@kvack.org List-ID: 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 --- mm/khugepaged.c | 158 ++++++++++++++++++++---------------------------- 1 file changed, 65 insertions(+), 93 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index d6992ba1f604..43598cc5998b 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1287,17 +1287,17 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) * * Basic scheme is simple, details are more complex: * - allocate and freeze a new huge page; - * - scan over radix tree replacing old pages the new one + * - scan page cache replacing old pages with the new one * + swap in pages if necessary; * + fill in gaps; - * + keep old pages around in case if rollback is required; - * - if replacing succeed: + * + keep old pages around in case rollback is required; + * - if replacing succeeds: * + copy data over; * + free old pages; * + unfreeze huge page; * - if replacing failed; * + put all pages back and unfreeze them; - * + restore gaps in the radix-tree; + * + restore gaps in the page cache; * + free huge page; */ static void collapse_shmem(struct mm_struct *mm, @@ -1305,12 +1305,11 @@ static void collapse_shmem(struct mm_struct *mm, struct page **hpage, int node) { gfp_t gfp; - struct page *page, *new_page, *tmp; + struct page *new_page; struct mem_cgroup *memcg; pgoff_t index, end = start + HPAGE_PMD_NR; LIST_HEAD(pagelist); - struct radix_tree_iter iter; - void **slot; + XA_STATE(xas, &mapping->i_pages, start); int nr_none = 0, result = SCAN_SUCCEED; VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); @@ -1335,48 +1334,48 @@ static void collapse_shmem(struct mm_struct *mm, __SetPageLocked(new_page); BUG_ON(!page_ref_freeze(new_page, 1)); - /* - * At this point the new_page is 'frozen' (page_count() is zero), locked - * and not up-to-date. It's safe to insert it into radix tree, because - * nobody would be able to map it or use it in other way until we - * unfreeze it. + * At this point the new_page is 'frozen' (page_count() is zero), + * locked and not up-to-date. It's safe to insert it into the page + * cache, because nobody would be able to map it or use it in other + * way until we unfreeze it. */ - index = start; - xa_lock_irq(&mapping->i_pages); - radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) { - int n = min(iter.index, end) - index; - - /* - * Handle holes in the radix tree: charge it from shmem and - * insert relevant subpage of new_page into the radix-tree. - */ - if (n && !shmem_charge(mapping->host, n)) { - result = SCAN_FAIL; + /* This will be less messy when we use multi-index entries */ + do { + xas_lock_irq(&xas); + xas_create_range(&xas, end - 1); + if (!xas_error(&xas)) break; - } - nr_none += n; - for (; index < min(iter.index, end); index++) { - radix_tree_insert(&mapping->i_pages, index, - new_page + (index % HPAGE_PMD_NR)); - } + xas_unlock_irq(&xas); + if (!xas_nomem(&xas, GFP_KERNEL)) + goto out; + } while (1); - /* We are done. */ - if (index >= end) - break; + for (index = start; index < end; index++) { + struct page *page = xas_next(&xas); + + VM_BUG_ON(index != xas.xa_index); + if (!page) { + if (!shmem_charge(mapping->host, 1)) { + result = SCAN_FAIL; + break; + } + xas_store(&xas, new_page + (index % HPAGE_PMD_NR)); + nr_none++; + continue; + } - page = radix_tree_deref_slot_protected(slot, - &mapping->i_pages.xa_lock); if (xa_is_value(page) || !PageUptodate(page)) { - xa_unlock_irq(&mapping->i_pages); + xas_unlock_irq(&xas); /* swap in or instantiate fallocated page */ if (shmem_getpage(mapping->host, index, &page, SGP_NOHUGE)) { result = SCAN_FAIL; - goto tree_unlocked; + goto xa_unlocked; } - xa_lock_irq(&mapping->i_pages); + xas_lock_irq(&xas); + xas_set(&xas, index); } else if (trylock_page(page)) { get_page(page); } else { @@ -1396,7 +1395,7 @@ static void collapse_shmem(struct mm_struct *mm, result = SCAN_TRUNCATED; goto out_unlock; } - xa_unlock_irq(&mapping->i_pages); + xas_unlock_irq(&xas); if (isolate_lru_page(page)) { result = SCAN_DEL_PAGE_LRU; @@ -1406,17 +1405,16 @@ static void collapse_shmem(struct mm_struct *mm, if (page_mapped(page)) unmap_mapping_pages(mapping, index, 