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authorHugh Dickins <hugh.dickins@tiscali.co.uk>2009-12-14 17:59:18 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-15 08:53:19 -0800
commit8dd3557a52f0bc8c960307721da307370ccad6fd (patch)
tree711a15d188b6679026ae818bd0635d271820ea7e /mm/ksm.c
parentksm: remove redundancies when merging page (diff)
downloadlinux-dev-8dd3557a52f0bc8c960307721da307370ccad6fd.tar.xz
linux-dev-8dd3557a52f0bc8c960307721da307370ccad6fd.zip
ksm: cleanup some function arguments
Cleanup: make argument names more consistent from cmp_and_merge_page() down to replace_page(), so that it's easier to follow the rmap_item's page and the matching tree_page and the merged kpage through that code. In some places, e.g. break_cow(), pass rmap_item instead of separate mm and address. cmp_and_merge_page() initialize tree_page to NULL, to avoid a "may be used uninitialized" warning seen in one config by Anil SB. 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>
Diffstat (limited to '')
-rw-r--r--mm/ksm.c234
1 files changed, 112 insertions, 122 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index fdd7d5faa90c..54fb3feebb59 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -356,8 +356,10 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
return (ret & VM_FAULT_OOM) ? -ENOMEM : 0;
}
-static void break_cow(struct mm_struct *mm, unsigned long addr)
+static void break_cow(struct rmap_item *rmap_item)
{
+ struct mm_struct *mm = rmap_item->mm;
+ unsigned long addr = rmap_item->address;
struct vm_area_struct *vma;
down_read(&mm->mmap_sem);
@@ -665,15 +667,15 @@ out:
/**
* replace_page - replace page in vma by new ksm page
- * @vma: vma that holds the pte pointing to oldpage
- * @oldpage: the page we are replacing by newpage
- * @newpage: the ksm page we replace oldpage by
+ * @vma: vma that holds the pte pointing to page
+ * @page: the page we are replacing by kpage
+ * @kpage: the ksm page we replace page by
* @orig_pte: the original value of the pte
*
* Returns 0 on success, -EFAULT on failure.
*/
-static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
- struct page *newpage, pte_t orig_pte)
+static int replace_page(struct vm_area_struct *vma, struct page *page,
+ struct page *kpage, pte_t orig_pte)
{
struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
@@ -684,7 +686,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
unsigned long addr;
int err = -EFAULT;
- addr = page_address_in_vma(oldpage, vma);
+ addr = page_address_in_vma(page, vma);
if (addr == -EFAULT)
goto out;
@@ -706,15 +708,15 @@ static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
goto out;
}
- get_page(newpage);
- page_add_ksm_rmap(newpage);
+ get_page(kpage);
+ page_add_ksm_rmap(kpage);
flush_cache_page(vma, addr, pte_pfn(*ptep));
ptep_clear_flush(vma, addr, ptep);
- set_pte_at_notify(mm, addr, ptep, mk_pte(newpage, vma->vm_page_prot));
+ set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
- page_remove_rmap(oldpage);
- put_page(oldpage);
+ page_remove_rmap(page);
+ put_page(page);
pte_unmap_unlock(ptep, ptl);
err = 0;
@@ -724,26 +726,22 @@ out:
/*
* try_to_merge_one_page - take two pages and merge them into one
- * @vma: the vma that hold the pte pointing into oldpage
- * @oldpage: the page that we want to replace with newpage
- * @newpage: the page that we want to map instead of oldpage
- *
- * Note:
- * oldpage should be a PageAnon page, while newpage should be a PageKsm page,
- * or a newly allocated kernel page which page_add_ksm_rmap will make PageKsm.
+ * @vma: the vma that holds the pte pointing to page
+ * @page: the PageAnon page that we want to replace with kpage
+ * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap
+ * will make PageKsm) that we want to map instead of page
*
* This function returns 0 if the pages were merged, -EFAULT otherwise.
*/
static int try_to_merge_one_page(struct vm_area_struct *vma,
- struct page *oldpage,
- struct page *newpage)
+ struct page *page, struct page *kpage)
{
pte_t orig_pte = __pte(0);
int err = -EFAULT;
if (!(vma->vm_flags & VM_MERGEABLE))
goto out;
- if (!PageAnon(oldpage))
+ if (!PageAnon(page))
goto out;
/*
@@ -753,7 +751,7 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
* prefer to continue scanning and merging different pages,
* then come back to this page when it is unlocked.
