From 4db96b71e3caea5bb39053d57683129e0682c66f Mon Sep 17 00:00:00 2001
From: Akinobu Mita <akinobu.mita@gmail.com>
Date: Thu, 9 Oct 2014 15:26:55 -0700
Subject: [PATCH] vfs: guard end of device for mpage interface

Add guard_bio_eod() check for mpage code in order to allow us to do IO
even on the odd last sectors of a device, even if the block size is some
multiple of the physical sector size.

Using mpage_readpages() for block device requires this guard check.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 fs/buffer.c   | 2 +-
 fs/internal.h | 5 +++++
 fs/mpage.c    | 2 ++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index e442a26e80f7..7bd5c4685e98 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2966,7 +2966,7 @@ static void end_bio_bh_io_sync(struct bio *bio, int err)
  * errors, this only handles the "we need to be able to
  * do IO at the final sector" case.
  */
-static void guard_bio_eod(int rw, struct bio *bio)
+void guard_bio_eod(int rw, struct bio *bio)
 {
 	sector_t maxsector;
 	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
diff --git a/fs/internal.h b/fs/internal.h
index e325b4f9c799..b2623200107b 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -34,6 +34,11 @@ static inline int __sync_blockdev(struct block_device *bdev, int wait)
 }
 #endif
 
+/*
+ * buffer.c
+ */
+extern void guard_bio_eod(int rw, struct bio *bio);
+
 /*
  * char_dev.c
  */
diff --git a/fs/mpage.c b/fs/mpage.c
index 5f9ed622274f..3e79220babac 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -28,6 +28,7 @@
 #include <linux/backing-dev.h>
 #include <linux/pagevec.h>
 #include <linux/cleancache.h>
+#include "internal.h"
 
 /*
  * I/O completion handler for multipage BIOs.
@@ -57,6 +58,7 @@ static void mpage_end_io(struct bio *bio, int err)
 static struct bio *mpage_bio_submit(int rw, struct bio *bio)
 {
 	bio->bi_end_io = mpage_end_io;
+	guard_bio_eod(rw, bio);
 	submit_bio(rw, bio);
 	return NULL;
 }