lightnvm: pblk: free padded entries in write buffer

When a REQ_FLUSH reaches pblk, the bio cannot be directly completed.
Instead, data on the write buffer is flushed and the bio is completed on
the completion pah. This might require some sectors to be padded in
order to guarantee a successful write.

This patch fixes a memory leak on the padded pages. A consequence of
this bad free was that internal bios not containing data (only a flush)
were not being completed.

Fixes: a4bd217b4326 ("lightnvm: physical block device (pblk) target")
Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-core.c

@@ -190,7 +190,6 @@ void pblk_bio_free_pages(struct pblk *pblk, struct bio *bio, int off,
 
 	WARN_ON(off + nr_pages != bio->bi_vcnt);
 
-	bio_advance(bio, off * PBLK_EXPOSED_PAGE_SIZE);
 	for (i = off; i < nr_pages + off; i++) {
 		bv = bio->bi_io_vec[i];
 		mempool_free(bv.bv_page, pblk->page_pool);

drivers/lightnvm/pblk-write.c

@@ -33,6 +33,10 @@ static unsigned long pblk_end_w_bio(struct pblk *pblk, struct nvm_rq *rqd,
 			bio_endio(original_bio);
 	}
 
+	if (c_ctx->nr_padded)
+		pblk_bio_free_pages(pblk, rqd->bio, c_ctx->nr_valid,
+							c_ctx->nr_padded);
+
 #ifdef CONFIG_NVM_DEBUG
 	atomic_long_add(c_ctx->nr_valid, &pblk->sync_writes);
 #endif
@@ -521,7 +525,8 @@ static void pblk_free_write_rqd(struct pblk *pblk, struct nvm_rq *rqd)
 	struct bio *bio = rqd->bio;
 
 	if (c_ctx->nr_padded)
-		pblk_bio_free_pages(pblk, bio, rqd->nr_ppas, c_ctx->nr_padded);
+		pblk_bio_free_pages(pblk, bio, c_ctx->nr_valid,
+							c_ctx->nr_padded);
 }
 
 static int pblk_submit_write(struct pblk *pblk)