linux-kernel - [PATCH 1/6] block: add bio_map

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1324429254-28383-2-git-send-email-minchan@kernel.org>
Date:	Wed, 21 Dec 2011 10:00:49 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Chris Wright <chrisw@...s-sol.org>, Jens Axboe <axboe@...nel.dk>,
	Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Christoph Hellwig <hch@....de>,
	Minchan Kim <minchan@...hat.com>
Subject: [PATCH 1/6] block: add bio_map_sg

From: Christoph Hellwig <hch@....de>

Add a helper to map a bio to a scatterlist, modelled after blk_rq_map_sg.
This helper is useful for any driver that wants to create a scatterlist
from its ->make_request method.

Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Minchan Kim <minchan@...hat.com>
---
 block/blk-merge.c      |   63 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h |    2 +
 2 files changed, 65 insertions(+), 0 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index cfcc37c..a8ac944 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -199,6 +199,69 @@ new_segment:
 }
 EXPORT_SYMBOL(blk_rq_map_sg);
 
+/*
+ * map a bio to a scatterlist, return number of sg entries setup. Caller
+ * must make sure sg can hold bio->bi_phys_segments entries
+ */
+int bio_map_sg(struct request_queue *q, struct bio *bio,
+		  struct scatterlist *sglist)
+{
+	struct bio_vec *bvec, *bvprv;
+	struct scatterlist *sg;
+	int nsegs, cluster;
+	unsigned long i;
+
+	nsegs = 0;
+	cluster = blk_queue_cluster(q);
+
+	bvprv = NULL;
+	sg = NULL;
+	bio_for_each_segment(bvec, bio, i) {
+		int nbytes = bvec->bv_len;
+
+		if (bvprv && cluster) {
+			if (sg->length + nbytes > queue_max_segment_size(q))
+				goto new_segment;
+
+			if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
+				goto new_segment;
+			if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
+				goto new_segment;
+
+			sg->length += nbytes;
+		} else {
+new_segment:
+			if (!sg)
+				sg = sglist;
+			else {
+				/*
+				 * If the driver previously mapped a shorter
+				 * list, we could see a termination bit
+				 * prematurely unless it fully inits the sg
+				 * table on each mapping. We KNOW that there
+				 * must be more entries here or the driver
+				 * would be buggy, so force clear the
+				 * termination bit to avoid doing a full
+				 * sg_init_table() in drivers for each command.
+				 */
+				sg->page_link &= ~0x02;
+				sg = sg_next(sg);
+			}
+
+			sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
+			nsegs++;
+		}
+		bvprv = bvec;
+	} /* segments in bio */
+
+	if (sg)
+		sg_mark_end(sg);
+
+	BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);
+	return nsegs;
+}
+EXPORT_SYMBOL(bio_map_sg);
+
 static inline int ll_new_hw_segment(struct request_queue *q,
 				    struct request *req,
 				    struct bio *bio)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 94acd81..7ad8e89 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -853,6 +853,8 @@ extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable);
 extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
 
 extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
+extern int bio_map_sg(struct request_queue *q, struct bio *bio,
+		struct scatterlist *sglist);
 extern void blk_dump_rq_flags(struct request *, char *);
 extern long nr_blockdev_pages(void);
 
-- 
1.7.6.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/