--- /dev/null
+/*
+ * fd-cache.c
+ *
+ * Babeltrace - File descriptor cache
+ *
+ * Copyright 2019 Francis Deslauriers <francis.deslauriers@efficios.com>
+ *
+ * Author: Francis Deslauriers <francis.deslauriers@efficios.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#define BT_LOG_TAG "FD-CACHE"
+#include "logging.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <glib.h>
+
+#include "common/assert.h"
+#include "fd-cache.h"
+
+struct file_key {
+ uint64_t dev;
+ uint64_t ino;
+};
+
+struct fd_handle_internal {
+ struct bt_fd_cache_handle fd_handle;
+ uint64_t ref_count;
+ struct file_key *key;
+};
+
+static
+void fd_cache_handle_internal_destroy(
+ struct fd_handle_internal *internal_fd)
+{
+ if (!internal_fd) {
+ goto end;
+ }
+
+ if (internal_fd->fd_handle.fd >= 0) {
+ close(internal_fd->fd_handle.fd);
+ internal_fd->fd_handle.fd = -1;
+ }
+
+end:
+ g_free(internal_fd);
+}
+
+/*
+ * Using simple hash algorithm found on stackoverflow:
+ * https://stackoverflow.com/questions/664014/
+ */
+static inline
+uint64_t hash_uint64_t(uint64_t x) {
+ x = (x ^ (x >> 30)) * UINT64_C(0xbf58476d1ce4e5b9);
+ x = (x ^ (x >> 27)) * UINT64_C(0x94d049bb133111eb);
+ x = x ^ (x >> 31);
+ return x;
+}
+
+static
+guint file_key_hash(gconstpointer v)
+{
+ const struct file_key *fk = v;
+ return hash_uint64_t(fk->dev) ^ hash_uint64_t(fk->ino);
+}
+
+static
+gboolean file_key_equal(gconstpointer v1, gconstpointer v2)
+{
+ const struct file_key *fk1 = v1;
+ const struct file_key *fk2 = v2;
+
+ return (fk1->dev == fk2->dev) && (fk1->ino == fk2->ino);
+}
+
+static
+void file_key_destroy(gpointer data)
+{
+ struct file_key *fk = data;
+ g_free(fk);
+}
+
+BT_HIDDEN
+int bt_fd_cache_init(struct bt_fd_cache *fdc)
+{
+ int ret = 0;
+
+ fdc->cache = g_hash_table_new_full(file_key_hash, file_key_equal,
+ file_key_destroy, (GDestroyNotify) fd_cache_handle_internal_destroy);
+ if (!fdc->cache) {
+ ret = -1;
+ }
+
+ return ret;
+}
+
+BT_HIDDEN
+void bt_fd_cache_fini(struct bt_fd_cache *fdc)
+{
+ BT_ASSERT(fdc->cache);
+ /*
+ * All handle should have been removed for the hashtable at this point.
+ */
+ BT_ASSERT(g_hash_table_size(fdc->cache) == 0);
+ g_hash_table_destroy(fdc->cache);
+
+ return;
+}
+
+BT_HIDDEN
+struct bt_fd_cache_handle *bt_fd_cache_get_handle(struct bt_fd_cache *fdc,
+ const char *path)
+{
+ struct fd_handle_internal *fd_internal = NULL;
+ struct stat statbuf;
+ struct file_key fk;
+ int ret, fd = -1;
+
+ ret = stat(path, &statbuf);
+ if (ret < 0) {
+ /*
+ * This is not necessarily an error as we sometimes try to open
+ * files to see if they exist. Log the error as DEBUG severity
+ * level.
+ */
+ BT_LOGD_ERRNO("Failed to stat file", ": path=%s", path);
+ goto end;
+ }
+
+ /*
+ * Use the device number and inode number to uniquely identify a file.
+ * Even if the file has the same path, it may have been replaced so we
+ * must open a new FD for it. This replacement of file is more likely
+ * to happen with a lttng-live source component.
+ */
+ fk.dev = statbuf.st_dev;
+ fk.ino = statbuf.st_ino;
+
+ fd_internal = g_hash_table_lookup(fdc->cache, &fk);
+ if (!fd_internal) {
+ struct file_key *file_key;
+
+ fd = open(path, O_RDONLY);
+ if (fd < 0) {
+ BT_LOGE_ERRNO("Failed to open file", "path=%s", path);
+ goto error;
+ }
+
+ fd_internal = g_new0(struct fd_handle_internal, 1);
+ if (!fd_internal) {
+ BT_LOGE("Failed to allocate fd internal handle");
+ goto error;
+ }
+
+ file_key = g_new0(struct file_key, 1);
+ if (!fd_internal) {
+ BT_LOGE("Failed to allocate file key");
+ goto error;
+ }
+
+ *file_key = fk;
+
+ fd_internal->fd_handle.fd = fd;
+ fd_internal->ref_count = 0;
+ fd_internal->key = file_key;
+
+ /* Insert the newly created fd handle. */
+ g_hash_table_insert(fdc->cache, fd_internal->key, fd_internal);
+ }
+
+ fd_internal->ref_count++;
+ goto end;
+
+error:
+ /*
+ * Close file descriptor if it was open() and we are currently on error
+ * path.
+ */
+ if (fd != -1) {
+ ret = close(fd);
+ if (ret) {
+ BT_LOGE_ERRNO("Failed to close file descriptor",
+ ": fd=%i, path=%s", fd, path);
+ }
+ }
+
+ fd_cache_handle_internal_destroy(fd_internal);
+ fd_internal = NULL;
+end:
+ return (struct bt_fd_cache_handle *) fd_internal;
+}
+
+BT_HIDDEN
+void bt_fd_cache_put_handle(struct bt_fd_cache *fdc,
+ struct bt_fd_cache_handle *handle)
+{
+ struct fd_handle_internal *fd_internal;
+
+ if (!handle) {
+ goto end;
+ }
+
+ fd_internal = (struct fd_handle_internal *) handle;
+
+ BT_ASSERT(fd_internal->ref_count > 0);
+
+ if (fd_internal->ref_count > 1) {
+ fd_internal->ref_count--;
+ } else {
+ gboolean ret;
+ int close_ret;
+
+ close_ret = close(fd_internal->fd_handle.fd);
+ if (close_ret == -1) {
+ BT_LOGW_ERRNO("Failed to close file descriptor",
+ ": fd=%d", fd_internal->fd_handle.fd);
+ }
+ ret = g_hash_table_remove(fdc->cache, fd_internal->key);
+ BT_ASSERT(ret);
+ }
+
+end:
+ return;
+}
projects / babeltrace.git / blobdiff