Tests: Add test to check shared-memory FD leaks after relayd dies

[lttng-tools.git] / src / common / trace-chunk.c

/*
 * Copyright (C) 2019 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 */

#include <common/compat/directory-handle.h>
#include <common/credentials.h>
#include <common/defaults.h>
#include <common/dynamic-array.h>
#include <common/error.h>
#include <common/fd-tracker/fd-tracker.h>
#include <common/fd-tracker/utils.h>
#include <common/fs-handle-internal.h>
#include <common/hashtable/hashtable.h>
#include <common/hashtable/utils.h>
#include <common/optional.h>
#include <common/string-utils/format.h>
#include <common/time.h>
#include <common/trace-chunk-registry.h>
#include <common/trace-chunk.h>
#include <common/utils.h>
#include <lttng/constant.h>

#include <inttypes.h>
#include <pthread.h>
#include <stdio.h>
#include <sys/stat.h>
#include <urcu/rculfhash.h>
#include <urcu/ref.h>

/*
 * Two ISO 8601-compatible timestamps, separated by a hypen, followed an
 * index, i.e. <start-iso-8601>-<end-iso-8601>-<id-uint64_t>.
 */
#define GENERATED_CHUNK_NAME_LEN (2 * sizeof("YYYYmmddTHHMMSS+HHMM") + MAX_INT_DEC_LEN(uint64_t))
#define DIR_CREATION_MODE (S_IRWXU | S_IRWXG)

enum trace_chunk_mode {
        TRACE_CHUNK_MODE_USER,
        TRACE_CHUNK_MODE_OWNER,
};

/*
 * Callback to invoke on release of a trace chunk. Note that there is no
 * need to 'lock' the trace chunk during the execution of these callbacks
 * since only one thread may access a chunk during its destruction (the last
 * to release its reference to the chunk).
 */
typedef int (*chunk_command)(struct lttng_trace_chunk *trace_chunk);

/* Move a completed trace chunk to the 'completed' trace archive folder. */
static
int lttng_trace_chunk_move_to_completed_post_release(struct lttng_trace_chunk *trace_chunk);
/* Empty callback. */
static
int lttng_trace_chunk_no_operation(struct lttng_trace_chunk *trace_chunk);
/* Unlink old chunk files. */
static
int lttng_trace_chunk_delete_post_release(struct lttng_trace_chunk *trace_chunk);
static
enum lttng_trace_chunk_status lttng_trace_chunk_rename_path_no_lock(
                struct lttng_trace_chunk *chunk, const char *path);

struct chunk_credentials {
        bool use_current_user;
        struct lttng_credentials user;
};

/*
 * NOTE: Make sure to update:
 * - lttng_trace_chunk_copy(),
 * - lttng_trace_chunk_registry_element_create_from_chunk()
 * if you modify this structure.
 */
struct lttng_trace_chunk {
        pthread_mutex_t lock;
        struct urcu_ref ref;
        LTTNG_OPTIONAL(enum trace_chunk_mode) mode;
        /*
         * First-level directories created within the trace chunk.
         * Elements are of type 'char *'.
         *
         * Only used by _owner_ mode chunks.
         */
        struct lttng_dynamic_pointer_array top_level_directories;
        /*
         * All files contained within the trace chunk.
         * Array of paths (char *).
         */
        struct lttng_dynamic_pointer_array files;
        /* Is contained within an lttng_trace_chunk_registry_element? */
        bool in_registry_element;
        bool name_overridden;
        char *name;
        char *path;
        /* An unset id means the chunk is anonymous. */
        LTTNG_OPTIONAL(uint64_t) id;

        /*
         * The creation and close timestamps are NOT monotonic.
         * They must not be used in context were monotonicity is required.
         */
        LTTNG_OPTIONAL(time_t) timestamp_creation;
        LTTNG_OPTIONAL(time_t) timestamp_close;

        LTTNG_OPTIONAL(struct chunk_credentials) credentials;
        struct lttng_directory_handle *session_output_directory;
        struct lttng_directory_handle *chunk_directory;
        LTTNG_OPTIONAL(enum lttng_trace_chunk_command_type) close_command;
        /*
         * fd_tracker instance through which file descriptors should be
         * created/closed.
         *
         * An fd_tracker always outlives any trace chunk; there is no
         * need to perform any reference counting of that object.
         */
        struct fd_tracker *fd_tracker;
};

/* A trace chunk is uniquely identified by its (session id, chunk id) tuple. */
struct lttng_trace_chunk_registry_element {
        struct lttng_trace_chunk chunk;
        uint64_t session_id;
        /* Weak and only set when added. */
        struct lttng_trace_chunk_registry *registry;
        struct cds_lfht_node trace_chunk_registry_ht_node;
        /* call_rcu delayed reclaim. */
        struct rcu_head rcu_node;
};

struct lttng_trace_chunk_registry {
        struct cds_lfht *ht;
};

struct fs_handle_untracked {
        struct fs_handle parent;
        int fd;
        struct {
                struct lttng_directory_handle *directory_handle;
                char *path;
        } location;
};

static
int fs_handle_untracked_get_fd(struct fs_handle *handle);
static
void fs_handle_untracked_put_fd(struct fs_handle *handle);
static
int fs_handle_untracked_unlink(struct fs_handle *handle);
static
int fs_handle_untracked_close(struct fs_handle *handle);

static const
char *close_command_names[] = {
        [LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED] =
                "move to completed chunk folder",
        [LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION] =
                "no operation",
        [LTTNG_TRACE_CHUNK_COMMAND_TYPE_DELETE] =
                "delete",
};

static const
chunk_command close_command_post_release_funcs[] = {
        [LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED] =
                        lttng_trace_chunk_move_to_completed_post_release,
        [LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION] =
                        lttng_trace_chunk_no_operation,
        [LTTNG_TRACE_CHUNK_COMMAND_TYPE_DELETE] =
                        lttng_trace_chunk_delete_post_release,
};

static
struct fs_handle *fs_handle_untracked_create(
                struct lttng_directory_handle *directory_handle,
                const char *path,
                int fd)
{
        struct fs_handle_untracked *handle = NULL;
        bool reference_acquired;
        char *path_copy = strdup(path);

        LTTNG_ASSERT(fd >= 0);
        if (!path_copy) {
                PERROR("Failed to copy file path while creating untracked filesystem handle");
                goto end;
        }

        handle = zmalloc(sizeof(typeof(*handle)));
        if (!handle) {
                PERROR("Failed to allocate untracked filesystem handle");
                goto end;
        }

        handle->parent = (typeof(handle->parent)) {
                .get_fd = fs_handle_untracked_get_fd,
                .put_fd = fs_handle_untracked_put_fd,
                .unlink = fs_handle_untracked_unlink,
                .close = fs_handle_untracked_close,
        };

        handle->fd = fd;
        reference_acquired = lttng_directory_handle_get(directory_handle);
        LTTNG_ASSERT(reference_acquired);
        handle->location.directory_handle = directory_handle;
        /* Ownership is transferred. */
        handle->location.path = path_copy;
        path_copy = NULL;
end:
        free(path_copy);
        return handle ? &handle->parent : NULL;
}

static
int fs_handle_untracked_get_fd(struct fs_handle *_handle)
{
        struct fs_handle_untracked *handle = container_of(
                        _handle, struct fs_handle_untracked, parent);

        return handle->fd;
}

static
void fs_handle_untracked_put_fd(struct fs_handle *_handle)
{
        /* no-op. */
}

static
int fs_handle_untracked_unlink(struct fs_handle *_handle)
{
        struct fs_handle_untracked *handle = container_of(
                        _handle, struct fs_handle_untracked, parent);

        return lttng_directory_handle_unlink_file(
                        handle->location.directory_handle,
                        handle->location.path);
}

static
void fs_handle_untracked_destroy(struct fs_handle_untracked *handle)
{
        lttng_directory_handle_put(handle->location.directory_handle);
        free(handle->location.path);
        free(handle);
}

