[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>

diff --git a/fs/splice.c b/fs/splice.c
index 27d6408ff490ff9976b8324fc4dc7b710657917b..22fac87e90b3d8cc5e87851355c35187f191f2c4 100644 (file)
--- 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;