[PATCH v3 05/49] fs/buffer: comment on direct access to bvec table

[Ming Lei]

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 fs/buffer.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 5715dac7821f..c821ed6a6f0e 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3054,8 +3054,13 @@ static void end_bio_bh_io_sync(struct bio *bio)
 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;
+       /*
+        * 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().
+        */
+       struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
        maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
        if (!maxsector)
-- 
2.9.4