[PATCH 08/13] pktcdvd: use bio_clone_fast() instead of bio_clone()

[NeilBrown]

pktcdvd doesn't change the bi_io_vec of the clone bio,
so it is more efficient to use bio_clone_fast(), and not clone
the bi_io_vec.
This requires providing a bio_set, and it is safest to
provide a dedicated bio_set rather than sharing
fs_bio_set, which filesytems use.
This new bio_set, pkt_bio_set, can also be use for the bio_split()
call as the two allocations (bio_clone_fast, and bio_split) are
independent, neither can block a bio allocated by the other.

Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: NeilBrown <ne...@suse.com>
---
 drivers/block/pktcdvd.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 1f363638b453..26c04baae967 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -98,6 +98,7 @@ static int write_congestion_on  = PKT_WRITE_CONGESTION_ON;
 static int write_congestion_off = PKT_WRITE_CONGESTION_OFF;
 static struct mutex ctl_mutex; /* Serialize open/close/setup/teardown */
 static mempool_t *psd_pool;
+static struct bio_set *pkt_bio_set;
 
 static struct class    *class_pktcdvd = NULL;    /* /sys/class/pktcdvd */
 static struct dentry   *pkt_debugfs_root = NULL; /* /sys/kernel/debug/pktcdvd 
*/
@@ -2310,7 +2311,7 @@ static void pkt_end_io_read_cloned(struct bio *bio)
 
 static void pkt_make_request_read(struct pktcdvd_device *pd, struct bio *bio)
 {
-       struct bio *cloned_bio = bio_clone(bio, GFP_NOIO);
+       struct bio *cloned_bio = bio_clone_fast(bio, GFP_NOIO, pkt_bio_set);
        struct packet_stacked_data *psd = mempool_alloc(psd_pool, GFP_NOIO);
 
        psd->pd = pd;
@@ -2455,7 +2456,7 @@ static blk_qc_t pkt_make_request(struct request_queue *q, 
struct bio *bio)
 
                        split = bio_split(bio, last_zone -
                                          bio->bi_iter.bi_sector,
-                                         GFP_NOIO, fs_bio_set);
+                                         GFP_NOIO, pkt_bio_set);
                        bio_chain(split, bio);
                } else {
                        split = bio;
@@ -2924,6 +2925,11 @@ static int __init pkt_init(void)
                                        sizeof(struct packet_stacked_data));
        if (!psd_pool)
                return -ENOMEM;
+       pkt_bio_set = bioset_create(BIO_POOL_SIZE, 0, 0);
+       if (!pkt_bio_set) {
+               mempool_destroy(psd_pool);
+               return -ENOMEM;
+       }
 
        ret = register_blkdev(pktdev_major, DRIVER_NAME);
        if (ret < 0) {
@@ -2956,6 +2962,7 @@ static int __init pkt_init(void)
        unregister_blkdev(pktdev_major, DRIVER_NAME);
 out2:
        mempool_destroy(psd_pool);
+       bioset_free(pkt_bio_set);
        return ret;
 }
 
@@ -2969,6 +2976,7 @@ static void __exit pkt_exit(void)
 
        unregister_blkdev(pktdev_major, DRIVER_NAME);
        mempool_destroy(psd_pool);
+       bioset_free(pkt_bio_set);
 }
 
 MODULE_DESCRIPTION("Packet writing layer for CD/DVD drives");