/src/dovecot/src/lib-index/mail-transaction-log-file.c

Source
/* Copyright (c) Dovecot authors, see top-level COPYING file */

#include "lib.h"
#include "array.h"
#include "ioloop.h"
#include "file-dotlock.h"
#include "nfs-workarounds.h"
#include "read-full.h"
#include "write-full.h"
#include "mmap-util.h"
#include "mail-index-private.h"
#include "mail-index-modseq.h"
#include "mail-transaction-log-private.h"

#define LOG_PREFETCH IO_BLOCK_SIZE
#define MEMORY_LOG_NAME "(in-memory transaction log file)"
#define LOG_NEW_DOTLOCK_SUFFIX ".newlock"

static int
mail_transaction_log_file_sync(struct mail_transaction_log_file *file,
             bool *retry_r, const char **reason_r);

static void
log_file_set_syscall_error(struct mail_transaction_log_file *file,
         const char *function)
{
  mail_index_file_set_syscall_error(file->log->index,
            file->filepath, function);
}

static void
mail_transaction_log_mark_corrupted(struct mail_transaction_log_file *file)
{
  unsigned int offset =
    offsetof(struct mail_transaction_log_header, indexid);
  int flags;

  if (MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file) ||
      file->log->index->readonly)
    return;

  /* indexid=0 marks the log file as corrupted. we opened the file with
     O_APPEND, and now we need to drop it for pwrite() to work (at least
     in Linux) */
  flags = fcntl(file->fd, F_GETFL, 0);
  if (flags < 0) {
    mail_index_file_set_syscall_error(file->log->index,
      file->filepath, "fcntl(F_GETFL)");
    return;
  }
  if (fcntl(file->fd, F_SETFL, flags & ~O_APPEND) < 0) {
    mail_index_file_set_syscall_error(file->log->index,
      file->filepath, "fcntl(F_SETFL)");
    return;
  }
  if (pwrite_full(file->fd, &file->hdr.indexid,
      sizeof(file->hdr.indexid), offset) < 0) {
    mail_index_file_set_syscall_error(file->log->index,
              file->filepath, "pwrite()");
  }
}

void mail_transaction_log_file_set_need_rotate(
  struct mail_transaction_log_file *file, const char *fmt, ...)
{
  va_list va;

  if (file->need_rotate != NULL)
    return;

  va_start(va, fmt);
  file->need_rotate = i_strdup_vprintf(fmt, va);
  va_end(va);
}

void mail_transaction_log_file_set_garbage_at_eof(
  struct mail_transaction_log_file *file, const char *fmt, ...)
{
  va_list va;

  if (file->garbage_at_eof) {
    /* Already known - don't log it again */
    return;
  }
  file->garbage_at_eof = TRUE;

  va_start(va, fmt);
  T_BEGIN {
    const char *reason = t_strdup_vprintf(fmt, va);

    mail_transaction_log_file_set_need_rotate(file, "%s", reason);
    e_debug(file->log->index->event,
      "Transaction log %s has garbage at EOF: %s",
      file->filepath, reason);
  } T_END;
  va_end(va);
}

void
mail_transaction_log_file_set_corrupted(struct mail_transaction_log_file *file,
          const char *fmt, ...)
{
  va_list va;

  file->corrupted = TRUE;
  file->hdr.indexid = 0;
  mail_transaction_log_mark_corrupted(file);

  va_start(va, fmt);
  T_BEGIN {
    mail_index_set_error(file->log->index,
      "Corrupted transaction log file %s seq %u: %s "
      "(sync_offset=%"PRIuUOFF_T")",
      file->filepath, file->hdr.file_seq,
      t_strdup_vprintf(fmt, va), file->sync_offset);
  } T_END;
  va_end(va);
}

struct mail_transaction_log_file *
mail_transaction_log_file_alloc(struct mail_transaction_log *log,
        const char *path)
{
  struct mail_transaction_log_file *file;

  file = i_new(struct mail_transaction_log_file, 1);
  file->log = log;
  file->filepath = i_strdup(path);
  file->fd = -1;
  return file;
}

void mail_transaction_log_file_free(struct mail_transaction_log_file **_file)
{
  struct mail_transaction_log_file *file = *_file;
  struct mail_transaction_log_file **p;
  int old_errno = errno;

  *_file = NULL;

  i_assert(!file->locked);
  i_assert(file->refcount == 0);

  for (p = &file->log->files; *p != NULL; p = &(*p)->next) {
    if (*p == file) {
      *p = file->next;
      break;
    }
  }

  if (file == file->log->head)
    file->log->head = NULL;

  buffer_free(&file->buffer);

  if (file->mmap_base != NULL) {
    if (munmap(file->mmap_base, file->mmap_size) < 0)
      log_file_set_syscall_error(file, "munmap()");
  }

  if (file->fd != -1) {
    if (close(file->fd) < 0)
      log_file_set_syscall_error(file, "close()");
  }

  i_free(file->filepath);
  i_free(file->need_rotate);
        i_free(file);

        errno = old_errno;
}

static void
mail_transaction_log_file_skip_to_head(struct mail_transaction_log_file *file)
{
  struct mail_transaction_log *log = file->log;
  struct mail_index_map *map = log->index->map;
  const struct mail_index_modseq_header *modseq_hdr;
  uoff_t head_offset;

  if (map == NULL || file->hdr.file_seq != map->hdr.log_file_seq ||
      map->hdr.log_file_head_offset == 0)
    return;

  /* we can get a valid log offset from index file. initialize
     sync_offset from it so we don't have to read the whole log
     file from beginning. */
  head_offset = map->hdr.log_file_head_offset;

  modseq_hdr = mail_index_map_get_modseq_header(map);
  if (head_offset < file->hdr.hdr_size) {
    mail_index_set_error(log->index,
             "%s: log_file_head_offset too small",
             log->index->filepath);
    file->sync_offset = file->hdr.hdr_size;
    file->sync_highest_modseq = file->hdr.initial_modseq;
  } else if (modseq_hdr == NULL && file->hdr.initial_modseq == 0) {
    /* modseqs not used yet */
    file->sync_offset = head_offset;
    file->sync_highest_modseq = 0;
  } else if (modseq_hdr == NULL ||
       modseq_hdr->log_seq != file->hdr.file_seq) {
    /* highest_modseq not synced, start from beginning */
    file->sync_offset = file->hdr.hdr_size;
    file->sync_highest_modseq = file->hdr.initial_modseq;
  } else if (modseq_hdr->log_offset > head_offset) {
    mail_index_set_error(log->index,
             "%s: modseq_hdr.log_offset too large",
             log->index->filepath);
    file->sync_offset = file->hdr.hdr_size;
    file->sync_highest_modseq = file->hdr.initial_modseq;
  } else {
    /* start from where we last stopped tracking modseqs */
    file->sync_offset = modseq_hdr->log_offset;
    file->sync_highest_modseq = modseq_hdr->highest_modseq;
  }
  if (file->hdr.file_seq == log->index->map->hdr.log_file_seq) {
    file->last_read_hdr_tail_offset =
      log->index->map->hdr.log_file_tail_offset;
  }
  if (file->last_read_hdr_tail_offset > file->max_tail_offset)
    file->max_tail_offset = file->last_read_hdr_tail_offset;
}

static void
mail_transaction_log_file_add_to_list(struct mail_transaction_log_file *file)
{
  struct mail_transaction_log_file **p;
  const char *reason;
  bool retry;

  file->sync_offset = file->hdr.hdr_size;
  file->sync_highest_modseq = file->hdr.initial_modseq;
  mail_transaction_log_file_skip_to_head(file);

