[PATCH 6/7] bcache: store a pointer to the on-disk sb in the cache and cached_dev structures

[Christoph Hellwig <hch@xxxxxx>]

This allows to properly build the superblock bio including the offset in the
page using the normal bio helpers.  This fixes writing the superblock for
page sizes larger than 4k where the sb write bio would need an offset in the
bio_vec.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/md/bcache/bcache.h |  2 ++
 drivers/md/bcache/super.c  | 34 +++++++++++++++-------------------
 2 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 9198c1b480d9..adf26a21fcd1 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -301,6 +301,7 @@ struct cached_dev {
 	struct block_device	*bdev;
 
 	struct cache_sb		sb;
+	struct cache_sb_disk	*sb_disk;
 	struct bio		sb_bio;
 	struct bio_vec		sb_bv[1];
 	struct closure		sb_write;
@@ -403,6 +404,7 @@ enum alloc_reserve {
 struct cache {
 	struct cache_set	*set;
 	struct cache_sb		sb;
+	struct cache_sb_disk	*sb_disk;
 	struct bio		sb_bio;
 	struct bio_vec		sb_bv[1];
 
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 0b7620d9f087..c3bfbc813daf 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -207,15 +207,15 @@ static void write_bdev_super_endio(struct bio *bio)
 	closure_put(&dc->sb_write);
 }
 
-static void __write_super(struct cache_sb *sb, struct bio *bio)
+static void __write_super(struct cache_sb *sb, struct cache_sb_disk *out,
+		struct bio *bio)
 {
-	struct cache_sb_disk *out = page_address(bio_first_page_all(bio));
 	unsigned int i;
 
+	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_META;
 	bio->bi_iter.bi_sector	= SB_SECTOR;
-	bio->bi_iter.bi_size	= SB_SIZE;
-	bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC|REQ_META);
-	bch_bio_map(bio, NULL);
+	__bio_add_page(bio, virt_to_page(out), SB_SIZE,
+			offset_in_page(out));
 
 	out->offset		= cpu_to_le64(sb->offset);
 	out->version		= cpu_to_le64(sb->version);
@@ -257,14 +257,14 @@ void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent)
 	down(&dc->sb_write_mutex);
 	closure_init(cl, parent);
 
-	bio_reset(bio);
+	bio_init(bio, dc->sb_bv, 1);
 	bio_set_dev(bio, dc->bdev);
 	bio->bi_end_io	= write_bdev_super_endio;
 	bio->bi_private = dc;
 
 	closure_get(cl);
 	/* I/O request sent to backing device */
-	__write_super(&dc->sb, bio);
+	__write_super(&dc->sb, dc->sb_disk, bio);
 
 	closure_return_with_destructor(cl, bch_write_bdev_super_unlock);
 }
@@ -306,13 +306,13 @@ void bcache_write_super(struct cache_set *c)
 
 		SET_CACHE_SYNC(&ca->sb, CACHE_SYNC(&c->sb));
 
-		bio_reset(bio);
+		bio_init(bio, ca->sb_bv, 1);
 		bio_set_dev(bio, ca->bdev);
 		bio->bi_end_io	= write_super_endio;
 		bio->bi_private = ca;
 
 		closure_get(cl);
-		__write_super(&ca->sb, bio);
+		__write_super(&ca->sb, ca->sb_disk, bio);
 	}
 
 	closure_return_with_destructor(cl, bcache_write_super_unlock);
@@ -1275,8 +1275,8 @@ static void cached_dev_free(struct closure *cl)
 
 	mutex_unlock(&bch_register_lock);
 
-	if (dc->sb_bio.bi_inline_vecs[0].bv_page)
-		put_page(bio_first_page_all(&dc->sb_bio));
+	if (dc->sb_disk)
+		put_page(virt_to_page(dc->sb_disk));
 
 	if (!IS_ERR_OR_NULL(dc->bdev))
 		blkdev_put(dc->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
@@ -1365,9 +1365,7 @@ static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
 	memcpy(&dc->sb, sb, sizeof(struct cache_sb));
 	dc->bdev = bdev;
 	dc->bdev->bd_holder = dc;
-
-	bio_init(&dc->sb_bio, dc->sb_bio.bi_inline_vecs, 1);
-	bio_first_bvec_all(&dc->sb_bio)->bv_page = virt_to_page(sb_disk);
+	dc->sb_disk = sb_disk;
 
 	if (cached_dev_init(dc, sb->block_size << 9))
 		goto err;
@@ -2137,8 +2135,8 @@ void bch_cache_release(struct kobject *kobj)
 	for (i = 0; i < RESERVE_NR; i++)
 		free_fifo(&ca->free[i]);
 
-	if (ca->sb_bio.bi_inline_vecs[0].bv_page)
-		put_page(bio_first_page_all(&ca->sb_bio));
+	if (ca->sb_disk)
+		put_page(virt_to_page(ca->sb_disk));
 
 	if (!IS_ERR_OR_NULL(ca->bdev))
 		blkdev_put(ca->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
@@ -2270,9 +2268,7 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
 	memcpy(&ca->sb, sb, sizeof(struct cache_sb));
 	ca->bdev = bdev;
 	ca->bdev->bd_holder = ca;
-
-	bio_init(&ca->sb_bio, ca->sb_bio.bi_inline_vecs, 1);
-	bio_first_bvec_all(&ca->sb_bio)->bv_page = virt_to_page(sb_disk);
+	ca->sb_disk = sb_disk;
 
 	if (blk_queue_discard(bdev_get_queue(bdev)))
 		ca->discard = CACHE_DISCARD(&ca->sb);
-- 
2.20.1