#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"

#include "config.h"

#include "entry.h"

#include "gettext.h"

#include "hash.h"

#include "hex.h"

#include "parallel-checkout.h"

#include "pkt-line.h"

#include "progress.h"

#include "read-cache-ll.h"

#include "run-command.h"

#include "sigchain.h"

#include "streaming.h"

#include "symlinks.h"

#include "thread-utils.h"

#include "trace2.h"

struct pc_worker {

  struct child_process cp;

  size_t next_item_to_complete, nr_items_to_complete;

};

struct parallel_checkout {

  enum pc_status status;

  struct parallel_checkout_item *items; /* The parallel checkout queue. */

  size_t nr, alloc;

  struct progress *progress;

  unsigned int *progress_cnt;

};

static struct parallel_checkout parallel_checkout;

enum pc_status parallel_checkout_status(void)

{

  return parallel_checkout.status;

}

static const int DEFAULT_THRESHOLD_FOR_PARALLELISM = 100;

static const int DEFAULT_NUM_WORKERS = 1;

void get_parallel_checkout_configs(int *num_workers, int *threshold)

{

  char *env_workers = getenv("GIT_TEST_CHECKOUT_WORKERS");

  if (env_workers && *env_workers) {

    if (strtol_i(env_workers, 10, num_workers)) {

      die(_("invalid value for '%s': '%s'"),

          "GIT_TEST_CHECKOUT_WORKERS", env_workers);

    }

    if (*num_workers < 1)

      *num_workers = online_cpus();

    *threshold = 0;

    return;

  }

  if (git_config_get_int("checkout.workers", num_workers))

    *num_workers = DEFAULT_NUM_WORKERS;

  else if (*num_workers < 1)

    *num_workers = online_cpus();

  if (git_config_get_int("checkout.thresholdForParallelism", threshold))

    *threshold = DEFAULT_THRESHOLD_FOR_PARALLELISM;

}

void init_parallel_checkout(void)

{

  if (parallel_checkout.status != PC_UNINITIALIZED)

    BUG("parallel checkout already initialized");

  parallel_checkout.status = PC_ACCEPTING_ENTRIES;

}

static void finish_parallel_checkout(void)

{

  if (parallel_checkout.status == PC_UNINITIALIZED)

    BUG("cannot finish parallel checkout: not initialized yet");

  free(parallel_checkout.items);

  memset(&parallel_checkout, 0, sizeof(parallel_checkout));

}

static int is_eligible_for_parallel_checkout(const struct cache_entry *ce,

               const struct conv_attrs *ca)

{

  enum conv_attrs_classification c;

  size_t packed_item_size;

  /*

   * Symlinks cannot be checked out in parallel as, in case of path

   * collision, they could racily replace leading directories of other

   * entries being checked out. Submodules are checked out in child

   * processes, which have their own parallel checkout queues.

   */

  if (!S_ISREG(ce->ce_mode))

    return 0;

  packed_item_size = sizeof(struct pc_item_fixed_portion) + ce->ce_namelen +

    (ca->working_tree_encoding ? strlen(ca->working_tree_encoding) : 0);

  /*

   * The amount of data we send to the workers per checkout item is

   * typically small (75~300B). So unless we find an insanely huge path

   * of 64KB, we should never reach the 65KB limit of one pkt-line. If

   * that does happen, we let the sequential code handle the item.

   */

  if (packed_item_size > LARGE_PACKET_DATA_MAX)

    return 0;

  c = classify_conv_attrs(ca);

  switch (c) {

  case CA_CLASS_INCORE:

    return 1;

  case CA_CLASS_INCORE_FILTER:

    /*

     * It would be safe to allow concurrent instances of

     * single-file smudge filters, like rot13, but we should not

     * assume that all filters are parallel-process safe. So we

     * don't allow this.

     */

    return 0;

  case CA_CLASS_INCORE_PROCESS:

    /*

     * The parallel queue and the delayed queue are not compatible,

     * so they must be kept completely separated. And we can't tell

     * if a long-running process will delay its response without

     * actually asking it to perform the filtering. Therefore, this

     * type of filter is not allowed in parallel checkout.

