[PATCH v2 05/51] fs/buffer: comment on direct access to bvec table

Ming Lei
2017-06-26T12:13:04Z

fs/buffer.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 4d5d03b42e11..1910f539770b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3052,8 +3052,13 @@ 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