  /* insert it to correct position */
  for (p = &file->log->files; *p != NULL; p = &(*p)->next) {
    if ((*p)->hdr.file_seq > file->hdr.file_seq)
      break;
    i_assert((*p)->hdr.file_seq < file->hdr.file_seq);
  }

  file->next = *p;
  *p = file;

  if (file->buffer != NULL) {
    /* if we read any unfinished data, make sure the buffer gets
       truncated. */
    (void)mail_transaction_log_file_sync(file, &retry, &reason);
    buffer_set_used_size(file->buffer,
             file->sync_offset - file->buffer_offset);
  }
}

static int
mail_transaction_log_init_hdr(struct mail_transaction_log *log,
            struct mail_transaction_log_header *hdr)
{
  struct mail_index *index = log->index;
  struct mail_transaction_log_file *file;

  i_assert(index->indexid != 0);

  i_zero(hdr);
  hdr->major_version = MAIL_TRANSACTION_LOG_MAJOR_VERSION;
  hdr->minor_version = MAIL_TRANSACTION_LOG_MINOR_VERSION;
  hdr->hdr_size = sizeof(struct mail_transaction_log_header);
  hdr->indexid = log->index->indexid;
  hdr->create_stamp = ioloop_time32;
#ifndef WORDS_BIGENDIAN
  hdr->compat_flags |= MAIL_INDEX_COMPAT_LITTLE_ENDIAN;
#endif

  if (index->fd != -1) {
    /* not creating index - make sure we have latest header */
    if (!index->mapping) {
      if (mail_index_map(index,
             MAIL_INDEX_SYNC_HANDLER_HEAD) <= 0)
        return -1;
    } else {
      /* if we got here from mapping, the .log file is
         corrupted. use whatever values we got from index
         file */
    }
  }
  if (index->map != NULL) {
    hdr->prev_file_seq = index->map->hdr.log_file_seq;
    hdr->prev_file_offset = index->map->hdr.log_file_head_offset;
    hdr->file_seq = index->map->hdr.log_file_seq + 1;
    hdr->initial_modseq =
      mail_index_map_modseq_get_highest(index->map);
  } else {
    hdr->file_seq = 1;
  }
  if (hdr->initial_modseq == 0) {
    /* modseq tracking in log files is required for many reasons
       nowadays, even if per-message modseqs aren't enabled in
       dovecot.index. */
    hdr->initial_modseq = 1;
  }

  if (log->head != NULL) {
    /* make sure the sequence always increases to avoid crashes
       later. this catches the buggy case where two processes
       happen to replace the same log file. */
    for (file = log->head->next; file != NULL; file = file->next) {
      if (hdr->file_seq <= file->hdr.file_seq)
        hdr->file_seq = file->hdr.file_seq + 1;
    }

    if (hdr->file_seq <= log->head->hdr.file_seq) {
      /* make sure the sequence grows */
      hdr->file_seq = log->head->hdr.file_seq+1;
    }
    if (hdr->initial_modseq < log->head->sync_highest_modseq) {
      /* this should be always up-to-date */
      hdr->initial_modseq = log->head->sync_highest_modseq;
    }
  }
  return 0;
}

struct mail_transaction_log_file *
mail_transaction_log_file_alloc_in_memory(struct mail_transaction_log *log)
{
  struct mail_transaction_log_file *file;

  file = mail_transaction_log_file_alloc(log, MEMORY_LOG_NAME);
  if (mail_transaction_log_init_hdr(log, &file->hdr) < 0) {
    i_free(file);
    return NULL;
  }

  file->buffer = buffer_create_dynamic(default_pool, 4096);
  file->buffer_offset = sizeof(file->hdr);

  mail_transaction_log_file_add_to_list(file);
  return file;
}

static int
mail_transaction_log_file_dotlock(struct mail_transaction_log_file *file)
{
  struct dotlock_settings dotlock_set;
  int ret;

  if (file->log->dotlock_refcount > 0)
    ret = 1;
  else {
    i_assert(file->log->dotlock_refcount == 0);
    mail_transaction_log_get_dotlock_set(file->log, &dotlock_set);
    ret = file_dotlock_create(&dotlock_set, file->filepath, 0,
            &file->log->dotlock);
  }
  if (ret > 0) {
    file->log->dotlock_refcount++;
    file->locked = TRUE;
    file->lock_create_time = time(NULL);
    return 0;
  }
  if (ret < 0) {
    log_file_set_syscall_error(file, "file_dotlock_create()");
    return -1;
  }

  mail_index_set_error(file->log->index,
           "Timeout (%us) while waiting for "
           "dotlock for transaction log file %s",
           dotlock_set.timeout, file->filepath);
  return -1;
}

static int
mail_transaction_log_file_undotlock(struct mail_transaction_log_file *file)
{
  int ret;

  i_assert(file->log->dotlock_refcount >= 0);
  if (--file->log->dotlock_refcount > 0)
    return 0;

  ret = file_dotlock_delete(&file->log->dotlock);
  if (ret < 0) {
    log_file_set_syscall_error(file, "file_dotlock_delete()");
    return -1;
  }

  if (ret == 0) {
    mail_index_set_error(file->log->index,
      "Dotlock was lost for transaction log file %s",
      file->filepath);
    return -1;
  }
  return 0;
}

int mail_transaction_log_file_lock(struct mail_transaction_log_file *file)
{
  struct mail_index *index = file->log->index;
  unsigned int lock_timeout_secs;
  int ret;

  if (file->locked)
    return 0;

  if (MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file)) {
    file->locked = TRUE;
    return 0;
  }

  if (index->readonly) {
    mail_index_set_error_code(
      index, MAIL_INDEX_ERROR_CODE_NO_ACCESS,
      "Index is read-only, can't write-lock %s",
      file->filepath);
    return -1;
  }

  if (index->set.lock_method == FILE_LOCK_METHOD_DOTLOCK)
    return mail_transaction_log_file_dotlock(file);

  i_assert(file->file_lock == NULL);
  lock_timeout_secs = I_MIN(MAIL_TRANSACTION_LOG_LOCK_TIMEOUT,
          index->set.max_lock_timeout_secs);
  ret = mail_index_lock_fd(index, file->filepath, file->fd,
         F_WRLCK, lock_timeout_secs,
         &file->file_lock);
  if (ret > 0) {
    file->locked = TRUE;
    file->lock_create_time = time(NULL);
    return 0;
  }
  if (ret < 0) {
    log_file_set_syscall_error(file, "mail_index_wait_lock_fd()");
    return -1;
  }

