[PATCH] swap 13/13 may_enter_fs?

[Hugh Dickins]

shrink_list's may_enter_fs (may_write_page would be a better name)
currently reflects that swapcache page I/O won't suffer from FS
complications, so can be done if __GFP_IO without __GFP_FS; but
the same is true of a tmpfs page (which is just this stage away
from being a swapcache page), so check bdi->memory_backed instead.

--- swap12/mm/vmscan.c	Tue Mar 25 20:43:07 2003
+++ swap13/mm/vmscan.c	Tue Mar 25 20:45:08 2003
@@ -235,7 +235,6 @@
 	pagevec_init(&freed_pvec, 1);
 	while (!list_empty(page_list)) {
 		struct page *page;
-		int may_enter_fs;
 
 		page = list_entry(page_list->prev, struct page, lru);
 		list_del(&page->lru);
@@ -248,8 +247,6 @@
 			(*nr_mapped)++;
 
 		BUG_ON(PageActive(page));
-		may_enter_fs = (gfp_mask & __GFP_FS) ||
-				(PageSwapCache(page) && (gfp_mask & __GFP_IO));
 
 		if (PageWriteback(page))
 			goto keep_locked;
@@ -315,15 +312,19 @@
 		 * See swapfile.c:page_queue_congested().
 		 */
 		if (PageDirty(page)) {
+			struct backing_dev_info *bdi;
+
 			if (!is_page_cache_freeable(page))
 				goto keep_locked;
 			if (!mapping)
 				goto keep_locked;
 			if (mapping->a_ops->writepage == NULL)
 				goto activate_locked;
-			if (!may_enter_fs)
+			bdi = mapping->backing_dev_info;
+			if (!(gfp_mask & (bdi->memory_backed?
+					__GFP_IO: __GFP_FS)))
 				goto keep_locked;
-			if (!may_write_to_queue(mapping->backing_dev_info))
+			if (!may_write_to_queue(bdi))
 				goto keep_locked;
 			write_lock(&mapping->page_lock);
 			if (test_clear_page_dirty(page)) {