     *

     * Furthermore, there should only be one instance of the

     * long-running process filter as we don't know how it is

     * managing its own concurrency. So, spreading the entries that

     * requisite such a filter among the parallel workers would

     * require a lot more inter-process communication. We would

     * probably have to designate a single process to interact with

     * the filter and send all the necessary data to it, for each

     * entry.

     */

    return 0;

  case CA_CLASS_STREAMABLE:

    return 1;

  default:

    BUG("unsupported conv_attrs classification '%d'", c);

  }

}

int enqueue_checkout(struct cache_entry *ce, struct conv_attrs *ca,

         int *checkout_counter)

{

  struct parallel_checkout_item *pc_item;

  if (parallel_checkout.status != PC_ACCEPTING_ENTRIES ||

      !is_eligible_for_parallel_checkout(ce, ca))

    return -1;

  ALLOC_GROW(parallel_checkout.items, parallel_checkout.nr + 1,

       parallel_checkout.alloc);

  pc_item = &parallel_checkout.items[parallel_checkout.nr];

  pc_item->ce = ce;

  memcpy(&pc_item->ca, ca, sizeof(pc_item->ca));

  pc_item->status = PC_ITEM_PENDING;

  pc_item->id = parallel_checkout.nr;

  pc_item->checkout_counter = checkout_counter;

  parallel_checkout.nr++;

  return 0;

}

size_t pc_queue_size(void)

{

  return parallel_checkout.nr;

}

static void advance_progress_meter(void)

{

  if (parallel_checkout.progress) {

    (*parallel_checkout.progress_cnt)++;

    display_progress(parallel_checkout.progress,

         *parallel_checkout.progress_cnt);

  }

}

static int handle_results(struct checkout *state)

{

  int ret = 0;

  size_t i;

  int have_pending = 0;

  /*

   * We first update the successfully written entries with the collected

   * stat() data, so that they can be found by mark_colliding_entries(),

   * in the next loop, when necessary.

   */

  for (i = 0; i < parallel_checkout.nr; i++) {

    struct parallel_checkout_item *pc_item = &parallel_checkout.items[i];

    if (pc_item->status == PC_ITEM_WRITTEN)

      update_ce_after_write(state, pc_item->ce, &pc_item->st);

  }

  for (i = 0; i < parallel_checkout.nr; i++) {

    struct parallel_checkout_item *pc_item = &parallel_checkout.items[i];

    switch(pc_item->status) {

    case PC_ITEM_WRITTEN:

      if (pc_item->checkout_counter)

        (*pc_item->checkout_counter)++;

      break;

    case PC_ITEM_COLLIDED:

      /*

       * The entry could not be checked out due to a path

       * collision with another entry. Since there can only

       * be one entry of each colliding group on the disk, we

       * could skip trying to check out this one and move on.

       * However, this would leave the unwritten entries with

       * null stat() fields on the index, which could

       * potentially slow down subsequent operations that

       * require refreshing it: git would not be able to

       * trust st_size and would have to go to the filesystem

       * to see if the contents match (see ie_modified()).

       *

       * Instead, let's pay the overhead only once, now, and

       * call checkout_entry_ca() again for this file, to

       * have its stat() data stored in the index. This also

       * has the benefit of adding this entry and its

       * colliding pair to the collision report message.

       * Additionally, this overwriting behavior is consistent

       * with what the sequential checkout does, so it doesn't

       * add any extra overhead.

       */

      ret |= checkout_entry_ca(pc_item->ce, &pc_item->ca,

             state, NULL,

             pc_item->checkout_counter);

      advance_progress_meter();

      break;

    case PC_ITEM_PENDING:

      have_pending = 1;

      /* fall through */

    case PC_ITEM_FAILED:

      ret = -1;

      break;

    default:

      BUG("unknown checkout item status in parallel checkout");

    }

  }

  if (have_pending)

    error("parallel checkout finished with pending entries");

  return ret;

}

static int reset_fd(int fd, const char *path)

{

  if (lseek(fd, 0, SEEK_SET) != 0)

    return error_errno("failed to rewind descriptor of '%s'", path);

  if (ftruncate(fd, 0))

    return error_errno("failed to truncate file '%s'", path);

  return 0;

}

static int write_pc_item_to_fd(struct parallel_checkout_item *pc_item, int fd,

             const char *path)