  mail_index_set_error(index,
    "Timeout (%us) while waiting for lock for "
    "transaction log file %s%s",
    lock_timeout_secs, file->filepath,
    file_lock_find(file->fd, index->set.lock_method, F_WRLCK));
  return -1;
}

void mail_transaction_log_file_unlock(struct mail_transaction_log_file *file,
              const char *lock_reason)
{
  unsigned int lock_time;

  if (!file->locked)
    return;

  file->locked = FALSE;
  file->locked_sync_offset_updated = FALSE;

  if (MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file))
    return;

  lock_time = time(NULL) - file->lock_create_time;
  if (lock_time >= MAIL_TRANSACTION_LOG_LOCK_WARN_SECS && lock_reason != NULL) {
    e_warning(file->log->index->event,
        "Transaction log file %s was locked for %u seconds (%s)",
        file->filepath, lock_time, lock_reason);
  }

  if (file->log->index->set.lock_method == FILE_LOCK_METHOD_DOTLOCK) {
    (void)mail_transaction_log_file_undotlock(file);
    return;
  }

  file_unlock(&file->file_lock);
}

static ssize_t
mail_transaction_log_file_read_header(struct mail_transaction_log_file *file)
{
  void *dest;
  size_t pos, dest_size;
  ssize_t ret;

  i_assert(file->buffer == NULL && file->mmap_base == NULL);

  i_zero(&file->hdr);
  if (file->last_size < mmap_get_page_size() && file->last_size > 0) {
    /* just read the entire transaction log to memory.
       note that if some of the data hasn't been fully committed
       yet (hdr.size=0), the buffer must be truncated later */
    file->buffer = buffer_create_dynamic(default_pool, 4096);
    file->buffer_offset = 0;
    dest_size = file->last_size;
    dest = buffer_append_space_unsafe(file->buffer, dest_size);
  } else {
    /* read only the header */
    dest = &file->hdr;
    dest_size = sizeof(file->hdr);
  }

  /* it's not necessarily an error to read less than wanted header size,
     since older versions of the log format used smaller headers. */
        pos = 0;
  do {
    ret = pread(file->fd, PTR_OFFSET(dest, pos),
          dest_size - pos, pos);
    if (ret > 0)
      pos += ret;
  } while (ret > 0 && pos < dest_size);

  if (file->buffer != NULL) {
    buffer_set_used_size(file->buffer, pos);
    memcpy(&file->hdr, file->buffer->data,
           I_MIN(pos, sizeof(file->hdr)));
  }

  return ret < 0 ? -1 : (ssize_t)pos;
}

static int
mail_transaction_log_file_fail_dupe(struct mail_transaction_log_file *file)
{
  int ret;

  /* mark the old file corrupted. we can't safely remove
     it from the list however, so return failure. */
  file->hdr.indexid = 0;
  if (strcmp(file->filepath, file->log->head->filepath) != 0) {
    /* only mark .2 corrupted, just to make sure we don't lose any
       changes from .log in case we're somehow wrong */
    mail_transaction_log_mark_corrupted(file);
    ret = 0;
  } else {
    ret = -1;
  }
  if (!file->corrupted) {
    file->corrupted = TRUE;
    mail_index_set_error(file->log->index,
             "Transaction log %s: "
             "duplicate transaction log sequence (%u)",
             file->filepath, file->hdr.file_seq);
  }
  return ret;
}

static int
mail_transaction_log_file_read_hdr(struct mail_transaction_log_file *file,
           bool ignore_estale)
{
        struct mail_transaction_log_file *f;
  int ret;

  i_assert(!MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file));

  if (file->corrupted)
    return 0;

  ret = mail_transaction_log_file_read_header(file);
  if (ret < 0) {
                if (errno != ESTALE || !ignore_estale)
      log_file_set_syscall_error(file, "pread()");
    return -1;
  }
  if (file->hdr.major_version != MAIL_TRANSACTION_LOG_MAJOR_VERSION) {
    /* incompatible version - fix silently */
    return 0;
  }
  if (ret < MAIL_TRANSACTION_LOG_HEADER_MIN_SIZE) {
    mail_transaction_log_file_set_corrupted(file,
      "unexpected end of file while reading header");
    return 0;
  }

  const unsigned int hdr_version =
    MAIL_TRANSACTION_LOG_HDR_VERSION(&file->hdr);
  if (MAIL_TRANSACTION_LOG_VERSION_HAVE(hdr_version, COMPAT_FLAGS)) {
    /* we have compatibility flags */
    enum mail_index_header_compat_flags compat_flags = 0;

#ifndef WORDS_BIGENDIAN
    compat_flags |= MAIL_INDEX_COMPAT_LITTLE_ENDIAN;
#endif
    if (file->hdr.compat_flags != compat_flags) {
      /* architecture change */
      mail_index_set_error(file->log->index,
               "Rebuilding index file %s: "
               "CPU architecture changed",
               file->log->index->filepath);
      return 0;
    }
  }
  if (file->hdr.hdr_size < MAIL_TRANSACTION_LOG_HEADER_MIN_SIZE) {
    mail_transaction_log_file_set_corrupted(file,
      "Header size too small");
    return 0;
  }
  if (file->hdr.hdr_size < sizeof(file->hdr)) {
    /* @UNSAFE: smaller than we expected - zero out the fields we
       shouldn't have filled */
    memset(PTR_OFFSET(&file->hdr, file->hdr.hdr_size), 0,
           sizeof(file->hdr) - file->hdr.hdr_size);
  }

  if (file->hdr.indexid == 0) {
    /* corrupted */
    file->corrupted = TRUE;
    mail_index_set_error(file->log->index,
      "Transaction log file %s: marked corrupted",
      file->filepath);
    return 0;
  }
  if (file->hdr.indexid != file->log->index->indexid) {
    if (file->log->index->indexid == 0 ||
        file->log->index->initial_create)
      ;
    else if (strcmp(file->filepath, file->log->filepath2) == 0) {
      /* .log.2 has a different indexid. This is rather
         unlikely situation to notice. We'll handle it by
         deleting the .log.2 so a permanently wrong indexid
         gets fixed automatically. Since .log.2 doesn't
         contain anything critical, it's not so bad even if
         the deletion wasn't really necessary. */
      mail_transaction_log_file_set_corrupted(file,
        "indexid changed: %u -> %u - deleting",
        file->log->index->indexid, file->hdr.indexid);
      return 0;
    } else {
      /* Index was just rebuilt, possibly because the whole
         mailbox was recreated under us. Handle it the same
         as if the mailbox directory had been deleted. */
      e_debug(file->log->index->event,
        "Transaction log file %s indexid changed: %u -> %u",
        file->filepath,
        file->log->index->indexid, file->hdr.indexid);
      file->log->index->index_deleted = TRUE;
      errno = ENOENT;
      return -1;
    }

    /* creating index file. since transaction log is created
       first, use the indexid in it to create the main index
       to avoid races. */
    file->log->index->indexid = file->hdr.indexid;
  }

