mm: make read_cache_page synchronous

Ensure pages are uptodate after returning from read_cache_page, which allows
us to cut out most of the filesystem-internal PageUptodate calls.

I didn't have a great look down the call chains, but this appears to fixes 7
possible use-before uptodate in hfs, 2 in hfsplus, 1 in jfs, a few in
ecryptfs, 1 in jffs2, and a possible cleared data overwritten with readpage in
block2mtd.  All depending on whether the filler is async and/or can return
with a !uptodate page.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 38 insertions, 14 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 5dfc093ceb3..070e7547d5b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1726,7 +1726,7 @@ int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
 EXPORT_SYMBOL(generic_file_mmap);
 EXPORT_SYMBOL(generic_file_readonly_mmap);
 
-static inline struct page *__read_cache_page(struct address_space *mapping,
+static struct page *__read_cache_page(struct address_space *mapping,
 				unsigned long index,
 				int (*filler)(void *,struct page*),
 				void *data)
@@ -1763,17 +1763,11 @@ repeat:
 	return page;
 }
 
-/**
- * read_cache_page - read into page cache, fill it if needed
- * @mapping:	the page's address_space
- * @index:	the page index
- * @filler:	function to perform the read
- * @data:	destination for read data
- *
- * Read into the page cache. If a page already exists,
- * and PageUptodate() is not set, try to fill the page.
+/*
+ * Same as read_cache_page, but don't wait for page to become unlocked
+ * after submitting it to the filler.
  */
-struct page *read_cache_page(struct address_space *mapping,
+struct page *read_cache_page_async(struct address_space *mapping,
 				unsigned long index,
 				int (*filler)(void *,struct page*),
 				void *data)
@@ -1805,6 +1799,39 @@ retry:
 		page = ERR_PTR(err);
 	}
  out:
+	mark_page_accessed(page);
+	return page;
+}
+EXPORT_SYMBOL(read_cache_page_async);
+
+/**
+ * read_cache_page - read into page cache, fill it if needed
+ * @mapping:	the page's address_space
+ * @index:	the page index
+ * @filler:	function to perform the read
+ * @data:	destination for read data
+ *
+ * Read into the page cache. If a page already exists, and PageUptodate() is
+ * not set, try to fill the page then wait for it to become unlocked.
+ *
+ * If the page does not get brought uptodate, return -EIO.
+ */
+struct page *read_cache_page(struct address_space *mapping,
+				unsigned long index,
+				int (*filler)(void *,struct page*),
+				void *data)
+{
+	struct page *page;
+
+	page = read_cache_page_async(mapping, index, filler, data);
+	if (IS_ERR(page))
+		goto out;
+	wait_on_page_locked(page);
+	if (!PageUptodate(page)) {
+		page_cache_release(page);
+		page = ERR_PTR(-EIO);
+	}
+ out:
 	return page;
 }
 EXPORT_SYMBOL(read_cache_page);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index a2d9bb4e80d..acc172cbe3a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1531,9 +1531,6 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
 		error = PTR_ERR(page);
 		goto bad_swap;
 	}
-	wait_on_page_locked(page);
-	if (!PageUptodate(page))
-		goto bad_swap;
 	kmap(page);
 	swap_header = page_address(page);