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Date: Mon, 09 Apr 2012 14:47:25 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC: linux-mm@...ck.org, mgorman@...e.de, dhillf@...il.com,
aarcange@...hat.com, mhocko@...e.cz, akpm@...ux-foundation.org,
hannes@...xchg.org, linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org
Subject: Re: [PATCH -V5 06/14] hugetlb: Simplify migrate_huge_page
(2012/04/07 3:50), Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
>
> Since we migrate only one hugepage don't use linked list for passing
> the page around. Directly pass page that need to be migrated as argument.
> This also remove the usage page->lru in migrate path.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
seems good to me. I have one question below.
> ---
> include/linux/migrate.h | 4 +--
> mm/memory-failure.c | 13 ++--------
> mm/migrate.c | 65 +++++++++++++++--------------------------------
> 3 files changed, 25 insertions(+), 57 deletions(-)
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 855c337..ce7e667 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -15,7 +15,7 @@ extern int migrate_page(struct address_space *,
> extern int migrate_pages(struct list_head *l, new_page_t x,
> unsigned long private, bool offlining,
> enum migrate_mode mode);
> -extern int migrate_huge_pages(struct list_head *l, new_page_t x,
> +extern int migrate_huge_page(struct page *, new_page_t x,
> unsigned long private, bool offlining,
> enum migrate_mode mode);
>
> @@ -36,7 +36,7 @@ static inline void putback_lru_pages(struct list_head *l) {}
> static inline int migrate_pages(struct list_head *l, new_page_t x,
> unsigned long private, bool offlining,
> enum migrate_mode mode) { return -ENOSYS; }
> -static inline int migrate_huge_pages(struct list_head *l, new_page_t x,
> +static inline int migrate_huge_page(struct page *page, new_page_t x,
> unsigned long private, bool offlining,
> enum migrate_mode mode) { return -ENOSYS; }
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 97cc273..1f092db 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1414,7 +1414,6 @@ static int soft_offline_huge_page(struct page *page, int flags)
> int ret;
> unsigned long pfn = page_to_pfn(page);
> struct page *hpage = compound_head(page);
> - LIST_HEAD(pagelist);
>
> ret = get_any_page(page, pfn, flags);
> if (ret < 0)
> @@ -1429,19 +1428,11 @@ static int soft_offline_huge_page(struct page *page, int flags)
> }
>
> /* Keep page count to indicate a given hugepage is isolated. */
> -
> - list_add(&hpage->lru, &pagelist);
> - ret = migrate_huge_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0,
> - true);
> + ret = migrate_huge_page(page, new_page, MPOL_MF_MOVE_ALL, 0, true);
> + put_page(page);
> if (ret) {
> - struct page *page1, *page2;
> - list_for_each_entry_safe(page1, page2, &pagelist, lru)
> - put_page(page1);
> -
> pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
> pfn, ret, page->flags);
> - if (ret > 0)
> - ret = -EIO;
> return ret;
> }
> done:
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 51c08a0..d7eb82d 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -929,15 +929,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> if (anon_vma)
> put_anon_vma(anon_vma);
> unlock_page(hpage);
> -
> out:
> - if (rc != -EAGAIN) {
> - list_del(&hpage->lru);
> - put_page(hpage);
> - }
> -
> put_page(new_hpage);
> -
> if (result) {
> if (rc)
> *result = rc;
> @@ -1013,48 +1006,32 @@ out:
> return nr_failed + retry;
> }
>
> -int migrate_huge_pages(struct list_head *from,
> - new_page_t get_new_page, unsigned long private, bool offlining,
> - enum migrate_mode mode)
> +int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
> + unsigned long private, bool offlining,
> + enum migrate_mode mode)
> {
> - int retry = 1;
> - int nr_failed = 0;
> - int pass = 0;
> - struct page *page;
> - struct page *page2;
> - int rc;
> -
> - for (pass = 0; pass < 10 && retry; pass++) {
> - retry = 0;
> -
> - list_for_each_entry_safe(page, page2, from, lru) {
> + int pass, rc;
> +
> + for (pass = 0; pass < 10; pass++) {
> + rc = unmap_and_move_huge_page(get_new_page,
> + private, hpage, pass > 2, offlining,
> + mode);
> + switch (rc) {
> + case -ENOMEM:
> + goto out;
> + case -EAGAIN:
> + /* try again */
> cond_resched();
> -
> - rc = unmap_and_move_huge_page(get_new_page,
> - private, page, pass > 2, offlining,
> - mode);
> -
> - switch(rc) {
> - case -ENOMEM:
> - goto out;
> - case -EAGAIN:
> - retry++;
> - break;
> - case 0:
> - break;
> - default:
> - /* Permanent failure */
> - nr_failed++;
> - break;
> - }
> + break;
> + case 0:
> + goto out;
> + default:
> + rc = -EIO;
> + goto out;
why -EIO ? Isn't this BUG() ??
Thanks,
-Kame
> }
> }
> - rc = 0;
> out:
> - if (rc)
> - return rc;
> -
> - return nr_failed + retry;
> + return rc;
> }
>
> #ifdef CONFIG_NUMA
--
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