block: don't allow multiple bio_iov_iter_get_pages calls per bio

No caller uses bio_iov_iter_get_pages multiple times on a given bio,
and that funtionality isn't all that useful.  Removing it will make
some future changes a little easier and also simplifies the function
a bit.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index ad34608..c2a389b 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -958,7 +958,10 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 {
        const bool is_bvec = iov_iter_is_bvec(iter);
-       unsigned short orig_vcnt = bio->bi_vcnt;
+       int ret;
+
+       if (WARN_ON_ONCE(bio->bi_vcnt))
+               return -EINVAL;
 
        /*
         * If this is a BVEC iter, then the pages are kernel pages. Don't
@@ -968,19 +971,13 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
                bio_set_flag(bio, BIO_NO_PAGE_REF);
 
        do {
-               int ret;
-
                if (is_bvec)
                        ret = __bio_iov_bvec_add_pages(bio, iter);
                else
                        ret = __bio_iov_iter_get_pages(bio, iter);
+       } while (!ret && iov_iter_count(iter) && !bio_full(bio));
 
-               if (unlikely(ret))
-                       return bio->bi_vcnt > orig_vcnt ? 0 : ret;
-
-       } while (iov_iter_count(iter) && !bio_full(bio));
-
-       return 0;
+       return bio->bi_vcnt ? 0 : ret;
 }
 
 static void submit_bio_wait_endio(struct bio *bio)