[PATCH] splice: LRU fixups

Nick says that the current construct isn't safe. This goes back to the
original, but sets PIPE_BUF_FLAG_LRU on user pages as well as they all
seem to be on the LRU in the first place.
Signed-off-by: Jens Axboe <axboe@suse.de>

fs/splice.c

@@ -78,6 +78,7 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
 		return 1;
 	}
 
+	buf->flags |= PIPE_BUF_FLAG_LRU;
 	return 0;
 }
 
@@ -85,6 +86,7 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
 					struct pipe_buffer *buf)
 {
 	page_cache_release(buf->page);
+	buf->flags &= ~PIPE_BUF_FLAG_LRU;
 }
 
 static int page_cache_pipe_buf_pin(struct pipe_inode_info *info,
@@ -141,6 +143,7 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 		return 1;
 
+	buf->flags |= PIPE_BUF_FLAG_LRU;
 	return generic_pipe_buf_steal(pipe, buf);
 }
 
@@ -566,37 +569,23 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 	 */
 	if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
 		/*
-		 * If steal succeeds, buf->page is now pruned from the vm
-		 * side (page cache) and we can reuse it. The page will also
-		 * be locked on successful return.
+		 * If steal succeeds, buf->page is now pruned from the
+		 * pagecache and we can reuse it. The page will also be
+		 * locked on successful return.
 		 */
 		if (buf->ops->steal(info, buf))
 			goto find_page;
 
 		page = buf->page;
-		page_cache_get(page);
-
-		/*
-		 * page must be on the LRU for adding to the pagecache.
-		 * Check this without grabbing the zone lock, if it isn't
-		 * the do grab the zone lock, recheck, and add if necessary.
-		 */
-		if (!PageLRU(page)) {
-			struct zone *zone = page_zone(page);
-
-			spin_lock_irq(&zone->lru_lock);
-			if (!PageLRU(page)) {
-				SetPageLRU(page);
-				add_page_to_inactive_list(zone, page);
-			}
-			spin_unlock_irq(&zone->lru_lock);
-		}
-
 		if (add_to_page_cache(page, mapping, index, gfp_mask)) {
-			page_cache_release(page);
 			unlock_page(page);
 			goto find_page;
 		}
+
+		page_cache_get(page);
+
+		if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+			lru_cache_add(page);
 	} else {
 find_page:
 		page = find_lock_page(mapping, index);

include/linux/pipe_fs_i.h

@@ -5,8 +5,9 @@
 
 #define PIPE_BUFFERS (16)
 
-#define PIPE_BUF_FLAG_ATOMIC	0x01	/* was atomically mapped */
-#define PIPE_BUF_FLAG_GIFT	0x02	/* page is a gift */
+#define PIPE_BUF_FLAG_LRU	0x01	/* page is on the LRU */
+#define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
+#define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
 
 struct pipe_buffer {
 	struct page *page;