lightnvm: pblk: fix bio leak when bio is split

For large size io where blk_queue_split needs to be called inside
pblk_rw_io, results in bio leak as bio_endio is not called on the
newly allocated. One way to observe this is to mounting ext4
filesystem on the target and issuing 1MB io with dd, e.g., dd bs=1MB
if=/dev/null of=/mount/myvolume. kmemleak reports:

unreferenced object 0xffff88803d7d0100 (size 256):
  comm "kworker/u16:1", pid 68, jiffies 4294899333 (age 284.120s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 60 e8 31 81 88 ff ff  .........`.1....
    01 40 00 00 06 06 00 00 00 00 00 00 05 00 00 00  .@..............
  backtrace:
    [<000000001f5aa04f>] kmem_cache_alloc+0x204/0x3c0
    [<0000000040945aab>] mempool_alloc_slab+0x1d/0x30
    [<00000000b4959ab4>] mempool_alloc+0x83/0x220
    [<00000000646bad9b>] bio_alloc_bioset+0x229/0x320
    [<000000009264b251>] bio_clone_fast+0x26/0xc0
    [<0000000008250252>] bio_split+0x41/0x110
    [<00000000e365cad0>] blk_queue_split+0x349/0x930
    [<00000000eb5426bc>] pblk_make_rq+0x1b5/0x1f0
    [<00000000eea09cec>] generic_make_request+0x2f9/0x690
    [<00000000ae6acede>] submit_bio+0x12e/0x1f0
    [<00000000f9b8b82a>] ext4_io_submit+0x64/0x80
    [<000000009e4f817d>] ext4_bio_write_page+0x32e/0x890
    [<00000000cbd0d106>] mpage_submit_page+0x65/0xc0
    [<000000000eec7359>] mpage_map_and_submit_buffers+0x171/0x330
    [<000000009a7afcb6>] ext4_writepages+0xd5e/0x1650
    [<000000004476b096>] do_writepages+0x39/0xc0

In case there is a need for a split, blk_queue_split returns the newly
allocated bio to the caller by changing the value of pointer passed as
a reference, while the original is passed to generic_make_requests.

Although pblk_rw_io's local variable bio* has changed and passed to
pblk_submit_read and pblk_write_to_cache, work is done on this new
bio*, and pblk_rw_io returns NVM_IO_DONE, pblk_make_rq calls bio_endio
on the old bio* because it passed bio pointer by value to pblk_rw_io.

pblk_rw_io is unfolded into pblk_make_rq so that there is no copying
of bio* and bio_endio is called on the correct bio*.
Signed-off-by: Chansol Kim <chansol.kim@samsung.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-init.c

@@ -47,36 +47,10 @@ static struct pblk_global_caches pblk_caches = {
 
 struct bio_set pblk_bio_set;
 
-static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
-			  struct bio *bio)
-{
-	int ret;
-
-	/* Read requests must be <= 256kb due to NVMe's 64 bit completion bitmap
-	 * constraint. Writes can be of arbitrary size.
-	 */
-	if (bio_data_dir(bio) == READ) {
-		blk_queue_split(q, &bio);
-		ret = pblk_submit_read(pblk, bio);
-		if (ret == NVM_IO_DONE && bio_flagged(bio, BIO_CLONED))
-			bio_put(bio);
-
-		return ret;
-	}
-
-	/* Prevent deadlock in the case of a modest LUN configuration and large
-	 * user I/Os. Unless stalled, the rate limiter leaves at least 256KB
-	 * available for user I/O.
-	 */
-	if (pblk_get_secs(bio) > pblk_rl_max_io(&pblk->rl))
-		blk_queue_split(q, &bio);
-
-	return pblk_write_to_cache(pblk, bio, PBLK_IOTYPE_USER);
-}
-
 static blk_qc_t pblk_make_rq(struct request_queue *q, struct bio *bio)
 {
 	struct pblk *pblk = q->queuedata;
+	int ret;
 
 	if (bio_op(bio) == REQ_OP_DISCARD) {
 		pblk_discard(pblk, bio);
@@ -86,7 +60,24 @@ static blk_qc_t pblk_make_rq(struct request_queue *q, struct bio *bio)
 		}
 	}
 
-	switch (pblk_rw_io(q, pblk, bio)) {
+	/* Read requests must be <= 256kb due to NVMe's 64 bit completion bitmap
+	 * constraint. Writes can be of arbitrary size.
+	 */
+	if (bio_data_dir(bio) == READ) {
+		blk_queue_split(q, &bio);
+		ret = pblk_submit_read(pblk, bio);
+	} else {
+		/* Prevent deadlock in the case of a modest LUN configuration
+		 * and large user I/Os. Unless stalled, the rate limiter
+		 * leaves at least 256KB available for user I/O.
+		 */
+		if (pblk_get_secs(bio) > pblk_rl_max_io(&pblk->rl))
+			blk_queue_split(q, &bio);
+
+		ret = pblk_write_to_cache(pblk, bio, PBLK_IOTYPE_USER);
+	}
+
+	switch (ret) {
 	case NVM_IO_ERR:
 		bio_io_error(bio);
 		break;