The new bio_split() can split arbitrary bios - it's not restricted to
single page bios, like the old bio_split() (previously renamed to
bio_pair_split()). It also has different semantics - it doesn't allocate
a struct bio_pair, leaving it up to the caller to handle completions.
We have to take that BUG_ON() out of bio_integrity_trim() because this
bio_split() needs to use it, and there's no reason it has to be used on
bios marked as cloned; BIO_CLONED doesn't seem to have clearly
documented semantics anyways.
v5: Take out current->bio_list check and make it the caller's
responsibility, per Boaz
v6: Rename @ret to @split, change to not return original bio or copy
bi_private/bi_end_io, per Tejun
Signed-off-by: Kent Overstreet <koverstreet@xxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxxxx>
CC: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
fs/bio-integrity.c | 1 -
fs/bio.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/bio.h | 13 ++++++++
3 files changed, 108 insertions(+), 1 deletion(-)
diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
index e85c04b..35ee3d4 100644
--- a/fs/bio-integrity.c
+++ b/fs/bio-integrity.c
@@ -672,7 +672,6 @@ void bio_integrity_trim(struct bio *bio, unsigned int offset,
BUG_ON(bip == NULL);
BUG_ON(bi == NULL);
- BUG_ON(!bio_flagged(bio, BIO_CLONED));
nr_sectors = bio_integrity_hw_sectors(bi, sectors);
bip->bip_sector = bip->bip_sector + offset;
diff --git a/fs/bio.c b/fs/bio.c
index 2f2cf19..c079006 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1541,6 +1541,101 @@ struct bio_pair *bio_pair_split(struct bio *bi, int first_sectors)
EXPORT_SYMBOL(bio_pair_split);
/**
+ * bio_split - split a bio
+ * @bio: bio to split
+ * @sectors: number of sectors to split from the front of @bio
+ * @gfp: gfp mask
+ * @bs: bio set to allocate from
+ *
+ * Allocates and returns a new bio which represents @sectors from the start of
+ * @bio, and updates @bio to represent the remaining sectors.
+ *
+ * If bio_sectors(@bio) was less than or equal to @sectors, returns @bio
+ * unchanged.
+ *
+ * The newly allocated bio will point to @bio's bi_io_vec, if the split was on a
+ * bvec boundry; it is the caller's responsibility to ensure that @bio is not
+ * freed before the split.
+ */
+struct bio *bio_split(struct bio *bio, int sectors,
+ gfp_t gfp, struct bio_set *bs)
+{
+ unsigned idx, vcnt = 0, nbytes = sectors << 9;
+ struct bio_vec *bv;
+ struct bio *split = NULL;
+
+ BUG_ON(sectors <= 0);
+ BUG_ON(sectors >= bio_sectors(bio));
+
+ trace_block_split(bdev_get_queue(bio->bi_bdev), bio,
+ bio->bi_sector + sectors);
+
+ if (bio->bi_rw & REQ_DISCARD) {
+ split = bio_alloc_bioset(gfp, 1, bs);
+
+ split->bi_io_vec = bio_iovec(bio);
+ idx = 0;
+ goto out;
+ }
+
+ bio_for_each_segment(bv, bio, idx) {
+ vcnt = idx - bio->bi_idx;
+
+ /*
+ * The split might occur on a bvec boundry (nbytes == 0) - in
+ * that case we can reuse the bvec from the old bio.
+ *
+ * Or, if the split isn't aligned, we'll have to allocate a new
+ * bvec and patch up the two copies of the bvec we split in.
+ */
+
+ if (!nbytes) {
+ split = bio_alloc_bioset(gfp, 0, bs);
+ if (!split)
+ return NULL;
+
+ split->bi_io_vec = bio_iovec(bio);
+ split->bi_flags |= 1 << BIO_CLONED;
+ break;
+ } else if (nbytes < bv->bv_len) {
+ split = bio_alloc_bioset(gfp, ++vcnt, bs);
+ if (!split)
+ return NULL;
+
+ memcpy(split->bi_io_vec, bio_iovec(bio),
+ sizeof(struct bio_vec) * vcnt);
+
+ split->bi_io_vec[vcnt - 1].bv_len = nbytes;
+ bv->bv_offset += nbytes;
+ bv->bv_len -= nbytes;
+ break;
+ }
+
+ nbytes -= bv->bv_len;
+ }
+out:
+ split->bi_bdev = bio->bi_bdev;
+ split->bi_sector = bio->bi_sector;
+ split->bi_size = sectors << 9;
+ split->bi_rw = bio->bi_rw;
+ split->bi_vcnt = vcnt;
+ split->bi_max_vecs = vcnt;
+
+ bio->bi_sector += sectors;
+ bio->bi_size -= sectors << 9;
+ bio->bi_idx = idx;
+
+ if (bio_integrity(bio)) {
+ bio_integrity_clone(split, bio, gfp, bs);
+ bio_integrity_trim(split, 0, bio_sectors(split));
+ bio_integrity_trim(bio, bio_sectors(split), bio_sectors(bio));
+ }
+
+ return split;
+}
+EXPORT_SYMBOL_GPL(bio_split);
+
+/**
* bio_sector_offset - Find hardware sector offset in bio
* @bio: bio to inspect
* @index: bio_vec index
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 13f4188..1c3bb47 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -201,6 +201,19 @@ struct bio_pair {
atomic_t cnt;
int error;
};
+
+extern struct bio *bio_split(struct bio *bio, int sectors,
+ gfp_t gfp, struct bio_set *bs);
+
+static inline struct bio *bio_next_split(struct bio *bio, int sectors,
+ gfp_t gfp, struct bio_set *bs)
+{
+ if (sectors >= bio_sectors(bio))
+ return bio;
+
+ return bio_split(bio, sectors, gfp, bs);
+}
+
extern struct bio_pair *bio_pair_split(struct bio *bi, int first_sectors);
extern void bio_pair_release(struct bio_pair *dbio);
--
1.7.12
--
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