1 files changed, 74 insertions, 97 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index d0cf700bf201..1146fcfa3215 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -126,7 +126,7 @@ static void page_cache_delete(struct address_space *mapping,
 	/* hugetlb pages are represented by a single entry in the xarray */
 	if (!PageHuge(page)) {
 		xas_set_order(&xas, page->index, compound_order(page));
-		nr = 1U << compound_order(page);
+		nr = compound_nr(page);
 	}
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -203,8 +203,9 @@ static void unaccount_page_cache_page(struct address_space *mapping,
 		__mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
 		if (PageTransHuge(page))
 			__dec_node_page_state(page, NR_SHMEM_THPS);
-	} else {
-		VM_BUG_ON_PAGE(PageTransHuge(page), page);
+	} else if (PageTransHuge(page)) {
+		__dec_node_page_state(page, NR_FILE_THPS);
+		filemap_nr_thps_dec(mapping);
 	}
 
 	/*
@@ -281,11 +282,11 @@ EXPORT_SYMBOL(delete_from_page_cache);
  * @pvec: pagevec with pages to delete
  *
  * The function walks over mapping->i_pages and removes pages passed in @pvec
- * from the mapping. The function expects @pvec to be sorted by page index.
+ * from the mapping. The function expects @pvec to be sorted by page index
+ * and is optimised for it to be dense.
  * It tolerates holes in @pvec (mapping entries at those indices are not
  * modified). The function expects only THP head pages to be present in the
- * @pvec and takes care to delete all corresponding tail pages from the
- * mapping as well.
+ * @pvec.
  *
  * The function expects the i_pages lock to be held.
  */
@@ -294,40 +295,43 @@ static void page_cache_delete_batch(struct address_space *mapping,
 {
 	XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);
 	int total_pages = 0;
-	int i = 0, tail_pages = 0;
+	int i = 0;
 	struct page *page;
 
 	mapping_set_update(&xas, mapping);
 	xas_for_each(&xas, page, ULONG_MAX) {
-		if (i >= pagevec_count(pvec) && !tail_pages)
+		if (i >= pagevec_count(pvec))
 			break;
+
+		/* A swap/dax/shadow entry got inserted? Skip it. */
 		if (xa_is_value(page))
 			continue;
-		if (!tail_pages) {
-			/*
-			 * Some page got inserted in our range? Skip it. We
-			 * have our pages locked so they are protected from
-			 * being removed.
-			 */
-			if (page != pvec->pages[i]) {
-				VM_BUG_ON_PAGE(page->index >
-						pvec->pages[i]->index, page);
-				continue;
-			}
-			WARN_ON_ONCE(!PageLocked(page));
-			if (PageTransHuge(page) && !PageHuge(page))
-				tail_pages = HPAGE_PMD_NR - 1;
+		/*
+		 * A page got inserted in our range? Skip it. We have our
+		 * pages locked so they are protected from being removed.
+		 * If we see a page whose index is higher than ours, it
+		 * means our page has been removed, which shouldn't be
+		 * possible because we're holding the PageLock.
+		 */
+		if (page != pvec->pages[i]) {
+			VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,
+					page);
+			continue;
+		}
+
+		WARN_ON_ONCE(!PageLocked(page));
+
+		if (page->index == xas.xa_index)
 			page->mapping = NULL;
-			/*
-			 * Leave page->index set: truncation lookup relies
-			 * upon it
-			 */
+		/* Leave page->index set: truncation lookup relies on it */
+
+		/*
+		 * Move to the next page in the vector if this is a regular
+		 * page or the index is of the last sub-page of this compound
+		 * page.
+		 */
+		if (page->index + compound_nr(page) - 1 == xas.xa_index)
 			i++;
-		} else {
-			VM_BUG_ON_PAGE(page->index + HPAGE_PMD_NR - tail_pages
-					!= pvec->pages[i]->index, page);
-			tail_pages--;
-		}
 		xas_store(&xas, NULL);
 		total_pages++;
 	}
@@ -408,7 +412,8 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 		.range_end = end,
 	};
 
