[dpdk-dev] [PATCH v2 1/5] mem: fix error code for segment fd API for external segs

[Anatoly Burakov <anatoly.burakov@intel.com>]

Segment fd API does not support getting segment fd's from
externally allocated memory, so return proper error code
on any attempts to do so. This changes API behavior, so
document the change as well.

Fixes: 5282bb1c3695 ("mem: allow memseg lists to be marked as external")
Cc: stable@dpdk.org

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---

Notes:
    The API is experimental, no deprecation notice needed.

 doc/guides/rel_notes/release_19_02.rst    |  6 ++++++
 lib/librte_eal/common/eal_common_memory.c | 12 ++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/doc/guides/rel_notes/release_19_02.rst b/doc/guides/rel_notes/release_19_02.rst
index a94fa86a7..ade41b9c8 100644
--- a/doc/guides/rel_notes/release_19_02.rst
+++ b/doc/guides/rel_notes/release_19_02.rst
@@ -84,6 +84,12 @@ API Changes
    =========================================================
 
 
+* eal: segment fd API on Linux now sets error code to ``ENOTSUP`` in more cases
+  where segment fd API is not expected to be supported:
+
+  - On attempt to get segment fd for an externally allocated memory segment
+
+
 ABI Changes
 -----------
 
diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index d47ea4938..999ba24b4 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -704,6 +704,12 @@ rte_memseg_get_fd_thread_unsafe(const struct rte_memseg *ms)
 		return -1;
 	}
 
+	/* segment fd API is not supported for external segments */
+	if (msl->external) {
+		rte_errno = ENOTSUP;
+		return -1;
+	}
+
 	ret = eal_memalloc_get_seg_fd(msl_idx, seg_idx);
 	if (ret < 0) {
 		rte_errno = -ret;
@@ -754,6 +760,12 @@ rte_memseg_get_fd_offset_thread_unsafe(const struct rte_memseg *ms,
 		return -1;
 	}
 
+	/* segment fd API is not supported for external segments */
+	if (msl->external) {
+		rte_errno = ENOTSUP;
+		return -1;
+	}
+
 	ret = eal_memalloc_get_seg_fd_offset(msl_idx, seg_idx, offset);
 	if (ret < 0) {
 		rte_errno = -ret;
-- 
2.17.1