On Tue, Feb 05, 2013 at 05:21:52PM +0800, 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.
>
>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>Cc: Mel Gorman <mgorman@xxxxxxx>
>Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
>Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
>Cc: Minchan Kim <minchan@xxxxxxxxxx>
>Cc: Zach Brown <zab@xxxxxxxxxx>
>Reviewed-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
>Reviewed-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
>Signed-off-by: Lin Feng <linfeng@xxxxxxxxxxxxxx>
>---
> include/linux/mm.h | 3 ++
> include/linux/mmzone.h | 4 ++
> mm/memory.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++
> mm/page_isolation.c | 5 +++
> 4 files changed, 95 insertions(+), 0 deletions(-)
>
>diff --git a/include/linux/mm.h b/include/linux/mm.h
>index 12f5a09..3ff9eba 100644
>--- a/include/linux/mm.h
>+++ b/include/linux/mm.h
>@@ -1049,6 +1049,9 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> struct page **pages, struct vm_area_struct **vmas);
> int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> struct page **pages);
>+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);
> 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 e25ab6f..1506351 100644
>--- a/include/linux/mmzone.h
>+++ b/include/linux/mmzone.h
>@@ -841,6 +841,10 @@ 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 bb1369f..ede53cc 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>
>@@ -1995,6 +1997,87 @@ int 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
How about "Otherwise migrate candidate pages which have already been
isolated to non movable zone."?
>+ * them to non movable zone, then retry. It will at most retry once.
>+ */
>+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, isolate_err, migrate_pre_flag;
>+ LIST_HEAD(pagelist);
>+
>+retry:
>+ ret = get_user_pages(tsk, mm, start, nr_pages, write, force, pages,
>+ vmas);
>+ if (ret <= 0)
>+ return ret;
>+
>+ isolate_err = 0;
>+ migrate_pre_flag = 0;
>+
>+ for (i = 0; i < ret; i++) {
>+ if (zone_is_movable(page_zone(pages[i]))) {
>+ if (!migrate_pre_flag) {
>+ if (migrate_prep())
>+ goto release_page;
>+ migrate_pre_flag = 1;
>+ }
>+
>+ if (!isolate_lru_page(pages[i])) {
>+ inc_zone_page_state(pages[i], NR_ISOLATED_ANON +
>+ page_is_file_cache(pages[i]));
>+ list_add_tail(&pages[i]->lru, &pagelist);
>+ } else {
>+ isolate_err = 1;
>+ goto release_page;
>+ }
>+ }
>+ }
>+
>+ /* All pages are non movable, we are done :) */
>+ if (i == ret && list_empty(&pagelist))
>+ return ret;
>+
>+release_page:
>+ /* Undo the effects of former get_user_pages(), we won't pin anything */
>+ release_pages(pages, ret, 1);
>+
>+ if (migrate_pre_flag && !isolate_err) {
>+ ret = migrate_pages(&pagelist, alloc_migrate_target, 1,
>+ false, MIGRATE_SYNC, MR_SYSCALL);
>+ /* Steal pages from non-movable zone successfully? */
>+ if (!ret)
>+ goto retry;
>+ }
>+
>+ putback_lru_pages(&pagelist);
>+ /* Migration failed, we pin 0 page, tell caller the truth */
>+ return 0;
>+}
>+#else
>+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
>+EXPORT_SYMBOL(get_user_pages_non_movable);
>+
> /**
> * 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..1b7bd17 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 +257,8 @@ struct page *alloc_migrate_target(struct page *page, unsigned long private,
>
> if (PageHighMem(page))
> gfp_mask |= __GFP_HIGHMEM;
>+ if (unlikely(private != 0))
>+ gfp_mask &= ~__GFP_MOVABLE;
>
> return alloc_page(gfp_mask);
> }
>--
>1.7.1
>
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