Once multi-page bvec is enabled, the last bvec may include more than one
page, this patch use bvec_last_segment() to truncate the bio.

Cc: Dave Chinner <dchin...@redhat.com>
Cc: Kent Overstreet <kent.overstr...@gmail.com>
Cc: Mike Snitzer <snit...@redhat.com>
Cc: dm-de...@redhat.com
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: linux-fsde...@vger.kernel.org
Cc: Shaohua Li <s...@kernel.org>
Cc: linux-r...@vger.kernel.org
Cc: linux-er...@lists.ozlabs.org
Cc: David Sterba <dste...@suse.com>
Cc: linux-bt...@vger.kernel.org
Cc: Darrick J. Wong <darrick.w...@oracle.com>
Cc: linux-...@vger.kernel.org
Cc: Gao Xiang <gaoxian...@huawei.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Theodore Ts'o <ty...@mit.edu>
Cc: linux-e...@vger.kernel.org
Cc: Coly Li <col...@suse.de>
Cc: linux-bca...@vger.kernel.org
Cc: Boaz Harrosh <o...@electrozaur.com>
Cc: Bob Peterson <rpete...@redhat.com>
Cc: cluster-devel@redhat.com
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 fs/buffer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 1286c2b95498..fa37ad52e962 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3032,7 +3032,10 @@ void guard_bio_eod(int op, struct bio *bio)
 
        /* ..and clear the end of the buffer for reads */
        if (op == REQ_OP_READ) {
-               zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
+               struct bio_vec bv;
+
+               bvec_last_segment(bvec, &bv);
+               zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
                                truncated_bytes);
        }
 }
-- 
2.9.5

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