diff options
Diffstat (limited to 'block/bio.c')
| -rw-r--r-- | block/bio.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/block/bio.c b/block/bio.c index a5d75f6bf4c7..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 * |