* collapse_shmem - collapse small tmpfs/shmem pages into huge one.
*
* Basic scheme is simple, details are more complex:
- * - allocate and freeze a new huge page;
+ * - allocate and lock a new huge page;
* - scan page cache replacing old pages with the new one
* + swap in pages if necessary;
* + fill in gaps;
* - if replacing succeeds:
* + copy data over;
* + free old pages;
- * + unfreeze huge page;
+ * + unlock huge page;
* - if replacing failed;
* + put all pages back and unfreeze them;
* + restore gaps in the page cache;
- * + free huge page;
+ * + unlock and free huge page;
*/
static void collapse_shmem(struct mm_struct *mm,
struct address_space *mapping, pgoff_t start,
goto out;
}
- new_page->index = start;
- new_page->mapping = mapping;
- __SetPageSwapBacked(new_page);
- __SetPageLocked(new_page);
- BUG_ON(!page_ref_freeze(new_page, 1));
-
- /*
- * At this point the new_page is 'frozen' (page_count() is zero),
- * locked and not up-to-date. It's safe to insert it into the page
- * cache, because nobody would be able to map it or use it in other
- * way until we unfreeze it.
- */
-
/* This will be less messy when we use multi-index entries */
do {
xas_lock_irq(&xas);
if (!xas_error(&xas))
break;
xas_unlock_irq(&xas);
- if (!xas_nomem(&xas, GFP_KERNEL))
+ if (!xas_nomem(&xas, GFP_KERNEL)) {
+ mem_cgroup_cancel_charge(new_page, memcg, true);
+ result = SCAN_FAIL;
goto out;
+ }
} while (1);
+ __SetPageLocked(new_page);
+ __SetPageSwapBacked(new_page);
+ new_page->index = start;
+ new_page->mapping = mapping;
+
+ /*
+ * At this point the new_page is locked and not up-to-date.
+ * It's safe to insert it into the page cache, because nobody would
+ * be able to map it or use it in another way until we unlock it.
+ */
+
xas_set(&xas, start);
for (index = start; index < end; index++) {
struct page *page = xas_next(&xas);
VM_BUG_ON(index != xas.xa_index);
if (!page) {
+ /*
+ * Stop if extent has been truncated or hole-punched,
+ * and is now completely empty.
+ */
+ if (index == start) {
+ if (!xas_next_entry(&xas, end - 1)) {
+ result = SCAN_TRUNCATED;
+ goto xa_locked;
+ }
+ xas_set(&xas, index);
+ }
if (!shmem_charge(mapping->host, 1)) {
result = SCAN_FAIL;
- break;
+ goto xa_locked;
}
xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
nr_none++;
result = SCAN_FAIL;
goto xa_unlocked;
}
- xas_lock_irq(&xas);
- xas_set(&xas, index);
} else if (trylock_page(page)) {
get_page(page);
+ xas_unlock_irq(&xas);
} else {
result = SCAN_PAGE_LOCK;
- break;
+ goto xa_locked;
}
/*
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageUptodate(page), page);
- VM_BUG_ON_PAGE(PageTransCompound(page), page);
+
+ /*
+ * If file was truncated then extended, or hole-punched, before
+ * we locked the first page, then a THP might be there already.
+ */
+ if (PageTransCompound(page)) {
+ result = SCAN_PAGE_COMPOUND;
+ goto out_unlock;
+ }
if (page_mapping(page) != mapping) {
result = SCAN_TRUNCATED;
goto out_unlock;
}
- xas_unlock_irq(&xas);
if (isolate_lru_page(page)) {
result = SCAN_DEL_PAGE_LRU;
- goto out_isolate_failed;
+ goto out_unlock;
}
if (page_mapped(page))
*/
if (!page_ref_freeze(page, 3)) {
result = SCAN_PAGE_COUNT;
- goto out_lru;
+ xas_unlock_irq(&xas);
+ putback_lru_page(page);
+ goto out_unlock;
}
/*
/* Finally, replace with the new page. */
xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
continue;
-out_lru:
- xas_unlock_irq(&xas);
- putback_lru_page(page);
-out_isolate_failed:
- unlock_page(page);
- put_page(page);
- goto xa_unlocked;
out_unlock:
unlock_page(page);
put_page(page);
- break;
+ goto xa_unlocked;
}
- xas_unlock_irq(&xas);
+ __inc_node_page_state(new_page, NR_SHMEM_THPS);
+ if (nr_none) {
+ struct zone *zone = page_zone(new_page);
+
+ __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
+ __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
+ }
+
+xa_locked:
+ xas_unlock_irq(&xas);
xa_unlocked:
+
if (result == SCAN_SUCCEED) {
struct page *page, *tmp;
- struct zone *zone = page_zone(new_page);
/*
* Replacing old pages with new one has succeeded, now we
* need to copy the content and free the old pages.
*/
+ index = start;
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
+ while (index < page->index) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
+ }
copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
page);
list_del(&page->lru);
- unlock_page(page);
- page_ref_unfreeze(page, 1);
page->mapping = NULL;
+ page_ref_unfreeze(page, 1);
ClearPageActive(page);
ClearPageUnevictable(page);
+ unlock_page(page);
put_page(page);
+ index++;
}
-
- local_irq_disable();
- __inc_node_page_state(new_page, NR_SHMEM_THPS);
- if (nr_none) {
- __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
- __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
+ while (index < end) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
}
- local_irq_enable();
- /*
- * Remove pte page tables, so we can re-fault
- * the page as huge.
- */
- retract_page_tables(mapping, start);
-
- /* Everything is ready, let's unfreeze the new_page */
- set_page_dirty(new_page);
SetPageUptodate(new_page);
- page_ref_unfreeze(new_page, HPAGE_PMD_NR);
+ page_ref_add(new_page, HPAGE_PMD_NR - 1);
+ set_page_dirty(new_page);
mem_cgroup_commit_charge(new_page, memcg, false, true);
lru_cache_add_anon(new_page);
- unlock_page(new_page);
+ /*
+ * Remove pte page tables, so we can re-fault the page as huge.
+ */
+ retract_page_tables(mapping, start);
*hpage = NULL;
khugepaged_pages_collapsed++;
} else {
struct page *page;
+
/* Something went wrong: roll back page cache changes */
- shmem_uncharge(mapping->host, nr_none);
xas_lock_irq(&xas);
+ mapping->nrpages -= nr_none;
+ shmem_uncharge(mapping->host, nr_none);
+
xas_set(&xas, start);
xas_for_each(&xas, page, end - 1) {
page = list_first_entry_or_null(&pagelist,
xas_store(&xas, page);
xas_pause(&xas);
xas_unlock_irq(&xas);
- putback_lru_page(page);
unlock_page(page);
+ putback_lru_page(page);
xas_lock_irq(&xas);
}
VM_BUG_ON(nr_none);
xas_unlock_irq(&xas);
- /* Unfreeze new_page, caller would take care about freeing it */
- page_ref_unfreeze(new_page, 1);
mem_cgroup_cancel_charge(new_page, memcg, true);
- unlock_page(new_page);
new_page->mapping = NULL;
}
+
+ unlock_page(new_page);
out:
VM_BUG_ON(!list_empty(&pagelist));
/* TODO: tracepoints */
git.samba.org / sfrench / cifs-2.6.git / blobdiff