{

  int ret;

  struct stream_filter *filter;

  struct strbuf buf = STRBUF_INIT;

  char *blob;

  size_t size;

  ssize_t wrote;

  /* Sanity check */

  assert(is_eligible_for_parallel_checkout(pc_item->ce, &pc_item->ca));

  filter = get_stream_filter_ca(&pc_item->ca, &pc_item->ce->oid);

  if (filter) {

    if (stream_blob_to_fd(fd, &pc_item->ce->oid, filter, 1)) {

      /* On error, reset fd to try writing without streaming */

      if (reset_fd(fd, path))

        return -1;

    } else {

      return 0;

    }

  }

  blob = read_blob_entry(pc_item->ce, &size);

  if (!blob)

    return error("cannot read object %s '%s'",

           oid_to_hex(&pc_item->ce->oid), pc_item->ce->name);

  /*

   * checkout metadata is used to give context for external process

   * filters. Files requiring such filters are not eligible for parallel

   * checkout, so pass NULL. Note: if that changes, the metadata must also

   * be passed from the main process to the workers.

   */

  ret = convert_to_working_tree_ca(&pc_item->ca, pc_item->ce->name,

           blob, size, &buf, NULL);

  if (ret) {

    size_t newsize;

    free(blob);

    blob = strbuf_detach(&buf, &newsize);

    size = newsize;

  }

  wrote = write_in_full(fd, blob, size);

  free(blob);

  if (wrote < 0)

    return error("unable to write file '%s'", path);

  return 0;

}

static int close_and_clear(int *fd)

{

  int ret = 0;

  if (*fd >= 0) {

    ret = close(*fd);

    *fd = -1;

  }

  return ret;

}

void write_pc_item(struct parallel_checkout_item *pc_item,

       struct checkout *state)

{

  unsigned int mode = (pc_item->ce->ce_mode & 0100) ? 0777 : 0666;

  int fd = -1, fstat_done = 0;

  struct strbuf path = STRBUF_INIT;

  const char *dir_sep;

  strbuf_add(&path, state->base_dir, state->base_dir_len);

  strbuf_add(&path, pc_item->ce->name, pc_item->ce->ce_namelen);

  dir_sep = find_last_dir_sep(path.buf);

  /*

   * The leading dirs should have been already created by now. But, in

   * case of path collisions, one of the dirs could have been replaced by

   * a symlink (checked out after we enqueued this entry for parallel

   * checkout). Thus, we must check the leading dirs again.

   */

  if (dir_sep && !has_dirs_only_path(path.buf, dir_sep - path.buf,

             state->base_dir_len)) {

    pc_item->status = PC_ITEM_COLLIDED;

    trace2_data_string("pcheckout", NULL, "collision/dirname", path.buf);

    goto out;

  }

  fd = open(path.buf, O_WRONLY | O_CREAT | O_EXCL, mode);

  if (fd < 0) {

    if (errno == EEXIST || errno == EISDIR) {

      /*

       * Errors which probably represent a path collision.

       * Suppress the error message and mark the item to be

       * retried later, sequentially. ENOTDIR and ENOENT are

       * also interesting, but the above has_dirs_only_path()

       * call should have already caught these cases.

       */

      pc_item->status = PC_ITEM_COLLIDED;

      trace2_data_string("pcheckout", NULL,

             "collision/basename", path.buf);

    } else {

      error_errno("failed to open file '%s'", path.buf);

      pc_item->status = PC_ITEM_FAILED;

    }

    goto out;

  }

  if (write_pc_item_to_fd(pc_item, fd, path.buf)) {

    /* Error was already reported. */

    pc_item->status = PC_ITEM_FAILED;

    close_and_clear(&fd);

    unlink(path.buf);

    goto out;

  }

  fstat_done = fstat_checkout_output(fd, state, &pc_item->st);

  if (close_and_clear(&fd)) {

    error_errno("unable to close file '%s'", path.buf);

    pc_item->status = PC_ITEM_FAILED;

    goto out;

  }

  if (state->refresh_cache && !fstat_done && lstat(path.buf, &pc_item->st) < 0) {

    error_errno("unable to stat just-written file '%s'",  path.buf);

    pc_item->status = PC_ITEM_FAILED;

    goto out;

  }

  pc_item->status = PC_ITEM_WRITTEN;

out:

  strbuf_release(&path);

}

static void send_one_item(int fd, struct parallel_checkout_item *pc_item)

{

  size_t len_data;

  char *data, *variant;

  struct pc_item_fixed_portion *fixed_portion;

  const char *working_tree_encoding = pc_item->ca.working_tree_encoding;

  size_t name_len = pc_item->ce->ce_namelen;

  size_t working_tree_encoding_len = working_tree_encoding ?

             strlen(working_tree_encoding) : 0;

  /*

   * Any changes in the calculation of the message size must also be made

   * in is_eligible_for_parallel_checkout().