-	if (!mapping_cap_writeback_dirty(mapping))
+	if (!mapping_cap_writeback_dirty(mapping) ||
+	    !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
 		return 0;
 
 	wbc_attach_fdatawrite_inode(&wbc, mapping->host);
@@ -617,10 +622,13 @@ int filemap_fdatawait_keep_errors(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
 
+/* Returns true if writeback might be needed or already in progress. */
 static bool mapping_needs_writeback(struct address_space *mapping)
 {
-	return (!dax_mapping(mapping) && mapping->nrpages) ||
-	    (dax_mapping(mapping) && mapping->nrexceptional);
+	if (dax_mapping(mapping))
+		return mapping->nrexceptional;
+
+	return mapping->nrpages;
 }
 
 int filemap_write_and_wait(struct address_space *mapping)
@@ -1516,7 +1524,7 @@ EXPORT_SYMBOL(page_cache_prev_miss);
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
 {
 	XA_STATE(xas, &mapping->i_pages, offset);
-	struct page *head, *page;
+	struct page *page;
 
 	rcu_read_lock();
 repeat:
@@ -1531,25 +1539,19 @@ repeat:
 	if (!page || xa_is_value(page))
 		goto out;
 
-	head = compound_head(page);
-	if (!page_cache_get_speculative(head))
-		goto repeat;
-
-	/* The page was split under us? */
-	if (compound_head(page) != head) {
-		put_page(head);
+	if (!page_cache_get_speculative(page))
 		goto repeat;
-	}
 
 	/*
-	 * Has the page moved?
+	 * Has the page moved or been split?
 	 * This is part of the lockless pagecache protocol. See
 	 * include/linux/pagemap.h for details.
 	 */
 	if (unlikely(page != xas_reload(&xas))) {
-		put_page(head);
+		put_page(page);
 		goto repeat;
 	}
+	page = find_subpage(page, offset);
 out:
 	rcu_read_unlock();
 
@@ -1646,7 +1648,7 @@ repeat:
 		}
 
 		/* Has the page been truncated? */
-		if (unlikely(page->mapping != mapping)) {
+		if (unlikely(compound_head(page)->mapping != mapping)) {
 			unlock_page(page);
 			put_page(page);
 			goto repeat;
@@ -1731,7 +1733,6 @@ unsigned find_get_entries(struct address_space *mapping,
 
 	rcu_read_lock();
 	xas_for_each(&xas, page, ULONG_MAX) {
-		struct page *head;
 		if (xas_retry(&xas, page))
 			continue;
 		/*
@@ -1742,17 +1743,13 @@ unsigned find_get_entries(struct address_space *mapping,
 		if (xa_is_value(page))
 			goto export;
 
-		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (!page_cache_get_speculative(page))
 			goto retry;
 
-		/* The page was split under us? */
-		if (compound_head(page) != head)
-			goto put_page;
-
-		/* Has the page moved? */
+		/* Has the page moved or been split? */
 		if (unlikely(page != xas_reload(&xas)))
 			goto put_page;
+		page = find_subpage(page, xas.xa_index);
 
 export:
 		indices[ret] = xas.xa_index;
@@ -1761,7 +1758,7 @@ export:
 			break;
 		continue;
 put_page:
-		put_page(head);
+		put_page(page);
 retry:
 		xas_reset(&xas);
 	}
@@ -1803,33 +1800,27 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
 
 	rcu_read_lock();
 	xas_for_each(&xas, page, end) {
-		struct page *head;
 		if (xas_retry(&xas, page))
 			continue;
 		/* Skip over shadow, swap and DAX entries */
 		if (xa_is_value(page))
 			continue;
 
-		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (!page_cache_get_speculative(page))
 			goto retry;
 
-		/* The page was split under us? */
-		if (compound_head(page) != head)
-			goto put_page;
-
-		/* Has the page moved? */
+		/* Has the page moved or been split? */
 		if (unlikely(page != xas_reload(&xas)))
 			goto put_page;
 
