RE: [PATCH] mbuf: de-inline sanity checking a reinitialized mbuf

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Morten Brørup [mailto:mb@smartsharesystems.com]
> Sent: Saturday, 19 July 2025 12.23
> 
> Sanity checking a reinitialized mbuf (a.k.a. raw mbuf) has been
> refactored
> to follow the same design pattern as sanity checking a normal mbuf, and
> now depends on RTE_LIBRTE_MBUF_DEBUG instead of RTE_ENABLE_ASSERT.
> 
> The details of the changes are as follows:
> 
> Non-inlined functions rte_mbuf_raw_sanity_check() and
> rte_mbuf_raw_check()
> have been added.
> They do for a reinitialized mbuf what rte_mbuf_sanity_check() and
> rte_mbuf_check() do for a normal mbuf.
> They basically check the same conditions as
> __rte_mbuf_raw_sanity_check()
> previously did, but use "if (!condition) rte_panic(message)" instead of
> RTE_ASSSERT(), so they don't depend on RTE_ENABLE_ASSERT.
> 
> The inline function __rte_mbuf_raw_sanity_check() has been replaced
> by the new macro __rte_mbuf_raw_sanity_check_mp(), which either calls
> rte_mbuf_raw_sanity_check() or does nothing, depending on
> RTE_LIBRTE_MBUF_DEBUG, just like the __rte_mbuf_sanity_check() macro
> does
> for a normal mbuf.
> 
> Note that the new macro __rte_mbuf_raw_sanity_check_mp() takes an
> optional
> mempool parameter to verify that the mbuf belongs to the expected mbuf
> pool.
> This addition is mainly relevant for sanity checking reinitialized mbufs
> freed directly into a given mempool by a PMD when using
> RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE.
> 
> The macro __rte_mbuf_raw_sanity_check() has been kept for backwards API
> compatibility.
> It simply calls __rte_mbuf_raw_sanity_check_mp() without specifying a
> mempool.
> 
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>

Building this with RTE_LIBRTE_MBUF_DEBUG 1 in rte_config.h spews out warnings like:

../lib/mbuf/rte_mbuf.h: In function ‘rte_mbuf_raw_free’:
../lib/mbuf/rte_mbuf.h:700:9: warning: ‘rte_mbuf_raw_sanity_check’ is deprecated: Symbol is not yet part of stable ABI [-Wdeprecated-declarations]
  700 |         __rte_mbuf_raw_sanity_check_mp(m, NULL);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../lib/mbuf/rte_mbuf.h:542:1: note: declared here
  542 | rte_mbuf_raw_sanity_check(const struct rte_mbuf *m, const struct rte_mempool *mp);
      | ^~~~~~~~~~~~~~~~~~~~~~~~~

Exporting the new APIs as non-experimental (i.e. using RTE_EXPORT_SYMBOL() instead of RTE_EXPORT_EXPERIMENTAL_SYMBOL() in the C file, and omitting __rte_experimental in the header file, as shown below) works, but is that acceptable?

Or is there a better way of avoiding these warnings?

> ---
>  lib/mbuf/rte_mbuf.c |  61 ++++++++++++++++++++++++++
>  lib/mbuf/rte_mbuf.h | 104 ++++++++++++++++++++++++++++----------------
>  2 files changed, 127 insertions(+), 38 deletions(-)
> 
> diff --git a/lib/mbuf/rte_mbuf.c b/lib/mbuf/rte_mbuf.c
> index 9e7731a8a2..ff4db73b50 100644
> --- a/lib/mbuf/rte_mbuf.c
> +++ b/lib/mbuf/rte_mbuf.c
> @@ -373,6 +373,67 @@ rte_pktmbuf_pool_create_extbuf(const char *name,
> unsigned int n,
>  	return mp;
>  }
> 
> +/* do some sanity checks on a reinitialized mbuf: panic if it fails */
> +RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_mbuf_raw_sanity_check, 25.11)

+// RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_mbuf_raw_sanity_check, 25.11)
+RTE_EXPORT_SYMBOL(rte_mbuf_raw_sanity_check)

> +void
> +rte_mbuf_raw_sanity_check(const struct rte_mbuf *m, const struct
> rte_mempool *mp)
> +{
> +	const char *reason;
> +
> +	if (rte_mbuf_raw_check(m, mp, &reason))
> +		rte_panic("%s\n", reason);
> +}
> +
> +RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_mbuf_raw_check, 25.11)

+// RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_mbuf_raw_check, 25.11)
+RTE_EXPORT_SYMBOL(rte_mbuf_raw_check)

