}
#endif
-#ifdef CONFIG_BLOCK
-/* Returns true if all buffers are successfully locked */
-static bool buffer_migrate_lock_buffers(struct buffer_head *head,
- enum migrate_mode mode)
+static int expected_page_refs(struct page *page)
{
- struct buffer_head *bh = head;
+ int expected_count = 1;
- /* Simple case, sync compaction */
- if (mode != MIGRATE_ASYNC) {
- do {
- get_bh(bh);
- lock_buffer(bh);
- bh = bh->b_this_page;
-
- } while (bh != head);
-
- return true;
- }
-
- /* async case, we cannot block on lock_buffer so use trylock_buffer */
- do {
- get_bh(bh);
- if (!trylock_buffer(bh)) {
- /*
- * We failed to lock the buffer and cannot stall in
- * async migration. Release the taken locks
- */
- struct buffer_head *failed_bh = bh;
- put_bh(failed_bh);
- bh = head;
- while (bh != failed_bh) {
- unlock_buffer(bh);
- put_bh(bh);
- bh = bh->b_this_page;
- }
- return false;
- }
+ /*
+ * Device public or private pages have an extra refcount as they are
+ * ZONE_DEVICE pages.
+ */
+ expected_count += is_device_private_page(page);
+ expected_count += is_device_public_page(page);
+ if (page_mapping(page))
+ expected_count += hpage_nr_pages(page) + page_has_private(page);
- bh = bh->b_this_page;
- } while (bh != head);
- return true;
+ return expected_count;
}
-#else
-static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
- enum migrate_mode mode)
-{
- return true;
-}
-#endif /* CONFIG_BLOCK */
/*
* Replace the page in the mapping.
* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
*/
int migrate_page_move_mapping(struct address_space *mapping,
- struct page *newpage, struct page *page,
- struct buffer_head *head, enum migrate_mode mode,
+ struct page *newpage, struct page *page, enum migrate_mode mode,
int extra_count)
{
XA_STATE(xas, &mapping->i_pages, page_index(page));
struct zone *oldzone, *newzone;
int dirty;
- int expected_count = 1 + extra_count;
-
- /*
- * Device public or private pages have an extra refcount as they are
- * ZONE_DEVICE pages.
- */
- expected_count += is_device_private_page(page);
- expected_count += is_device_public_page(page);
+ int expected_count = expected_page_refs(page) + extra_count;
if (!mapping) {
/* Anonymous page without mapping */
newzone = page_zone(newpage);
xas_lock_irq(&xas);
-
- expected_count += hpage_nr_pages(page) + page_has_private(page);
if (page_count(page) != expected_count || xas_load(&xas) != page) {
xas_unlock_irq(&xas);
return -EAGAIN;
return -EAGAIN;
}
- /*
- * In the async migration case of moving a page with buffers, lock the
- * buffers using trylock before the mapping is moved. If the mapping
- * was moved, we later failed to lock the buffers and could not move
- * the mapping back due to an elevated page count, we would have to
- * block waiting on other references to be dropped.
- */
- if (mode == MIGRATE_ASYNC && head &&
- !buffer_migrate_lock_buffers(head, mode)) {
- page_ref_unfreeze(page, expected_count);
- xas_unlock_irq(&xas);
- return -EAGAIN;
- }
-
/*
* Now we know that no one else is looking at the page:
* no turning back from here.
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
- rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
+ rc = migrate_page_move_mapping(mapping, newpage, page, mode, 0);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
EXPORT_SYMBOL(migrate_page);
#ifdef CONFIG_BLOCK
-/*
- * Migration function for pages with buffers. This function can only be used
- * if the underlying filesystem guarantees that no other references to "page"
- * exist.