static
int fs_handle_untracked_close(struct fs_handle *_handle)
{
        struct fs_handle_untracked *handle = container_of(
                        _handle, struct fs_handle_untracked, parent);
        int ret = close(handle->fd);

        fs_handle_untracked_destroy(handle);
        return ret;
}

static
bool lttng_trace_chunk_registry_element_equals(
                const struct lttng_trace_chunk_registry_element *a,
                const struct lttng_trace_chunk_registry_element *b)
{
        if (a->session_id != b->session_id) {
                goto not_equal;
        }
        if (a->chunk.id.is_set != b->chunk.id.is_set) {
                goto not_equal;
        }
        if (a->chunk.id.is_set && a->chunk.id.value != b->chunk.id.value) {
                goto not_equal;
        }
        return true;
not_equal:
        return false;
}

static
int lttng_trace_chunk_registry_element_match(struct cds_lfht_node *node,
                const void *key)
{
        const struct lttng_trace_chunk_registry_element *element_a, *element_b;

        element_a = (const struct lttng_trace_chunk_registry_element *) key;
        element_b = caa_container_of(node, typeof(*element_b),
                        trace_chunk_registry_ht_node);
        return lttng_trace_chunk_registry_element_equals(element_a, element_b);
}

static
unsigned long lttng_trace_chunk_registry_element_hash(
                const struct lttng_trace_chunk_registry_element *element)
{
        unsigned long hash = hash_key_u64(&element->session_id,
                        lttng_ht_seed);

        if (element->chunk.id.is_set) {
                hash ^= hash_key_u64(&element->chunk.id.value, lttng_ht_seed);
        }

        return hash;
}

static
char *generate_chunk_name(uint64_t chunk_id, time_t creation_timestamp,
                const time_t *close_timestamp)
{
        int ret = 0;
        char *new_name= NULL;
        char start_datetime[ISO8601_STR_LEN] = {};
        /* Add 1 for a '-' prefix. */
        char end_datetime_suffix[ISO8601_STR_LEN + 1] = {};

        ret = time_to_iso8601_str(
                        creation_timestamp,
                        start_datetime, sizeof(start_datetime));
        if (ret) {
                ERR("Failed to format trace chunk start date time");
                goto error;
        }
        if (close_timestamp) {
                *end_datetime_suffix = '-';
                ret = time_to_iso8601_str(
                                *close_timestamp,
                                end_datetime_suffix + 1,
                                sizeof(end_datetime_suffix) - 1);
                if (ret) {
                        ERR("Failed to format trace chunk end date time");
                        goto error;
                }
        }
        new_name = zmalloc(GENERATED_CHUNK_NAME_LEN);
        if (!new_name) {
                ERR("Failed to allocate buffer for automatically-generated trace chunk name");
                goto error;
        }
        ret = snprintf(new_name, GENERATED_CHUNK_NAME_LEN, "%s%s-%" PRIu64,
                        start_datetime, end_datetime_suffix, chunk_id);
        if (ret >= GENERATED_CHUNK_NAME_LEN || ret == -1) {
                ERR("Failed to format trace chunk name");
                goto error;
        }

        return new_name;
error:
        free(new_name);
        return NULL;
}

static
void lttng_trace_chunk_init(struct lttng_trace_chunk *chunk)
{
        urcu_ref_init(&chunk->ref);
        pthread_mutex_init(&chunk->lock, NULL);
        lttng_dynamic_pointer_array_init(&chunk->top_level_directories, free);
        lttng_dynamic_pointer_array_init(&chunk->files, free);
}

static
void lttng_trace_chunk_fini(struct lttng_trace_chunk *chunk)
{
        if (chunk->session_output_directory) {
                lttng_directory_handle_put(
                                chunk->session_output_directory);
                chunk->session_output_directory = NULL;
        }
        if (chunk->chunk_directory) {
                lttng_directory_handle_put(chunk->chunk_directory);
                chunk->chunk_directory = NULL;
        }
        free(chunk->name);
        chunk->name = NULL;
        free(chunk->path);
        chunk->path = NULL;
        lttng_dynamic_pointer_array_reset(&chunk->top_level_directories);
        lttng_dynamic_pointer_array_reset(&chunk->files);
        pthread_mutex_destroy(&chunk->lock);
}

static
struct lttng_trace_chunk *lttng_trace_chunk_allocate(void)
{
        struct lttng_trace_chunk *chunk = NULL;

        chunk = zmalloc(sizeof(*chunk));
        if (!chunk) {
                ERR("Failed to allocate trace chunk");
                goto end;
        }
        lttng_trace_chunk_init(chunk);
end:
        return chunk;
}

struct lttng_trace_chunk *lttng_trace_chunk_create_anonymous(void)
{
        DBG("Creating anonymous trace chunk");
        return lttng_trace_chunk_allocate();
}

struct lttng_trace_chunk *lttng_trace_chunk_create(
                uint64_t chunk_id, time_t chunk_creation_time, const char *path)
{
        struct lttng_trace_chunk *chunk;
        char chunk_creation_datetime_buf[16] = {};
        const char *chunk_creation_datetime_str = "(formatting error)";
        struct tm timeinfo_buf, *timeinfo;

        timeinfo = localtime_r(&chunk_creation_time, &timeinfo_buf);
        if (timeinfo) {
                size_t strftime_ret;

                /* Don't fail because of this; it is only used for logging. */
                strftime_ret = strftime(chunk_creation_datetime_buf,
                                sizeof(chunk_creation_datetime_buf),
                                "%Y%m%d-%H%M%S", timeinfo);
                if (strftime_ret) {
                        chunk_creation_datetime_str =
                                        chunk_creation_datetime_buf;
                }
        }

        DBG("Creating trace chunk: chunk_id = %" PRIu64 ", creation time = %s",
                        chunk_id, chunk_creation_datetime_str);
        chunk = lttng_trace_chunk_allocate();
        if (!chunk) {
                goto end;
        }

        LTTNG_OPTIONAL_SET(&chunk->id, chunk_id);
        LTTNG_OPTIONAL_SET(&chunk->timestamp_creation, chunk_creation_time);
        if (chunk_id != 0) {
                chunk->name = generate_chunk_name(chunk_id,
                                chunk_creation_time, NULL);
                if (!chunk->name) {
                        ERR("Failed to allocate trace chunk name storage");
                        goto error;
                }
        }
        if (path) {
                chunk->path = strdup(path);
                if (!chunk->path) {
                        goto error;
                }
        } else {
                if (chunk->name) {
                        chunk->path = strdup(chunk->name);
                        if (!chunk->path) {
                                goto error;
                        }
                }
        }

        DBG("Chunk name set to \"%s\"", chunk->name ? : "(none)");
end:
        return chunk;
error:
        lttng_trace_chunk_put(chunk);
        return NULL;
}

void lttng_trace_chunk_set_fd_tracker(struct lttng_trace_chunk *chunk,
                struct fd_tracker *fd_tracker)
{
        LTTNG_ASSERT(!chunk->session_output_directory);
        LTTNG_ASSERT(!chunk->chunk_directory);
        LTTNG_ASSERT(lttng_dynamic_pointer_array_get_count(&chunk->files) == 0);
        chunk->fd_tracker = fd_tracker;
}

struct lttng_trace_chunk *lttng_trace_chunk_copy(
                struct lttng_trace_chunk *source_chunk)
{
        struct lttng_trace_chunk *new_chunk = lttng_trace_chunk_allocate();

        if (!new_chunk) {
                goto end;
        }

        pthread_mutex_lock(&source_chunk->lock);
        /*
         * A new chunk is always a user; it shall create no new trace
         * subdirectories.
         */
        new_chunk->mode = (typeof(new_chunk->mode)) {
                .is_set = true,
                .value = TRACE_CHUNK_MODE_USER,
        };
        /*
         * top_level_directories is not copied as it is never used
         * by _user_ mode chunks.
         */
        /* The new chunk is not part of a registry (yet, at least). */
        new_chunk->in_registry_element = false;
        new_chunk->name_overridden = source_chunk->name_overridden;
        if (source_chunk->name) {
                new_chunk->name = strdup(source_chunk->name);
                if (!new_chunk->name) {
                        ERR("Failed to copy source trace chunk name in %s()",
                                        __FUNCTION__);
                        goto error_unlock;
                }
        }
        if (source_chunk->path) {
                new_chunk->path = strdup(source_chunk->path);
                if (!new_chunk->path) {
                        ERR("Failed to copy source trace chunk path in %s()",
                                        __FUNCTION__);
                }
        }
        new_chunk->id = source_chunk->id;
        new_chunk->timestamp_creation = source_chunk->timestamp_creation;
        new_chunk->timestamp_close = source_chunk->timestamp_close;
        new_chunk->credentials = source_chunk->credentials;
        if (source_chunk->session_output_directory) {
                const bool reference_acquired = lttng_directory_handle_get(
                                source_chunk->session_output_directory);

