[RFC PATCH 12/28] block: Create helper for bvec_should_split()

Logan Gunthorpe
2019-06-20T16:12:24Z

In order to support dma-direct bios, blk_bio_segment_split() will
need to operate on both bio_vecs and dma_vecs. In order to do
this, the code inside bio_for_each_bvec() is moved into a generic
helper called bvec_should_split().

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
block/blk-merge.c | 86 +++++++++++++++++++++++++----------------------
1 file changed, 46 insertions(+), 40 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 414e61a714bf..d9e89c0ad40d 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -212,6 +212,48 @@ struct blk_segment_split_ctx {
const unsigned max_segs;
};

+static bool bvec_should_split(struct request_queue *q, struct bio_vec *bv,
+ struct blk_segment_split_ctx *ctx)
+{
+ /*
+ * If the queue doesn't support SG gaps and adding this
+ * offset would create a gap, disallow it.
+ */
+ if (ctx->prv_valid && bvec_gap_to_prev(q, &ctx->bvprv, bv->bv_offset))
+ return true;
+
+ if (ctx->sectors + (bv->bv_len >> 9) > ctx->max_sectors) {
+ /*
+ * Consider this a new segment if we're splitting in
+ * the middle of this vector.
+ */
+ if (ctx->nsegs < ctx->max_segs &&
+ ctx->sectors < ctx->max_sectors) {
+ /* split in the middle of bvec */
+ bv->bv_len = (ctx->max_sectors - ctx->sectors) << 9;
+ bvec_split_segs(q, bv, &ctx->nsegs,
+ &ctx->sectors, ctx->max_segs);
+ }
+ return true;
+ }
+
+ if (ctx->nsegs == ctx->max_segs)
+ return true;
+
+ ctx->bvprv = *bv;
+ ctx->prv_valid = true;
+
+ if (bv->bv_offset + bv->bv_len <= PAGE_SIZE) {
+ ctx->nsegs++;
+ ctx->sectors += bv->bv_len >> 9;
+ } else if (bvec_split_segs(q, bv, &ctx->nsegs, &ctx->sectors,
+ ctx->max_segs)) {
+ return true;
+ }
+
+ return false;
+}
+
static struct bio *blk_bio_segment_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
@@ -219,7 +261,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
{
struct bio_vec bv;
struct bvec_iter iter;
- bool do_split = true;
+ bool do_split = false;
struct bio *new = NULL;

struct blk_segment_split_ctx ctx = {
@@ -228,47 +270,11 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
};

bio_for_each_bvec(bv, bio, iter) {
- /*
- * If the queue doesn't support SG gaps and adding this
- * offset would create a gap, disallow it.
- */
- if (ctx.prv_valid && bvec_gap_to_prev(q, &ctx.bvprv,
- bv.bv_offset))
- goto split;
-
- if (ctx.sectors + (bv.bv_len >> 9) > ctx.max_sectors) {
- /*
- * Consider this a new segment if we're splitting in
- * the middle of this vector.
- */
- if (ctx.nsegs < ctx.max_segs &&
- ctx.sectors < ctx.max_sectors) {
- /* split in the middle of bvec */
- bv.bv_len =
- (ctx.max_sectors - ctx.sectors) << 9;
- bvec_split_segs(q, &bv, &ctx.nsegs,
- &ctx.sectors, ctx.max_segs);
- }
- goto split;
- }
-
- if (ctx.nsegs == ctx.max_segs)
- goto split;
-
- ctx.bvprv = bv;
- ctx.prv_valid = true;
-
- if (bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
- ctx.nsegs++;
- ctx.sectors += bv.bv_len >> 9;
- } else if (bvec_split_segs(q, &bv, &ctx.nsegs, &ctx.sectors,
- ctx.max_segs)) {
- goto split;
- }
+ do_split = bvec_should_split(q, &bv, &ctx);
+ if (do_split)
+ break;
}

- do_split = false;
-split:
*segs = ctx.nsegs;

if (do_split) {
--
2.20.1