Implement file-backed ring buffer

[lttng-ust.git] / libringbuffer / ring_buffer_backend.c

diff --git a/libringbuffer/ring_buffer_backend.c b/libringbuffer/ring_buffer_backend.c
index 7d3a37809e73da27b25d43d8914ed285545075f7..3a667adce53c8ccdda4f15b872c13d054907f7ed 100644 (file)
--- a/libringbuffer/ring_buffer_backend.c
+++ b/libringbuffer/ring_buffer_backend.c
@@ -29,6 +29,8 @@
 #include "smp.h"
 #include "shm.h"
 
+#define UINT_MAX_STR_LEN 11    /* includes \0 */
+
 /**
  * lib_ring_buffer_backend_allocate - allocate a channel buffer
  * @config: ring buffer instance configuration
@@ -115,7 +117,6 @@ int lib_ring_buffer_backend_allocate(const struct lttng_ust_lib_ring_buffer_conf
                        mmap_offset += subbuf_size;
                }
        }
-
        return 0;
 
 free_array:
@@ -199,6 +200,7 @@ void channel_backend_reset(struct channel_backend *chanb)
  * @subbuf_size: size of sub-buffers (> PAGE_SIZE, power of 2)
  * @num_subbuf: number of sub-buffers (power of 2)
  * @lttng_ust_shm_handle: shared memory handle
+ * @shm_path: shared memory files path
  *
  * Returns channel pointer if successful, %NULL otherwise.
  *
@@ -212,7 +214,8 @@ int channel_backend_init(struct channel_backend *chanb,
                         const char *name,
                         const struct lttng_ust_lib_ring_buffer_config *config,
                         size_t subbuf_size, size_t num_subbuf,
-                        struct lttng_ust_shm_handle *handle)
+                        struct lttng_ust_shm_handle *handle,
+                        const char *shm_path)
 {
        struct channel *chan = caa_container_of(chanb, struct channel, backend);
        unsigned int i;
@@ -285,9 +288,21 @@ int channel_backend_init(struct channel_backend *chanb,
                 */
                for_each_possible_cpu(i) {
                        struct shm_object *shmobj;
-
+                       char shm_buf_path[PATH_MAX];
+
+                       if (shm_path) {
+                               char cpu_nr[UINT_MAX_STR_LEN];  /* unsigned int max len */
+
+                               strncpy(shm_buf_path, shm_path, PATH_MAX);
+                               shm_buf_path[PATH_MAX - 1] = '\0';
+                               ret = snprintf(cpu_nr, UINT_MAX_STR_LEN, "%u", i);
+                               if (ret != 1)
+                                       goto end;
+                               strncat(shm_buf_path, cpu_nr,
+                                       PATH_MAX - strlen(shm_buf_path) - 1);
+                       }
                        shmobj = shm_object_table_alloc(handle->table, shmsize,
-                                       SHM_OBJECT_SHM);
+                                       SHM_OBJECT_SHM, shm_path ? shm_buf_path : NULL);
                        if (!shmobj)
                                goto end;
                        align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
@@ -306,7 +321,7 @@ int channel_backend_init(struct channel_backend *chanb,
                struct lttng_ust_lib_ring_buffer *buf;
 
                shmobj = shm_object_table_alloc(handle->table, shmsize,
-                                       SHM_OBJECT_SHM);
+                                       SHM_OBJECT_SHM, shm_path);
                if (!shmobj)
                        goto end;
                align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));