                LTTNG_ASSERT(reference_acquired);
                new_chunk->session_output_directory =
                                source_chunk->session_output_directory;
        }
        if (source_chunk->chunk_directory) {
                const bool reference_acquired = lttng_directory_handle_get(
                                source_chunk->chunk_directory);

                LTTNG_ASSERT(reference_acquired);
                new_chunk->chunk_directory = source_chunk->chunk_directory;
        }
        new_chunk->close_command = source_chunk->close_command;
        new_chunk->fd_tracker = source_chunk->fd_tracker;
        pthread_mutex_unlock(&source_chunk->lock);
end:
        return new_chunk;
error_unlock:
        pthread_mutex_unlock(&source_chunk->lock);
        lttng_trace_chunk_put(new_chunk);
        return NULL;
}

enum lttng_trace_chunk_status lttng_trace_chunk_get_id(
                struct lttng_trace_chunk *chunk, uint64_t *id)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->id.is_set) {
                *id = chunk->id.value;
        } else {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
        }
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_get_creation_timestamp(
                struct lttng_trace_chunk *chunk, time_t *creation_ts)

{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->timestamp_creation.is_set) {
                *creation_ts = chunk->timestamp_creation.value;
        } else {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
        }
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_get_close_timestamp(
                struct lttng_trace_chunk *chunk, time_t *close_ts)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->timestamp_close.is_set) {
                *close_ts = chunk->timestamp_close.value;
        } else {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
        }
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_set_close_timestamp(
                struct lttng_trace_chunk *chunk, time_t close_ts)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (!chunk->timestamp_creation.is_set) {
                ERR("Failed to set trace chunk close timestamp: creation timestamp is unset");
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
                goto end;
        }

        /*
         * Note: we do not enforce that the closing timestamp be greater or
         * equal to the begin timestamp. These timestamps are used for
         * generating the chunk name and should only be used in context where
         * the monotonicity of time is not important. The source of those
         * timestamps is NOT monotonic and represent the system calendar time,
         * also know as the wall time.
         */
        if (chunk->timestamp_creation.value > close_ts) {
                WARN("Set trace chunk close timestamp: close timestamp is before creation timestamp, begin : %ld, close : %ld",
                                chunk->timestamp_creation.value, close_ts);
        }

        LTTNG_OPTIONAL_SET(&chunk->timestamp_close, close_ts);
        if (!chunk->name_overridden) {
                free(chunk->name);
                chunk->name = generate_chunk_name(LTTNG_OPTIONAL_GET(chunk->id),
                                LTTNG_OPTIONAL_GET(chunk->timestamp_creation),
                                &close_ts);
                if (!chunk->name) {
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                }
        }
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_get_name(
                struct lttng_trace_chunk *chunk, const char **name,
                bool *name_overridden)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (name_overridden) {
                *name_overridden = chunk->name_overridden;
        }
        if (!chunk->name) {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
                goto end;
        }
        *name = chunk->name;
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

bool lttng_trace_chunk_get_name_overridden(struct lttng_trace_chunk *chunk)
{
        bool name_overridden;

        pthread_mutex_lock(&chunk->lock);
        name_overridden = chunk->name_overridden;
        pthread_mutex_unlock(&chunk->lock);
        return name_overridden;
}

static
bool is_valid_chunk_name(const char *name)
{
        size_t len;

        if (!name) {
                return false;
        }

        len = lttng_strnlen(name, LTTNG_NAME_MAX);
        if (len == 0 || len == LTTNG_NAME_MAX) {
                return false;
        }

        if (strchr(name, '/') || strchr(name, '.')) {
                return false;
        }

        return true;
}

enum lttng_trace_chunk_status lttng_trace_chunk_override_name(
                struct lttng_trace_chunk *chunk, const char *name)

{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
        char *new_name, *new_path;

        DBG("Override trace chunk name from %s to %s", chunk->name, name);
        if (!is_valid_chunk_name(name)) {
                ERR("Attempted to set an invalid name on a trace chunk: name = %s",
                                name ? : "NULL");
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
                goto end;
        }

        pthread_mutex_lock(&chunk->lock);
        if (!chunk->id.is_set) {
                ERR("Attempted to set an override name on an anonymous trace chunk: name = %s",
                                name);
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
                goto end_unlock;
        }

        new_name = strdup(name);
        if (!new_name) {
                ERR("Failed to allocate new trace chunk name");
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end_unlock;
        }
        free(chunk->name);
        chunk->name = new_name;

        new_path = strdup(name);
        if (!new_path) {
                ERR("Failed to allocate new trace chunk path");
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end_unlock;
        }
        free(chunk->path);
        chunk->path = new_path;

        chunk->name_overridden = true;
end_unlock:
        pthread_mutex_unlock(&chunk->lock);
end:
        return status;
}

static
enum lttng_trace_chunk_status lttng_trace_chunk_rename_path_no_lock(
                struct lttng_trace_chunk *chunk, const char *path)

{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
        struct lttng_directory_handle *rename_directory = NULL;
        char *new_path, *old_path;
        int ret;

        if (chunk->name_overridden) {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }

        old_path = chunk->path;
        DBG("lttng_trace_chunk_rename_path from %s to %s", old_path, path);

        if ((!old_path && !path) ||
                        (old_path && path && !strcmp(old_path, path)))  {
                goto end;
        }
        /*
         * Use chunk name as path if NULL path is specified.
         */
        if (!path) {
                path = chunk->name;
        }

        /* Renaming from "" to "" is not accepted. */
        if (path[0] == '\0' && old_path[0] == '\0') {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }

        /*
         * If a rename is performed on a chunk for which the chunk_directory
         * is not set (yet), or the session_output_directory is not set
         * (interacting with a relay daemon), there is no rename to perform.
         */
        if (!chunk->chunk_directory ||
                        !chunk->session_output_directory) {
                goto skip_move;
        }

        if (old_path && old_path[0] != '\0' && path[0] != '\0') {
                /* Rename chunk directory. */
                ret = lttng_directory_handle_rename_as_user(
                        chunk->session_output_directory,
                        old_path,
                        chunk->session_output_directory,
                        path,
                        LTTNG_OPTIONAL_GET(chunk->credentials).use_current_user ?
                                NULL :
                                &chunk->credentials.value.user);
                if (ret) {
                        PERROR("Failed to move trace chunk directory \"%s\" to \"%s\"",
                                        old_path, path);
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                        goto end;
                }
                rename_directory = chunk->fd_tracker ?
                                fd_tracker_create_directory_handle_from_handle(
                                                chunk->fd_tracker,
                                                chunk->session_output_directory,
                                                path) :
                                lttng_directory_handle_create_from_handle(
                                                path,
                                                chunk->session_output_directory);
                if (!rename_directory) {
                        ERR("Failed to get handle to trace chunk rename directory");
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                        goto end;
                }