  /* make sure we already don't have a file with the same sequence
     opened. it shouldn't happen unless the old log file was
     corrupted. */
  for (f = file->log->files; f != NULL; f = f->next) {
    if (f->hdr.file_seq == file->hdr.file_seq) {
      if (strcmp(f->filepath, f->log->head->filepath) != 0) {
        /* old "f" is the .log.2 */
        return mail_transaction_log_file_fail_dupe(f);
      } else {
        /* new "file" is probably the .log.2 */
        return mail_transaction_log_file_fail_dupe(file);
      }
    }
  }

  file->sync_highest_modseq = file->hdr.initial_modseq;
  return 1;
}

static int
mail_transaction_log_file_stat(struct mail_transaction_log_file *file,
             bool ignore_estale)
{
  struct stat st;

  if (fstat(file->fd, &st) < 0) {
                if (!ESTALE_FSTAT(errno) || !ignore_estale)
      log_file_set_syscall_error(file, "fstat()");
    return -1;
  }

  file->st_dev = st.st_dev;
  file->st_ino = st.st_ino;
  file->last_mtime = st.st_mtime;
  file->last_size = st.st_size;
  return 0;
}

static bool
mail_transaction_log_file_is_dupe(struct mail_transaction_log_file *file)
{
  struct mail_transaction_log_file *tmp;

  for (tmp = file->log->files; tmp != NULL; tmp = tmp->next) {
    if (tmp->st_ino == file->st_ino &&
        CMP_DEV_T(tmp->st_dev, file->st_dev))
      return TRUE;
  }
  return FALSE;
}

static void log_write_ext_hdr_init_data(struct mail_index *index, buffer_t *buf)
{
  const struct mail_index_registered_ext *rext;
  struct mail_transaction_header *hdr;
  struct mail_transaction_ext_intro *intro;
  struct mail_transaction_ext_hdr_update *ext_hdr;
  unsigned int hdr_offset;

  rext = array_idx(&index->extensions, index->set.ext_hdr_init_id);

  /* introduce the extension */
  hdr_offset = buf->used;
  hdr = buffer_append_space_unsafe(buf, sizeof(*hdr));
  hdr->type = MAIL_TRANSACTION_EXT_INTRO;

  intro = buffer_append_space_unsafe(buf, sizeof(*intro));
  intro->ext_id = (uint32_t)-1;
  intro->hdr_size = rext->hdr_size;
  intro->record_size = rext->record_size;
  intro->record_align = rext->record_align;
  intro->name_size = strlen(rext->name);
  buffer_append(buf, rext->name, intro->name_size);
  if (buf->used % 4 != 0)
    buffer_append_zero(buf, 4 - buf->used % 4);

  hdr = buffer_get_space_unsafe(buf, hdr_offset, sizeof(*hdr));
  hdr->size = mail_index_uint32_to_offset(buf->used - hdr_offset);

  /* add the extension header data */
  hdr_offset = buf->used;
  hdr = buffer_append_space_unsafe(buf, sizeof(*hdr));
  hdr->type = MAIL_TRANSACTION_EXT_HDR_UPDATE;

  ext_hdr = buffer_append_space_unsafe(buf, sizeof(*ext_hdr));
  ext_hdr->size = rext->hdr_size;
  buffer_append(buf, index->set.ext_hdr_init_data, rext->hdr_size);

  hdr = buffer_get_space_unsafe(buf, hdr_offset, sizeof(*hdr));
  hdr->size = mail_index_uint32_to_offset(buf->used - hdr_offset);
}

static int
mail_transaction_log_file_create2(struct mail_transaction_log_file *file,
          int new_fd, bool reset,
          struct dotlock **dotlock)
{
  struct mail_index *index = file->log->index;
  struct stat st;
  const char *path2;
  buffer_t *writebuf;
  int fd, ret;
  bool rename_existing, need_lock;

  need_lock = file->log->head != NULL && file->log->head->locked;

  if (fcntl(new_fd, F_SETFL, O_APPEND) < 0) {
    log_file_set_syscall_error(file, "fcntl(O_APPEND)");
    return -1;
  }

  if ((index->flags & MAIL_INDEX_OPEN_FLAG_NFS_FLUSH) != 0) {
    /* although we check also mtime and file size below, it's done
       only to fix broken log files. we don't bother flushing
       attribute cache just for that. */
    nfs_flush_file_handle_cache(file->filepath);
  }

  /* log creation is locked now - see if someone already created it.
     note that if we're rotating, we need to keep the log locked until
     the file has been rewritten. and because fcntl() locks are stupid,
     if we go and open()+close() the file and we had it already opened,
     its locks are lost. so we use stat() to check if the file has been
     recreated, although it almost never is. */
  if (reset)
    rename_existing = FALSE;
  else if (nfs_safe_stat(file->filepath, &st) < 0) {
    if (errno != ENOENT) {
      log_file_set_syscall_error(file, "stat()");
      return -1;
    }
    rename_existing = FALSE;
  } else if (st.st_ino == file->st_ino &&
       CMP_DEV_T(st.st_dev, file->st_dev) &&
       /* inode/dev checks are enough when we're rotating the file,
          but not when we're replacing a broken log file */
       st.st_mtime == file->last_mtime &&
       (uoff_t)st.st_size == file->last_size) {
    /* no-one else recreated the file */
    rename_existing = TRUE;
  } else {
    /* recreated. use the file if its header is ok */
    fd = nfs_safe_open(file->filepath, O_RDWR | O_APPEND);
    if (fd == -1) {
      if (errno != ENOENT) {
        log_file_set_syscall_error(file, "open()");
        return -1;
      }
    } else {
      file->fd = fd;
      file->last_size = 0;
      if (mail_transaction_log_file_read_hdr(file,
                     FALSE) > 0 &&
          mail_transaction_log_file_stat(file, FALSE) == 0) {
        /* yes, it was ok */
        file_dotlock_delete(dotlock);
        mail_transaction_log_file_add_to_list(file);
        return 0;
      }
      file->fd = -1;
      if (close(fd) < 0)
        log_file_set_syscall_error(file, "close()");
    }
    rename_existing = FALSE;
  }

  if (index->fd == -1 && !rename_existing) {
    /* creating the initial index */
    reset = TRUE;
  }

  if (mail_transaction_log_init_hdr(file->log, &file->hdr) < 0)
    return -1;

  if (reset) {
    /* don't reset modseqs. if we're resetting due to rebuilding
       indexes we'll probably want to keep uidvalidity and in such
       cases we really don't want to shrink modseqs. */
    file->hdr.prev_file_seq = 0;
    file->hdr.prev_file_offset = 0;
  }

  writebuf = t_buffer_create(128);
  buffer_append(writebuf, &file->hdr, sizeof(file->hdr));

  if (index->set.ext_hdr_init_data != NULL && reset)
    log_write_ext_hdr_init_data(index, writebuf);
  if (write_full(new_fd, writebuf->data, writebuf->used) < 0) {
    log_file_set_syscall_error(file, "write_full()");
    return -1;
  }

  if (file->log->index->set.fsync_mode == FSYNC_MODE_ALWAYS) {
    /* the header isn't important, so don't bother calling
       fdatasync() unless it's required */
    if (fdatasync(new_fd) < 0) {
      log_file_set_syscall_error(file, "fdatasync()");
      return -1;
    }
  }

  file->fd = new_fd;
  ret = mail_transaction_log_file_stat(file, FALSE);

  if (need_lock && ret == 0) {
    /* we'll need to preserve the lock */
    if (mail_transaction_log_file_lock(file) < 0)
      ret = -1;
  }

