Re: [PATCH] memcg: clean up migration
From: Daisuke Nishimura <hidden>
Date: 2011-02-28 02:27:37
Also in:
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On Mon, 28 Feb 2011 00:49:25 +0900 Minchan Kim [off-list ref] wrote:
This patch cleans up unncessary BUG_ON check and confusing charge variable. That's because memcg charge/uncharge could be handled by mem_cgroup_[prepare/end] migration itself so charge local variable in unmap_and_move lost the role since we introduced 01b1ae63c2. And mem_cgroup_prepare_migratio return 0 if only it is successful. Otherwise, it jumps to unlock label to clean up so BUG_ON(charge) isn;t meaningless. Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Balbir Singh <redacted> Cc: Daisuke Nishimura <redacted> Cc: KAMEZAWA Hiroyuki <redacted> Signed-off-by: Minchan Kim <redacted>
It looks good to me, but I have one minor comment.
quoted hunk ↗ jump to hunk
--- mm/memcontrol.c | 1 + mm/migrate.c | 14 ++++---------- 2 files changed, 5 insertions(+), 10 deletions(-)diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2fc97fc..6832926 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c@@ -2872,6 +2872,7 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry, /* * Before starting migration, account PAGE_SIZE to mem_cgroup that the old * page belongs to. + * Return 0 if charge is successful. Otherwise return -errno. */ int mem_cgroup_prepare_migration(struct page *page, struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask)diff --git a/mm/migrate.c b/mm/migrate.c index eb083a6..737c2e5 100644 --- a/mm/migrate.c +++ b/mm/migrate.c@@ -622,7 +622,6 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, int *result = NULL; struct page *newpage = get_new_page(page, private, &result); int remap_swapcache = 1; - int charge = 0; struct mem_cgroup *mem; struct anon_vma *anon_vma = NULL;@@ -637,9 +636,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, if (unlikely(split_huge_page(page))) goto move_newpage; - /* prepare cgroup just returns 0 or -ENOMEM */ rc = -EAGAIN; - if (!trylock_page(page)) { if (!force) goto move_newpage;@@ -678,13 +675,11 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, } /* charge against new page */ - charge = mem_cgroup_prepare_migration(page, newpage, &mem, GFP_KERNEL); - if (charge == -ENOMEM) { - rc = -ENOMEM; + rc = mem_cgroup_prepare_migration(page, newpage, &mem, GFP_KERNEL); + if (rc) goto unlock; - } - BUG_ON(charge); + rc = -EAGAIN; if (PageWriteback(page)) { if (!force || !sync) goto uncharge;
How about
if (mem_cgroup_prepare_migration(..)) {
rc = -ENOMEM;
goto unlock;
}
?
Re-setting "rc" to -EAGAIN is not necessary in this case.
"if (mem_cgroup_...)" is commonly used in many places.
Anyway,
Acked-by: Daisuke Nishimura [off-list ref]
Thanks,
Daisuke Nishimura.
quoted hunk ↗ jump to hunk
@@ -767,8 +762,7 @@ skip_unmap: drop_anon_vma(anon_vma); uncharge: - if (!charge) - mem_cgroup_end_migration(mem, page, newpage, rc == 0); + mem_cgroup_end_migration(mem, page, newpage, rc == 0); unlock: unlock_page(page);-- 1.7.1
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