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ksm: cleanup some function arguments

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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>
This commit is contained in:
Hugh Dickins 2009-12-14 17:59:18 -08:00 committed by Linus Torvalds
parent 31e855ea71
commit 8dd3557a52
1 changed files with 112 additions and 122 deletions
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234
mm/ksm.c
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@ -356,8 +356,10 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; 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; struct vm_area_struct *vma;
down_read(&mm->mmap_sem); down_read(&mm->mmap_sem);
@ -665,15 +667,15 @@ out:
/** /**
* replace_page - replace page in vma by new ksm page * replace_page - replace page in vma by new ksm page
* @vma: vma that holds the pte pointing to oldpage * @vma: vma that holds the pte pointing to page
* @oldpage: the page we are replacing by newpage * @page: the page we are replacing by kpage
* @newpage: the ksm page we replace oldpage by * @kpage: the ksm page we replace page by
* @orig_pte: the original value of the pte * @orig_pte: the original value of the pte
* *
* Returns 0 on success, -EFAULT on failure. * Returns 0 on success, -EFAULT on failure.
*/ */
static int replace_page(struct vm_area_struct *vma, struct page *oldpage, static int replace_page(struct vm_area_struct *vma, struct page *page,
struct page *newpage, pte_t orig_pte) struct page *kpage, pte_t orig_pte)
{ {
struct mm_struct *mm = vma->vm_mm; struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd; pgd_t *pgd;
@ -684,7 +686,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
unsigned long addr; unsigned long addr;
int err = -EFAULT; int err = -EFAULT;
addr = page_address_in_vma(oldpage, vma); addr = page_address_in_vma(page, vma);
if (addr == -EFAULT) if (addr == -EFAULT)
goto out; goto out;
@ -706,15 +708,15 @@ static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
goto out; goto out;
} }
get_page(newpage); get_page(kpage);
page_add_ksm_rmap(newpage); page_add_ksm_rmap(kpage);
flush_cache_page(vma, addr, pte_pfn(*ptep)); flush_cache_page(vma, addr, pte_pfn(*ptep));
ptep_clear_flush(vma, addr, 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); page_remove_rmap(page);
put_page(oldpage); put_page(page);
pte_unmap_unlock(ptep, ptl); pte_unmap_unlock(ptep, ptl);
err = 0; err = 0;
@ -724,26 +726,22 @@ out:
/* /*
* try_to_merge_one_page - take two pages and merge them into one * try_to_merge_one_page - take two pages and merge them into one
* @vma: the vma that hold the pte pointing into oldpage * @vma: the vma that holds the pte pointing to page
* @oldpage: the page that we want to replace with newpage * @page: the PageAnon page that we want to replace with kpage
* @newpage: the page that we want to map instead of oldpage * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap
* * will make PageKsm) that we want to map instead of page
* 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.
* *
* This function returns 0 if the pages were merged, -EFAULT otherwise. * This function returns 0 if the pages were merged, -EFAULT otherwise.
*/ */
static int try_to_merge_one_page(struct vm_area_struct *vma, static int try_to_merge_one_page(struct vm_area_struct *vma,
struct page *oldpage, struct page *page, struct page *kpage)
struct page *newpage)
{ {
pte_t orig_pte = __pte(0); pte_t orig_pte = __pte(0);
int err = -EFAULT; int err = -EFAULT;
if (!(vma->vm_flags & VM_MERGEABLE)) if (!(vma->vm_flags & VM_MERGEABLE))
goto out; goto out;
if (!PageAnon(oldpage)) if (!PageAnon(page))
goto out; 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, * prefer to continue scanning and merging different pages,
* then come back to this page when it is unlocked. * then come back to this page when it is unlocked.
*/ */
if (!trylock_page(oldpage)) if (!trylock_page(page))
goto out; goto out;
/* /*
* If this anonymous page is mapped only here, its pte may need * 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 * ptes are necessarily already write-protected. But in either
* case, we need to lock and check page_count is not raised. * case, we need to lock and check page_count is not raised.
*/ */
if (write_protect_page(vma, oldpage, &orig_pte) == 0 && if (write_protect_page(vma, page, &orig_pte) == 0 &&
pages_identical(oldpage, newpage)) pages_identical(page, kpage))
err = replace_page(vma, oldpage, newpage, orig_pte); err = replace_page(vma, page, kpage, orig_pte);
unlock_page(oldpage); unlock_page(page);
out: out:
return err; return err;
} }
@ -773,26 +771,26 @@ out:
/* /*
* try_to_merge_with_ksm_page - like try_to_merge_two_pages, * 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. * 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, static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
unsigned long addr1, struct page *page, struct page *kpage)
struct page *page1,
struct page *kpage)
{ {
struct mm_struct *mm = rmap_item->mm;
struct vm_area_struct *vma; struct vm_area_struct *vma;
int err = -EFAULT; int err = -EFAULT;
down_read(&mm1->mmap_sem); down_read(&mm->mmap_sem);
if (ksm_test_exit(mm1)) if (ksm_test_exit(mm))
goto out;
vma = find_vma(mm, rmap_item->address);
if (!vma || vma->vm_start > rmap_item->address)
goto out; goto out;
vma = find_vma(mm1, addr1); err = try_to_merge_one_page(vma, page, kpage);
if (!vma || vma->vm_start > addr1)
goto out;
err = try_to_merge_one_page(vma, page1, kpage);
out: out:
up_read(&mm1->mmap_sem); up_read(&mm->mmap_sem);
return err; return err;
} }
@ -800,16 +798,18 @@ out:
* try_to_merge_two_pages - take two identical pages and prepare them * try_to_merge_two_pages - take two identical pages and prepare them
* to be merged into one page. * to be merged into one page.