   */

  len_data = sizeof(struct pc_item_fixed_portion) + name_len +

       working_tree_encoding_len;

  data = xmalloc(len_data);

  fixed_portion = (struct pc_item_fixed_portion *)data;

  fixed_portion->id = pc_item->id;

  fixed_portion->ce_mode = pc_item->ce->ce_mode;

  fixed_portion->crlf_action = pc_item->ca.crlf_action;

  fixed_portion->ident = pc_item->ca.ident;

  fixed_portion->name_len = name_len;

  fixed_portion->working_tree_encoding_len = working_tree_encoding_len;

  oidcpy(&fixed_portion->oid, &pc_item->ce->oid);

  variant = data + sizeof(*fixed_portion);

  if (working_tree_encoding_len) {

    memcpy(variant, working_tree_encoding, working_tree_encoding_len);

    variant += working_tree_encoding_len;

  }

  memcpy(variant, pc_item->ce->name, name_len);

  packet_write(fd, data, len_data);

  free(data);

}

static void send_batch(int fd, size_t start, size_t nr)

{

  size_t i;

  sigchain_push(SIGPIPE, SIG_IGN);

  for (i = 0; i < nr; i++)

    send_one_item(fd, &parallel_checkout.items[start + i]);

  packet_flush(fd);

  sigchain_pop(SIGPIPE);

}

static struct pc_worker *setup_workers(struct checkout *state, int num_workers)

{

  struct pc_worker *workers;

  int i, workers_with_one_extra_item;

  size_t base_batch_size, batch_beginning = 0;

  ALLOC_ARRAY(workers, num_workers);

  for (i = 0; i < num_workers; i++) {

    struct child_process *cp = &workers[i].cp;

    child_process_init(cp);

    cp->git_cmd = 1;

    cp->in = -1;

    cp->out = -1;

    cp->clean_on_exit = 1;

    strvec_push(&cp->args, "checkout--worker");

    if (state->base_dir_len)

      strvec_pushf(&cp->args, "--prefix=%s", state->base_dir);

    if (start_command(cp))

      die("failed to spawn checkout worker");

  }

  base_batch_size = parallel_checkout.nr / num_workers;

  workers_with_one_extra_item = parallel_checkout.nr % num_workers;

  for (i = 0; i < num_workers; i++) {

    struct pc_worker *worker = &workers[i];

    size_t batch_size = base_batch_size;

    /* distribute the extra work evenly */

    if (i < workers_with_one_extra_item)

      batch_size++;

    send_batch(worker->cp.in, batch_beginning, batch_size);

    worker->next_item_to_complete = batch_beginning;

    worker->nr_items_to_complete = batch_size;

    batch_beginning += batch_size;

  }

  return workers;

}

static void finish_workers(struct pc_worker *workers, int num_workers)

{

  int i;

  /*

   * Close pipes before calling finish_command() to let the workers

   * exit asynchronously and avoid spending extra time on wait().

   */

  for (i = 0; i < num_workers; i++) {

    struct child_process *cp = &workers[i].cp;

    if (cp->in >= 0)

      close(cp->in);

    if (cp->out >= 0)

      close(cp->out);

  }

  for (i = 0; i < num_workers; i++) {

    int rc = finish_command(&workers[i].cp);

    if (rc > 128) {

      /*

       * For a normal non-zero exit, the worker should have

       * already printed something useful to stderr. But a

       * death by signal should be mentioned to the user.