                /* Release old handle. */
                lttng_directory_handle_put(chunk->chunk_directory);
                /*
                 * Transfer new handle reference to chunk as the current chunk
                 * handle.
                 */
                chunk->chunk_directory = rename_directory;
                rename_directory = NULL;
        } else if (old_path && old_path[0] == '\0') {
                size_t i, count = lttng_dynamic_pointer_array_get_count(
                                &chunk->top_level_directories);

                ret = lttng_directory_handle_create_subdirectory_as_user(
                                chunk->session_output_directory,
                                path,
                                DIR_CREATION_MODE,
                                LTTNG_OPTIONAL_GET(chunk->credentials).use_current_user ?
                                        NULL :
                                        &chunk->credentials.value.user);
                if (ret) {
                        PERROR("Failed to create trace chunk rename directory \"%s\"",
                                        path);
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                        goto end;
                }

                rename_directory = lttng_directory_handle_create_from_handle(
                                path, chunk->session_output_directory);
                if (!rename_directory) {
                        ERR("Failed to get handle to trace chunk rename directory");
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                        goto end;
                }

                /* Move toplevel directories. */
                for (i = 0; i < count; i++) {
                        const char *top_level_name =
                                lttng_dynamic_pointer_array_get_pointer(
                                        &chunk->top_level_directories, i);

                        ret = lttng_directory_handle_rename_as_user(
                                        chunk->chunk_directory,
                                        top_level_name,
                                        rename_directory,
                                        top_level_name,
                                        LTTNG_OPTIONAL_GET(chunk->credentials).use_current_user ?
                                                NULL :
                                                &chunk->credentials.value.user);
                        if (ret) {
                                PERROR("Failed to move \"%s\" to trace chunk rename directory",
                                                top_level_name);
                                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                                goto end;
                        }
                }
                /* Release old handle. */
                lttng_directory_handle_put(chunk->chunk_directory);
                /*
                 * Transfer new handle reference to chunk as the current chunk
                 * handle.
                 */
                chunk->chunk_directory = rename_directory;
                rename_directory = NULL;
        } else if (old_path) {
                size_t i, count = lttng_dynamic_pointer_array_get_count(
                                &chunk->top_level_directories);
                const bool reference_acquired = lttng_directory_handle_get(
                                chunk->session_output_directory);

                LTTNG_ASSERT(reference_acquired);
                rename_directory = chunk->session_output_directory;

                /* Move toplevel directories. */
                for (i = 0; i < count; i++) {
                        const char *top_level_name =
                                lttng_dynamic_pointer_array_get_pointer(
                                        &chunk->top_level_directories, i);

                        ret = lttng_directory_handle_rename_as_user(
                                        chunk->chunk_directory,
                                        top_level_name,
                                        rename_directory,
                                        top_level_name,
                                        LTTNG_OPTIONAL_GET(chunk->credentials).use_current_user ?
                                                NULL :
                                                &chunk->credentials.value.user);
                        if (ret) {
                                PERROR("Failed to move \"%s\" to trace chunk rename directory",
                                                top_level_name);
                                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                                goto end;
                        }
                }
                /* Release old handle. */
                lttng_directory_handle_put(chunk->chunk_directory);
                /*
                 * Transfer new handle reference to chunk as the current chunk
                 * handle.
                 */
                chunk->chunk_directory = rename_directory;
                rename_directory = NULL;

                /* Remove old directory. */
                status = lttng_directory_handle_remove_subdirectory(
                                chunk->session_output_directory,
                                old_path);
                if (status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                        ERR("Error removing subdirectory '%s' file when deleting chunk",
                                old_path);
                        goto end;
                }
        } else {
                /* Unexpected !old_path && !path. */
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
                goto end;
        }

skip_move:
        new_path = strdup(path);
        if (!new_path) {
                ERR("Failed to allocate new trace chunk path");
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        free(chunk->path);
        chunk->path = new_path;
end:
        lttng_directory_handle_put(rename_directory);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_rename_path(
                struct lttng_trace_chunk *chunk, const char *path)

{
        enum lttng_trace_chunk_status status;

        pthread_mutex_lock(&chunk->lock);
        status = lttng_trace_chunk_rename_path_no_lock(chunk, path);
        pthread_mutex_unlock(&chunk->lock);

        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_get_credentials(
                struct lttng_trace_chunk *chunk,
                struct lttng_credentials *credentials)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->credentials.is_set) {
                if (chunk->credentials.value.use_current_user) {
                        LTTNG_OPTIONAL_SET(&credentials->uid, geteuid());
                        LTTNG_OPTIONAL_SET(&credentials->gid, getegid());
                } else {
                        *credentials = chunk->credentials.value.user;
                }
        } else {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
        }
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_set_credentials(
                struct lttng_trace_chunk *chunk,
                const struct lttng_credentials *user_credentials)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
        const struct chunk_credentials credentials = {
                .user = *user_credentials,
                .use_current_user = false,
        };

        pthread_mutex_lock(&chunk->lock);
        if (chunk->credentials.is_set) {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        LTTNG_OPTIONAL_SET(&chunk->credentials, credentials);
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_set_credentials_current_user(
                struct lttng_trace_chunk *chunk)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
        const struct chunk_credentials credentials = {
                .use_current_user = true,
        };

        pthread_mutex_lock(&chunk->lock);
        if (chunk->credentials.is_set) {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        LTTNG_OPTIONAL_SET(&chunk->credentials, credentials);
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}


enum lttng_trace_chunk_status lttng_trace_chunk_set_as_owner(
                struct lttng_trace_chunk *chunk,
                struct lttng_directory_handle *session_output_directory)
{
        int ret;
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
        struct lttng_directory_handle *chunk_directory_handle = NULL;
        bool reference_acquired;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->mode.is_set) {
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
                goto end;
        }
        if (!chunk->credentials.is_set) {
                /*
                 * Fatal error, credentials must be set before a
                 * directory is created.
                 */
                ERR("Credentials of trace chunk are unset: refusing to set session output directory");
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        if (chunk->path && chunk->path[0] != '\0') {
                ret = lttng_directory_handle_create_subdirectory_as_user(
                                session_output_directory,
                                chunk->path,
                                DIR_CREATION_MODE,
                                !chunk->credentials.value.use_current_user ?
                                        &chunk->credentials.value.user : NULL);
                if (ret) {
                        PERROR("Failed to create chunk output directory \"%s\"",
                                chunk->path);
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                        goto end;
                }
                chunk_directory_handle =
                                chunk->fd_tracker ?
                                        fd_tracker_create_directory_handle_from_handle(
                                                        chunk->fd_tracker,
                                                        session_output_directory,
                                                        chunk->path) :
                                        lttng_directory_handle_create_from_handle(
                                                        chunk->path,
                                                        session_output_directory);
                if (!chunk_directory_handle) {
                        /* The function already logs on all error paths. */
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                        goto end;
                }
        } else {
                /*
                 * A nameless chunk does not need its own output directory.
                 * The session's output directory will be used.
                 */
                reference_acquired = lttng_directory_handle_get(
                                session_output_directory);

                LTTNG_ASSERT(reference_acquired);
                chunk_directory_handle = session_output_directory;
        }
        chunk->chunk_directory = chunk_directory_handle;
        chunk_directory_handle = NULL;
        reference_acquired = lttng_directory_handle_get(
                        session_output_directory);
        LTTNG_ASSERT(reference_acquired);
        chunk->session_output_directory = session_output_directory;
        LTTNG_OPTIONAL_SET(&chunk->mode, TRACE_CHUNK_MODE_OWNER);
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_set_as_user(
                struct lttng_trace_chunk *chunk,
                struct lttng_directory_handle *chunk_directory)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
        bool reference_acquired;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->mode.is_set) {
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
                goto end;
        }
        if (!chunk->credentials.is_set) {
                ERR("Credentials of trace chunk are unset: refusing to set chunk output directory");
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        reference_acquired = lttng_directory_handle_get(chunk_directory);
        LTTNG_ASSERT(reference_acquired);
        chunk->chunk_directory = chunk_directory;
        LTTNG_OPTIONAL_SET(&chunk->mode, TRACE_CHUNK_MODE_USER);
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status
lttng_trace_chunk_get_session_output_directory_handle(
                struct lttng_trace_chunk *chunk,
                struct lttng_directory_handle **handle)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (!chunk->session_output_directory) {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
                *handle = NULL;
                goto end;
        } else {
                const bool reference_acquired = lttng_directory_handle_get(
                                chunk->session_output_directory);

