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: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/ksm.c b/mm/ksm.c
index 5575f86..133ea2c 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -453,6 +453,7 @@
}
rmap_item->next = NULL;
+ rmap_item->address &= PAGE_MASK;
} else if (rmap_item->address & NODE_FLAG) {
unsigned char age;
@@ -467,10 +468,10 @@
BUG_ON(age > 1);
if (!age)
rb_erase(&rmap_item->node, &root_unstable_tree);
- ksm_pages_unshared--;
- }
- rmap_item->address &= PAGE_MASK;
+ ksm_pages_unshared--;
+ rmap_item->address &= PAGE_MASK;
+ }
cond_resched(); /* we're called from many long loops */
}
@@ -1086,8 +1087,7 @@
unsigned int checksum;
int err;
- if (in_stable_tree(rmap_item))
- remove_rmap_item_from_tree(rmap_item);
+ remove_rmap_item_from_tree(rmap_item);
/* We first start with searching the page inside the stable tree */
tree_rmap_item = stable_tree_search(page, page2, rmap_item);
@@ -1143,9 +1143,7 @@
* 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 @@
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;