  /* if we return -1 the dotlock deletion code closes the fd */
  file->fd = -1;
  if (ret < 0)
    return -1;

  /* keep two log files */
  if (rename_existing) {
    /* rename() would be nice and easy way to do this, except then
       there's a race condition between the rename and
       file_dotlock_replace(). during that time the log file
       doesn't exist, which could cause problems. */
    path2 = t_strconcat(file->filepath, ".2", NULL);
    if (i_unlink_if_exists(path2) < 0) {
      /* try to link() anyway */
    }
    if (nfs_safe_link(file->filepath, path2, FALSE) < 0 &&
        errno != ENOENT && errno != EEXIST) {
                        mail_index_set_error(index, "link(%s, %s) failed: %m",
               file->filepath, path2);
      /* ignore the error. we don't care that much about the
         second log file and we're going to overwrite this
         first one. */
    }
    /* NOTE: here's a race condition where both .log and .log.2
       point to the same file. our reading code should ignore that
       though by comparing the inodes. */
  }

  if (file_dotlock_replace(dotlock,
         DOTLOCK_REPLACE_FLAG_DONT_CLOSE_FD) <= 0) {
    /* need to unlock to avoid assert-crash in
       mail_transaction_log_file_free() */
    mail_transaction_log_file_unlock(file, "creation failed");
    return -1;
  }

  /* success */
  file->fd = new_fd;
  mail_transaction_log_file_add_to_list(file);

  i_assert(!need_lock || file->locked);
  return 1;
}

int mail_transaction_log_file_create(struct mail_transaction_log_file *file,
             bool reset)
{
  struct mail_index *index = file->log->index;
  struct dotlock_settings new_dotlock_set;
  struct dotlock *dotlock;
  mode_t old_mask;
  int fd, ret;

  i_assert(!MAIL_INDEX_IS_IN_MEMORY(index));

  if (file->log->index->readonly) {
    mail_index_set_error(index,
      "Can't create log file %s: Index is read-only",
      file->filepath);
    return -1;
  }

  if (index->indexid == 0) {
    mail_index_set_error(index,
      "Can't create log file %s: Index is marked corrupted",
      file->filepath);
    return -1;
  }

  mail_transaction_log_get_dotlock_set(file->log, &new_dotlock_set);
  new_dotlock_set.lock_suffix = LOG_NEW_DOTLOCK_SUFFIX;

  /* With dotlocking we might already have path.lock created, so this
     filename has to be different. */
  old_mask = umask(index->set.mode ^ 0666);
  fd = file_dotlock_open(&new_dotlock_set, file->filepath, 0, &dotlock);
  umask(old_mask);

  if (fd == -1) {
    log_file_set_syscall_error(file, "file_dotlock_open()");
    return -1;
  }
  mail_index_fchown(index, fd, file_dotlock_get_lock_path(dotlock));

        /* either fd gets used or the dotlock gets deleted and returned fd
           is for the existing file */
  ret = mail_transaction_log_file_create2(file, fd, reset, &dotlock);
  if (ret < 0) {
    if (dotlock != NULL)
      file_dotlock_delete(&dotlock);
    return -1;
  }
  return ret;
}

int mail_transaction_log_file_open(struct mail_transaction_log_file *file,
           const char **reason_r)
{
  struct mail_index *index = file->log->index;
        unsigned int i;
  bool ignore_estale;
  int ret;

        for (i = 0;; i++) {
    if (!index->readonly) {
      file->fd = nfs_safe_open(file->filepath,
             O_RDWR | O_APPEND);
    } else {
      file->fd = nfs_safe_open(file->filepath, O_RDONLY);
    }
    if (file->fd == -1 && ENOACCESS(errno)) {
      file->fd = nfs_safe_open(file->filepath, O_RDONLY);
      index->readonly = TRUE;
    }
    if (file->fd == -1) {
      if (errno == ENOENT) {
        *reason_r = "File doesn't exist";
        return 0;
      }

      log_file_set_syscall_error(file, "open()");
      *reason_r = t_strdup_printf("open() failed: %m");
      return -1;
                }

    ignore_estale = i < MAIL_INDEX_ESTALE_RETRY_COUNT;
    if (mail_transaction_log_file_stat(file, ignore_estale) < 0)
      ret = -1;
    else if (mail_transaction_log_file_is_dupe(file)) {
      /* probably our already opened .log file has been
         renamed to .log.2 and we're trying to reopen it.
         also possible that hit a race condition where .log
         and .log.2 are linked. */
      *reason_r = "File is already open";
      return 0;
    } else {
      ret = mail_transaction_log_file_read_hdr(file,
                 ignore_estale);
    }
    if (ret > 0) {
      /* success */
      break;
    }

    if (ret == 0) {
      /* corrupted */
      if (index->readonly) {
        /* don't delete */
      } else {
        i_unlink_if_exists(file->filepath);
      }
      *reason_r = "File is corrupted";
      return 0;
    }
    if (errno != ESTALE ||
        i == MAIL_INDEX_ESTALE_RETRY_COUNT) {
      /* syscall error */
      *reason_r = t_strdup_printf("fstat() failed: %m");
      return -1;
    }

    /* ESTALE - try again */
    buffer_free(&file->buffer);
        }

  mail_transaction_log_file_add_to_list(file);
  return 1;
}

static int
log_file_track_mailbox_sync_offset_hdr(struct mail_transaction_log_file *file,
               const void *data, unsigned int trans_size,
               const char **error_r)
{
  const struct mail_transaction_header_update *u = data;
  const struct mail_index_header *ihdr;
  const unsigned int size = trans_size - sizeof(struct mail_transaction_header);
  const unsigned int offset_pos =
    offsetof(struct mail_index_header, log_file_tail_offset);
  const unsigned int offset_size = sizeof(ihdr->log_file_tail_offset);
  uint32_t tail_offset;

  i_assert(offset_size == sizeof(tail_offset));

  if (size < sizeof(*u) || size < sizeof(*u) + u->size) {
    *error_r = "header update extends beyond record size";
    mail_transaction_log_file_set_corrupted(file, "%s", *error_r);
    return -1;
  }

  if (u->offset <= offset_pos &&
      u->offset + u->size >= offset_pos + offset_size) {
    memcpy(&tail_offset,
           CONST_PTR_OFFSET(u + 1, offset_pos - u->offset),
           sizeof(tail_offset));

