fs/buffer.c: use bvec iterator to truncate the bio

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

Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 52d024bfdbc1..817871274c77 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;
+
+                mp_bvec_last_segment(bvec, &bv);
+                zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
                                 truncated_bytes);
         }
 }