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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>
This commit is contained in:
Hugh Dickins 2009-12-14 17:59:16 -08:00 committed by Linus Torvalds
parent 338fde9093
commit 93d17715a5
1 changed files with 7 additions and 12 deletions
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19
mm/ksm.c
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@ -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--;
}
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 @@ 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);
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 @@ 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;