On Mon, Oct 31, 2016 at 11:35 PM, Christoph Hellwig [off-list ref] wrote:

I think we'll just need a version zero_fill_bio with a length argument
and let that handle all the bvec access.  I have vague memories that
Kent posted one a while ago, Ccing him.

I will try to find zero_fill_bio() in Kent's tree later.

BTW, patch 59 switches to use bvec iterator to do that too.

On Sat, Oct 29, 2016 at 04:08:18PM +0800, Ming Lei wrote:

quoted

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

diff --git a/fs/buffer.c b/fs/buffer.c
index b205a629001d..81c3793948b4 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c

@@ -3018,8 +3018,13 @@ 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)
--

2.7.4

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---end quoted text---

thanks,
Ming Lei