Re: [dpdk-dev] [PATCH v3] mbuf: minor cleanup

[Olivier Matz <olivier.matz@6wind.com>]

Hi Morten,

Thanks for this cleanup. Please see some comments below.

On Wed, Sep 16, 2020 at 12:40:13PM +0200, Morten Brørup wrote:
> The mbuf header files had some commenting style errors that affected the
> API documentation.
> Also, the RTE_ prefix was missing on a macro and a definition.
> 
> Note: This patch does not touch the offload and attachment flags that are
> also missing the RTE_ prefix.
> 
> Changes only affecting documentation:
> * Removed the MBUF_INVALID_PORT definition from rte_mbuf.h; it is
>   already defined in rte_mbuf_core.h.
>   This removal also reestablished the description of the
>   rte_pktmbuf_reset() function.
> * Corrected the comment related to RTE_MBUF_MAX_NB_SEGS.
> * Corrected the comment related to PKT_TX_QINQ_PKT.
> 
> Changes regarding missing RTE_ prefix:
> * Converted the MBUF_RAW_ALLOC_CHECK() macro to an
>   __rte_mbuf_raw_sanity_check() inline function.
>   Added backwards compatible macro with the original name.
> * Renamed the MBUF_INVALID_PORT definition to RTE_MBUF_PORT_INVALID.
>   Added backwards compatible definition with the original name.
> 
> v2:
> * Use RTE_MBUF_PORT_INVALID instead of MBUF_INVALID_PORT in rte_mbuf.c.
> 
> v3:
> * The functions/macros used in __rte_mbuf_raw_sanity_check() require
>   RTE_ENABLE_ASSERT or RTE_LIBRTE_MBUF_DEBUG, or they don't use the mbuf
>   parameter, which generates a compiler waning. So mark the mbuf parameter
>   __rte_unused if none of them are defined.
> 
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> ---
>  doc/guides/rel_notes/deprecation.rst |  7 ----
>  lib/librte_mbuf/rte_mbuf.c           |  4 +-
>  lib/librte_mbuf/rte_mbuf.h           | 55 +++++++++++++++++++---------
>  lib/librte_mbuf/rte_mbuf_core.h      |  9 +++--
>  4 files changed, 45 insertions(+), 30 deletions(-)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index 279eccb04..88d7d0761 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -294,13 +294,6 @@ Deprecation Notices
>    - https://patches.dpdk.org/patch/71457/
>    - https://patches.dpdk.org/patch/71456/
>  
> -* rawdev: The rawdev APIs which take a device-specific structure as
> -  parameter directly, or indirectly via a "private" pointer inside another
> -  structure, will be modified to take an additional parameter of the
> -  structure size. The affected APIs will include ``rte_rawdev_info_get``,
> -  ``rte_rawdev_configure``, ``rte_rawdev_queue_conf_get`` and
> -  ``rte_rawdev_queue_setup``.
> -
>  * acl: ``RTE_ACL_CLASSIFY_NUM`` enum value will be removed.
>    This enum value is not used inside DPDK, while it prevents to add new
>    classify algorithms without causing an ABI breakage.

I think this change is not related.

This makes me think that a deprecation notice could be done for the
old names without the RTE_ prefix, to be removed in 21.11.


> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index 8a456e5e6..53a015311 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -104,7 +104,7 @@ rte_pktmbuf_init(struct rte_mempool *mp,
>  	/* init some constant fields */
>  	m->pool = mp;
>  	m->nb_segs = 1;
> -	m->port = MBUF_INVALID_PORT;
> +	m->port = RTE_MBUF_PORT_INVALID;
>  	rte_mbuf_refcnt_set(m, 1);
>  	m->next = NULL;
>  }
> @@ -207,7 +207,7 @@ __rte_pktmbuf_init_extmem(struct rte_mempool *mp,
>  	/* init some constant fields */
>  	m->pool = mp;
>  	m->nb_segs = 1;
> -	m->port = MBUF_INVALID_PORT;
> +	m->port = RTE_MBUF_PORT_INVALID;
>  	m->ol_flags = EXT_ATTACHED_MBUF;
>  	rte_mbuf_refcnt_set(m, 1);
>  	m->next = NULL;
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 7259575a7..406d3abb2 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -554,12 +554,36 @@ __rte_experimental
>  int rte_mbuf_check(const struct rte_mbuf *m, int is_header,
>  		   const char **reason);
>  
> -#define MBUF_RAW_ALLOC_CHECK(m) do {				\
> -	RTE_ASSERT(rte_mbuf_refcnt_read(m) == 1);		\
> -	RTE_ASSERT((m)->next == NULL);				\
> -	RTE_ASSERT((m)->nb_segs == 1);				\
> -	__rte_mbuf_sanity_check(m, 0);				\
> -} while (0)
> +#if defined(RTE_ENABLE_ASSERT) || defined(RTE_LIBRTE_MBUF_DEBUG)

I don't see why this #if is needed. Wouldn't it work to have only
one function definition with the __rte_unused attribute?

> +/**
> + * Sanity checks on a reinitialized mbuf.
> + *
> + * Check the consistency of the given reinitialized mbuf.
> + * The function will cause a panic if corruption is detected.
> + *
> + * Check that the mbuf is properly reinitialized (refcnt=1, next=NULL,
> + * nb_segs=1), as done by rte_pktmbuf_prefree_seg().
> + *

Maybe indicate that these checks are only done when debug is on.

