MMap only part of devdax

Signed-off-by: Lukasz Dorau <[email protected]>

Author: ldorau

src/provider/provider_devdax_memory.c

@@ -373,6 +373,7 @@ typedef struct devdax_ipc_data_t {
     size_t size;         // size of the /dev/dax
     unsigned protection; // combination of OS-specific memory protection flags
     size_t offset;       // offset of the data
+    size_t length;       // length of the data
 } devdax_ipc_data_t;
 
 static umf_result_t devdax_get_ipc_handle_size(void *provider, size_t *size) {
@@ -397,12 +398,13 @@ static umf_result_t devdax_get_ipc_handle(void *provider, const void *ptr,
         (devdax_memory_provider_t *)provider;
 
     devdax_ipc_data_t *devdax_ipc_data = (devdax_ipc_data_t *)providerIpcData;
-    devdax_ipc_data->offset =
-        (size_t)((uintptr_t)ptr - (uintptr_t)devdax_provider->base);
     strncpy(devdax_ipc_data->path, devdax_provider->path, PATH_MAX - 1);
     devdax_ipc_data->path[PATH_MAX - 1] = '\0';
     devdax_ipc_data->size = devdax_provider->size;
     devdax_ipc_data->protection = devdax_provider->protection;
+    devdax_ipc_data->offset =
+        (size_t)((uintptr_t)ptr - (uintptr_t)devdax_provider->base);
+    devdax_ipc_data->length = size;
 
     return UMF_RESULT_SUCCESS;
 }
@@ -453,27 +455,27 @@ static umf_result_t devdax_open_ipc_handle(void *provider,
     utils_translate_mem_visibility_flag(UMF_MEM_MAP_SYNC, &map_sync_flag);
 
     // mmap /dev/dax with the MAP_SYNC xor MAP_SHARED flag (if MAP_SYNC fails)
-    char *base = utils_mmap_file(NULL, devdax_ipc_data->size,
+    char *addr = utils_mmap_file(NULL, devdax_ipc_data->length,
                                  devdax_ipc_data->protection, map_sync_flag, fd,
-                                 0 /* offset */);
-    if (base == NULL) {
+                                 devdax_ipc_data->offset);
+    if (addr == NULL) {
         devdax_store_last_native_error(UMF_DEVDAX_RESULT_ERROR_ALLOC_FAILED,
                                        errno);
         LOG_PERR("devdax mapping failed (path: %s, size: %zu, protection: %i, "
-                 "fd: %i)",
-                 devdax_ipc_data->path, devdax_ipc_data->size,
-                 devdax_ipc_data->protection, fd);
+                 "fd: %i, offset: %zu)",
+                 devdax_ipc_data->path, devdax_ipc_data->length,
+                 devdax_ipc_data->protection, fd, devdax_ipc_data->offset);
         ret = UMF_RESULT_ERROR_MEMORY_PROVIDER_SPECIFIC;
     }
 
     LOG_DEBUG("devdax mapped (path: %s, size: %zu, protection: %i, fd: %i, "
               "offset: %zu)",
-              devdax_ipc_data->path, devdax_ipc_data->size,
+              devdax_ipc_data->path, devdax_ipc_data->length,
               devdax_ipc_data->protection, fd, devdax_ipc_data->offset);
 
     (void)utils_close_fd(fd);
 
-    *ptr = base + devdax_ipc_data->offset;
+    *ptr = addr;
 
     return ret;
 }
@@ -484,11 +486,8 @@ static umf_result_t devdax_close_ipc_handle(void *provider, void *ptr,
         return UMF_RESULT_ERROR_INVALID_ARGUMENT;
     }
 
-    devdax_memory_provider_t *devdax_provider =
-        (devdax_memory_provider_t *)provider;
-
     errno = 0;
-    int ret = utils_munmap(devdax_provider->base, devdax_provider->size);
+    int ret = utils_munmap(ptr, size);
     // ignore error when size == 0
     if (ret && (size > 0)) {
         devdax_store_last_native_error(UMF_DEVDAX_RESULT_ERROR_FREE_FAILED,