[dpdk-dev] [PATCH 7/8] mem: add external API to retrieve page fd from EAL

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

Now that we can retrieve page fd's internally, we can expose it
as an external API. This will add two flavors of API - thread-safe
and non-thread-safe.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/common/eal_common_memory.c  | 47 ++++++++++++++++++++++
 lib/librte_eal/common/include/rte_memory.h | 44 ++++++++++++++++++++
 lib/librte_eal/rte_eal_version.map         |  2 +
 3 files changed, 93 insertions(+)

diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index 034c2026a..cd3805b46 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -550,6 +550,53 @@ rte_memseg_list_walk(rte_memseg_list_walk_t func, void *arg)
 	return ret;
 }
 
+int __rte_experimental
+rte_memseg_get_fd_thread_unsafe(const struct rte_memseg *ms)
+{
+	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
+	struct rte_memseg_list *msl;
+	struct rte_fbarray *arr;
+	int msl_idx, seg_idx, fd;
+
+	if (ms == NULL) {
+		rte_errno = EINVAL;
+		return -1;
+	}
+
+	msl = rte_mem_virt2memseg_list(ms->addr);
+	if (msl == NULL) {
+		rte_errno = EINVAL;
+		return -1;
+	}
+	arr = &msl->memseg_arr;
+
+	msl_idx = msl - mcfg->memsegs;
+	seg_idx = rte_fbarray_find_idx(arr, ms);
+
+	if (!rte_fbarray_is_used(arr, seg_idx)) {
+		rte_errno = ENOENT;
+		return -1;
+	}
+
+	fd = eal_memalloc_get_seg_fd(msl_idx, seg_idx);
+	if (fd < 0)
+		rte_errno = ENOENT;
+	return fd;
+}
+
+int __rte_experimental
+rte_memseg_get_fd(const struct rte_memseg *ms)
+{
+	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
+	int ret;
+
+	rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
+	ret = rte_memseg_get_fd_thread_unsafe(ms);
+	rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+
+	return ret;
+}
+
 /* init memory subsystem */
 int
 rte_eal_memory_init(void)
diff --git a/lib/librte_eal/common/include/rte_memory.h b/lib/librte_eal/common/include/rte_memory.h
index c4b7f4cff..4d075b1cc 100644
--- a/lib/librte_eal/common/include/rte_memory.h
+++ b/lib/librte_eal/common/include/rte_memory.h
@@ -317,6 +317,50 @@ rte_memseg_contig_walk_thread_unsafe(rte_memseg_contig_walk_t func, void *arg);
 int __rte_experimental
 rte_memseg_list_walk_thread_unsafe(rte_memseg_list_walk_t func, void *arg);
 
+/**
+ * Return file descriptor associated with a particular memseg (if available).
+ *
+ * @note This function read-locks the memory hotplug subsystem, and thus cannot
+ *       be used within memory-related callback functions.
+ *
+ * @note This returns the internal file descriptor - no operations should ever
+ *       be performed on it, and it should be treated as read-only for all
+ *       intents and purposes.
+ *
+ * @param ms
+ *   A pointer to memseg for which to get file descriptor.
+ *
+ * @return
+ *   Valid file descriptor in case of success.
+ *   -1 in case of error, with ``rte_errno`` set to the following values:
+ *     - EINVAL - ``ms`` pointer was NULL or did not point to a valid memseg
+ *     - ENOENT - ``ms`` pointed to an unused segment, or fd is not available
+ */
+int __rte_experimental
+rte_memseg_get_fd(const struct rte_memseg *ms);
+
+/**
+ * Return file descriptor associated with a particular memseg (if available).
+ *
+ * @note This function does not perform any locking, and is only safe to call
+ *       from within memory-related callback functions.
+ *
+ * @note This returns the internal file descriptor - no operations should ever
+ *       be performed on it, and it should be treated as read-only for all
+ *       intents and purposes.
+ *
+ * @param ms
+ *   A pointer to memseg for which to get file descriptor.
+ *
+ * @return
+ *   Valid file descriptor in case of success.
+ *   -1 in case of error, with ``rte_errno`` set to the following values:
+ *     - EINVAL - ``ms`` pointer was NULL or did not point to a valid memseg
+ *     - ENOENT - ``ms`` pointed to an unused segment, or fd is not available
+ */
+int __rte_experimental
+rte_memseg_get_fd_thread_unsafe(const struct rte_memseg *ms);
+
 /**
  * Dump the physical memory layout to a file.
  *
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index 344a43d32..e659e19d6 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -320,6 +320,8 @@ EXPERIMENTAL {
 	rte_mem_virt2memseg_list;
 	rte_memseg_contig_walk;
 	rte_memseg_contig_walk_thread_unsafe;
+	rte_memseg_get_fd;
+	rte_memseg_get_fd_thread_unsafe;
 	rte_memseg_list_walk;
 	rte_memseg_list_walk_thread_unsafe;
 	rte_memseg_walk;
-- 
2.17.1