[PATCH v3 29/49] fs/buffer.c: use bvec iterator to truncate the bio

[Ming Lei]

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

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 fs/buffer.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index c821ed6a6f0e..32a63e5b00f3 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3057,8 +3057,7 @@ void guard_bio_eod(int op, struct bio *bio)
 	unsigned truncated_bytes;
 	/*
 	 * It is safe to truncate the last bvec in the following way
-	 * even though multipage bvec is supported, but we need to
-	 * fix the parameters passed to zero_user().
+	 * even though multipage bvec is supported.
 	 */
 	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
@@ -3087,7 +3086,10 @@ 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_get_last_page(bvec, &bv);
+		zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
 				truncated_bytes);
 	}
 }
-- 
2.9.4