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@xxxxxxxxxx> --- 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 7e2ab9c..be21c49 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 9ac2625..7fc08a5 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -1997,7 +1997,10 @@ 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 cf3669d..b2e0fdb 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -837,7 +837,10 @@ 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 d9ae86f..c08cbcc 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 48e2484..78a0fdc 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -43,6 +43,7 @@ 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); @@ -63,6 +64,10 @@ 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 ebf3d89..bdf66af 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 da91df5..145b903 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 5cfe3c2..5176772 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -601,15 +601,10 @@ 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)) @@ -663,6 +658,17 @@ 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); /************************************************************ @@ -688,7 +694,10 @@ 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); @@ -738,12 +747,15 @@ 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); @@ -802,8 +814,13 @@ 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); } @@ -940,7 +957,11 @@ 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; } @@ -1210,8 +1231,15 @@ 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 b7b1fb6..37afd65 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1982,6 +1982,14 @@ 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); -- 2.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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