mm: Wait for writeback when grabbing pages to begin a write

When grabbing a page for a buffered IO write, the mm should wait for writeback on the page to complete so that the page does not become writable during the IO operation. This change is needed to provide page stability during writes for all filesystems. Signed-off-by: Darrick J. Wong <[email protected]> Signed-off-by: Al Viro <[email protected]>
ambv · May 28, 2011 · 3d08bcc · 3d08bcc
1 parent 9870246
commit 3d08bcc
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/mm/filemap.c b/mm/filemap.c
@@ -2327,7 +2327,7 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
 repeat:
 	page = find_lock_page(mapping, index);
 	if (page)
-		return page;
+		goto found;
 
 	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
 	if (!page)
@@ -2340,6 +2340,8 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
 			goto repeat;
 		return NULL;
 	}
+found:
+	wait_on_page_writeback(page);
 	return page;
 }
 EXPORT_SYMBOL(grab_cache_page_write_begin);