[PATCH 2/2] fs: Make mpage_readpage synchronous

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

A synchronous readpage lets us report the actual errno instead of
ineffectively setting PageError.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/mpage.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/fs/mpage.c b/fs/mpage.c
index 830e6cc2a9e7..88aba79a1861 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -406,11 +406,30 @@ int mpage_readpage(struct page *page, get_block_t get_block)
 		.nr_pages = 1,
 		.get_block = get_block,
 	};
+	int err;
 
 	args.bio = do_mpage_readpage(&args);
-	if (args.bio)
-		mpage_bio_submit(REQ_OP_READ, 0, args.bio);
-	return 0;
+	/*
+	 * XXX: We can't tell the difference between "fell back to
+	 * block_read_full_page" and "this was a hole".  If we could,
+	 * we'd avoid unlocking the page in do_mpage_readpage() and
+	 * return AOP_UPDATED_PAGE here.
+	 */
+	if (!args.bio)
+		return 0;
+	bio_set_op_attrs(args.bio, REQ_OP_READ, 0);
+	guard_bio_eod(args.bio);
+	err = submit_bio_killable(args.bio, mpage_end_io);
+	if (unlikely(err))
+		goto err;
+
+	SetPageUptodate(page);
+	return AOP_UPDATED_PAGE;
+
+err:
+	if (err != -ERESTARTSYS)
+		unlock_page(page);
+	return err;
 }
 EXPORT_SYMBOL(mpage_readpage);
 
-- 
2.28.0