-		pages[ret] = page;
+		pages[ret] = find_subpage(page, xas.xa_index);
 		if (++ret == nr_pages) {
 			*start = xas.xa_index + 1;
 			goto out;
 		}
 		continue;
 put_page:
-		put_page(head);
+		put_page(page);
 retry:
 		xas_reset(&xas);
 	}
@@ -1874,7 +1865,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 
 	rcu_read_lock();
 	for (page = xas_load(&xas); page; page = xas_next(&xas)) {
-		struct page *head;
 		if (xas_retry(&xas, page))
 			continue;
 		/*
@@ -1884,24 +1874,19 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 		if (xa_is_value(page))
 			break;
 
-		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (!page_cache_get_speculative(page))
 			goto retry;
 
-		/* The page was split under us? */
-		if (compound_head(page) != head)
-			goto put_page;
-
-		/* Has the page moved? */
+		/* Has the page moved or been split? */
 		if (unlikely(page != xas_reload(&xas)))
 			goto put_page;
 
-		pages[ret] = page;
+		pages[ret] = find_subpage(page, xas.xa_index);
 		if (++ret == nr_pages)
 			break;
 		continue;
 put_page:
-		put_page(head);
+		put_page(page);
 retry:
 		xas_reset(&xas);
 	}
@@ -1937,7 +1922,6 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
 
 	rcu_read_lock();
 	xas_for_each_marked(&xas, page, end, tag) {
-		struct page *head;
 		if (xas_retry(&xas, page))
 			continue;
 		/*
@@ -1948,26 +1932,21 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
 		if (xa_is_value(page))
 			continue;
 
-		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (!page_cache_get_speculative(page))
 			goto retry;
 
-		/* The page was split under us? */
-		if (compound_head(page) != head)
-			goto put_page;
-
-		/* Has the page moved? */
+		/* Has the page moved or been split? */
 		if (unlikely(page != xas_reload(&xas)))
 			goto put_page;
 
-		pages[ret] = page;
+		pages[ret] = find_subpage(page, xas.xa_index);
 		if (++ret == nr_pages) {
 			*index = xas.xa_index + 1;
 			goto out;
 		}
 		continue;
 put_page:
-		put_page(head);
+		put_page(page);
 retry:
 		xas_reset(&xas);
 	}
@@ -2562,12 +2541,12 @@ retry_find:
 		goto out_retry;
 
 	/* Did it get truncated? */
-	if (unlikely(page->mapping != mapping)) {
+	if (unlikely(compound_head(page)->mapping != mapping)) {
 		unlock_page(page);
 		put_page(page);
 		goto retry_find;
 	}
-	VM_BUG_ON_PAGE(page->index != offset, page);
+	VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
 
 	/*
 	 * We have a locked page in the page cache, now we need to check
@@ -2648,7 +2627,7 @@ void filemap_map_pages(struct vm_fault *vmf,
 	pgoff_t last_pgoff = start_pgoff;
 	unsigned long max_idx;
 	XA_STATE(xas, &mapping->i_pages, start_pgoff);
-	struct page *head, *page;
+	struct page *page;
 
 	rcu_read_lock();
 	xas_for_each(&xas, page, end_pgoff) {
@@ -2657,24 +2636,19 @@ void filemap_map_pages(struct vm_fault *vmf,
 		if (xa_is_value(page))
 			goto next;
 
-		head = compound_head(page);
-
 		/*
 		 * Check for a locked page first, as a speculative
 		 * reference may adversely influence page migration.
 		 */
-		if (PageLocked(head))
+		if (PageLocked(page))
 			goto next;
-		if (!page_cache_get_speculative(head))
+		if (!page_cache_get_speculative(page))
 			goto next;
 
-		/* The page was split under us? */
-		if (compound_head(page) != head)
-			goto skip;
-
-		/* Has the page moved? */
+		/* Has the page moved or been split? */
 		if (unlikely(page != xas_reload(&xas)))
 			goto skip;
+		page = find_subpage(page, xas.xa_index);
 
 		if (!PageUptodate(page) ||
 				PageReadahead(page) ||
@@ -2988,6 +2962,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	loff_t count;
 	int ret;
 
+	if (IS_SWAPFILE(inode))
+		return -ETXTBSY;
+
 	if (!iov_iter_count(from))
 		return 0;