* *
* This function returns 0 if we successfully mapped two identical pages * This function returns the kpage if we successfully merged two identical
* into one page, -EFAULT otherwise. * pages into one ksm page, NULL otherwise.
* *
* Note that this function allocates a new kernel page: if one of the pages * 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. * 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, static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item,
struct page *page1, struct mm_struct *mm2, struct page *page,
unsigned long addr2, struct page *page2) struct rmap_item *tree_rmap_item,
struct page *tree_page)
{ {
struct mm_struct *mm = rmap_item->mm;
struct vm_area_struct *vma; struct vm_area_struct *vma;
struct page *kpage; struct page *kpage;
int err = -EFAULT; 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 && if (ksm_max_kernel_pages &&
ksm_max_kernel_pages <= ksm_pages_shared) ksm_max_kernel_pages <= ksm_pages_shared)
return err; return NULL;
kpage = alloc_page(GFP_HIGHUSER); kpage = alloc_page(GFP_HIGHUSER);
if (!kpage) if (!kpage)
return err; return NULL;
down_read(&mm1->mmap_sem); down_read(&mm->mmap_sem);
if (ksm_test_exit(mm1)) { if (ksm_test_exit(mm))
up_read(&mm1->mmap_sem); goto up;
goto out; vma = find_vma(mm, rmap_item->address);
} if (!vma || vma->vm_start > rmap_item->address)
vma = find_vma(mm1, addr1); goto up;
if (!vma || vma->vm_start > addr1) {
up_read(&mm1->mmap_sem);
goto out;
}
copy_user_highpage(kpage, page1, addr1, vma); copy_user_highpage(kpage, page, rmap_item->address, vma);
err = try_to_merge_one_page(vma, page1, kpage); err = try_to_merge_one_page(vma, page, kpage);
up_read(&mm1->mmap_sem); up:
up_read(&mm->mmap_sem);
if (!err) { 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 * If that fails, we have a ksm page with only one pte
* pointing to it: so break it. * pointing to it: so break it.
*/ */
if (err) if (err)
break_cow(mm1, addr1); break_cow(rmap_item);
} }
out: if (err) {
put_page(kpage); put_page(kpage);
return err; kpage = NULL;
}
return kpage;
} }
/* /*
* stable_tree_search - search page inside the stable tree * stable_tree_search - search for 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
* *
* This function checks if there is a 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. * with identical content to the page that we are scanning right now.
@ -869,21 +865,21 @@ out:
* NULL otherwise. * NULL otherwise.
*/ */
static struct rmap_item *stable_tree_search(struct page *page, static struct rmap_item *stable_tree_search(struct page *page,
struct page **page2, struct page **tree_pagep)
struct rmap_item *rmap_item)
{ {
struct rb_node *node = root_stable_tree.rb_node; struct rb_node *node = root_stable_tree.rb_node;
while (node) { while (node) {
struct rmap_item *tree_rmap_item, *next_rmap_item; struct rmap_item *tree_rmap_item, *next_rmap_item;
struct page *tree_page;
int ret; int ret;
tree_rmap_item = rb_entry(node, struct rmap_item, node); tree_rmap_item = rb_entry(node, struct rmap_item, node);
while (tree_rmap_item) { while (tree_rmap_item) {
BUG_ON(!in_stable_tree(tree_rmap_item)); BUG_ON(!in_stable_tree(tree_rmap_item));
cond_resched(); cond_resched();
page2[0] = get_ksm_page(tree_rmap_item); tree_page = get_ksm_page(tree_rmap_item);
if (page2[0]) if (tree_page)
break; break;
next_rmap_item = tree_rmap_item->next; next_rmap_item = tree_rmap_item->next;
remove_rmap_item_from_tree(tree_rmap_item); 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) if (!tree_rmap_item)
return NULL; return NULL;
ret = memcmp_pages(page, page2[0]); ret = memcmp_pages(page, tree_page);
if (ret < 0) { if (ret < 0) {
put_page(page2[0]); put_page(tree_page);
node = node->rb_left; node = node->rb_left;
} else if (ret > 0) { } else if (ret > 0) {
put_page(page2[0]); put_page(tree_page);
node = node->rb_right; node = node->rb_right;
} else { } else {
*tree_pagep = tree_page;
return tree_rmap_item; 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 * stable_tree_insert - insert rmap_item pointing to new ksm page
* into the stable tree. * 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. * 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 rmap_item *rmap_item)
{ {
struct rb_node **new = &root_stable_tree.rb_node; 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) if (!tree_rmap_item)
return NULL; return NULL;
ret = memcmp_pages(page, tree_page); ret = memcmp_pages(kpage, tree_page);
put_page(tree_page); put_page(tree_page);
parent = *new; 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. * unstable_tree_search_insert - search for identical page,
* * else insert rmap_item 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
* *
* This function searches for a page in the unstable tree identical to the * 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 * 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 * This function does both searching and inserting, because they share
* the same walking algorithm in an rbtree. * the same walking algorithm in an rbtree.
