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-rw-r--r--fs/bio.c60
1 files changed, 47 insertions, 13 deletions
diff --git a/fs/bio.c b/fs/bio.c
index a082ce2d197b..1628917e262a 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -549,36 +549,70 @@ void __bio_clone(struct bio *bio, struct bio *bio_src)
EXPORT_SYMBOL(__bio_clone);
/**
- * bio_clone_bioset - clone a bio
- * @bio: bio to clone
+ * bio_clone_bioset - clone a bio
+ * @bio_src: bio to clone
* @gfp_mask: allocation priority
* @bs: bio_set to allocate from
*
- * Like __bio_clone, only also allocates the returned bio
+ * Clone bio. Caller will own the returned bio, but not the actual data it
+ * points to. Reference count of returned bio will be one.
*/
-struct bio *bio_clone_bioset(struct bio *bio, gfp_t gfp_mask,
+struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
struct bio_set *bs)
{
- struct bio *b;
+ unsigned nr_iovecs = 0;
+ struct bvec_iter iter;
+ struct bio_vec bv;
+ struct bio *bio;
+
+ /*
+ * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
+ * bio_src->bi_io_vec to bio->bi_io_vec.
+ *
+ * We can't do that anymore, because:
+ *
+ * - The point of cloning the biovec is to produce a bio with a biovec
+ * the caller can modify: bi_idx and bi_bvec_done should be 0.
+ *
+ * - The original bio could've had more than BIO_MAX_PAGES biovecs; if
+ * we tried to clone the whole thing bio_alloc_bioset() would fail.
+ * But the clone should succeed as long as the number of biovecs we
+ * actually need to allocate is fewer than BIO_MAX_PAGES.
+ *
+ * - Lastly, bi_vcnt should not be looked at or relied upon by code
+ * that does not own the bio - reason being drivers don't use it for
+ * iterating over the biovec anymore, so expecting it to be kept up
+ * to date (i.e. for clones that share the parent biovec) is just
+ * asking for trouble and would force extra work on
+ * __bio_clone_fast() anyways.
+ */
+
+ bio_for_each_segment(bv, bio_src, iter)
+ nr_iovecs++;
- b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, bs);
- if (!b)
+ bio = bio_alloc_bioset(gfp_mask, nr_iovecs, bs);
+ if (!bio)
return NULL;
- __bio_clone(b, bio);
+ bio->bi_bdev = bio_src->bi_bdev;
+ bio->bi_rw = bio_src->bi_rw;
+ bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
+ bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
- if (bio_integrity(bio)) {
- int ret;
+ bio_for_each_segment(bv, bio_src, iter)
+ bio->bi_io_vec[bio->bi_vcnt++] = bv;
- ret = bio_integrity_clone(b, bio, gfp_mask);
+ if (bio_integrity(bio_src)) {
+ int ret;
+ ret = bio_integrity_clone(bio, bio_src, gfp_mask);
if (ret < 0) {
- bio_put(b);
+ bio_put(bio);
return NULL;
}
}
- return b;
+ return bio;
}
EXPORT_SYMBOL(bio_clone_bioset);