    if (tail_offset < file->last_read_hdr_tail_offset) {
      /* ignore shrinking tail offsets */
      return 1;
    } else if (tail_offset > file->sync_offset + trans_size) {
      mail_transaction_log_file_set_corrupted(file,
        "log_file_tail_offset %u goes past sync offset %"PRIuUOFF_T,
        tail_offset, file->sync_offset + trans_size);
    } else {
      file->last_read_hdr_tail_offset = tail_offset;
      if (tail_offset > file->max_tail_offset)
        file->max_tail_offset = tail_offset;
      return 1;
    }
  }
  return 0;
}

static bool
flag_updates_have_non_internal(const struct mail_transaction_flag_update *u,
             unsigned int count, unsigned int version)
{
  /* Hide internal flags from modseqs if the log file's version
     is new enough. This allows upgrading without the modseqs suddenly
     shrinking. */
  if (!MAIL_TRANSACTION_LOG_VERSION_HAVE(version, HIDE_INTERNAL_MODSEQS))
    return TRUE;

  for (unsigned int i = 0; i < count; i++) {
    if (!MAIL_TRANSACTION_FLAG_UPDATE_IS_INTERNAL(&u[i]))
      return TRUE;
  }
  return FALSE;
}

void mail_transaction_update_modseq(const struct mail_transaction_header *hdr,
            const void *data, uint64_t *cur_modseq,
            unsigned int version)
{
  uint32_t trans_size;

  trans_size = mail_index_offset_to_uint32(hdr->size);
  i_assert(trans_size != 0);

  if (*cur_modseq != 0) {
    /* tracking modseqs */
  } else if ((hdr->type & MAIL_TRANSACTION_TYPE_MASK) ==
       MAIL_TRANSACTION_EXT_INTRO) {
    /* modseqs not tracked yet. see if this is a modseq
       extension introduction. */
    const struct mail_transaction_ext_intro *intro = data;
    const unsigned int modseq_ext_len =
      strlen(MAIL_INDEX_MODSEQ_EXT_NAME);

    if (intro->name_size == modseq_ext_len &&
        memcmp(intro + 1, MAIL_INDEX_MODSEQ_EXT_NAME,
         modseq_ext_len) == 0) {
      /* modseq tracking started */
      *cur_modseq += 1;
    }
    return;
  } else {
    /* not tracking modseqs */
    return;
  }

  switch (hdr->type & MAIL_TRANSACTION_TYPE_MASK) {
  case MAIL_TRANSACTION_EXPUNGE | MAIL_TRANSACTION_EXPUNGE_PROT:
  case MAIL_TRANSACTION_EXPUNGE_GUID | MAIL_TRANSACTION_EXPUNGE_PROT:
    if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0) {
      /* ignore expunge requests */
      break;
    }
    /* fall through */
  case MAIL_TRANSACTION_APPEND:
  case MAIL_TRANSACTION_KEYWORD_UPDATE:
  case MAIL_TRANSACTION_KEYWORD_RESET:
  case MAIL_TRANSACTION_ATTRIBUTE_UPDATE:
    /* these changes increase modseq */
    *cur_modseq += 1;
    break;
  case MAIL_TRANSACTION_FLAG_UPDATE: {
    const struct mail_transaction_flag_update *rec = data;
    unsigned int count;

    count = (trans_size - sizeof(*hdr)) / sizeof(*rec);
    if (flag_updates_have_non_internal(rec, count, version))
      *cur_modseq += 1;
    break;
  }
  case MAIL_TRANSACTION_MODSEQ_UPDATE: {
    const struct mail_transaction_modseq_update *rec, *end;

    end = CONST_PTR_OFFSET(data, trans_size - sizeof(*hdr));
    for (rec = data; rec < end; rec++) {
      uint64_t modseq = ((uint64_t)rec->modseq_high32 << 32) |
        rec->modseq_low32;
      if (*cur_modseq < modseq)
        *cur_modseq = modseq;
    }
  }
  }
}

static int
log_file_track_sync(struct mail_transaction_log_file *file,
        const struct mail_transaction_header *hdr,
        unsigned int trans_size, const char **error_r)
{
  const void *data = hdr + 1;
  int ret;

  mail_transaction_update_modseq(hdr, hdr + 1, &file->sync_highest_modseq,
    MAIL_TRANSACTION_LOG_HDR_VERSION(&file->hdr));
  if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0)
    return 1;

  /* external transactions: */
  switch (hdr->type & MAIL_TRANSACTION_TYPE_MASK) {
  case MAIL_TRANSACTION_HEADER_UPDATE:
    /* see if this updates mailbox_sync_offset */
    ret = log_file_track_mailbox_sync_offset_hdr(file, data,
                   trans_size, error_r);
    if (ret != 0)
      return ret < 0 ? -1 : 1;
    break;
  case MAIL_TRANSACTION_INDEX_DELETED:
    if (file->sync_offset < file->index_undeleted_offset ||
        file->hdr.file_seq < file->log->index->index_delete_changed_file_seq)
      break;
    file->log->index->index_deleted = TRUE;
    file->log->index->index_delete_requested = FALSE;
    file->log->index->index_delete_changed_file_seq = file->hdr.file_seq;
    file->index_deleted_offset = file->sync_offset + trans_size;
    break;
  case MAIL_TRANSACTION_INDEX_UNDELETED:
    if (file->sync_offset < file->index_deleted_offset ||
        file->hdr.file_seq < file->log->index->index_delete_changed_file_seq)
      break;
    file->log->index->index_deleted = FALSE;
    file->log->index->index_delete_requested = FALSE;
    file->log->index->index_delete_changed_file_seq = file->hdr.file_seq;
    file->index_undeleted_offset = file->sync_offset + trans_size;
    break;
  case MAIL_TRANSACTION_BOUNDARY: {
    const struct mail_transaction_boundary *boundary =
      (const void *)(hdr + 1);
    size_t wanted_buffer_size;

    wanted_buffer_size = file->sync_offset - file->buffer_offset +
      boundary->size;
    if (wanted_buffer_size > file->buffer->used) {
      /* the full transaction hasn't been written yet */
      return 0;
    }
    break;
  }
  }

  if (file->max_tail_offset == file->sync_offset) {
    /* external transactions aren't synced to mailbox. we can
       update mailbox sync offset to skip this transaction to
       avoid re-reading it at the next sync. */
    file->max_tail_offset += trans_size;
  }
  return 1;
}

/* Returns TRUE if the index has already been synced past the given offset in
   this log file, i.e. the log has lost data that was already used. */
static bool
log_file_is_index_synced_past(const struct mail_transaction_log_file *file,
            uoff_t offset)
{
  const struct mail_index_map *map = file->log->index->map;

  if (map == NULL || map->hdr.log_file_seq != file->hdr.file_seq)
    return FALSE;
  return map->hdr.log_file_head_offset > offset;
}

static int
mail_transaction_log_file_sync(struct mail_transaction_log_file *file,
             bool *retry_r, const char **reason_r)
{
        const struct mail_transaction_header *hdr;
  const void *data;
  struct stat st;
  size_t size, avail;
  uint32_t trans_size = 0;
  int ret;

  i_assert(file->sync_offset >= file->buffer_offset);