> +int rte_mbuf_raw_check(const struct rte_mbuf *m, const struct
> rte_mempool *mp,
> +		   const char **reason)
> +{
> +	/* check sanity */
> +	if (rte_mbuf_check(m, 0, reason) == -1)
> +		return -1;
> +
> +	/* check initialized */
> +	if (rte_mbuf_refcnt_read(m) != 1) {
> +		*reason = "uninitialized ref cnt";
> +		return -1;
> +	}
> +	if (m->next != NULL) {
> +		*reason = "uninitialized next ptr";
> +		return -1;
> +	}
> +	if (m->nb_segs != 1) {
> +		*reason = "uninitialized nb_segs";
> +		return -1;
> +	}
> +	if (RTE_MBUF_CLONED(m)) {
> +		*reason = "cloned";
> +		return -1;
> +	}
> +	if (RTE_MBUF_HAS_EXTBUF(m)) {
> +		if (!RTE_MBUF_HAS_PINNED_EXTBUF(m)) {
> +			*reason = "external buffer not pinned";
> +			return -1;
> +		}
> +
> +		uint16_t cnt = rte_mbuf_ext_refcnt_read(m->shinfo);
> +		if ((cnt == 0) || (cnt == UINT16_MAX)) {
> +			*reason = "pinned external buffer bad ref cnt";
> +			return -1;
> +		}
> +		if (cnt != 1) {
> +			*reason = "pinned external buffer uninitialized ref
> cnt";
> +			return -1;
> +		}
> +	}
> +
> +	if (mp != NULL && m->pool != mp) {
> +		*reason = "wrong mbuf pool";
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
>  /* do some sanity checks on a mbuf: panic if it fails */
>  RTE_EXPORT_SYMBOL(rte_mbuf_sanity_check)
>  void
> diff --git a/lib/mbuf/rte_mbuf.h b/lib/mbuf/rte_mbuf.h
> index 06ab7502a5..2621cc385c 100644
> --- a/lib/mbuf/rte_mbuf.h
> +++ b/lib/mbuf/rte_mbuf.h
> @@ -339,11 +339,17 @@ rte_pktmbuf_priv_flags(struct rte_mempool *mp)
> 
>  #ifdef RTE_LIBRTE_MBUF_DEBUG
> 
> +/**  check reinitialized mbuf type in debug mode */
> +#define __rte_mbuf_raw_sanity_check_mp(m, mp)
> rte_mbuf_raw_sanity_check(m, mp)
> +
>  /**  check mbuf type in debug mode */
>  #define __rte_mbuf_sanity_check(m, is_h) rte_mbuf_sanity_check(m, is_h)
> 
>  #else /*  RTE_LIBRTE_MBUF_DEBUG */
> 
> +/**  check reinitialized mbuf type in debug mode */
> +#define __rte_mbuf_raw_sanity_check_mp(m, mp) do { } while (0)
> +
>  /**  check mbuf type in debug mode */
>  #define __rte_mbuf_sanity_check(m, is_h) do { } while (0)
> 
> @@ -513,6 +519,54 @@ rte_mbuf_ext_refcnt_update(struct
> rte_mbuf_ext_shared_info *shinfo,
>  } while (0)
> 
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: This API may change, or be removed, without prior
> notice.
> + *
> + * 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().
> + *
> + * @param m
> + *   The mbuf to be checked.
> + * @param mp
> + *   The mempool to which the mbuf belongs.
> + *   NULL if unknown, not to be checked.
> + */
> +__rte_experimental

+// __rte_experimental

> +void
> +rte_mbuf_raw_sanity_check(const struct rte_mbuf *m, const struct
> rte_mempool *mp);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: This API may change, or be removed, without prior
> notice.
> + *
> + * Sanity checks on a reinitialized mbuf.
> + *
> + * Almost like rte_mbuf_raw_sanity_check(), but this function gives the
> reason
> + * if corruption is detected rather than panic.
> + *
> + * @param m
> + *   The mbuf to be checked.
> + * @param mp
> + *   The mempool to which the mbuf belongs.
> + *   NULL if unknown, not to be checked.
> + * @param reason
> + *   A reference to a string pointer where to store the reason why a
> mbuf is
> + *   considered invalid.
> + * @return
> + *   - 0 if no issue has been found, reason is left untouched.
> + *   - -1 if a problem is detected, reason then points to a string
> describing
> + *     the reason why the mbuf is deemed invalid.
> + */
> +__rte_experimental