- */
-int buffer_migrate_page(struct address_space *mapping,
- struct page *newpage, struct page *page, enum migrate_mode mode)
+/* Returns true if all buffers are successfully locked */
+static bool buffer_migrate_lock_buffers(struct buffer_head *head,
+ enum migrate_mode mode)
+{
+ struct buffer_head *bh = head;
+
+ /* Simple case, sync compaction */
+ if (mode != MIGRATE_ASYNC) {
+ do {
+ get_bh(bh);
+ lock_buffer(bh);
+ bh = bh->b_this_page;
+
+ } while (bh != head);
+
+ return true;
+ }
+
+ /* async case, we cannot block on lock_buffer so use trylock_buffer */
+ do {
+ get_bh(bh);
+ if (!trylock_buffer(bh)) {
+ /*
+ * We failed to lock the buffer and cannot stall in
+ * async migration. Release the taken locks
+ */
+ struct buffer_head *failed_bh = bh;
+ put_bh(failed_bh);
+ bh = head;
+ while (bh != failed_bh) {
+ unlock_buffer(bh);
+ put_bh(bh);
+ bh = bh->b_this_page;
+ }
+ return false;
+ }
+
+ bh = bh->b_this_page;
+ } while (bh != head);
+ return true;
+}
+
+static int __buffer_migrate_page(struct address_space *mapping,
+ struct page *newpage, struct page *page, enum migrate_mode mode,
+ bool check_refs)
{
struct buffer_head *bh, *head;
int rc;
+ int expected_count;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page, mode);
+ /* Check whether page does not have extra refs before we do more work */
+ expected_count = expected_page_refs(page);
+ if (page_count(page) != expected_count)
+ return -EAGAIN;
+
head = page_buffers(page);
+ if (!buffer_migrate_lock_buffers(head, mode))
+ return -EAGAIN;
- rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
+ if (check_refs) {
+ bool busy;
+ bool invalidated = false;
- if (rc != MIGRATEPAGE_SUCCESS)
- return rc;
+recheck_buffers:
+ busy = false;
+ spin_lock(&mapping->private_lock);
+ bh = head;
+ do {
+ if (atomic_read(&bh->b_count)) {
+ busy = true;
+ break;
+ }
+ bh = bh->b_this_page;
+ } while (bh != head);
+ spin_unlock(&mapping->private_lock);
+ if (busy) {
+ if (invalidated) {
+ rc = -EAGAIN;
+ goto unlock_buffers;
+ }
+ invalidate_bh_lrus();
+ invalidated = true;
+ goto recheck_buffers;
+ }
+ }
- /*
- * In the async case, migrate_page_move_mapping locked the buffers
- * with an IRQ-safe spinlock held. In the sync case, the buffers
- * need to be locked now
- */
- if (mode != MIGRATE_ASYNC)
- BUG_ON(!buffer_migrate_lock_buffers(head, mode));
+ rc = migrate_page_move_mapping(mapping, newpage, page, mode, 0);
+ if (rc != MIGRATEPAGE_SUCCESS)
+ goto unlock_buffers;
ClearPagePrivate(page);
set_page_private(newpage, page_private(page));
else
migrate_page_states(newpage, page);
+ rc = MIGRATEPAGE_SUCCESS;
+unlock_buffers:
bh = head;
do {
unlock_buffer(bh);
} while (bh != head);
- return MIGRATEPAGE_SUCCESS;
+ return rc;
+}
+
+/*
+ * Migration function for pages with buffers. This function can only be used
+ * if the underlying filesystem guarantees that no other references to "page"
+ * exist. For example attached buffer heads are accessed only under page lock.
+ */
+int buffer_migrate_page(struct address_space *mapping,
+ struct page *newpage, struct page *page, enum migrate_mode mode)
+{
+ return __buffer_migrate_page(mapping, newpage, page, mode, false);
}
EXPORT_SYMBOL(buffer_migrate_page);
+
+/*
+ * Same as above except that this variant is more careful and checks that there
+ * are also no buffer head references. This function is the right one for
+ * mappings where buffer heads are directly looked up and referenced (such as
+ * block device mappings).
+ */
+int buffer_migrate_page_norefs(struct address_space *mapping,
+ struct page *newpage, struct page *page, enum migrate_mode mode)
+{
+ return __buffer_migrate_page(mapping, newpage, page, mode, true);
+}
#endif
/*
goto put_anon;
if (page_mapped(hpage)) {
+ struct address_space *mapping = page_mapping(hpage);
+
+ /*
+ * try_to_unmap could potentially call huge_pmd_unshare.
+ * Because of this, take semaphore in write mode here and
+ * set TTU_RMAP_LOCKED to let lower levels know we have
+ * taken the lock.
+ */
+ i_mmap_lock_write(mapping);
try_to_unmap(hpage,
- TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
+ TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS|
+ TTU_RMAP_LOCKED);
+ i_mmap_unlock_write(mapping);
page_was_mapped = 1;
}
projects / linux-2.6-microblaze.git / blobdiff