  *retry_r = FALSE;

  data = buffer_get_data(file->buffer, &size);
  if (file->buffer_offset + size < file->sync_offset) {
    *reason_r = t_strdup_printf(
      "log file shrank (%"PRIuUOFF_T" < %"PRIuUOFF_T")",
      file->buffer_offset + (uoff_t)size, file->sync_offset);
    mail_transaction_log_file_set_corrupted(file, "%s", *reason_r);
    /* fix the sync_offset to avoid crashes later on */
    file->sync_offset = file->buffer_offset + size;
    return 0;
  }
  while (file->sync_offset - file->buffer_offset + sizeof(*hdr) <= size) {
    hdr = CONST_PTR_OFFSET(data, file->sync_offset -
               file->buffer_offset);
    trans_size = mail_index_offset_to_uint32(hdr->size);
    if (trans_size == 0) {
      /* unfinished or corrupted */
      break;
    }
    if (trans_size < sizeof(*hdr)) {
      *reason_r = t_strdup_printf(
        "hdr.size too small (%u)", trans_size);
      mail_transaction_log_file_set_corrupted(file, "%s", *reason_r);
      return 0;
    }

    if (file->sync_offset - file->buffer_offset + trans_size > size)
      break;

    /* transaction has been fully written */
    if ((ret = log_file_track_sync(file, hdr, trans_size, reason_r)) <= 0) {
      if (ret < 0)
        return 0;
      break;
    }

    file->sync_offset += trans_size;
  }

  if (file->mmap_base != NULL && !file->locked) {
    /* Now that all the mmaped pages have page faulted, check if
       the file had changed while doing that. Only after the last
       page has faulted, the size returned by fstat() can be
       trusted. Otherwise it might point to a page boundary while
       the next page is still being written.

       Without this check we might see partial transactions,
       sometimes causing "Extension record updated without intro
       prefix" errors. */
    if (fstat(file->fd, &st) < 0) {
      log_file_set_syscall_error(file, "fstat()");
      *reason_r = t_strdup_printf("fstat() failed: %m");
      return -1;
    }
    if ((uoff_t)st.st_size != file->last_size) {
      file->last_size = st.st_size;
      *retry_r = TRUE;
      *reason_r = "File size changed - retrying";
      return 0;
    }
  }

  avail = file->sync_offset - file->buffer_offset;
  if (avail != size) {
    /* There's more data than we could sync at the moment. If the
       last record's size wasn't valid, we can't know if it will
       be updated unless we've locked the log. */
    if (file->locked &&
        !log_file_is_index_synced_past(file, file->sync_offset)) {
      /* A previous write to the log wasn't fully written.
         The log isn't corrupted - the partially written
         transaction is simply ignored - but it can't be
         appended to anymore. */
      mail_transaction_log_file_set_garbage_at_eof(file,
        "Partially written transaction at "
        "offset %"PRIuUOFF_T, file->sync_offset);
    } else if (file->locked) {
      /* The index has already been synced past this point,
         so the log has really lost data that was used. */
      *reason_r = "Unexpected garbage at EOF";
      mail_transaction_log_file_set_corrupted(file, "%s",
                *reason_r);
      return 0;
    } else {
      /* The size field will be updated soon */
      mail_index_flush_read_cache(file->log->index,
                file->filepath,
                file->fd, file->locked);
    }
  }

  if (file->next != NULL &&
      file->hdr.file_seq == file->next->hdr.prev_file_seq &&
      file->next->hdr.prev_file_offset != file->sync_offset) {
    *reason_r = t_strdup_printf(
      "Invalid transaction log size "
      "(%"PRIuUOFF_T" vs %u): %s", file->sync_offset,
      file->log->head->hdr.prev_file_offset, file->filepath);
    mail_transaction_log_file_set_corrupted(file, "%s", *reason_r);
    return 0;
  }

  return 1;
}

static int
mail_transaction_log_file_insert_read(struct mail_transaction_log_file *file,
              uoff_t offset, const char **reason_r)
{
  void *data;
  size_t size;
  ssize_t ret;

  size = file->buffer_offset - offset;
  buffer_copy(file->buffer, size, file->buffer, 0, SIZE_MAX);

  data = buffer_get_space_unsafe(file->buffer, 0, size);
  ret = pread_full(file->fd, data, size, offset);
  if (ret > 0) {
    /* success */
    file->buffer_offset -= size;
    return 1;
  }

  /* failure. don't leave ourself to inconsistent state */
  buffer_copy(file->buffer, 0, file->buffer, size, SIZE_MAX);
  buffer_set_used_size(file->buffer, file->buffer->used - size);

  if (ret == 0) {
    *reason_r = "file shrank unexpectedly";
    mail_transaction_log_file_set_corrupted(file, "%s", *reason_r);
    return 0;
  } else if (errno == ESTALE) {
    /* log file was deleted in NFS server, fail silently */
    *reason_r = t_strdup_printf("read() failed: %m");
    return 0;
  } else {
    log_file_set_syscall_error(file, "pread()");
    *reason_r = t_strdup_printf("read() failed: %m");
    return -1;
  }
}

static int
mail_transaction_log_file_read_more(struct mail_transaction_log_file *file,
            const char **reason_r)
{
  void *data;
  size_t size;
  uint32_t read_offset;
  ssize_t ret;

  read_offset = file->buffer_offset + file->buffer->used;

  do {
    data = buffer_append_space_unsafe(file->buffer, LOG_PREFETCH);
    ret = pread(file->fd, data, LOG_PREFETCH, read_offset);
    if (ret > 0)
      read_offset += ret;

    size = read_offset - file->buffer_offset;
    buffer_set_used_size(file->buffer, size);
  } while (ret > 0 || (ret < 0 && errno == EINTR));

  file->last_size = read_offset;

  if (ret < 0) {
    *reason_r = t_strdup_printf("pread() failed: %m");
    if (errno == ESTALE) {
      /* log file was deleted in NFS server, fail silently */
      return 0;
    }
    log_file_set_syscall_error(file, "pread()");
    return -1;
  }
  return 1;
}

static bool
mail_transaction_log_file_need_nfs_flush(struct mail_transaction_log_file *file)
{
  const struct mail_index_header *hdr = &file->log->index->map->hdr;
  uoff_t max_offset = file->last_size;

  if (file->next != NULL &&
      file->hdr.file_seq == file->next->hdr.prev_file_seq &&
      file->next->hdr.prev_file_offset != max_offset) {
    /* we already have a newer log file which says that we haven't
       synced the entire file. */
    return TRUE;
  }

  if (file->hdr.file_seq == hdr->log_file_seq &&
      max_offset < hdr->log_file_head_offset)
    return TRUE;

  return FALSE;
}

static int
mail_transaction_log_file_read(struct mail_transaction_log_file *file,
             uoff_t start_offset, bool nfs_flush,
             const char **reason_r)
{
  bool retry;
  int ret;

  i_assert(file->mmap_base == NULL);