+// __rte_experimental

> +int rte_mbuf_raw_check(const struct rte_mbuf *m, const struct
> rte_mempool *mp,
> +		   const char **reason);
> +
>  /**
>   * Sanity checks on an mbuf.
>   *
> @@ -550,33 +604,11 @@ rte_mbuf_sanity_check(const struct rte_mbuf *m,
> int is_header);
>  int rte_mbuf_check(const struct rte_mbuf *m, int is_header,
>  		   const char **reason);
> 
> -/**
> - * Sanity checks on a reinitialized mbuf in debug mode.
> - *
> - * 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().
> - *
> - * @param m
> - *   The mbuf to be checked.
> - */
> -static __rte_always_inline void
> -__rte_mbuf_raw_sanity_check(__rte_unused 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_ASSERT(!RTE_MBUF_CLONED(m));
> -	RTE_ASSERT(!RTE_MBUF_HAS_EXTBUF(m) ||
> -			(RTE_MBUF_HAS_PINNED_EXTBUF(m) &&
> -			rte_mbuf_ext_refcnt_read(m->shinfo) == 1));
> -	__rte_mbuf_sanity_check(m, 0);
> -}
> +/** For backwards compatibility. */
> +#define __rte_mbuf_raw_sanity_check(m)
> __rte_mbuf_raw_sanity_check_mp(m, NULL)
> 
>  /** For backwards compatibility. */
> -#define MBUF_RAW_ALLOC_CHECK(m) __rte_mbuf_raw_sanity_check(m)
> +#define MBUF_RAW_ALLOC_CHECK(m) __rte_mbuf_raw_sanity_check_mp(m, NULL)
> 
>  /**
>   * Allocate an uninitialized mbuf from mempool *mp*.
> @@ -606,7 +638,7 @@ static inline struct rte_mbuf
> *rte_mbuf_raw_alloc(struct rte_mempool *mp)
> 
>  	if (rte_mempool_get(mp, &ret.ptr) < 0)
>  		return NULL;
> -	__rte_mbuf_raw_sanity_check(ret.m);
> +	__rte_mbuf_raw_sanity_check_mp(ret.m, mp);
>  	return ret.m;
>  }
> 
> @@ -644,7 +676,7 @@ rte_mbuf_raw_alloc_bulk(struct rte_mempool *mp,
> struct rte_mbuf **mbufs, unsigne
>  	int rc = rte_mempool_get_bulk(mp, (void **)mbufs, count);
>  	if (likely(rc == 0))
>  		for (unsigned int idx = 0; idx < count; idx++)
> -			__rte_mbuf_raw_sanity_check(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check_mp(mbufs[idx], mp);
>  	return rc;
>  }
> 
> @@ -665,7 +697,7 @@ rte_mbuf_raw_alloc_bulk(struct rte_mempool *mp,
> struct rte_mbuf **mbufs, unsigne
>  static __rte_always_inline void
>  rte_mbuf_raw_free(struct rte_mbuf *m)
>  {
> -	__rte_mbuf_raw_sanity_check(m);
> +	__rte_mbuf_raw_sanity_check_mp(m, NULL);
>  	rte_mempool_put(m->pool, m);
>  }
> 
> @@ -696,12 +728,8 @@ __rte_experimental
>  static __rte_always_inline void
>  rte_mbuf_raw_free_bulk(struct rte_mempool *mp, struct rte_mbuf **mbufs,
> unsigned int count)
>  {
> -	for (unsigned int idx = 0; idx < count; idx++) {
> -		const struct rte_mbuf *m = mbufs[idx];
> -		RTE_ASSERT(m != NULL);
> -		RTE_ASSERT(m->pool == mp);
> -		__rte_mbuf_raw_sanity_check(m);
> -	}
> +	for (unsigned int idx = 0; idx < count; idx++)
> +		__rte_mbuf_raw_sanity_check_mp(mbufs[idx], mp);
> 
>  	rte_mempool_put_bulk(mp, (void **)mbufs, count);
>  }
> @@ -1021,22 +1049,22 @@ static inline int rte_pktmbuf_alloc_bulk(struct
> rte_mempool *pool,
>  	switch (count % 4) {
>  	case 0:
>  		while (idx != count) {
> -			__rte_mbuf_raw_sanity_check(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check_mp(mbufs[idx], pool);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
>  	case 3:
> -			__rte_mbuf_raw_sanity_check(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check_mp(mbufs[idx], pool);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
>  	case 2:
> -			__rte_mbuf_raw_sanity_check(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check_mp(mbufs[idx], pool);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
>  	case 1:
> -			__rte_mbuf_raw_sanity_check(mbufs[idx]);
> +			__rte_mbuf_raw_sanity_check_mp(mbufs[idx], pool);
>  			rte_pktmbuf_reset(mbufs[idx]);
>  			idx++;
>  			/* fall-through */
> --
> 2.43.0