> + * @param m
> + *   The mbuf to be checked.
> + */
> +static __rte_always_inline void
> +__rte_mbuf_raw_sanity_check(const struct rte_mbuf *m)
> +{
> +	RTE_ASSERT(rte_mbuf_refcnt_read(m) == 1);
> +	RTE_ASSERT(m->next == NULL);
> +	RTE_ASSERT(m->nb_segs == 1);
> +	__rte_mbuf_sanity_check(m, 0);
> +}
> +#else
> +static __rte_always_inline void
> +__rte_mbuf_raw_sanity_check(const struct rte_mbuf *m __rte_unused)
> +{
> +    /* Nothing here. */
> +}
> +#endif
> +/** For backwards compatibility. */
> +#define MBUF_RAW_ALLOC_CHECK(m) __rte_mbuf_raw_sanity_check(m)

It looks that MBUF_RAW_ALLOC_CHECK() is also used in drivers/net/sfc,
I think it should be updated too.

>  
>  /**
>   * Allocate an uninitialized mbuf from mempool *mp*.
> @@ -586,7 +610,7 @@ static inline struct rte_mbuf *rte_mbuf_raw_alloc(struct rte_mempool *mp)
>  
>  	if (rte_mempool_get(mp, (void **)&m) < 0)
>  		return NULL;
> -	MBUF_RAW_ALLOC_CHECK(m);
> +	__rte_mbuf_raw_sanity_check(m);
>  	return m;
>  }
>  
> @@ -609,10 +633,7 @@ rte_mbuf_raw_free(struct rte_mbuf *m)
>  {
>  	RTE_ASSERT(!RTE_MBUF_CLONED(m) &&
>  		  (!RTE_MBUF_HAS_EXTBUF(m) || RTE_MBUF_HAS_PINNED_EXTBUF(m)));
> -	RTE_ASSERT(rte_mbuf_refcnt_read(m) == 1);
> -	RTE_ASSERT(m->next == NULL);
> -	RTE_ASSERT(m->nb_segs == 1);
> -	__rte_mbuf_sanity_check(m, 0);
> +	__rte_mbuf_raw_sanity_check(m);
>  	rte_mempool_put(m->pool, m);
>  }
>  
> @@ -858,8 +879,6 @@ static inline void rte_pktmbuf_reset_headroom(struct rte_mbuf *m)
>   * @param m
>   *   The packet mbuf to be reset.
>   */
> -#define MBUF_INVALID_PORT UINT16_MAX
> -
>  static inline void rte_pktmbuf_reset(struct rte_mbuf *m)
>  {
>  	m->next = NULL;
> @@ -868,7 +887,7 @@ static inline void rte_pktmbuf_reset(struct rte_mbuf *m)
>  	m->vlan_tci = 0;
>  	m->vlan_tci_outer = 0;
>  	m->nb_segs = 1;
> -	m->port = MBUF_INVALID_PORT;
> +	m->port = RTE_MBUF_PORT_INVALID;
>  
>  	m->ol_flags &= EXT_ATTACHED_MBUF;
>  	m->packet_type = 0;
> @@ -931,22 +950,22 @@ static inline int rte_pktmbuf_alloc_bulk(struct rte_mempool *pool,
>  	switch (count % 4) {
>  	case 0:
>  		while (idx != count) {
> -			MBUF_RAW_ALLOC_CHECK(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check(mbufs[idx]);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
>  	case 3:
> -			MBUF_RAW_ALLOC_CHECK(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check(mbufs[idx]);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
>  	case 2:
> -			MBUF_RAW_ALLOC_CHECK(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check(mbufs[idx]);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
>  	case 1:
> -			MBUF_RAW_ALLOC_CHECK(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check(mbufs[idx]);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
> diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
> index 8cd7137ac..4ac5609e3 100644
> --- a/lib/librte_mbuf/rte_mbuf_core.h
> +++ b/lib/librte_mbuf/rte_mbuf_core.h
> @@ -272,7 +272,7 @@ extern "C" {
>   * mbuf 'vlan_tci' & 'vlan_tci_outer' must be valid when this flag is set.
>   */
>  #define PKT_TX_QINQ        (1ULL << 49)
> -/* this old name is deprecated */
> +/** This old name is deprecated. */
>  #define PKT_TX_QINQ_PKT    PKT_TX_QINQ
>  
>  /**
> @@ -686,7 +686,7 @@ struct rte_mbuf_ext_shared_info {
>  	};
>  };
>  
> -/**< Maximum number of nb_segs allowed. */
> +/** Maximum number of nb_segs allowed. */
>  #define RTE_MBUF_MAX_NB_SEGS	UINT16_MAX
>  
>  /**
> @@ -714,7 +714,10 @@ struct rte_mbuf_ext_shared_info {
>  #define RTE_MBUF_DIRECT(mb) \
>  	(!((mb)->ol_flags & (IND_ATTACHED_MBUF | EXT_ATTACHED_MBUF)))
>  
> -#define MBUF_INVALID_PORT UINT16_MAX
> +/** NULL value for the uint16_t port type. */
> +#define RTE_MBUF_PORT_INVALID UINT16_MAX

I don't really like talking about "NULL". What do you think instead of
this wording?

  /** Uninitialized or unspecified port */

> +/** For backwards compatibility. */
> +#define MBUF_INVALID_PORT RTE_MBUF_PORT_INVALID
>  
>  /**
>   * A macro that points to an offset into the data in the mbuf.
> -- 
> 2.17.1
> 

Thanks,
Olivier