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@@ -216,6 +216,56 @@ out:
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pte_unmap_unlock(ptep, ptl);
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}
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+#ifdef CONFIG_BLOCK
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+/* Returns true if all buffers are successfully locked */
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+static bool buffer_migrate_lock_buffers(struct buffer_head *head,
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+ enum migrate_mode mode)
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+{
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+ struct buffer_head *bh = head;
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+
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+ /* Simple case, sync compaction */
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+ if (mode != MIGRATE_ASYNC) {
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+ do {
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+ get_bh(bh);
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+ lock_buffer(bh);
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+ bh = bh->b_this_page;
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+
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+ } while (bh != head);
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+
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+ return true;
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+ }
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+
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+ /* async case, we cannot block on lock_buffer so use trylock_buffer */
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+ do {
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+ get_bh(bh);
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+ if (!trylock_buffer(bh)) {
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+ /*
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+ * We failed to lock the buffer and cannot stall in
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+ * async migration. Release the taken locks
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+ */
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+ struct buffer_head *failed_bh = bh;
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+ put_bh(failed_bh);
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+ bh = head;
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+ while (bh != failed_bh) {
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+ unlock_buffer(bh);
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+ put_bh(bh);
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+ bh = bh->b_this_page;
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+ }
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+ return false;
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+ }
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+
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+ bh = bh->b_this_page;
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+ } while (bh != head);
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+ return true;
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+}
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+#else
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+static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
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+ enum migrate_mode mode)
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+{
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+ return true;
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+}
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+#endif /* CONFIG_BLOCK */
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+
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/*
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* Replace the page in the mapping.
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*
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@@ -225,7 +275,8 @@ out:
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* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
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*/
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static int migrate_page_move_mapping(struct address_space *mapping,
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- struct page *newpage, struct page *page)
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+ struct page *newpage, struct page *page,
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+ struct buffer_head *head, enum migrate_mode mode)
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{
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int expected_count;
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void **pslot;
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@@ -254,6 +305,20 @@ static int migrate_page_move_mapping(struct address_space *mapping,
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return -EAGAIN;
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}
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+ /*
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+ * In the async migration case of moving a page with buffers, lock the
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+ * buffers using trylock before the mapping is moved. If the mapping
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+ * was moved, we later failed to lock the buffers and could not move
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+ * the mapping back due to an elevated page count, we would have to
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+ * block waiting on other references to be dropped.
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+ */
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+ if (mode == MIGRATE_ASYNC && head &&
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+ !buffer_migrate_lock_buffers(head, mode)) {
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+ page_unfreeze_refs(page, expected_count);
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+ spin_unlock_irq(&mapping->tree_lock);
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+ return -EAGAIN;
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+ }
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+
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/*
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* Now we know that no one else is looking at the page.
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*/
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@@ -409,13 +474,14 @@ EXPORT_SYMBOL(fail_migrate_page);
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* Pages are locked upon entry and exit.
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*/
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int migrate_page(struct address_space *mapping,
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- struct page *newpage, struct page *page)
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+ struct page *newpage, struct page *page,
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+ enum migrate_mode mode)
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{
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int rc;
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BUG_ON(PageWriteback(page)); /* Writeback must be complete */
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- rc = migrate_page_move_mapping(mapping, newpage, page);
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+ rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
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if (rc)
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return rc;
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@@ -432,28 +498,28 @@ EXPORT_SYMBOL(migrate_page);
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* exist.
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*/
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int buffer_migrate_page(struct address_space *mapping,
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- struct page *newpage, struct page *page)
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+ struct page *newpage, struct page *page, enum migrate_mode mode)
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{
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struct buffer_head *bh, *head;
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int rc;
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if (!page_has_buffers(page))
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- return migrate_page(mapping, newpage, page);
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+ return migrate_page(mapping, newpage, page, mode);
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head = page_buffers(page);
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- rc = migrate_page_move_mapping(mapping, newpage, page);
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+ rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
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if (rc)
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return rc;
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- bh = head;
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- do {
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- get_bh(bh);
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- lock_buffer(bh);
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- bh = bh->b_this_page;
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-
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- } while (bh != head);
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+ /*
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+ * In the async case, migrate_page_move_mapping locked the buffers
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+ * with an IRQ-safe spinlock held. In the sync case, the buffers
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+ * need to be locked now
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+ */
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+ if (mode != MIGRATE_ASYNC)
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+ BUG_ON(!buffer_migrate_lock_buffers(head, mode));
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ClearPagePrivate(page);
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set_page_private(newpage, page_private(page));
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@@ -530,10 +596,14 @@ static int writeout(struct address_space *mapping, struct page *page)
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* Default handling if a filesystem does not provide a migration function.