                LTTNG_ASSERT(reference_acquired);
                *handle = chunk->session_output_directory;
        }
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_borrow_chunk_directory_handle(
                struct lttng_trace_chunk *chunk,
                const struct lttng_directory_handle **handle)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (!chunk->chunk_directory) {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
                goto end;
        }

        *handle = chunk->chunk_directory;
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

/* Add a top-level directory to the trace chunk if it was previously unknown. */
static
int add_top_level_directory_unique(struct lttng_trace_chunk *chunk,
                const char *new_path)
{
        int ret = 0;
        bool found = false;
        size_t i, count = lttng_dynamic_pointer_array_get_count(
                        &chunk->top_level_directories);
        const char *new_path_separator_pos = strchr(new_path, '/');
        const ptrdiff_t new_path_top_level_len = new_path_separator_pos ?
                        new_path_separator_pos - new_path : strlen(new_path);

        for (i = 0; i < count; i++) {
                const char *path = lttng_dynamic_pointer_array_get_pointer(
                                &chunk->top_level_directories, i);
                const ptrdiff_t path_top_level_len = strlen(path);

                if (path_top_level_len != new_path_top_level_len) {
                        continue;
                }
                if (!strncmp(path, new_path, path_top_level_len)) {
                        found = true;
                        break;
                }
        }

        if (!found) {
                char *copy = lttng_strndup(new_path, new_path_top_level_len);

                DBG("Adding new top-level directory \"%s\" to trace chunk \"%s\"",
                                new_path, chunk->name ? : "(unnamed)");
                if (!copy) {
                        PERROR("Failed to copy path");
                        ret = -1;
                        goto end;
                }
                ret = lttng_dynamic_pointer_array_add_pointer(
                                &chunk->top_level_directories, copy);
                if (ret) {
                        ERR("Allocation failure while adding top-level directory entry to a trace chunk");
                        free(copy);
                        goto end;
                }
        }
end:
        return ret;
}

enum lttng_trace_chunk_status lttng_trace_chunk_create_subdirectory(
                struct lttng_trace_chunk *chunk,
                const char *path)
{
        int ret;
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        DBG("Creating trace chunk subdirectory \"%s\"", path);
        pthread_mutex_lock(&chunk->lock);
        if (!chunk->credentials.is_set) {
                /*
                 * Fatal error, credentials must be set before a
                 * directory is created.
                 */
                ERR("Credentials of trace chunk are unset: refusing to create subdirectory \"%s\"",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        if (!chunk->mode.is_set ||
                        chunk->mode.value != TRACE_CHUNK_MODE_OWNER) {
                ERR("Attempted to create trace chunk subdirectory \"%s\" through a non-owner chunk",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
                goto end;
        }
        if (!chunk->chunk_directory) {
                ERR("Attempted to create trace chunk subdirectory \"%s\" before setting the chunk output directory",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        if (*path == '/') {
                ERR("Refusing to create absolute trace chunk directory \"%s\"",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
                goto end;
        }
        ret = lttng_directory_handle_create_subdirectory_recursive_as_user(
                        chunk->chunk_directory, path,
                        DIR_CREATION_MODE,
                        chunk->credentials.value.use_current_user ?
                                        NULL : &chunk->credentials.value.user);
        if (ret) {
                PERROR("Failed to create trace chunk subdirectory \"%s\"",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        ret = add_top_level_directory_unique(chunk, path);
        if (ret) {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

/*
 * TODO: Implement O(1) lookup.
 */
static
bool lttng_trace_chunk_find_file(struct lttng_trace_chunk *chunk,
                const char *path, size_t *index)
{
        size_t i, count;

        count = lttng_dynamic_pointer_array_get_count(&chunk->files);
        for (i = 0; i < count; i++) {
                const char *iter_path =
                                lttng_dynamic_pointer_array_get_pointer(
                                        &chunk->files, i);
                if (!strcmp(iter_path, path)) {
                        if (index) {
                                *index = i;
                        }
                        return true;
                }
        }
        return false;
}

static
enum lttng_trace_chunk_status lttng_trace_chunk_add_file(
                struct lttng_trace_chunk *chunk,
                const char *path)
{
        char *copy;
        int ret;
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        if (lttng_trace_chunk_find_file(chunk, path, NULL)) {
                return LTTNG_TRACE_CHUNK_STATUS_OK;
        }
        DBG("Adding new file \"%s\" to trace chunk \"%s\"",
                        path, chunk->name ? : "(unnamed)");
        copy = strdup(path);
        if (!copy) {
                PERROR("Failed to copy path");
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        ret = lttng_dynamic_pointer_array_add_pointer(
                        &chunk->files, copy);
        if (ret) {
                ERR("Allocation failure while adding file to a trace chunk");
                free(copy);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
end:
        return status;
}

static
void lttng_trace_chunk_remove_file(
                struct lttng_trace_chunk *chunk,
                const char *path)
{
        size_t index;
        bool found;
        int ret;

        found = lttng_trace_chunk_find_file(chunk, path, &index);
        if (!found) {
                return;
        }
        ret = lttng_dynamic_pointer_array_remove_pointer(
                        &chunk->files, index);
        LTTNG_ASSERT(!ret);
}

static
enum lttng_trace_chunk_status _lttng_trace_chunk_open_fs_handle_locked(
                struct lttng_trace_chunk *chunk,
                const char *file_path,
                int flags,
                mode_t mode,
                struct fs_handle **out_handle,
                bool expect_no_file)
{
        int ret;
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        DBG("Opening trace chunk file \"%s\"", file_path);
        if (!chunk->credentials.is_set) {
                /*
                 * Fatal error, credentials must be set before a
                 * file is created.
                 */
                ERR("Credentials of trace chunk are unset: refusing to open file \"%s\"",
                                file_path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        if (!chunk->chunk_directory) {
                ERR("Attempted to open trace chunk file \"%s\" before setting the chunk output directory",
                                file_path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        status = lttng_trace_chunk_add_file(chunk, file_path);
        if (status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                goto end;
        }
        if (chunk->fd_tracker) {
                LTTNG_ASSERT(chunk->credentials.value.use_current_user);
                *out_handle = fd_tracker_open_fs_handle(chunk->fd_tracker,
                                chunk->chunk_directory, file_path, flags, &mode);
                ret = *out_handle ? 0 : -1;
        } else {
                ret = lttng_directory_handle_open_file_as_user(
                                chunk->chunk_directory, file_path, flags, mode,
                                chunk->credentials.value.use_current_user ?
                                                NULL :
                                                &chunk->credentials.value.user);
                if (ret >= 0) {
                        *out_handle = fs_handle_untracked_create(
                                        chunk->chunk_directory, file_path, ret);
                        if (!*out_handle) {
                                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                                goto end;
                        }
                }
        }
        if (ret < 0) {
                if (errno == ENOENT && expect_no_file) {
                        status = LTTNG_TRACE_CHUNK_STATUS_NO_FILE;
                } else {
                        PERROR("Failed to open file relative to trace chunk file_path = \"%s\", flags = %d, mode = %d",
                                file_path, flags, (int) mode);
                        status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                }
                lttng_trace_chunk_remove_file(chunk, file_path);
                goto end;
        }
end:
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_open_fs_handle(
                struct lttng_trace_chunk *chunk,
                const char *file_path,
                int flags,
                mode_t mode,
                struct fs_handle **out_handle,
                bool expect_no_file)
{
        enum lttng_trace_chunk_status status;

        pthread_mutex_lock(&chunk->lock);
        status = _lttng_trace_chunk_open_fs_handle_locked(chunk, file_path,
                        flags, mode, out_handle, expect_no_file);
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_open_file(
                struct lttng_trace_chunk *chunk,
                const char *file_path,
                int flags,
                mode_t mode,
                int *out_fd,
                bool expect_no_file)
{
        enum lttng_trace_chunk_status status;
        struct fs_handle *fs_handle;