       */

      error("checkout worker %d died of signal %d", i, rc - 128);

    }

  }

  free(workers);

}

static inline void assert_pc_item_result_size(int got, int exp)

{

  if (got != exp)

    BUG("wrong result size from checkout worker (got %dB, exp %dB)",

        got, exp);

}

static void parse_and_save_result(const char *buffer, int len,

          struct pc_worker *worker)

{

  struct pc_item_result *res;

  struct parallel_checkout_item *pc_item;

  struct stat *st = NULL;

  if (len < PC_ITEM_RESULT_BASE_SIZE)

    BUG("too short result from checkout worker (got %dB, exp >=%dB)",

        len, (int)PC_ITEM_RESULT_BASE_SIZE);

  res = (struct pc_item_result *)buffer;

  /*

   * Worker should send either the full result struct on success, or

   * just the base (i.e. no stat data), otherwise.

   */

  if (res->status == PC_ITEM_WRITTEN) {

    assert_pc_item_result_size(len, (int)sizeof(struct pc_item_result));

    st = &res->st;

  } else {

    assert_pc_item_result_size(len, (int)PC_ITEM_RESULT_BASE_SIZE);

  }

  if (!worker->nr_items_to_complete)

    BUG("received result from supposedly finished checkout worker");

  if (res->id != worker->next_item_to_complete)

    BUG("unexpected item id from checkout worker (got %"PRIuMAX", exp %"PRIuMAX")",

        (uintmax_t)res->id, (uintmax_t)worker->next_item_to_complete);

  worker->next_item_to_complete++;

  worker->nr_items_to_complete--;

  pc_item = &parallel_checkout.items[res->id];

  pc_item->status = res->status;

  if (st)

    pc_item->st = *st;

  if (res->status != PC_ITEM_COLLIDED)

    advance_progress_meter();

}

static void gather_results_from_workers(struct pc_worker *workers,

          int num_workers)

{

  int i, active_workers = num_workers;

  struct pollfd *pfds;

  CALLOC_ARRAY(pfds, num_workers);

  for (i = 0; i < num_workers; i++) {

    pfds[i].fd = workers[i].cp.out;

    pfds[i].events = POLLIN;

  }

  while (active_workers) {

    int nr = poll(pfds, num_workers, -1);

    if (nr < 0) {

      if (errno == EINTR)

        continue;

      die_errno("failed to poll checkout workers");

    }

    for (i = 0; i < num_workers && nr > 0; i++) {

      struct pc_worker *worker = &workers[i];

      struct pollfd *pfd = &pfds[i];

      if (!pfd->revents)

        continue;

      if (pfd->revents & POLLIN) {

        int len = packet_read(pfd->fd, packet_buffer,

                  sizeof(packet_buffer), 0);

        if (len < 0) {

          BUG("packet_read() returned negative value");

        } else if (!len) {

          pfd->fd = -1;

          active_workers--;

        } else {

          parse_and_save_result(packet_buffer,

                    len, worker);

        }

      } else if (pfd->revents & POLLHUP) {

        pfd->fd = -1;

        active_workers--;

      } else if (pfd->revents & (POLLNVAL | POLLERR)) {

        die("error polling from checkout worker");

      }

      nr--;

    }

  }

  free(pfds);

}

static void write_items_sequentially(struct checkout *state)

{

  size_t i;

  for (i = 0; i < parallel_checkout.nr; i++) {

    struct parallel_checkout_item *pc_item = &parallel_checkout.items[i];

    write_pc_item(pc_item, state);

    if (pc_item->status != PC_ITEM_COLLIDED)

      advance_progress_meter();

  }

}

int run_parallel_checkout(struct checkout *state, int num_workers, int threshold,

        struct progress *progress, unsigned int *progress_cnt)

{

  int ret;

  if (parallel_checkout.status != PC_ACCEPTING_ENTRIES)

    BUG("cannot run parallel checkout: uninitialized or already running");

  parallel_checkout.status = PC_RUNNING;

  parallel_checkout.progress = progress;

  parallel_checkout.progress_cnt = progress_cnt;

  if (parallel_checkout.nr < num_workers)

    num_workers = parallel_checkout.nr;

  if (num_workers <= 1 || parallel_checkout.nr < threshold) {

    write_items_sequentially(state);

  } else {

    struct pc_worker *workers = setup_workers(state, num_workers);

    gather_results_from_workers(workers, num_workers);

    finish_workers(workers, num_workers);

  }

  ret = handle_results(state);

  finish_parallel_checkout();

  return ret;

}