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Date: Wed, 28 Jun 2017 14:00:43 -0400
From: Jérôme Glisse <jglisse@...hat.com>
To: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Cc: John Hubbard <jhubbard@...dia.com>,
Dan Williams <dan.j.williams@...el.com>,
David Nellans <dnellans@...dia.com>,
Jérôme Glisse <jglisse@...hat.com>
Subject: [PATCH 11/15] mm/migrate: new migrate mode MIGRATE_SYNC_NO_COPY
Introduce a new migration mode that allow to offload the copy to
a device DMA engine. This changes the workflow of migration and
not all address_space migratepage callback can support this. So
it needs to be tested in those cases.
This is intended to be use by migrate_vma() which itself is use
for thing like HMM (see include/linux/hmm.h).
Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
---
fs/aio.c | 8 +++++++
fs/f2fs/data.c | 5 ++++-
fs/hugetlbfs/inode.c | 5 ++++-
fs/ubifs/file.c | 5 ++++-
include/linux/migrate.h | 5 +++++
include/linux/migrate_mode.h | 5 +++++
mm/balloon_compaction.c | 8 +++++++
mm/migrate.c | 52 ++++++++++++++++++++++++++++++++++----------
mm/zsmalloc.c | 8 +++++++
9 files changed, 86 insertions(+), 15 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 34027b67e2f4..e908a30a1c8a 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -373,6 +373,14 @@ static int aio_migratepage(struct address_space *mapping, struct page *new,
pgoff_t idx;
int rc;
+ /*
+ * We cannot support the _NO_COPY case here, because copy needs to
+ * happen under the ctx->completion_lock. That does not work with the
+ * migration workflow of MIGRATE_SYNC_NO_COPY.
+ */
+ if (mode == MIGRATE_SYNC_NO_COPY)
+ return -EINVAL;
+
rc = 0;
/* mapping->private_lock here protects against the kioctx teardown. */
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 7697d03e8a98..1d441c091a38 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2235,7 +2235,10 @@ int f2fs_migrate_page(struct address_space *mapping,
SetPagePrivate(newpage);
set_page_private(newpage, page_private(page));
- migrate_page_copy(newpage, page);
+ if (mode != MIGRATE_SYNC_NO_COPY)
+ migrate_page_copy(newpage, page);
+ else
+ migrate_page_states(newpage, page);
return MIGRATEPAGE_SUCCESS;
}
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 52388611635e..1db9c8df886d 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -846,7 +846,10 @@ static int hugetlbfs_migrate_page(struct address_space *mapping,
rc = migrate_huge_page_move_mapping(mapping, newpage, page);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
- migrate_page_copy(newpage, page);
+ if (mode != MIGRATE_SYNC_NO_COPY)
+ migrate_page_copy(newpage, page);
+ else
+ migrate_page_states(newpage, page);
return MIGRATEPAGE_SUCCESS;
}
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 2cda3d67e2d0..b2292be50de0 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1482,7 +1482,10 @@ static int ubifs_migrate_page(struct address_space *mapping,
SetPagePrivate(newpage);
}
- migrate_page_copy(newpage, page);
+ if (mode != MIGRATE_SYNC_NO_COPY)
+ migrate_page_copy(newpage, page);
+ else
+ migrate_page_states(newpage, page);
return MIGRATEPAGE_SUCCESS;
}
#endif
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 3e0d405dc842..e646ae44077d 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -59,6 +59,7 @@ extern void putback_movable_page(struct page *page);
extern int migrate_prep(void);
extern int migrate_prep_local(void);
+extern void migrate_page_states(struct page *newpage, struct page *page);
extern void migrate_page_copy(struct page *newpage, struct page *page);
extern int migrate_huge_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page);
@@ -79,6 +80,10 @@ static inline int isolate_movable_page(struct page *page, isolate_mode_t mode)
static inline int migrate_prep(void) { return -ENOSYS; }
static inline int migrate_prep_local(void) { return -ENOSYS; }
+static inline void migrate_page_states(struct page *newpage, struct page *page)
+{
+}
+
static inline void migrate_page_copy(struct page *newpage,
struct page *page) {}
diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
index ebf3d89a3919..bdf66af9b937 100644
--- a/include/linux/migrate_mode.h
+++ b/include/linux/migrate_mode.h
@@ -6,11 +6,16 @@
* on most operations but not ->writepage as the potential stall time
* is too significant
* MIGRATE_SYNC will block when migrating pages
+ * MIGRATE_SYNC_NO_COPY will block when migrating pages but will not copy pages
+ * with the CPU. Instead, page copy happens outside the migratepage()
+ * callback and is likely using a DMA engine. See migrate_vma() and HMM
+ * (mm/hmm.c) for users of this mode.
