diff options
Diffstat (limited to 'mm/ksm.c')
| -rw-r--r-- | mm/ksm.c | 51 |
1 files changed, 45 insertions, 6 deletions
@@ -25,7 +25,7 @@ #include <linux/pagemap.h> #include <linux/rmap.h> #include <linux/spinlock.h> -#include <linux/jhash.h> +#include <linux/xxhash.h> #include <linux/delay.h> #include <linux/kthread.h> #include <linux/wait.h> @@ -667,7 +667,7 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) } /* - * get_ksm_page: checks if the page indicated by the stable node + * __get_ksm_page: checks if the page indicated by the stable node * is still its ksm page, despite having held no reference to it. * In which case we can trust the content of the page, and it * returns the gotten page; but if the page has now been zapped, @@ -685,7 +685,8 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) * a page to put something that might look like our key in page->mapping. * is on its way to being freed; but it is an anomaly to bear in mind. */ -static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) +static struct page *__get_ksm_page(struct stable_node *stable_node, + bool lock_it, bool async) { struct page *page; void *expected_mapping; @@ -728,7 +729,15 @@ again: } if (lock_it) { - lock_page(page); + if (async) { + if (!trylock_page(page)) { + put_page(page); + return ERR_PTR(-EBUSY); + } + } else { + lock_page(page); + } + if (READ_ONCE(page->mapping) != expected_mapping) { unlock_page(page); put_page(page); @@ -751,6 +760,11 @@ stale: return NULL; } +static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) +{ + return __get_ksm_page(stable_node, lock_it, false); +} + /* * Removing rmap_item from stable or unstable tree. * This function will clean the information from the stable/unstable tree. @@ -1009,7 +1023,7 @@ static u32 calc_checksum(struct page *page) { u32 checksum; void *addr = kmap_atomic(page); - checksum = jhash2(addr, PAGE_SIZE / 4, 17); + checksum = xxhash(addr, PAGE_SIZE, 0); kunmap_atomic(addr); return checksum; } @@ -1321,6 +1335,23 @@ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, { int err; + if (IS_ENABLED(CONFIG_COMPACTION)) { + unsigned long pfn; + + /* + * Find neighbour of @page containing 1-order pair in buddy + * allocator and check whether its count is 0. If so, we + * consider the neighbour as a free page (this is more + * probable than it's freezed via page_ref_freeze()), and + * we try to use @tree_page as ksm page and to free @page. + */ + pfn = page_to_pfn(page) ^ 1; + if (pfn_valid(pfn) && page_count(pfn_to_page(pfn)) == 0) { + swap(rmap_item, tree_rmap_item); + swap(page, tree_page); + } + } + err = try_to_merge_with_ksm_page(rmap_item, page, NULL); if (!err) { err = try_to_merge_with_ksm_page(tree_rmap_item, @@ -1675,7 +1706,11 @@ again: * It would be more elegant to return stable_node * than kpage, but that involves more changes. */ - tree_page = get_ksm_page(stable_node_dup, true); + tree_page = __get_ksm_page(stable_node_dup, true, true); + + if (PTR_ERR(tree_page) == -EBUSY) + return ERR_PTR(-EBUSY); + if (unlikely(!tree_page)) /* * The tree may have been rebalanced, @@ -2062,6 +2097,10 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) /* We first start with searching the page inside the stable tree */ kpage = stable_tree_search(page); + + if (PTR_ERR(kpage) == -EBUSY) + return; + if (kpage == page && rmap_item->head == stable_node) { put_page(kpage); return; |