        pthread_mutex_lock(&chunk->lock);
        /*
         * Using this method is never valid when an fd_tracker is being
         * used since the resulting file descriptor would not be tracked.
         */
        LTTNG_ASSERT(!chunk->fd_tracker);
        status = _lttng_trace_chunk_open_fs_handle_locked(chunk, file_path,
                        flags, mode, &fs_handle, expect_no_file);
        pthread_mutex_unlock(&chunk->lock);

        if (status == LTTNG_TRACE_CHUNK_STATUS_OK) {
                *out_fd = fs_handle_get_fd(fs_handle);
                /*
                 * Does not close the fd; we just "unbox" it from the fs_handle.
                 */
                fs_handle_untracked_destroy(container_of(
                                fs_handle, struct fs_handle_untracked, parent));
        }

        return status;
}

int lttng_trace_chunk_unlink_file(struct lttng_trace_chunk *chunk,
                const char *file_path)
{
        int ret;
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        DBG("Unlinking trace chunk file \"%s\"", file_path);
        pthread_mutex_lock(&chunk->lock);
        if (!chunk->credentials.is_set) {
                /*
                 * Fatal error, credentials must be set before a
                 * file is unlinked.
                 */
                ERR("Credentials of trace chunk are unset: refusing to unlink file \"%s\"",
                                file_path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        if (!chunk->chunk_directory) {
                ERR("Attempted to unlink trace chunk file \"%s\" before setting the chunk output directory",
                                file_path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        ret = lttng_directory_handle_unlink_file_as_user(
                        chunk->chunk_directory, file_path,
                        chunk->credentials.value.use_current_user ?
                                        NULL : &chunk->credentials.value.user);
        if (ret < 0) {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        lttng_trace_chunk_remove_file(chunk, file_path);
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

static
int lttng_trace_chunk_remove_subdirectory_recursive(struct lttng_trace_chunk *chunk,
                const char *path)
{
        int ret;
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        DBG("Recursively removing trace chunk directory \"%s\"", path);
        pthread_mutex_lock(&chunk->lock);
        if (!chunk->credentials.is_set) {
                /*
                 * Fatal error, credentials must be set before a
                 * directory is removed.
                 */
                ERR("Credentials of trace chunk are unset: refusing to recursively remove directory \"%s\"",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        if (!chunk->chunk_directory) {
                ERR("Attempted to recursively remove trace chunk directory \"%s\" before setting the chunk output directory",
                                path);
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
        ret = lttng_directory_handle_remove_subdirectory_recursive_as_user(
                        chunk->chunk_directory, path,
                        chunk->credentials.value.use_current_user ?
                                        NULL : &chunk->credentials.value.user,
                        LTTNG_DIRECTORY_HANDLE_SKIP_NON_EMPTY_FLAG);
        if (ret < 0) {
                status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
                goto end;
        }
end:
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

static
int lttng_trace_chunk_move_to_completed_post_release(
                struct lttng_trace_chunk *trace_chunk)
{
        int ret = 0;
        char *archived_chunk_name = NULL;
        const uint64_t chunk_id = LTTNG_OPTIONAL_GET(trace_chunk->id);
        const time_t creation_timestamp =
                        LTTNG_OPTIONAL_GET(trace_chunk->timestamp_creation);
        const time_t close_timestamp =
                        LTTNG_OPTIONAL_GET(trace_chunk->timestamp_close);
        struct lttng_directory_handle *archived_chunks_directory = NULL;
        enum lttng_trace_chunk_status status;

        if (!trace_chunk->mode.is_set ||
                        trace_chunk->mode.value != TRACE_CHUNK_MODE_OWNER ||
                        !trace_chunk->session_output_directory) {
                /*
                 * This command doesn't need to run if the output is remote
                 * or if the trace chunk is not owned by this process.
                 */
                goto end;
        }

        LTTNG_ASSERT(trace_chunk->mode.value == TRACE_CHUNK_MODE_OWNER);
        LTTNG_ASSERT(!trace_chunk->name_overridden);
        LTTNG_ASSERT(trace_chunk->path);

        archived_chunk_name = generate_chunk_name(chunk_id, creation_timestamp,
                        &close_timestamp);
        if (!archived_chunk_name) {
                ERR("Failed to generate archived trace chunk name while renaming trace chunk");
                ret = -1;
                goto end;
        }

        ret = lttng_directory_handle_create_subdirectory_as_user(
                        trace_chunk->session_output_directory,
                        DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY,
                        DIR_CREATION_MODE,
                        !trace_chunk->credentials.value.use_current_user ?
                                        &trace_chunk->credentials.value.user :
                                        NULL);
        if (ret) {
                PERROR("Failed to create \"" DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY
                                "\" directory for archived trace chunks");
                goto end;
        }

        archived_chunks_directory = trace_chunk->fd_tracker ?
                        fd_tracker_create_directory_handle_from_handle(
                                        trace_chunk->fd_tracker,
                                        trace_chunk->session_output_directory,
                                        DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY) :
                        lttng_directory_handle_create_from_handle(
                                        DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY,
                                        trace_chunk->session_output_directory);
        if (!archived_chunks_directory) {
                PERROR("Failed to get handle to archived trace chunks directory");
                ret = -1;
                goto end;
        }

        /*
         * Make sure chunk is renamed to old directory if not already done by
         * the creation of the next chunk. This happens if a rotation is
         * performed while tracing is stopped.
         */
        if (!trace_chunk->path || strcmp(trace_chunk->path,
                        DEFAULT_CHUNK_TMP_OLD_DIRECTORY)) {
                status = lttng_trace_chunk_rename_path_no_lock(trace_chunk,
                                DEFAULT_CHUNK_TMP_OLD_DIRECTORY);
                if (status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                        ERR("Failed to rename chunk to %s", DEFAULT_CHUNK_TMP_OLD_DIRECTORY);
                        ret = -1;
                        goto end;
                }
        }

        ret = lttng_directory_handle_rename_as_user(
                        trace_chunk->session_output_directory,
                        trace_chunk->path,
                        archived_chunks_directory,
                        archived_chunk_name,
                        LTTNG_OPTIONAL_GET(trace_chunk->credentials).use_current_user ?
                                NULL :
                                &trace_chunk->credentials.value.user);
        if (ret) {
                PERROR("Failed to rename folder \"%s\" to \"%s\"",
                                trace_chunk->path,
                                archived_chunk_name);
        }

end:
        lttng_directory_handle_put(archived_chunks_directory);
        free(archived_chunk_name);
        return ret;
}

static
int lttng_trace_chunk_no_operation(struct lttng_trace_chunk *trace_chunk)
{
        return 0;
}

static
int lttng_trace_chunk_delete_post_release_user(
                struct lttng_trace_chunk *trace_chunk)
{
        int ret = 0;

        DBG("Trace chunk \"delete\" close command post-release (User)");

        /* Unlink all files. */
        while (lttng_dynamic_pointer_array_get_count(&trace_chunk->files) != 0) {
                enum lttng_trace_chunk_status status;
                const char *path;

                /* Remove first. */
                path = lttng_dynamic_pointer_array_get_pointer(
                                &trace_chunk->files, 0);
                DBG("Unlink file: %s", path);
                status = lttng_trace_chunk_unlink_file(trace_chunk, path);
                if (status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                        ERR("Error unlinking file '%s' when deleting chunk", path);
                        ret = -1;
                        goto end;
                }
        }
end:
        return ret;
}

static
int lttng_trace_chunk_delete_post_release_owner(
                struct lttng_trace_chunk *trace_chunk)
{
        enum lttng_trace_chunk_status status;
        size_t i, count;
        int ret = 0;

        ret = lttng_trace_chunk_delete_post_release_user(trace_chunk);
        if (ret) {
                goto end;
        }

        DBG("Trace chunk \"delete\" close command post-release (Owner)");

        LTTNG_ASSERT(trace_chunk->session_output_directory);
        LTTNG_ASSERT(trace_chunk->chunk_directory);