*/
enum migrate_mode {
MIGRATE_ASYNC,
MIGRATE_SYNC_LIGHT,
MIGRATE_SYNC,
+ MIGRATE_SYNC_NO_COPY,
};
#endif /* MIGRATE_MODE_H_INCLUDED */
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index da91df50ba31..145b903eb023 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -139,6 +139,14 @@ int balloon_page_migrate(struct address_space *mapping,
{
struct balloon_dev_info *balloon = balloon_page_device(page);
+ /*
+ * We can not easily support the no copy case here so ignore it as it
+ * is unlikely to be use with ballon pages. See include/linux/hmm.h for
+ * user of the MIGRATE_SYNC_NO_COPY mode.
+ */
+ if (mode == MIGRATE_SYNC_NO_COPY)
+ return -EINVAL;
+
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
diff --git a/mm/migrate.c b/mm/migrate.c
index 627671551873..37568e4e2ba6 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -603,15 +603,10 @@ static void copy_huge_page(struct page *dst, struct page *src)
/*
* Copy the page to its new location
*/
-void migrate_page_copy(struct page *newpage, struct page *page)
+void migrate_page_states(struct page *newpage, struct page *page)
{
int cpupid;
- if (PageHuge(page) || PageTransHuge(page))
- copy_huge_page(newpage, page);
- else
- copy_highpage(newpage, page);
-
if (PageError(page))
SetPageError(newpage);
if (PageReferenced(page))
@@ -665,6 +660,17 @@ void migrate_page_copy(struct page *newpage, struct page *page)
mem_cgroup_migrate(page, newpage);
}
+EXPORT_SYMBOL(migrate_page_states);
+
+void migrate_page_copy(struct page *newpage, struct page *page)
+{
+ if (PageHuge(page) || PageTransHuge(page))
+ copy_huge_page(newpage, page);
+ else
+ copy_highpage(newpage, page);
+
+ migrate_page_states(newpage, page);
+}
EXPORT_SYMBOL(migrate_page_copy);
/************************************************************
@@ -690,7 +696,10 @@ int migrate_page(struct address_space *mapping,
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
- migrate_page_copy(newpage, page);
+ if (mode != MIGRATE_SYNC_NO_COPY)
+ migrate_page_copy(newpage, page);
+ else
+ migrate_page_states(newpage, page);
return MIGRATEPAGE_SUCCESS;
}
EXPORT_SYMBOL(migrate_page);
@@ -740,12 +749,15 @@ int buffer_migrate_page(struct address_space *mapping,
SetPagePrivate(newpage);
- migrate_page_copy(newpage, page);
+ if (mode != MIGRATE_SYNC_NO_COPY)
+ migrate_page_copy(newpage, page);
+ else
+ migrate_page_states(newpage, page);
bh = head;
do {
unlock_buffer(bh);
- put_bh(bh);
+ put_bh(bh);
bh = bh->b_this_page;
} while (bh != head);
@@ -804,8 +816,13 @@ static int fallback_migrate_page(struct address_space *mapping,
{
if (PageDirty(page)) {
/* Only writeback pages in full synchronous migration */
- if (mode != MIGRATE_SYNC)
+ switch (mode) {
+ case MIGRATE_SYNC:
+ case MIGRATE_SYNC_NO_COPY:
+ break;
+ default:
return -EBUSY;
+ }
return writeout(mapping, page);
}
@@ -942,7 +959,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
* the retry loop is too short and in the sync-light case,
* the overhead of stalling is too much
*/
- if (mode != MIGRATE_SYNC) {
+ switch (mode) {
+ case MIGRATE_SYNC:
+ case MIGRATE_SYNC_NO_COPY:
+ break;
+ default:
rc = -EBUSY;
goto out_unlock;
}
@@ -1212,8 +1233,15 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
return -ENOMEM;
if (!trylock_page(hpage)) {
- if (!force || mode != MIGRATE_SYNC)
+ if (!force)
goto out;
+ switch (mode) {
+ case MIGRATE_SYNC:
+ case MIGRATE_SYNC_NO_COPY:
+ break;
+ default:
+ goto out;
+ }
lock_page(hpage);
}
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 15959d35fc26..a2c111046e1c 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1983,6 +1983,14 @@ int zs_page_migrate(struct address_space *mapping, struct page *newpage,
unsigned int obj_idx;
int ret = -EAGAIN;
+ /*
+ * We cannot support the _NO_COPY case here, because copy needs to
+ * happen under the zs lock, which does not work with
+ * MIGRATE_SYNC_NO_COPY workflow.
+ */
+ if (mode == MIGRATE_SYNC_NO_COPY)
+ return -EINVAL;
+
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
--
2.13.0
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