net: disable BRIDGE_NETFILTER by default

[linux.git] / block / bio.c

diff --git a/block/bio.c b/block/bio.c
index a5d75f6bf4c7eedc96454bade72dbc9fe88af74d..94d697217887aa1b9e8b214c7606a6f1e7bf8b42 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -538,6 +538,55 @@ void zero_fill_bio_iter(struct bio *bio, struct bvec_iter start)
 }
 EXPORT_SYMBOL(zero_fill_bio_iter);
 
+/**
+ * bio_truncate - truncate the bio to small size of @new_size
+ * @bio:       the bio to be truncated
+ * @new_size:  new size for truncating the bio
+ *
+ * Description:
+ *   Truncate the bio to new size of @new_size. If bio_op(bio) is
+ *   REQ_OP_READ, zero the truncated part. This function should only
+ *   be used for handling corner cases, such as bio eod.
+ */
+void bio_truncate(struct bio *bio, unsigned new_size)
+{
+       struct bio_vec bv;
+       struct bvec_iter iter;
+       unsigned int done = 0;
+       bool truncated = false;
+
+       if (new_size >= bio->bi_iter.bi_size)
+               return;
+
+       if (bio_op(bio) != REQ_OP_READ)
+               goto exit;
+
+       bio_for_each_segment(bv, bio, iter) {
+               if (done + bv.bv_len > new_size) {
+                       unsigned offset;
+
+                       if (!truncated)
+                               offset = new_size - done;
+                       else
+                               offset = 0;
+                       zero_user(bv.bv_page, offset, bv.bv_len - offset);
+                       truncated = true;
+               }
+               done += bv.bv_len;
+       }
+
+ exit:
+       /*
+        * Don't touch bvec table here and make it really immutable, since
+        * fs bio user has to retrieve all pages via bio_for_each_segment_all
+        * in its .end_bio() callback.
+        *
+        * It is enough to truncate bio by updating .bi_size since we can make
+        * correct bvec with the updated .bi_size for drivers.
+        */
+       bio->bi_iter.bi_size = new_size;
+}
+
 /**
  * bio_put - release a reference to a bio
  * @bio:   bio to release reference to