Commit 3e9646c7 authored by Hugh Dickins's avatar Hugh Dickins Committed by Greg Kroah-Hartman
Browse files

mm/khugepaged: minor reorderings in collapse_shmem() 

commit 042a3082 upstream.

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>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent ee13d69b

mm/khugepaged.c

+30 −43
Original line number Diff line number Diff line
@@ -1330,13 +1330,12 @@ 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));





	/*

	 * 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
@@ -1365,13 +1364,13 @@ static void collapse_shmem(struct mm_struct *mm, 
		 */

		if (n && !shmem_charge(mapping->host, n)) {

			result = SCAN_FAIL;

			break;

			goto tree_locked;

		}

		nr_none += n;

		for (; index < min(iter.index, end); index++) {

			radix_tree_insert(&mapping->i_pages, index,

					new_page + (index % HPAGE_PMD_NR));

		}

		nr_none += n;



		/* We are done. */

		if (index >= end)
@@ -1387,12 +1386,12 @@ static void collapse_shmem(struct mm_struct *mm, 
				result = SCAN_FAIL;

				goto tree_unlocked;

			}

			xa_lock_irq(&mapping->i_pages);

		} else if (trylock_page(page)) {

			get_page(page);

			xa_unlock_irq(&mapping->i_pages);

		} else {

			result = SCAN_PAGE_LOCK;

			break;

			goto tree_locked;

		}



		/*
@@ -1407,11 +1406,10 @@ static void collapse_shmem(struct mm_struct *mm, 
			result = SCAN_TRUNCATED;

			goto out_unlock;

		}

		xa_unlock_irq(&mapping->i_pages);



		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;

			xa_unlock_irq(&mapping->i_pages);

			putback_lru_page(page);

			goto out_unlock;

		}



		/*
@@ -1448,17 +1448,10 @@ static void collapse_shmem(struct mm_struct *mm, 
		slot = radix_tree_iter_resume(slot, &iter);

		index++;

		continue;

out_lru:

		xa_unlock_irq(&mapping->i_pages);

		putback_lru_page(page);

out_isolate_failed:

		unlock_page(page);

		put_page(page);

		goto tree_unlocked;

out_unlock:

		unlock_page(page);

		put_page(page);

		break;

		goto tree_unlocked;

	}



	/*
@@ -1466,7 +1459,7 @@ static void collapse_shmem(struct mm_struct *mm, 
	 * This code only triggers if there's nothing in radix tree

	 * beyond 'end'.

	 */

	if (result == SCAN_SUCCEED && index < end) {

	if (index < end) {

		int n = end - index;



		/* Stop if extent has been truncated, and is now empty */
@@ -1478,7 +1471,6 @@ static void collapse_shmem(struct mm_struct *mm, 
			result = SCAN_FAIL;

			goto tree_locked;

		}



		for (; index < end; index++) {

			radix_tree_insert(&mapping->i_pages, index,

					new_page + (index % HPAGE_PMD_NR));
@@ -1486,14 +1478,19 @@ static void collapse_shmem(struct mm_struct *mm, 
		nr_none += n;

	}



	__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);

	}



tree_locked:

	xa_unlock_irq(&mapping->i_pages);

tree_unlocked:



	if (result == SCAN_SUCCEED) {

		unsigned long flags;

		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.
@@ -1507,11 +1504,11 @@ static void collapse_shmem(struct mm_struct *mm, 
			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++;

		}
@@ -1520,28 +1517,17 @@ static void collapse_shmem(struct mm_struct *mm, 
			index++;

		}



		local_irq_save(flags);

		__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);



		/*

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

		 * 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++;
@@ -1573,8 +1559,8 @@ static void collapse_shmem(struct mm_struct *mm, 
			radix_tree_replace_slot(&mapping->i_pages, slot, page);

			slot = radix_tree_iter_resume(slot, &iter);

			xa_unlock_irq(&mapping->i_pages);

			putback_lru_page(page);

			unlock_page(page);

			putback_lru_page(page);

			xa_lock_irq(&mapping->i_pages);

		}

		VM_BUG_ON(nr_none);
@@ -1583,9 +1569,10 @@ static void collapse_shmem(struct mm_struct *mm, 
		/* 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 */