*/ */
static struct rmap_item *unstable_tree_search_insert(struct page *page, static
struct page **page2, struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item,
struct rmap_item *rmap_item) struct page *page,
struct page **tree_pagep)
{ {
struct rb_node **new = &root_unstable_tree.rb_node; struct rb_node **new = &root_unstable_tree.rb_node;
struct rb_node *parent = NULL; struct rb_node *parent = NULL;
while (*new) { while (*new) {
struct rmap_item *tree_rmap_item; struct rmap_item *tree_rmap_item;
struct page *tree_page;
int ret; int ret;
cond_resched(); cond_resched();
tree_rmap_item = rb_entry(*new, struct rmap_item, node); tree_rmap_item = rb_entry(*new, struct rmap_item, node);
page2[0] = get_mergeable_page(tree_rmap_item); tree_page = get_mergeable_page(tree_rmap_item);
if (!page2[0]) if (!tree_page)
return NULL; return NULL;
/* /*
* Don't substitute an unswappable ksm page * Don't substitute a ksm page for a forked page.
* just for one good swappable forked page.
*/ */
if (page == page2[0]) { if (page == tree_page) {
put_page(page2[0]); put_page(tree_page);
return NULL; return NULL;
} }
ret = memcmp_pages(page, page2[0]); ret = memcmp_pages(page, tree_page);
parent = *new; parent = *new;
if (ret < 0) { if (ret < 0) {
put_page(page2[0]); put_page(tree_page);
new = &parent->rb_left; new = &parent->rb_left;
} else if (ret > 0) { } else if (ret > 0) {
put_page(page2[0]); put_page(tree_page);
new = &parent->rb_right; new = &parent->rb_right;
} else { } else {
*tree_pagep = tree_page;
return tree_rmap_item; 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) 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 rmap_item *tree_rmap_item;
struct page *tree_page = NULL;
struct page *kpage;
unsigned int checksum; unsigned int checksum;
int err; int err;
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 */ /* 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 (tree_rmap_item) {
if (page == page2[0]) /* forked */ kpage = tree_page;
if (page == kpage) /* forked */
err = 0; err = 0;
else else
err = try_to_merge_with_ksm_page(rmap_item->mm, err = try_to_merge_with_ksm_page(rmap_item,
rmap_item->address, page, kpage);
page, page2[0]);
put_page(page2[0]);
if (!err) { if (!err) {
/* /*
* The page was successfully merged: * 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); stable_tree_append(rmap_item, tree_rmap_item);
} }
put_page(kpage);
return; 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. * when the mem_cgroup had reached its limit: try again now.
*/ */
if (PageKsm(page)) 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 * 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; 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) { if (tree_rmap_item) {
err = try_to_merge_two_pages(rmap_item->mm, kpage = try_to_merge_two_pages(rmap_item, page,
rmap_item->address, page, tree_rmap_item, tree_page);
tree_rmap_item->mm, put_page(tree_page);
tree_rmap_item->address, page2[0]);
/* /*
* As soon as we merge this page, we want to remove the * As soon as we merge this page, we want to remove the
* rmap_item of the page we have merged with from the unstable * rmap_item of the page we have merged with from the unstable
* tree, and insert it instead as new node in the stable tree. * tree, and insert it instead as new node in the stable tree.
*/ */
if (!err) { if (kpage) {
remove_rmap_item_from_tree(tree_rmap_item); 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, * to a ksm page left outside the stable tree,
* in which case we need to break_cow on both. * 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); stable_tree_append(rmap_item, tree_rmap_item);
else { else {
break_cow(tree_rmap_item->mm, break_cow(tree_rmap_item);
tree_rmap_item->address); break_cow(rmap_item);
break_cow(rmap_item->mm, rmap_item->address);
} }
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. * 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); remove_rmap_item_from_tree(rmap_item);
rmap_item->oldchecksum = calc_checksum(page); rmap_item->oldchecksum = calc_checksum(page);
} }