linux-kernel - [PATCH v4 1/3] memcg: clean up existing move charge code

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Message-Id: <1331591456-20769-1-git-send-email-n-horiguchi@ah.jp.nec.com>
Date:	Mon, 12 Mar 2012 18:30:54 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Hillf Danton <dhillf@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: [PATCH v4 1/3] memcg: clean up existing move charge code

We'll introduce the thp variant of move charge code in later patches,
but before doing that let's start with refactoring existing code.
Here we replace lengthy function name is_target_pte_for_mc() with
shorter one in order to avoid ugly line breaks.
And for better readability, we explicitly use MC_TARGET_* instead of
simply using integers.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 mm/memcontrol.c |   20 ++++++++++----------
 1 files changed, 10 insertions(+), 10 deletions(-)

diff --git linux-next-20120307.orig/mm/memcontrol.c linux-next-20120307/mm/memcontrol.c
index a288855..3d16618 100644
--- linux-next-20120307.orig/mm/memcontrol.c
+++ linux-next-20120307/mm/memcontrol.c
@@ -5069,7 +5069,7 @@ one_by_one:
 }
 
 /**
- * is_target_pte_for_mc - check a pte whether it is valid for move charge
+ * get_mctgt_type - get target type of moving charge
  * @vma: the vma the pte to be checked belongs
  * @addr: the address corresponding to the pte to be checked
  * @ptent: the pte to be checked
@@ -5092,7 +5092,7 @@ union mc_target {
 };
 
 enum mc_target_type {
-	MC_TARGET_NONE,	/* not used */
+	MC_TARGET_NONE,
 	MC_TARGET_PAGE,
 	MC_TARGET_SWAP,
 };
@@ -5173,12 +5173,12 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
 	return page;
 }
 
-static int is_target_pte_for_mc(struct vm_area_struct *vma,
+static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		unsigned long addr, pte_t ptent, union mc_target *target)
 {
 	struct page *page = NULL;
 	struct page_cgroup *pc;
-	int ret = 0;
+	enum mc_target_type ret = MC_TARGET_NONE;
 	swp_entry_t ent = { .val = 0 };
 
 	if (pte_present(ptent))
@@ -5189,7 +5189,7 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
 		page = mc_handle_file_pte(vma, addr, ptent, &ent);
 
 	if (!page && !ent.val)
-		return 0;
+		return ret;
 	if (page) {
 		pc = lookup_page_cgroup(page);
 		/*
@@ -5206,7 +5206,7 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
 			put_page(page);
 	}
 	/* There is a swap entry and a page doesn't exist or isn't charged */
-	if (ent.val && !ret &&
+	if (ent.val && ret != MC_TARGET_NONE &&
 			css_id(&mc.from->css) == lookup_swap_cgroup_id(ent)) {
 		ret = MC_TARGET_SWAP;
 		if (target)
@@ -5227,7 +5227,7 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	for (; addr != end; pte++, addr += PAGE_SIZE)
-		if (is_target_pte_for_mc(vma, addr, *pte, NULL))
+		if (get_mctgt_type(vma, addr, *pte, NULL))
 			mc.precharge++;	/* increment precharge temporarily */
 	pte_unmap_unlock(pte - 1, ptl);
 	cond_resched();
@@ -5397,8 +5397,8 @@ retry:
 		if (!mc.precharge)
 			break;
 
-		type = is_target_pte_for_mc(vma, addr, ptent, &target);
-		switch (type) {
+		target_type = get_mctgt_type(vma, addr, ptent, &target);
+		switch (target_type) {
 		case MC_TARGET_PAGE:
 			page = target.page;
 			if (isolate_lru_page(page))
@@ -5411,7 +5411,7 @@ retry:
 				mc.moved_charge++;
 			}
 			putback_lru_page(page);
-put:			/* is_target_pte_for_mc() gets the page */
+put:			/* get_mctgt_type() gets the page */
 			put_page(page);
 			break;
 		case MC_TARGET_SWAP:
-- 
1.7.7.6

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