[PATCH] splice: fixup writeout path after ->map changes

Since ->map() no longer locks the page, we need to adjust the handling
of those pages (and stealing) a little. This now passes full regressions
again.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 30 insertions, 19 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 27d6408ff490..22fac87e90b3 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -50,7 +50,8 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
         struct page *page = buf->page;
         struct address_space *mapping = page_mapping(page);
 
-        WARN_ON(!PageLocked(page));
+        lock_page(page);
+
         WARN_ON(!PageUptodate(page));
 
         /*
@@ -65,8 +66,10 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
         if (PagePrivate(page))
                 try_to_release_page(page, mapping_gfp_mask(mapping));
 
-        if (!remove_mapping(mapping, page))
+        if (!remove_mapping(mapping, page)) {
+                unlock_page(page);
                 return 1;
+        }
 
         buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
         return 0;
@@ -507,14 +510,12 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
         if (sd->flags & SPLICE_F_MOVE) {
                 /*
                  * If steal succeeds, buf->page is now pruned from the vm
-                 * side (LRU and page cache) and we can reuse it.
+                 * side (LRU and page cache) and we can reuse it. The page
+                 * will also be looked on successful return.
                  */
                 if (buf->ops->steal(info, buf))
                         goto find_page;
 
-                /*
-                 * this will also set the page locked
-                 */
                 page = buf->page;
                 if (add_to_page_cache(page, mapping, index, gfp_mask))
                         goto find_page;
@@ -523,15 +524,27 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
                         lru_cache_add(page);
         } else {
 find_page:
-                ret = -ENOMEM;
-                page = find_or_create_page(mapping, index, gfp_mask);
-                if (!page)
-                        goto out_nomem;
+                page = find_lock_page(mapping, index);
+                if (!page) {
+                        ret = -ENOMEM;
+                        page = page_cache_alloc_cold(mapping);
+                        if (unlikely(!page))
+                                goto out_nomem;
+
+                        /*
+                         * This will also lock the page
+                         */
+                        ret = add_to_page_cache_lru(page, mapping, index,
+                                                    gfp_mask);
+                        if (unlikely(ret))
+                                goto out;
+                }
 
                 /*
-                 * If the page is uptodate, it is also locked. If it isn't
-                 * uptodate, we can mark it uptodate if we are filling the
-                 * full page. Otherwise we need to read it in first...
+                 * We get here with the page locked. If the page is also
+                 * uptodate, we don't need to do more. If it isn't, we
+                 * may need to bring it in if we are not going to overwrite
+                 * the full page.
                  */
                 if (!PageUptodate(page)) {
                         if (sd->len < PAGE_CACHE_SIZE) {
@@ -553,10 +566,8 @@ find_page:
                                         ret = -EIO;
                                         goto out;
                                 }
-                        } else {
-                                WARN_ON(!PageLocked(page));
+                        } else
                                 SetPageUptodate(page);
-                        }
                 }
         }
 
@@ -585,10 +596,10 @@ find_page:
         mark_page_accessed(page);
         balance_dirty_pages_ratelimited(mapping);
 out:
-        if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
+        if (!(buf->flags & PIPE_BUF_FLAG_STOLEN))
                 page_cache_release(page);
-                unlock_page(page);
-        }
+
+        unlock_page(page);
 out_nomem:
         buf->ops->unmap(info, buf);
         return ret;