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Date: Tue, 26 Feb 2013 17:10:43 +0800
From: Lin Feng <linfeng@...fujitsu.com>
To: akpm@...ux-foundation.org, mgorman@...e.de
CC: Lin Feng <linfeng@...fujitsu.com>, bcrl@...ck.org,
viro@...iv.linux.org.uk, khlebnikov@...nvz.org, walken@...gle.com,
kamezawa.hiroyu@...fujitsu.com, minchan@...nel.org,
riel@...hat.com, rientjes@...gle.com,
isimatu.yasuaki@...fujitsu.com, wency@...fujitsu.com,
laijs@...fujitsu.com, tangchen@...fujitsu.com,
guz.fnst@...fujitsu.com, jiang.liu@...wei.com, zab@...hat.com,
jmoyer@...hat.com, linux-mm@...ck.org, linux-aio@...ck.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 1/2] mm: hotplug: implement non-movable version of
get_user_pages() called get_user_pages_non_movable()
Hi Andrew, Mel and other guys,
How about this V3 patch, any comments?
thanks,
linfeng
On 02/21/2013 07:01 PM, Lin Feng wrote:
> get_user_pages() always tries to allocate pages from movable zone, which is not
> reliable to memory hotremove framework in some case.
>
> This patch introduces a new library function called get_user_pages_non_movable()
> to pin pages only from zone non-movable in memory.
> It's a wrapper of get_user_pages() but it makes sure that all pages come from
> non-movable zone via additional page migration. But if migration fails it
> will at least keep the base functionality of get_user_pages().
>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: Jeff Moyer <jmoyer@...hat.com>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Zach Brown <zab@...hat.com>
> Reviewed-by: Tang Chen <tangchen@...fujitsu.com>
> Reviewed-by: Gu Zheng <guz.fnst@...fujitsu.com>
> Signed-off-by: Lin Feng <linfeng@...fujitsu.com>
> ---
> include/linux/mm.h | 14 ++++++
> include/linux/mmzone.h | 4 ++
> mm/memory.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++
> mm/page_isolation.c | 8 ++++
> 4 files changed, 129 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5625c1c..737dc39 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1025,6 +1025,20 @@ long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> struct vm_area_struct **vmas);
> int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> struct page **pages);
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +int get_user_pages_non_movable(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, int nr_pages, int write, int force,
> + struct page **pages, struct vm_area_struct **vmas);
> +#else
> +static inline
> +int get_user_pages_non_movable(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, int nr_pages, int write, int force,
> + struct page **pages, struct vm_area_struct **vmas)
> +{
> + return get_user_pages(tsk, mm, start, nr_pages, write, force, pages,
> + vmas);
> +}
> +#endif
> struct kvec;
> int get_kernel_pages(const struct kvec *iov, int nr_pages, int write,
> struct page **pages);
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index ab20a60..c31007e 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -851,6 +851,10 @@ static inline int is_normal_idx(enum zone_type idx)
> return (idx == ZONE_NORMAL);
> }
>
> +static inline int zone_is_movable(struct zone *zone)
> +{
> + return zone_idx(zone) == ZONE_MOVABLE;
> +}
> /**
> * is_highmem - helper function to quickly check if a struct zone is a
> * highmem zone or not. This is an attempt to keep references
> diff --git a/mm/memory.c b/mm/memory.c
> index 16ca5d0..83db7dd 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -58,6 +58,8 @@
> #include <linux/elf.h>
> #include <linux/gfp.h>
> #include <linux/migrate.h>
> +#include <linux/page-isolation.h>
> +#include <linux/mm_inline.h>
> #include <linux/string.h>
>
> #include <asm/io.h>
> @@ -2014,6 +2016,107 @@ long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> }
> EXPORT_SYMBOL(get_user_pages);
>
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +/**
> + * It's a wrapper of get_user_pages() but it makes sure that all pages come from
> + * non-movable zone via additional page migration. It's designed for memory
> + * hotremove framework.
> + *
> + * Currently get_user_pages() always tries to allocate pages from movable zone,
> + * in some case users of get_user_pages() is easy to pin user pages for a long
> + * time(for now we found that pages pinned as aio ring pages is such case),
> + * which is fatal for memory hotremove framework.