        /* Remove empty directories. */
        count = lttng_dynamic_pointer_array_get_count(
                        &trace_chunk->top_level_directories);

        for (i = 0; i < count; i++) {
                const char *top_level_name =
                                lttng_dynamic_pointer_array_get_pointer(
                                        &trace_chunk->top_level_directories, i);

                status = lttng_trace_chunk_remove_subdirectory_recursive(trace_chunk, top_level_name);
                if (status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                        ERR("Error recursively removing subdirectory '%s' file when deleting chunk",
                                        top_level_name);
                        ret = -1;
                        break;
                }
        }
        if (!ret) {
                lttng_directory_handle_put(trace_chunk->chunk_directory);
                trace_chunk->chunk_directory = NULL;

                if (trace_chunk->path && trace_chunk->path[0] != '\0') {
                        status = lttng_directory_handle_remove_subdirectory(
                                        trace_chunk->session_output_directory,
                                        trace_chunk->path);
                        if (status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                                ERR("Error removing subdirectory '%s' file when deleting chunk",
                                        trace_chunk->path);
                                ret = -1;
                        }
                }
        }
        free(trace_chunk->path);
        trace_chunk->path = NULL;
end:
        return ret;
}

/*
 * For local files, session and consumer daemons all run the delete hook. The
 * consumer daemons have the list of files to unlink, and technically the
 * session daemon is the owner of the chunk. Unlink all files owned by each
 * consumer daemon.
 */
static
int lttng_trace_chunk_delete_post_release(
                struct lttng_trace_chunk *trace_chunk)
{
        if (!trace_chunk->chunk_directory) {
                return 0;
        }

        if (trace_chunk->mode.value == TRACE_CHUNK_MODE_OWNER) {
                return lttng_trace_chunk_delete_post_release_owner(trace_chunk);
        } else {
                return lttng_trace_chunk_delete_post_release_user(trace_chunk);
        }
}

enum lttng_trace_chunk_status lttng_trace_chunk_get_close_command(
                struct lttng_trace_chunk *chunk,
                enum lttng_trace_chunk_command_type *command_type)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        pthread_mutex_lock(&chunk->lock);
        if (chunk->close_command.is_set) {
                *command_type = chunk->close_command.value;
                status = LTTNG_TRACE_CHUNK_STATUS_OK;
        } else {
                status = LTTNG_TRACE_CHUNK_STATUS_NONE;
        }
        pthread_mutex_unlock(&chunk->lock);
        return status;
}

enum lttng_trace_chunk_status lttng_trace_chunk_set_close_command(
                struct lttng_trace_chunk *chunk,
                enum lttng_trace_chunk_command_type close_command)
{
        enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;

        if (close_command < LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED ||
                        close_command >= LTTNG_TRACE_CHUNK_COMMAND_TYPE_MAX) {
                status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
                goto end;
        }

        pthread_mutex_lock(&chunk->lock);
        if (chunk->close_command.is_set) {
                DBG("Overriding trace chunk close command from \"%s\" to \"%s\"",
                                close_command_names[chunk->close_command.value],
                                close_command_names[close_command]);
        } else {
                DBG("Setting trace chunk close command to \"%s\"",
                                close_command_names[close_command]);
        }
        /*
         * Unset close command for no-op for backward compatibility with relayd
         * 2.11.
         */
        if (close_command != LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION) {
                LTTNG_OPTIONAL_SET(&chunk->close_command, close_command);
        } else {
                LTTNG_OPTIONAL_UNSET(&chunk->close_command);
        }
        pthread_mutex_unlock(&chunk->lock);
end:
        return status;
}

const char *lttng_trace_chunk_command_type_get_name(
                enum lttng_trace_chunk_command_type command)
{
        switch (command) {
        case LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED:
                return "move to completed trace chunk folder";
        case LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION:
                return "no operation";
        case LTTNG_TRACE_CHUNK_COMMAND_TYPE_DELETE:
                return "delete";
        default:
                abort();
        }
}

bool lttng_trace_chunk_ids_equal(const struct lttng_trace_chunk *chunk_a,
                const struct lttng_trace_chunk *chunk_b)
{
        bool equal = false;

        if (chunk_a == chunk_b) {
                equal = true;
                goto end;
        }

        if (!!chunk_a ^ !!chunk_b) {
                goto end;
        }

        if (chunk_a->id.is_set ^ chunk_a->id.is_set) {
                /* One id is set and not the other, thus they are not equal. */
                goto end;
        }

        if (!chunk_a->id.is_set) {
                /* Both ids are unset. */
                equal = true;
        } else {
                equal = chunk_a->id.value == chunk_b->id.value;
        }

end:
        return equal;
}

bool lttng_trace_chunk_get(struct lttng_trace_chunk *chunk)
{
        return urcu_ref_get_unless_zero(&chunk->ref);
}

static
void free_lttng_trace_chunk_registry_element(struct rcu_head *node)
{
        struct lttng_trace_chunk_registry_element *element =
                        container_of(node, typeof(*element), rcu_node);

        lttng_trace_chunk_fini(&element->chunk);
        free(element);
}

static
void lttng_trace_chunk_release(struct urcu_ref *ref)
{
        struct lttng_trace_chunk *chunk = container_of(ref, typeof(*chunk),
                        ref);

        if (chunk->close_command.is_set) {
                if (close_command_post_release_funcs[
                                chunk->close_command.value](chunk)) {
                        ERR("Trace chunk post-release command %s has failed.",
                                        close_command_names[chunk->close_command.value]);
                }
        }

        if (chunk->in_registry_element) {
                struct lttng_trace_chunk_registry_element *element;

                element = container_of(chunk, typeof(*element), chunk);
                if (element->registry) {
                        rcu_read_lock();
                        cds_lfht_del(element->registry->ht,
                                        &element->trace_chunk_registry_ht_node);
                        rcu_read_unlock();
                        call_rcu(&element->rcu_node,
                                        free_lttng_trace_chunk_registry_element);
                } else {
                        /* Never published, can be free'd immediately. */
                        free_lttng_trace_chunk_registry_element(
                                        &element->rcu_node);
                }
        } else {
                /* Not RCU-protected, free immediately. */
                lttng_trace_chunk_fini(chunk);
                free(chunk);
        }
}

void lttng_trace_chunk_put(struct lttng_trace_chunk *chunk)
{
        if (!chunk) {
                return;
        }
        LTTNG_ASSERT(chunk->ref.refcount);
        urcu_ref_put(&chunk->ref, lttng_trace_chunk_release);
}

struct lttng_trace_chunk_registry *lttng_trace_chunk_registry_create(void)
{
        struct lttng_trace_chunk_registry *registry;

        registry = zmalloc(sizeof(*registry));
        if (!registry) {
                goto end;
        }

        registry->ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
                        CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
        if (!registry->ht) {
                goto error;
        }
end:
        return registry;
error:
        lttng_trace_chunk_registry_destroy(registry);
        return NULL;
}

void lttng_trace_chunk_registry_destroy(
                struct lttng_trace_chunk_registry *registry)
{
        if (!registry) {
                return;
        }
        if (registry->ht) {
                int ret = cds_lfht_destroy(registry->ht, NULL);
                LTTNG_ASSERT(!ret);
        }
        free(registry);
}

static
struct lttng_trace_chunk_registry_element *
lttng_trace_chunk_registry_element_create_from_chunk(
                struct lttng_trace_chunk *chunk, uint64_t session_id)
{
        struct lttng_trace_chunk_registry_element *element =
                        zmalloc(sizeof(*element));

        if (!element) {
                goto end;
        }
        cds_lfht_node_init(&element->trace_chunk_registry_ht_node);
        element->session_id = session_id;

