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-rw-r--r--block/bio.c53
1 files changed, 52 insertions, 1 deletions
diff --git a/block/bio.c b/block/bio.c
index 9d54aa37ce6c..94d697217887 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -539,6 +539,55 @@ 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
*
@@ -754,10 +803,12 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
return false;
- if (bio->bi_vcnt > 0 && !bio_full(bio, len)) {
+ if (bio->bi_vcnt > 0) {
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
if (page_is_mergeable(bv, page, len, off, same_page)) {
+ if (bio->bi_iter.bi_size > UINT_MAX - len)
+ return false;
bv->bv_len += len;
bio->bi_iter.bi_size += len;
return true;