1, false); - xa_lock_irq(&mapping->i_pages); + xas_lock(&xas); + xas_set(&xas, index); - slot = radix_tree_lookup_slot(&mapping->i_pages, index); - VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot, - &mapping->i_pages.xa_lock), page); + VM_BUG_ON_PAGE(page != xas_load(&xas), page); VM_BUG_ON_PAGE(page_mapped(page), page); /* * The page is expected to have page_count() == 3: * - we hold a pin on it; - * - one reference from radix tree; + * - one reference from page cache; * - one from isolate_lru_page; */ if (!page_ref_freeze(page, 3)) { @@ -1431,56 +1429,30 @@ static void collapse_shmem(struct mm_struct *mm, list_add_tail(&page->lru, &pagelist); /* Finally, replace with the new page. */ - radix_tree_replace_slot(&mapping->i_pages, slot, - new_page + (index % HPAGE_PMD_NR)); - - slot = radix_tree_iter_resume(slot, &iter); - index++; + xas_store(&xas, new_page + (index % HPAGE_PMD_NR)); continue; out_lru: - xa_unlock_irq(&mapping->i_pages); + xas_unlock_irq(&xas); putback_lru_page(page); out_isolate_failed: unlock_page(page); put_page(page); - goto tree_unlocked; + goto xa_unlocked; out_unlock: unlock_page(page); put_page(page); break; } + xas_unlock_irq(&xas); - /* - * Handle hole in radix tree at the end of the range. - * This code only triggers if there's nothing in radix tree - * beyond 'end'. - */ - if (result == SCAN_SUCCEED && index < end) { - int n = end - index; - - if (!shmem_charge(mapping->host, n)) { - result = SCAN_FAIL; - goto tree_locked; - } - - for (; index < end; index++) { - radix_tree_insert(&mapping->i_pages, index, - new_page + (index % HPAGE_PMD_NR)); - } - nr_none += n; - } - -tree_locked: - xa_unlock_irq(&mapping->i_pages); -tree_unlocked: - +xa_unlocked: if (result == SCAN_SUCCEED) { - unsigned long flags; + struct page *page, *tmp; struct zone *zone = page_zone(new_page); /* - * Replacing old pages with new one has succeed, now we need to - * copy the content and free old pages. + * Replacing old pages with new one has succeeded, now we + * need to copy the content and free the old pages. */ list_for_each_entry_safe(page, tmp, &pagelist, lru) { copy_highpage(new_page + (page->index % HPAGE_PMD_NR), @@ -1494,16 +1466,16 @@ static void collapse_shmem(struct mm_struct *mm, put_page(page); } - local_irq_save(flags); + local_irq_disable(); __inc_node_page_state(new_page, NR_SHMEM_THPS); if (nr_none) { __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); } - local_irq_restore(flags); + local_irq_enable(); /* - * Remove pte page tables, so we can re-faulti + * Remove pte page tables, so we can re-fault * the page as huge. */ retract_page_tables(mapping, start); @@ -1518,37 +1490,37 @@ static void collapse_shmem(struct mm_struct *mm, *hpage = NULL; } else { - /* Something went wrong: rollback changes to the radix-tree */ + struct page *page; + /* Something went wrong: roll back page cache changes */ shmem_uncharge(mapping->host, nr_none); - xa_lock_irq(&mapping->i_pages); - radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) { - if (iter.index >= end) - break; + xas_lock_irq(&xas); + xas_set(&xas, start); + xas_for_each(&xas, page, end - 1) { page = list_first_entry_or_null(&pagelist, struct page, lru); - if (!page || iter.index < page->index) { + if (!page || xas.xa_index < page->index) { if (!nr_none) break; nr_none--; /* Put holes back where they were */ - radix_tree_delete(&mapping->i_pages, iter.index); + xas_store(&xas, NULL); continue; } - VM_BUG_ON_PAGE(page->index != iter.index, page); + VM_BUG_ON_PAGE(page->index != xas.xa_index, page); /* Unfreeze the page. */ list_del(&page->lru); page_ref_unfreeze(page, 2); - radix_tree_replace_slot(&mapping->i_pages, slot, page); - slot = radix_tree_iter_resume(slot, &iter); - xa_unlock_irq(&mapping->i_pages); + xas_store(&xas, page); + xas_pause(&xas); + xas_unlock_irq(&xas); putback_lru_page(page); unlock_page(page); - xa_lock_irq(&mapping->i_pages); + xas_lock_irq(&xas); } VM_BUG_ON(nr_none); - xa_unlock_irq(&mapping->i_pages); + xas_unlock_irq(&xas); /* Unfreeze new_page, caller would take care about freeing it */ page_ref_unfreeze(new_page, 1); -- 2.17.1