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Commit 93d17715 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

ksm: three remove_rmap_item_from_tree cleanups 



1. remove_rmap_item_from_tree() is called as a precaution from
   various places: don't dirty the rmap_item cacheline unnecessarily,
   just mask the flags out of the address when they have been set.

2. First get_next_rmap_item() removes an unstable rmap_item from its tree,
   then shortly afterwards cmp_and_merge_page() removes a stable rmap_item
   from its tree: it's easier just to do both at once (but definitely keep
   the BUG_ON(age > 1) which guards against a future omission).

3. When cmp_and_merge_page() moves an rmap_item from unstable to stable
   tree, it does its own rb_erase() and accounting: that's better
   expressed by remove_rmap_item_from_tree().

Signed-off-by: default avatarHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 338fde90

mm/ksm.c

+6 −11
Original line number Diff line number Diff line
@@ -453,6 +453,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) 
		}



		rmap_item->next = NULL;

		rmap_item->address &= PAGE_MASK;



	} else if (rmap_item->address & NODE_FLAG) {

		unsigned char age;
@@ -467,10 +468,10 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) 
		BUG_ON(age > 1);

		if (!age)

			rb_erase(&rmap_item->node, &root_unstable_tree);

		ksm_pages_unshared--;

	}



		ksm_pages_unshared--;

		rmap_item->address &= PAGE_MASK;

	}



	cond_resched();		/* we're called from many long loops */

}
@@ -1086,7 +1087,6 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) 
	unsigned int checksum;

	int err;



	if (in_stable_tree(rmap_item))

	remove_rmap_item_from_tree(rmap_item);



	/* We first start with searching the page inside the stable tree */
@@ -1143,9 +1143,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) 
		 * tree, and insert it instead as new node in the stable tree.

		 */

		if (!err) {

			rb_erase(&tree_rmap_item->node, &root_unstable_tree);

			tree_rmap_item->address &= ~NODE_FLAG;

			ksm_pages_unshared--;

			remove_rmap_item_from_tree(tree_rmap_item);



			/*

			 * If we fail to insert the page into the stable tree,
@@ -1174,11 +1172,8 @@ static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, 


	while (cur != &mm_slot->rmap_list) {

		rmap_item = list_entry(cur, struct rmap_item, link);

		if ((rmap_item->address & PAGE_MASK) == addr) {

			if (!in_stable_tree(rmap_item))

				remove_rmap_item_from_tree(rmap_item);

		if ((rmap_item->address & PAGE_MASK) == addr)

			return rmap_item;

		}

		if (rmap_item->address > addr)

			break;

		cur = cur->next;