[PATCH] rmap 21 try_to_unmap_one mapcount

Hugh Dickins
2004-05-04T22:20:27Z

Why should try_to_unmap_anon and try_to_unmap_file take a copy of
page->mapcount and pass it down for try_to_unmap_one to decrement?
why not just check page->mapcount itself? asks akpm. Perhaps there
used to be a good reason, but not any more: remove the mapcount arg.

mm/rmap.c | 26 ++++++++++----------------
1 files changed, 10 insertions(+), 16 deletions(-)

--- rmap20/mm/rmap.c 2004-05-04 21:21:28.897449704 +0100
+++ rmap21/mm/rmap.c 2004-05-04 21:21:39.928772688 +0100
@@ -466,9 +466,8 @@ int fastcall mremap_move_anon_rmap(struc
** repeatedly from either try_to_unmap_anon or try_to_unmap_file.
**/

-static int try_to_unmap_one(struct page *page,
- struct mm_struct *mm, unsigned long address,
- unsigned int *mapcount, struct vm_area_struct *vma)
+static int try_to_unmap_one(struct page *page, struct mm_struct *mm,
+ unsigned long address, struct vm_area_struct *vma)
{
pgd_t *pgd;
pmd_t *pmd;
@@ -498,8 +497,6 @@ static int try_to_unmap_one(struct page
if (page_to_pfn(page) != pte_pfn(*pte))
goto out_unmap;

- (*mapcount)--;
-
if (!vma) {
vma = find_vma(mm, address);
/* unmap_vmas drops page_table_lock with vma unlinked */
@@ -643,7 +640,6 @@ out_unlock:

static inline int try_to_unmap_anon(struct page *page)
{
- unsigned int mapcount = page->mapcount;
struct anonmm *anonmm = (struct anonmm *) page->mapping;
struct anonmm *anonhd = anonmm->head;
struct list_head *seek_head;
@@ -654,9 +650,8 @@ static inline int try_to_unmap_anon(stru
* First try the indicated mm, it's the most likely.
*/
if (anonmm->mm && anonmm->mm->rss) {
- ret = try_to_unmap_one(page,
- anonmm->mm, page->index, &mapcount, NULL);
- if (ret == SWAP_FAIL || !mapcount)
+ ret = try_to_unmap_one(page, anonmm->mm, page->index, NULL);
+ if (ret == SWAP_FAIL || !page->mapcount)
goto out;
}

@@ -670,9 +665,8 @@ static inline int try_to_unmap_anon(stru
list_for_each_entry(anonmm, seek_head, list) {
if (!anonmm->mm || !anonmm->mm->rss)
continue;
- ret = try_to_unmap_one(page,
- anonmm->mm, page->index, &mapcount, NULL);
- if (ret == SWAP_FAIL || !mapcount)
+ ret = try_to_unmap_one(page, anonmm->mm, page->index, NULL);
+ if (ret == SWAP_FAIL || !page->mapcount)
goto out;
}
out:
@@ -694,7 +688,6 @@ out:
*/
static inline int try_to_unmap_file(struct page *page)
{
- unsigned int mapcount = page->mapcount;
struct address_space *mapping = page->mapping;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
struct vm_area_struct *vma = NULL;
@@ -704,6 +697,7 @@ static inline int try_to_unmap_file(stru
unsigned long cursor;
unsigned long max_nl_cursor = 0;
unsigned long max_nl_size = 0;
+ unsigned int mapcount;

if (!spin_trylock(&mapping->i_shared_lock))
return ret;
@@ -712,9 +706,8 @@ static inline int try_to_unmap_file(stru
&iter, pgoff, pgoff)) != NULL) {
if (vma->vm_mm->rss) {
address = vma_address(vma, pgoff);
- ret = try_to_unmap_one(page,
- vma->vm_mm, address, &mapcount, vma);
- if (ret == SWAP_FAIL || !mapcount)
+ ret = try_to_unmap_one(page, vma->vm_mm, address, vma);
+ if (ret == SWAP_FAIL || !page->mapcount)
goto out;
}
}
@@ -744,6 +737,7 @@ static inline int try_to_unmap_file(stru
* The mapcount of the page we came in with is irrelevant,
* but even so use it as a guide to how hard we should try?
*/
+ mapcount = page->mapcount;
rmap_unlock(page);
cond_resched_lock(&mapping->i_shared_lock);