[PATCH 59/60] fs/buffer.c: use bvec iterator to truncate the bio

[Ming Lei]

For making multipage bvec working well.

Signed-off-by: Ming Lei <tom.leim...@gmail.com>
---
 fs/buffer.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 81c3793948b4..293e081a4b5f 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3021,8 +3021,7 @@ 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];
 
@@ -3045,15 +3044,21 @@ void guard_bio_eod(int op, struct bio *bio)
        /* Uhhuh. We've got a bio that straddles the device size! */
        truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
 
-       /* Truncate the bio.. */
-       bio->bi_iter.bi_size -= truncated_bytes;
-       bvec->bv_len -= truncated_bytes;
-
        /* ..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,
-                               truncated_bytes);
+               struct bvec_iter start = BVEC_ITER_ALL_INIT;
+               struct bvec_iter iter;
+               struct bio_vec bv;
+
+               start.bi_bvec_done = bvec->bv_len - truncated_bytes;
+
+               __bvec_for_each_sp_bvec(bv, bvec, iter, start)
+                       zero_user(bv.bv_page, bv.bv_offset, bv.bv_len);
        }
+
+       /* Truncate the bio.. */
+       bio->bi_iter.bi_size -= truncated_bytes;
+       bvec->bv_len -= truncated_bytes;
 }
 
 static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
-- 
2.7.4