*/
- if (!trylock_page(oldpage))
+ if (!trylock_page(page))
goto out;
/*
* If this anonymous page is mapped only here, its pte may need
@@ -761,11 +759,11 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
* ptes are necessarily already write-protected. But in either
* case, we need to lock and check page_count is not raised.
*/
- if (write_protect_page(vma, oldpage, &orig_pte) == 0 &&
- pages_identical(oldpage, newpage))
- err = replace_page(vma, oldpage, newpage, orig_pte);
+ if (write_protect_page(vma, page, &orig_pte) == 0 &&
+ pages_identical(page, kpage))
+ err = replace_page(vma, page, kpage, orig_pte);
- unlock_page(oldpage);
+ unlock_page(page);
out:
return err;
}
@@ -773,26 +771,26 @@ out:
/*
* try_to_merge_with_ksm_page - like try_to_merge_two_pages,
* but no new kernel page is allocated: kpage must already be a ksm page.
+ *
+ * This function returns 0 if the pages were merged, -EFAULT otherwise.
*/
-static int try_to_merge_with_ksm_page(struct mm_struct *mm1,
- unsigned long addr1,
- struct page *page1,
- struct page *kpage)
+static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
+ struct page *page, struct page *kpage)
{
+ struct mm_struct *mm = rmap_item->mm;
struct vm_area_struct *vma;
int err = -EFAULT;
- down_read(&mm1->mmap_sem);
- if (ksm_test_exit(mm1))
+ down_read(&mm->mmap_sem);
+ if (ksm_test_exit(mm))
goto out;
-
- vma = find_vma(mm1, addr1);
- if (!vma || vma->vm_start > addr1)
+ vma = find_vma(mm, rmap_item->address);
+ if (!vma || vma->vm_start > rmap_item->address)
goto out;
- err = try_to_merge_one_page(vma, page1, kpage);
+ err = try_to_merge_one_page(vma, page, kpage);
out:
- up_read(&mm1->mmap_sem);
+ up_read(&mm->mmap_sem);
return err;
}
@@ -800,16 +798,18 @@ out:
* try_to_merge_two_pages - take two identical pages and prepare them
* to be merged into one page.
*
- * This function returns 0 if we successfully mapped two identical pages
- * into one page, -EFAULT otherwise.
+ * This function returns the kpage if we successfully merged two identical
+ * pages into one ksm page, NULL otherwise.
*
* Note that this function allocates a new kernel page: if one of the pages
* is already a ksm page, try_to_merge_with_ksm_page should be used.
*/
-static int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1,
- struct page *page1, struct mm_struct *mm2,
- unsigned long addr2, struct page *page2)
+static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item,
+ struct page *page,
+ struct rmap_item *tree_rmap_item,
+ struct page *tree_page)
{
+ struct mm_struct *mm = rmap_item->mm;
struct vm_area_struct *vma;
struct page *kpage;
int err = -EFAULT;
@@ -820,47 +820,43 @@ static int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1,
*/
if (ksm_max_kernel_pages &&
ksm_max_kernel_pages <= ksm_pages_shared)
- return err;
+ return NULL;
kpage = alloc_page(GFP_HIGHUSER);
if (!kpage)
- return err;
-
- down_read(&mm1->mmap_sem);
- if (ksm_test_exit(mm1)) {
- up_read(&mm1->mmap_sem);
- goto out;
- }
- vma = find_vma(mm1, addr1);
- if (!vma || vma->vm_start > addr1) {
- up_read(&mm1->mmap_sem);
- goto out;
- }
+ return NULL;
- copy_user_highpage(kpage, page1, addr1, vma);
- err = try_to_merge_one_page(vma, page1, kpage);
- up_read(&mm1->mmap_sem);
+ down_read(&mm->mmap_sem);
+ if (ksm_test_exit(mm))
+ goto up;
+ vma = find_vma(mm, rmap_item->address);
+ if (!vma || vma->vm_start > rmap_item->address)
+ goto up;
+
+ copy_user_highpage(kpage, page, rmap_item->address, vma);
+ err = try_to_merge_one_page(vma, page, kpage);
+up:
+ up_read(&mm->mmap_sem);
if (!err) {
- err = try_to_merge_with_ksm_page(mm2, addr2, page2, kpage);
+ err = try_to_merge_with_ksm_page(tree_rmap_item,
+ tree_page, kpage);
/*
* If that fails, we have a ksm page with only one pte
* pointing to it: so break it.
