Function arc_buf_alloc_impl

freebsd/contrib/openzfs/module/zfs/arc.c:2781–2888

* Allocate a buf for this hdr. If you care about the data that's in the hdr, * or if you want a compressed buffer, pass those flags in. Returns 0 if the * copy was made successfully, or an error code otherwise. */

 * copy was made successfully, or an error code otherwise.
 */
static int
arc_buf_alloc_impl(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb,
    void *tag, boolean_t encrypted, boolean_t compressed, boolean_t noauth,
    boolean_t fill, arc_buf_t **ret)
{
	arc_buf_t *buf;
	arc_fill_flags_t flags = ARC_FILL_LOCKED;

	ASSERT(HDR_HAS_L1HDR(hdr));
	ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
	VERIFY(hdr->b_type == ARC_BUFC_DATA ||
	    hdr->b_type == ARC_BUFC_METADATA);
	ASSERT3P(ret, !=, NULL);
	ASSERT3P(*ret, ==, NULL);
	IMPLY(encrypted, compressed);

	hdr->b_l1hdr.b_mru_hits = 0;
	hdr->b_l1hdr.b_mru_ghost_hits = 0;
	hdr->b_l1hdr.b_mfu_hits = 0;
	hdr->b_l1hdr.b_mfu_ghost_hits = 0;
	hdr->b_l1hdr.b_l2_hits = 0;

	buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
	buf->b_hdr = hdr;
	buf->b_data = NULL;
	buf->b_next = hdr->b_l1hdr.b_buf;
	buf->b_flags = 0;

	add_reference(hdr, tag);

	/*
	 * We're about to change the hdr's b_flags. We must either
	 * hold the hash_lock or be undiscoverable.
	 */
	ASSERT(HDR_EMPTY_OR_LOCKED(hdr));

	/*
	 * Only honor requests for compressed bufs if the hdr is actually
	 * compressed. This must be overridden if the buffer is encrypted since
	 * encrypted buffers cannot be decompressed.
	 */
	if (encrypted) {
		buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
		buf->b_flags |= ARC_BUF_FLAG_ENCRYPTED;
		flags |= ARC_FILL_COMPRESSED | ARC_FILL_ENCRYPTED;
	} else if (compressed &&
	    arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
		buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
		flags |= ARC_FILL_COMPRESSED;
	}

	if (noauth) {
		ASSERT0(encrypted);
		flags |= ARC_FILL_NOAUTH;
	}

	/*
	 * If the hdr's data can be shared then we share the data buffer and