fs: guard_bio_eod() needs to consider partitions

guard_bio_eod() needs to look at the partition capacity, not just the
capacity of the whole device, when determining if truncation is
necessary.

[   60.268688] attempt to access beyond end of device
[   60.268690] unknown-block(9,1): rw=0, want=67103509, limit=67103506
[   60.268693] buffer_io_error: 2 callbacks suppressed
[   60.268696] Buffer I/O error on dev md1p7, logical block 4524305, async page read

Fixes: 74d46992e0d9 ("block: replace bi_bdev with a gendisk pointer and partitions index")
Cc: stable@vger.kernel.org # v4.13
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Edwards <gedwards@ddn.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 10 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index bff571dc7bc3..bcabb69e7462 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3015,8 +3015,16 @@ void guard_bio_eod(int op, struct bio *bio)
         sector_t maxsector;
         struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
         unsigned truncated_bytes;
+        struct hd_struct *part;
+
+        rcu_read_lock();
+        part = __disk_get_part(bio->bi_disk, bio->bi_partno);
+        if (part)
+                maxsector = part_nr_sects_read(part);
+        else
+                maxsector = get_capacity(bio->bi_disk);
+        rcu_read_unlock();
 
-        maxsector = get_capacity(bio->bi_disk);
         if (!maxsector)
                 return;
 
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 93aae3476f58..ca10cc292187 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -243,6 +243,7 @@ static inline dev_t part_devt(struct hd_struct *part)
         return part_to_dev(part)->devt;
 }
 
+extern struct hd_struct *__disk_get_part(struct gendisk *disk, int partno);
 extern struct hd_struct *disk_get_part(struct gendisk *disk, int partno);
 
 static inline void disk_put_part(struct hd_struct *part)