*/
if (err)
- break_cow(mm1, addr1);
+ break_cow(rmap_item);
}
-out:
- put_page(kpage);
- return err;
+ if (err) {
+ put_page(kpage);
+ kpage = NULL;
+ }
+ return kpage;
}
/*
- * stable_tree_search - search page inside the stable tree
- * @page: the page that we are searching identical pages to.
- * @page2: pointer into identical page that we are holding inside the stable
- * tree that we have found.
- * @rmap_item: the reverse mapping item
+ * stable_tree_search - search for page inside the stable tree
*
* This function checks if there is a page inside the stable tree
* with identical content to the page that we are scanning right now.
@@ -869,21 +865,21 @@ out:
* NULL otherwise.
*/
static struct rmap_item *stable_tree_search(struct page *page,
- struct page **page2,
- struct rmap_item *rmap_item)
+ struct page **tree_pagep)
{
struct rb_node *node = root_stable_tree.rb_node;
while (node) {
struct rmap_item *tree_rmap_item, *next_rmap_item;
+ struct page *tree_page;
int ret;
tree_rmap_item = rb_entry(node, struct rmap_item, node);
while (tree_rmap_item) {
BUG_ON(!in_stable_tree(tree_rmap_item));
cond_resched();
- page2[0] = get_ksm_page(tree_rmap_item);
- if (page2[0])
+ tree_page = get_ksm_page(tree_rmap_item);
+ if (tree_page)
break;
next_rmap_item = tree_rmap_item->next;
remove_rmap_item_from_tree(tree_rmap_item);
@@ -892,15 +888,16 @@ static struct rmap_item *stable_tree_search(struct page *page,
if (!tree_rmap_item)
return NULL;
- ret = memcmp_pages(page, page2[0]);
+ ret = memcmp_pages(page, tree_page);
if (ret < 0) {
- put_page(page2[0]);
+ put_page(tree_page);
node = node->rb_left;
} else if (ret > 0) {
- put_page(page2[0]);
+ put_page(tree_page);
node = node->rb_right;
} else {
+ *tree_pagep = tree_page;
return tree_rmap_item;
}
}
@@ -912,13 +909,9 @@ static struct rmap_item *stable_tree_search(struct page *page,
* stable_tree_insert - insert rmap_item pointing to new ksm page
* into the stable tree.
*
- * @page: the page that we are searching identical page to inside the stable
- * tree.
- * @rmap_item: pointer to the reverse mapping item.
- *
* This function returns rmap_item if success, NULL otherwise.
*/
-static struct rmap_item *stable_tree_insert(struct page *page,
+static struct rmap_item *stable_tree_insert(struct page *kpage,
struct rmap_item *rmap_item)
{
struct rb_node **new = &root_stable_tree.rb_node;
@@ -943,7 +936,7 @@ static struct rmap_item *stable_tree_insert(struct page *page,
if (!tree_rmap_item)
return NULL;
- ret = memcmp_pages(page, tree_page);
+ ret = memcmp_pages(kpage, tree_page);
put_page(tree_page);
parent = *new;
@@ -971,12 +964,8 @@ static struct rmap_item *stable_tree_insert(struct page *page,
}
/*
- * unstable_tree_search_insert - search and insert items into the unstable tree.
- *
- * @page: the page that we are going to search for identical page or to insert
- * into the unstable tree
- * @page2: pointer into identical page that was found inside the unstable tree
- * @rmap_item: the reverse mapping item of page
+ * unstable_tree_search_insert - search for identical page,
+ * else insert rmap_item into the unstable tree.
*
* This function searches for a page in the unstable tree identical to the
* page currently being scanned; and if no identical page is found in the
@@ -988,42 +977,45 @@ static struct rmap_item *stable_tree_insert(struct page *page,
* This function does both searching and inserting, because they share
* the same walking algorithm in an rbtree.
