Commit 042a3082 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

mm/khugepaged: minor reorderings in collapse_shmem() 

Several cleanups in collapse_shmem(): most of which probably do not
really matter, beyond doing things in a more familiar and reassuring
order.  Simplify the failure gotos in the main loop, and on success
update stats while interrupts still disabled from the last iteration.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261526400.2275@eggly.anvils


Fixes: f3f0e1d2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.8+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2af8ff29

mm/khugepaged.c

+32 −40
Original line number Diff line number Diff line
@@ -1329,10 +1329,10 @@ static void collapse_shmem(struct mm_struct *mm, 
		goto out;

	}



	__SetPageLocked(new_page);

	__SetPageSwapBacked(new_page);

	new_page->index = start;

	new_page->mapping = mapping;

	__SetPageSwapBacked(new_page);

	__SetPageLocked(new_page);

	BUG_ON(!page_ref_freeze(new_page, 1));



	/*
@@ -1366,13 +1366,13 @@ static void collapse_shmem(struct mm_struct *mm, 
			if (index == start) {

				if (!xas_next_entry(&xas, end - 1)) {

					result = SCAN_TRUNCATED;

					break;

					goto xa_locked;

				}

				xas_set(&xas, index);

			}

			if (!shmem_charge(mapping->host, 1)) {

				result = SCAN_FAIL;

				break;

				goto xa_locked;

			}

			xas_store(&xas, new_page + (index % HPAGE_PMD_NR));

			nr_none++;
@@ -1387,13 +1387,12 @@ static void collapse_shmem(struct mm_struct *mm, 
				result = SCAN_FAIL;

				goto xa_unlocked;

			}

			xas_lock_irq(&xas);

			xas_set(&xas, index);

		} else if (trylock_page(page)) {

			get_page(page);

			xas_unlock_irq(&xas);

		} else {

			result = SCAN_PAGE_LOCK;

			break;

			goto xa_locked;

		}



		/*
@@ -1408,11 +1407,10 @@ static void collapse_shmem(struct mm_struct *mm, 
			result = SCAN_TRUNCATED;

			goto out_unlock;

		}

		xas_unlock_irq(&xas);



		if (isolate_lru_page(page)) {

			result = SCAN_DEL_PAGE_LRU;

			goto out_isolate_failed;

			goto out_unlock;

		}



		if (page_mapped(page))
@@ -1432,7 +1430,9 @@ static void collapse_shmem(struct mm_struct *mm, 
		 */

		if (!page_ref_freeze(page, 3)) {

			result = SCAN_PAGE_COUNT;

			goto out_lru;

			xas_unlock_irq(&xas);

			putback_lru_page(page);

			goto out_unlock;

		}



		/*
@@ -1444,24 +1444,26 @@ static void collapse_shmem(struct mm_struct *mm, 
		/* Finally, replace with the new page. */

		xas_store(&xas, new_page + (index % HPAGE_PMD_NR));

		continue;

out_lru:

		xas_unlock_irq(&xas);

		putback_lru_page(page);

out_isolate_failed:

		unlock_page(page);

		put_page(page);

		goto xa_unlocked;

out_unlock:

		unlock_page(page);

		put_page(page);

		break;

		goto xa_unlocked;

	}

	xas_unlock_irq(&xas);



	__inc_node_page_state(new_page, NR_SHMEM_THPS);

	if (nr_none) {

		struct zone *zone = page_zone(new_page);



		__mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);

		__mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);

	}



xa_locked:

	xas_unlock_irq(&xas);

xa_unlocked:



	if (result == SCAN_SUCCEED) {

		struct page *page, *tmp;

		struct zone *zone = page_zone(new_page);



		/*

		 * Replacing old pages with new one has succeeded, now we
@@ -1476,11 +1478,11 @@ xa_unlocked: 
			copy_highpage(new_page + (page->index % HPAGE_PMD_NR),

					page);

			list_del(&page->lru);

			unlock_page(page);

			page_ref_unfreeze(page, 1);

			page->mapping = NULL;

			page_ref_unfreeze(page, 1);

			ClearPageActive(page);

			ClearPageUnevictable(page);

			unlock_page(page);

			put_page(page);

			index++;

		}
@@ -1489,28 +1491,17 @@ xa_unlocked: 
			index++;

		}



		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_enable();



		/*

		 * Remove pte page tables, so we can re-fault

		 * the page as huge.

		 */

		retract_page_tables(mapping, start);



		/* Everything is ready, let's unfreeze the new_page */

		set_page_dirty(new_page);

		SetPageUptodate(new_page);

		page_ref_unfreeze(new_page, HPAGE_PMD_NR);

		set_page_dirty(new_page);

		mem_cgroup_commit_charge(new_page, memcg, false, true);

		lru_cache_add_anon(new_page);

		unlock_page(new_page);



		/*

		 * Remove pte page tables, so we can re-fault the page as huge.

		 */

		retract_page_tables(mapping, start);

		*hpage = NULL;



		khugepaged_pages_collapsed++;
@@ -1543,8 +1534,8 @@ xa_unlocked: 
			xas_store(&xas, page);

			xas_pause(&xas);

			xas_unlock_irq(&xas);

			putback_lru_page(page);

			unlock_page(page);

			putback_lru_page(page);

			xas_lock_irq(&xas);

		}

		VM_BUG_ON(nr_none);
@@ -1553,9 +1544,10 @@ xa_unlocked: 
		/* Unfreeze new_page, caller would take care about freeing it */

		page_ref_unfreeze(new_page, 1);

		mem_cgroup_cancel_charge(new_page, memcg, true);

		unlock_page(new_page);

		new_page->mapping = NULL;

	}



	unlock_page(new_page);

out:

	VM_BUG_ON(!list_empty(&pagelist));

	/* TODO: tracepoints */

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