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*/
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static int fallback_migrate_page(struct address_space *mapping,
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- struct page *newpage, struct page *page)
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+ struct page *newpage, struct page *page, enum migrate_mode mode)
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{
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- if (PageDirty(page))
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+ if (PageDirty(page)) {
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+ /* Only writeback pages in full synchronous migration */
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+ if (mode != MIGRATE_SYNC)
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+ return -EBUSY;
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return writeout(mapping, page);
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+ }
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/*
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* Buffers may be managed in a filesystem specific way.
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@@ -543,7 +613,7 @@ static int fallback_migrate_page(struct address_space *mapping,
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!try_to_release_page(page, GFP_KERNEL))
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return -EAGAIN;
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- return migrate_page(mapping, newpage, page);
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+ return migrate_page(mapping, newpage, page, mode);
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}
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/*
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@@ -558,7 +628,7 @@ static int fallback_migrate_page(struct address_space *mapping,
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* == 0 - success
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*/
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static int move_to_new_page(struct page *newpage, struct page *page,
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- int remap_swapcache, bool sync)
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+ int remap_swapcache, enum migrate_mode mode)
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{
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struct address_space *mapping;
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int rc;
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@@ -579,29 +649,18 @@ static int move_to_new_page(struct page *newpage, struct page *page,
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mapping = page_mapping(page);
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if (!mapping)
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- rc = migrate_page(mapping, newpage, page);
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- else {
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+ rc = migrate_page(mapping, newpage, page, mode);
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+ else if (mapping->a_ops->migratepage)
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/*
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- * Do not writeback pages if !sync and migratepage is
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- * not pointing to migrate_page() which is nonblocking
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- * (swapcache/tmpfs uses migratepage = migrate_page).
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+ * Most pages have a mapping and most filesystems provide a
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+ * migratepage callback. Anonymous pages are part of swap
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+ * space which also has its own migratepage callback. This
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+ * is the most common path for page migration.
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*/
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- if (PageDirty(page) && !sync &&
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- mapping->a_ops->migratepage != migrate_page)
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- rc = -EBUSY;
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- else if (mapping->a_ops->migratepage)
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- /*
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- * Most pages have a mapping and most filesystems
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- * should provide a migration function. Anonymous
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- * pages are part of swap space which also has its
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- * own migration function. This is the most common
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- * path for page migration.
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- */
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- rc = mapping->a_ops->migratepage(mapping,
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- newpage, page);
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- else
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- rc = fallback_migrate_page(mapping, newpage, page);
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- }
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+ rc = mapping->a_ops->migratepage(mapping,
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+ newpage, page, mode);
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+ else
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+ rc = fallback_migrate_page(mapping, newpage, page, mode);
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if (rc) {
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newpage->mapping = NULL;
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@@ -616,7 +675,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
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}
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static int __unmap_and_move(struct page *page, struct page *newpage,
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- int force, bool offlining, bool sync)
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+ int force, bool offlining, enum migrate_mode mode)
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{
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int rc = -EAGAIN;
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int remap_swapcache = 1;
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@@ -625,7 +684,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
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struct anon_vma *anon_vma = NULL;
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if (!trylock_page(page)) {
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- if (!force || !sync)
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+ if (!force || mode == MIGRATE_ASYNC)
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goto out;
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/*
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@@ -671,10 +730,12 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
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if (PageWriteback(page)) {
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/*
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- * For !sync, there is no point retrying as the retry loop
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- * is expected to be too short for PageWriteback to be cleared
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+ * Only in the case of a full syncronous migration is it
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+ * necessary to wait for PageWriteback. In the async case,
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+ * the retry loop is too short and in the sync-light case,
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+ * the overhead of stalling is too much
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*/
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- if (!sync) {
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+ if (mode != MIGRATE_SYNC) {
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rc = -EBUSY;
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goto uncharge;
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}
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@@ -745,7 +806,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
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skip_unmap:
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if (!page_mapped(page))
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- rc = move_to_new_page(newpage, page, remap_swapcache, sync);
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+ rc = move_to_new_page(newpage, page, remap_swapcache, mode);
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if (rc && remap_swapcache)
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remove_migration_ptes(page, page);
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@@ -768,7 +829,8 @@ out:
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* to the newly allocated page in newpage.