        element->chunk = *chunk;
        lttng_trace_chunk_init(&element->chunk);
        if (chunk->session_output_directory) {
                /* Transferred ownership. */
                element->chunk.session_output_directory =
                                chunk->session_output_directory;
                chunk->session_output_directory = NULL;
        }
        if (chunk->chunk_directory) {
                /* Transferred ownership. */
                element->chunk.chunk_directory = chunk->chunk_directory;
                chunk->chunk_directory = NULL;
        }
        /*
         * The original chunk becomes invalid; the name and path attributes are
         * transferred to the new chunk instance.
         */
        chunk->name = NULL;
        chunk->path = NULL;
        element->chunk.fd_tracker = chunk->fd_tracker;
        element->chunk.in_registry_element = true;
end:
        return element;
}

struct lttng_trace_chunk *
lttng_trace_chunk_registry_publish_chunk(
                struct lttng_trace_chunk_registry *registry,
                uint64_t session_id, struct lttng_trace_chunk *chunk)
{
        struct lttng_trace_chunk_registry_element *element;
        unsigned long element_hash;

        pthread_mutex_lock(&chunk->lock);
        element = lttng_trace_chunk_registry_element_create_from_chunk(chunk,
                        session_id);
        pthread_mutex_unlock(&chunk->lock);
        if (!element) {
                goto end;
        }
        /*
         * chunk is now invalid, the only valid operation is a 'put' from the
         * caller.
         */
        chunk = NULL;
        element_hash = lttng_trace_chunk_registry_element_hash(element);

        rcu_read_lock();
        while (1) {
                struct cds_lfht_node *published_node;
                struct lttng_trace_chunk *published_chunk;
                struct lttng_trace_chunk_registry_element *published_element;

                published_node = cds_lfht_add_unique(registry->ht,
                                element_hash,
                                lttng_trace_chunk_registry_element_match,
                                element,
                                &element->trace_chunk_registry_ht_node);
                if (published_node == &element->trace_chunk_registry_ht_node) {
                        /* Successfully published the new element. */
                        element->registry = registry;
                        /* Acquire a reference for the caller. */
                        if (lttng_trace_chunk_get(&element->chunk)) {
                                break;
                        } else {
                                /*
                                 * Another thread concurrently unpublished the
                                 * trace chunk. This is currently unexpected.
                                 *
                                 * Re-attempt to publish.
                                 */
                                ERR("Attempt to publish a trace chunk to the chunk registry raced with a trace chunk deletion");
                                continue;
                        }
                }

                /*
                 * An equivalent trace chunk was published before this trace
                 * chunk. Attempt to acquire a reference to the one that was
                 * already published and release the reference to the copy we
                 * created if successful.
                 */
                published_element = container_of(published_node,
                                typeof(*published_element),
                                trace_chunk_registry_ht_node);
                published_chunk = &published_element->chunk;
                if (lttng_trace_chunk_get(published_chunk)) {
                        lttng_trace_chunk_put(&element->chunk);
                        element = published_element;
                        break;
                }
                /*
                 * A reference to the previously published trace chunk could not
                 * be acquired. Hence, retry to publish our copy of the trace 
                 * chunk.
                 */
        }
        rcu_read_unlock();
end:
        return element ? &element->chunk : NULL;
}

/*
 * Note that the caller must be registered as an RCU thread.
 * However, it does not need to hold the RCU read lock. The RCU read lock is
 * acquired to perform the look-up in the registry's hash table and held until
 * after a reference to the "found" trace chunk is acquired.
 *
 * IOW, holding a reference guarantees the existence of the object for the
 * caller.
 */
static
struct lttng_trace_chunk *_lttng_trace_chunk_registry_find_chunk(
                const struct lttng_trace_chunk_registry *registry,
                uint64_t session_id, uint64_t *chunk_id)
{
        const struct lttng_trace_chunk_registry_element target_element = {
                .chunk.id.is_set = !!chunk_id,
                .chunk.id.value = chunk_id ? *chunk_id : 0,
                .session_id = session_id,
        };
        const unsigned long element_hash =
                        lttng_trace_chunk_registry_element_hash(
                                &target_element);
        struct cds_lfht_node *published_node;
        struct lttng_trace_chunk_registry_element *published_element;
        struct lttng_trace_chunk *published_chunk = NULL;
        struct cds_lfht_iter iter;

        rcu_read_lock();
        cds_lfht_lookup(registry->ht,
                        element_hash,
                        lttng_trace_chunk_registry_element_match,
                        &target_element,
                        &iter);
        published_node = cds_lfht_iter_get_node(&iter);
        if (!published_node) {
                goto end;
        }

        published_element = container_of(published_node,
                        typeof(*published_element),
                        trace_chunk_registry_ht_node);
        if (lttng_trace_chunk_get(&published_element->chunk)) {
                published_chunk = &published_element->chunk;
        }
end:
        rcu_read_unlock();
        return published_chunk;
}

struct lttng_trace_chunk *
lttng_trace_chunk_registry_find_chunk(
                const struct lttng_trace_chunk_registry *registry,
                uint64_t session_id, uint64_t chunk_id)
{
        return _lttng_trace_chunk_registry_find_chunk(registry,
                        session_id, &chunk_id);
}

int lttng_trace_chunk_registry_chunk_exists(
                const struct lttng_trace_chunk_registry *registry,
                uint64_t session_id, uint64_t chunk_id, bool *chunk_exists)
{
        int ret = 0;
        const struct lttng_trace_chunk_registry_element target_element = {
                .chunk.id.is_set = true,
                .chunk.id.value = chunk_id,
                .session_id = session_id,
        };
        const unsigned long element_hash =
                        lttng_trace_chunk_registry_element_hash(
                                &target_element);
        struct cds_lfht_node *published_node;
        struct cds_lfht_iter iter;

        rcu_read_lock();
        cds_lfht_lookup(registry->ht,
                        element_hash,
                        lttng_trace_chunk_registry_element_match,
                        &target_element,
                        &iter);
        published_node = cds_lfht_iter_get_node(&iter);
        if (!published_node) {
                *chunk_exists = false;
                goto end;
        }

        *chunk_exists = !cds_lfht_is_node_deleted(published_node);
end:
        rcu_read_unlock();
        return ret;
}

struct lttng_trace_chunk *
lttng_trace_chunk_registry_find_anonymous_chunk(
                const struct lttng_trace_chunk_registry *registry,
                uint64_t session_id)
{
        return _lttng_trace_chunk_registry_find_chunk(registry,
                        session_id, NULL);
}

unsigned int lttng_trace_chunk_registry_put_each_chunk(
                const struct lttng_trace_chunk_registry *registry)
{
        struct cds_lfht_iter iter;
        struct lttng_trace_chunk_registry_element *chunk_element;
        unsigned int trace_chunks_left = 0;

        DBG("Releasing trace chunk registry to all trace chunks");
        rcu_read_lock();
        cds_lfht_for_each_entry(registry->ht,
                        &iter, chunk_element, trace_chunk_registry_ht_node) {
                const char *chunk_id_str = "none";
                char chunk_id_buf[MAX_INT_DEC_LEN(uint64_t)];

                pthread_mutex_lock(&chunk_element->chunk.lock);
                if (chunk_element->chunk.id.is_set) {
                        int fmt_ret;

                        fmt_ret = snprintf(chunk_id_buf, sizeof(chunk_id_buf),
                                        "%" PRIu64,
                                        chunk_element->chunk.id.value);
                        if (fmt_ret < 0 || fmt_ret >= sizeof(chunk_id_buf)) {
                                chunk_id_str = "formatting error";
                        } else {
                                chunk_id_str = chunk_id_buf;
                        }
                }

                DBG("Releasing reference to trace chunk: session_id = %" PRIu64
                                "chunk_id = %s, name = \"%s\", status = %s",
                                chunk_element->session_id,
                                chunk_id_str,
                                chunk_element->chunk.name ? : "none",
                                chunk_element->chunk.close_command.is_set ?
                                                "open" : "closed");
                pthread_mutex_unlock(&chunk_element->chunk.lock);
                lttng_trace_chunk_put(&chunk_element->chunk);
                trace_chunks_left++;
        }
        rcu_read_unlock();
        DBG("Released reference to %u trace chunks in %s()", trace_chunks_left,
                        __FUNCTION__);

        return trace_chunks_left;
}