block: turn bio_kmalloc into a simple kmalloc wrapper

Remove the magic autofree semantics and require the callers to explicitly
call bio_init to initialize the bio.

This allows bio_free to catch accidental bio_put calls on bio_init()ed
bios as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Coly Li <colyli@suse.de>
Acked-by: Mike Snitzer <snitzer@kernel.org>
Link: https://lore.kernel.org/r/20220406061228.410163-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 18 insertions, 29 deletions

diff --git a/block/bio.c b/block/bio.c
index 643a3a052c7e..212ccd5b5212 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -224,24 +224,13 @@ EXPORT_SYMBOL(bio_uninit);
 static void bio_free(struct bio *bio)
 {
 	struct bio_set *bs = bio->bi_pool;
-	void *p;
-
-	bio_uninit(bio);
+	void *p = bio;
 
-	if (bs) {
-		bvec_free(&bs->bvec_pool, bio->bi_io_vec, bio->bi_max_vecs);
+	WARN_ON_ONCE(!bs);
 
-		/*
-		 * If we have front padding, adjust the bio pointer before freeing
-		 */
-		p = bio;
-		p -= bs->front_pad;
-
-		mempool_free(p, &bs->bio_pool);
-	} else {
-		/* Bio was allocated by bio_kmalloc() */
-		kfree(bio);
-	}
+	bio_uninit(bio);
+	bvec_free(&bs->bvec_pool, bio->bi_io_vec, bio->bi_max_vecs);
+	mempool_free(p - bs->front_pad, &bs->bio_pool);
 }
 
 /*
@@ -568,28 +557,28 @@ err_free:
 EXPORT_SYMBOL(bio_alloc_bioset);
 
 /**
- * bio_kmalloc - kmalloc a bio for I/O
+ * bio_kmalloc - kmalloc a bio
+ * @nr_vecs:	number of bio_vecs to allocate
  * @gfp_mask:   the GFP_* mask given to the slab allocator
- * @nr_iovecs:	number of iovecs to pre-allocate
  *
- * Use kmalloc to allocate and initialize a bio.
+ * Use kmalloc to allocate a bio (including bvecs).  The bio must be initialized
+ * using bio_init() before use.  To free a bio returned from this function use
+ * kfree() after calling bio_uninit().  A bio returned from this function can
+ * be reused by calling bio_uninit() before calling bio_init() again.
+ *
+ * Note that unlike bio_alloc() or bio_alloc_bioset() allocations from this
+ * function are not backed by a mempool can can fail.  Do not use this function
+ * for allocations in the file system I/O path.
  *
  * Returns: Pointer to new bio on success, NULL on failure.
  */
-struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned short nr_iovecs)
+struct bio *bio_kmalloc(unsigned short nr_vecs, gfp_t gfp_mask)
 {
 	struct bio *bio;
 
-	if (nr_iovecs > UIO_MAXIOV)
+	if (nr_vecs > UIO_MAXIOV)
 		return NULL;
-
-	bio = kmalloc(struct_size(bio, bi_inline_vecs, nr_iovecs), gfp_mask);
-	if (unlikely(!bio))
-		return NULL;
-	bio_init(bio, NULL, nr_iovecs ? bio->bi_inline_vecs : NULL, nr_iovecs,
-		 0);
-	bio->bi_pool = NULL;
-	return bio;
+	return kmalloc(struct_size(bio, bi_inline_vecs, nr_vecs), gfp_mask);
 }
 EXPORT_SYMBOL(bio_kmalloc);