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*/
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static int unmap_and_move(new_page_t get_new_page, unsigned long private,
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- struct page *page, int force, bool offlining, bool sync)
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+ struct page *page, int force, bool offlining,
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+ enum migrate_mode mode)
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{
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int rc = 0;
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int *result = NULL;
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@@ -777,6 +839,8 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
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if (!newpage)
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return -ENOMEM;
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+ mem_cgroup_reset_owner(newpage);
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+
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if (page_count(page) == 1) {
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/* page was freed from under us. So we are done. */
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goto out;
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@@ -786,7 +850,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
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if (unlikely(split_huge_page(page)))
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goto out;
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- rc = __unmap_and_move(page, newpage, force, offlining, sync);
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+ rc = __unmap_and_move(page, newpage, force, offlining, mode);
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out:
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if (rc != -EAGAIN) {
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/*
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@@ -834,7 +898,8 @@ out:
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*/
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static int unmap_and_move_huge_page(new_page_t get_new_page,
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unsigned long private, struct page *hpage,
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- int force, bool offlining, bool sync)
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+ int force, bool offlining,
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+ enum migrate_mode mode)
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{
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int rc = 0;
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int *result = NULL;
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@@ -847,7 +912,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
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rc = -EAGAIN;
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if (!trylock_page(hpage)) {
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- if (!force || !sync)
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+ if (!force || mode != MIGRATE_SYNC)
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goto out;
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lock_page(hpage);
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}
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@@ -858,7 +923,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
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try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
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if (!page_mapped(hpage))
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- rc = move_to_new_page(new_hpage, hpage, 1, sync);
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+ rc = move_to_new_page(new_hpage, hpage, 1, mode);
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if (rc)
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remove_migration_ptes(hpage, hpage);
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@@ -901,7 +966,7 @@ out:
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*/
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int migrate_pages(struct list_head *from,
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new_page_t get_new_page, unsigned long private, bool offlining,
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- bool sync)
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+ enum migrate_mode mode)
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{
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int retry = 1;
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int nr_failed = 0;
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@@ -922,7 +987,7 @@ int migrate_pages(struct list_head *from,
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rc = unmap_and_move(get_new_page, private,
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page, pass > 2, offlining,
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- sync);
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+ mode);
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switch(rc) {
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case -ENOMEM:
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@@ -952,7 +1017,7 @@ out:
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|
|
|
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int migrate_huge_pages(struct list_head *from,
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|
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new_page_t get_new_page, unsigned long private, bool offlining,
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- bool sync)
|
|
|
+ enum migrate_mode mode)
|
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{
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|
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int retry = 1;
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int nr_failed = 0;
|
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@@ -969,7 +1034,7 @@ int migrate_huge_pages(struct list_head *from,
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rc = unmap_and_move_huge_page(get_new_page,
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private, page, pass > 2, offlining,
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- sync);
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+ mode);
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|
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switch(rc) {
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case -ENOMEM:
|
|
@@ -1098,7 +1163,7 @@ set_status:
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err = 0;
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if (!list_empty(&pagelist)) {
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err = migrate_pages(&pagelist, new_page_node,
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- (unsigned long)pm, 0, true);
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+ (unsigned long)pm, 0, MIGRATE_SYNC);
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if (err)
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|
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putback_lru_pages(&pagelist);
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|
|
}
|