> + *
> + * This function first calls get_user_pages() to get the candidate pages, and
> + * then check to ensure all pages are from non movable zone. Otherwise migrate
> + * them to non movable zone, then retry. It will at most retry once. If
> + * migration fails, it will keep the base functionality of get_user_pages()
> + * and issue WARN message for memory hot-remove people.
> + *
> + * Fixme: now we don't support non movable version of GUP for hugepage.
> + */
> +int get_user_pages_non_movable(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, int nr_pages, int write, int force,
> + struct page **pages, struct vm_area_struct **vmas)
> +{
> + int ret, i, tried = 0;
> + bool isolate_err, migrate_prepped;
> + LIST_HEAD(pagelist);
> +
> +retry:
> + BUG_ON(tried == 2);
> + ret = get_user_pages(tsk, mm, start, nr_pages, write, force, pages,
> + vmas);
> + /* No ZONE_MOVABLE populated, all pages are from non movable zone */
> + if (movable_zone == ZONE_MOVABLE || ret <= 0)
> + return ret;
> +
> + isolate_err = false;
> + migrate_prepped = false;
> +
> + for (i = 0; i < ret; i++) {
> + if (zone_is_movable(page_zone(pages[i]))) {
> + /* Fixme: improve for hugepage non movable support */
> + if (PageHuge(pages[i])) {
> + WARN_ONCE(1, "Non movable GUP for hugepages "
> + "haven't been implemented yet, it may "
> + "lead to memory hot-remove failure.\n");
> + continue;
> + }
> +
> + /* Hugepage or THP's head page has covered tail pages */
> + if (PageTail(pages[i]) && (page_count(pages[i]) == 1))
> + continue;
> +
> + if (!migrate_prepped) {
> + BUG_ON(migrate_prep());
> + migrate_prepped = true;
> + }
> +
> + /* Fixme: isolate_lru_page() takes the LRU lock every
> + * time, batching the lock could avoid potential lock
> + * contention problems. -Mel Gorman
> + */
> + if (!isolate_lru_page(pages[i])) {
> + inc_zone_page_state(pages[i], NR_ISOLATED_ANON +
> + page_is_file_cache(pages[i]));
> + list_add(&pages[i]->lru, &pagelist);
> + } else {
> + isolate_err = true;
> + break;
> + }
> + }
> + }
> +
> + /* All pages are non movable, we are done :) */
> + if (i == ret && list_empty(&pagelist))
> + return ret;
> +
> + /* Undo the effects of former get_user_pages(), ready for another try */
> + release_pages(pages, ret, 1);
> +
> + if (!isolate_err) {
> + ret = migrate_pages(&pagelist, alloc_migrate_target, 1,
> + MIGRATE_SYNC, MR_SYSCALL);
> + /* Steal pages from non-movable zone successfully? */
> + if (!ret) {
> + tried++;
> + goto retry;
> + }
> + }
> +
> + putback_lru_pages(&pagelist);
> + /* Migration failed, in order to keep at least the base functionality of
> + * get_user_pages(), we pin pages again but give WARN info to remind
> + * memory hot-remove people, which is a trade-off.
> + */
> + WARN_ONCE(1, "Non movable zone migration failed, "
> + "it may lead to memroy hot-remove failure.\n");
> + return get_user_pages(tsk, mm, start, nr_pages, write, force, pages,
> + vmas);
> +}
> +EXPORT_SYMBOL(get_user_pages_non_movable);
> +#endif
> /**
> * get_dump_page() - pin user page in memory while writing it to core dump
> * @addr: user address
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 383bdbb..7823ea5 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -247,6 +247,9 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
> return ret ? 0 : -EBUSY;
> }
>
> +/**
> + * @private: 0 means page can be alloced from movable zone, otherwise forbidden
> + */
> struct page *alloc_migrate_target(struct page *page, unsigned long private,
> int **resultp)
> {
> @@ -254,6 +257,11 @@ struct page *alloc_migrate_target(struct page *page, unsigned long private,
>
> if (PageHighMem(page))
> gfp_mask |= __GFP_HIGHMEM;
> +#if defined(CONFIG_MEMORY_HOTREMOVE) && defined(CONFIG_HIGHMEM)
> + BUILD_BUG_ON(1);
> +#endif
> + if (unlikely(private != 0))
> + gfp_mask &= ~__GFP_HIGHMEM;
>
> return alloc_page(gfp_mask);
> }
>
--
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