[Devel] [PATCH rh7 2/2] vfs: guard end of device for mpage interface

[Maxim Patlasov]

The patch backports 4db96b71e3caea5bb39053d57683129e0682c66f from mainline:

    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 at gmail.com>
    Cc: Jens Axboe <axboe at kernel.dk>
    Cc: Alexander Viro <viro at zeniv.linux.org.uk>
    Cc: Jeff Moyer <jmoyer at redhat.com>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
---
 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 a7cb15c..c45200d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2982,7 +2982,7 @@ 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 b538b3d..6f4120e 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -38,6 +38,11 @@ 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
  */
 extern void __init chrdev_init(void);
diff --git a/fs/mpage.c b/fs/mpage.c
index 0face1c..c4f7bf6c 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.
@@ -74,6 +75,7 @@ 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;
 }