*/
-static struct rmap_item *unstable_tree_search_insert(struct page *page,
- struct page **page2,
- struct rmap_item *rmap_item)
+static
+struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item,
+ struct page *page,
+ struct page **tree_pagep)
+
{
struct rb_node **new = &root_unstable_tree.rb_node;
struct rb_node *parent = NULL;
while (*new) {
struct rmap_item *tree_rmap_item;
+ struct page *tree_page;
int ret;
cond_resched();
tree_rmap_item = rb_entry(*new, struct rmap_item, node);
- page2[0] = get_mergeable_page(tree_rmap_item);
- if (!page2[0])
+ tree_page = get_mergeable_page(tree_rmap_item);
+ if (!tree_page)
return NULL;
/*
- * Don't substitute an unswappable ksm page
- * just for one good swappable forked page.
+ * Don't substitute a ksm page for a forked page.
*/
- if (page == page2[0]) {
- put_page(page2[0]);
+ if (page == tree_page) {
+ put_page(tree_page);
return NULL;
}
- ret = memcmp_pages(page, page2[0]);
+ ret = memcmp_pages(page, tree_page);
parent = *new;
if (ret < 0) {
- put_page(page2[0]);
+ put_page(tree_page);
new = &parent->rb_left;
} else if (ret > 0) {
- put_page(page2[0]);
+ put_page(tree_page);
new = &parent->rb_right;
} else {
+ *tree_pagep = tree_page;
return tree_rmap_item;
}
}
@@ -1068,24 +1060,23 @@ static void stable_tree_append(struct rmap_item *rmap_item,
*/
static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
{
- struct page *page2[1];
struct rmap_item *tree_rmap_item;
+ struct page *tree_page = NULL;
+ struct page *kpage;
unsigned int checksum;
int err;
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);
+ tree_rmap_item = stable_tree_search(page, &tree_page);
if (tree_rmap_item) {
- if (page == page2[0]) /* forked */
+ kpage = tree_page;
+ if (page == kpage) /* forked */
err = 0;
else
- err = try_to_merge_with_ksm_page(rmap_item->mm,
- rmap_item->address,
- page, page2[0]);
- put_page(page2[0]);
-
+ err = try_to_merge_with_ksm_page(rmap_item,
+ page, kpage);
if (!err) {
/*
* The page was successfully merged:
@@ -1093,6 +1084,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
*/
stable_tree_append(rmap_item, tree_rmap_item);
}
+ put_page(kpage);
return;
}
@@ -1103,7 +1095,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
* when the mem_cgroup had reached its limit: try again now.
*/
if (PageKsm(page))
- break_cow(rmap_item->mm, rmap_item->address);
+ break_cow(rmap_item);
/*
* In case the hash value of the page was changed from the last time we
@@ -1117,18 +1109,18 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
return;
}
- tree_rmap_item = unstable_tree_search_insert(page, page2, rmap_item);
+ tree_rmap_item =
+ unstable_tree_search_insert(rmap_item, page, &tree_page);
if (tree_rmap_item) {
- err = try_to_merge_two_pages(rmap_item->mm,
- rmap_item->address, page,
- tree_rmap_item->mm,
- tree_rmap_item->address, page2[0]);
+ kpage = try_to_merge_two_pages(rmap_item, page,
+ tree_rmap_item, tree_page);
+ put_page(tree_page);
/*
* As soon as we merge this page, we want to remove the
* rmap_item of the page we have merged with from the unstable
* tree, and insert it instead as new node in the stable tree.
*/
- if (!err) {
+ if (kpage) {
remove_rmap_item_from_tree(tree_rmap_item);
/*
@@ -1137,16 +1129,14 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
* to a ksm page left outside the stable tree,
* in which case we need to break_cow on both.
*/
- if (stable_tree_insert(page2[0], tree_rmap_item))
+ if (stable_tree_insert(kpage, tree_rmap_item))
stable_tree_append(rmap_item, tree_rmap_item);
else {
- break_cow(tree_rmap_item->mm,
- tree_rmap_item->address);
- break_cow(rmap_item->mm, rmap_item->address);
+ break_cow(tree_rmap_item);
+ break_cow(rmap_item);
}
+ put_page(kpage);
}
-
- put_page(page2[0]);
}
}
@@ -1308,7 +1298,7 @@ static void ksm_do_scan(unsigned int scan_npages)
/*
* Replace now-unshared ksm page by ordinary page.
*/
- break_cow(rmap_item->mm, rmap_item->address);
+ break_cow(rmap_item);
remove_rmap_item_from_tree(rmap_item);
rmap_item->oldchecksum = calc_checksum(page);
}