  /* NFS: if file isn't locked, we're optimistic that we can read enough
     data without flushing attribute cache. if after reading we notice
     that we really should have read more, flush the cache and try again.
     if file is locked, the attribute cache was already flushed when
     refreshing the log. */
  if (nfs_flush &&
      (file->log->index->flags & MAIL_INDEX_OPEN_FLAG_NFS_FLUSH) != 0) {
    if (!file->locked)
      nfs_flush_attr_cache_unlocked(file->filepath);
    else
      nfs_flush_attr_cache_fd_locked(file->filepath, file->fd);
  }

  if (file->buffer != NULL && file->buffer_offset > start_offset) {
    /* we have to insert missing data to beginning of buffer */
    ret = mail_transaction_log_file_insert_read(file, start_offset, reason_r);
    if (ret <= 0)
      return ret;
  }

  if (file->buffer == NULL) {
    file->buffer =
      buffer_create_dynamic(default_pool, LOG_PREFETCH);
    file->buffer_offset = start_offset;
  }

  if ((ret = mail_transaction_log_file_read_more(file, reason_r)) <= 0)
    ;
  else if (!nfs_flush &&
     (file->log->index->flags & MAIL_INDEX_OPEN_FLAG_NFS_FLUSH) != 0 &&
     mail_transaction_log_file_need_nfs_flush(file)) {
    /* we didn't read enough data. flush and try again. */
    return mail_transaction_log_file_read(file, start_offset, TRUE, reason_r);
  } else if ((ret = mail_transaction_log_file_sync(file, &retry, reason_r)) == 0) {
    i_assert(!retry); /* retry happens only with mmap */
  }
  i_assert(file->sync_offset >= file->buffer_offset);
  buffer_set_used_size(file->buffer,
           file->sync_offset - file->buffer_offset);
  return ret;
}

static bool
log_file_map_check_offsets(struct mail_transaction_log_file *file,
         uoff_t start_offset, uoff_t end_offset,
         const char **reason_r)
{
  struct stat st, st2;

  if (start_offset > file->sync_offset) {
    /* broken start offset */
    if (MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file)) {
      *reason_r = t_strdup_printf(
        "%s: start_offset (%"PRIuUOFF_T") > "
        "current sync_offset (%"PRIuUOFF_T")",
        file->filepath, start_offset, file->sync_offset);
      return FALSE;
    }

    if (fstat(file->fd, &st) < 0) {
      log_file_set_syscall_error(file, "fstat()");
      st.st_size = -1;
    }
    *reason_r = t_strdup_printf(
      "%s: start_offset (%"PRIuUOFF_T") > "
      "current sync_offset (%"PRIuUOFF_T"), file size=%"PRIuUOFF_T,
      file->filepath, start_offset, file->sync_offset,
      st.st_size);
    if (stat(file->filepath, &st2) == 0) {
      if (st.st_ino != st2.st_ino) {
        *reason_r = t_strdup_printf(
          "%s, file unexpectedly replaced", *reason_r);
      }
    } else if (errno == ENOENT) {
      *reason_r = t_strdup_printf(
        "%s, file unexpectedly deleted", *reason_r);
    } else {
      log_file_set_syscall_error(file, "stat()");
    }
    return FALSE;
  }
  if (end_offset != UOFF_T_MAX && end_offset > file->sync_offset) {
    *reason_r = t_strdup_printf(
      "%s: end_offset (%"PRIuUOFF_T") > "
      "current sync_offset (%"PRIuUOFF_T")",
      file->filepath, start_offset, file->sync_offset);
    return FALSE;
  }

  return TRUE;
}

static int
mail_transaction_log_file_mmap(struct mail_transaction_log_file *file,
             const char **reason_r)
{
  /* we may have switched to mmaping */
  buffer_free(&file->buffer);

  file->mmap_size = file->last_size;
  file->mmap_base = mmap(NULL, file->mmap_size, PROT_READ, MAP_SHARED,
             file->fd, 0);
  if (file->mmap_base == MAP_FAILED) {
    file->mmap_base = NULL;
    if (ioloop_time != file->last_mmap_error_time) {
      file->last_mmap_error_time = ioloop_time;
      log_file_set_syscall_error(file, t_strdup_printf(
        "mmap(size=%zu)", file->mmap_size));
    }
    *reason_r = t_strdup_printf("mmap(size=%zu) failed: %m",
              file->mmap_size);
    file->mmap_size = 0;
    return -1;
  }

  if (file->mmap_size > mmap_get_page_size()) {
    errno = posix_madvise(file->mmap_base, file->mmap_size,
          POSIX_MADV_SEQUENTIAL);
    if (errno != 0)
      log_file_set_syscall_error(file, "posix_madvise()");
  }

  buffer_create_from_const_data(&file->mmap_buffer,
              file->mmap_base, file->mmap_size);
  file->buffer = &file->mmap_buffer;
  file->buffer_offset = 0;
  return 0;
}

static void
mail_transaction_log_file_munmap(struct mail_transaction_log_file *file)
{
  if (file->mmap_base == NULL)
    return;

  i_assert(file->buffer != NULL);
  if (munmap(file->mmap_base, file->mmap_size) < 0)
    log_file_set_syscall_error(file, "munmap()");
  file->mmap_base = NULL;
  file->mmap_size = 0;
  buffer_free(&file->buffer);
}

static int
mail_transaction_log_file_map_mmap(struct mail_transaction_log_file *file,
           uoff_t start_offset, const char **reason_r)
{
  struct stat st;
  bool retry;
  int ret;

  /* we are going to mmap() this file, but it's not necessarily
     mmaped currently. */
  i_assert(file->buffer_offset == 0 || file->mmap_base == NULL);
  i_assert(file->mmap_size == 0 || file->mmap_base != NULL);

  if (fstat(file->fd, &st) < 0) {
    log_file_set_syscall_error(file, "fstat()");
    *reason_r = t_strdup_printf("fstat() failed: %m");
    return -1;
  }
  file->last_size = st.st_size;

  if ((uoff_t)st.st_size < file->sync_offset) {
    *reason_r = t_strdup_printf(
      "file size shrank (%"PRIuUOFF_T" < %"PRIuUOFF_T")",
      (uoff_t)st.st_size, file->sync_offset);
    mail_transaction_log_file_set_corrupted(file, "%s", *reason_r);
    return 0;
  }

  if (file->buffer != NULL && file->buffer_offset <= start_offset &&
      (uoff_t)st.st_size == file->buffer_offset + file->buffer->used) {
    /* we already have the whole file mapped */
    if ((ret = mail_transaction_log_file_sync(file, &retry, reason_r)) != 0 ||
        !retry)
      return ret;
    /* size changed, re-mmap */
  }

  do {
    mail_transaction_log_file_munmap(file);

    if (file->last_size - start_offset < mmap_get_page_size()) {
      /* just reading the file is probably faster */
      return mail_transaction_log_file_read(file,
                    start_offset,
                    FALSE, reason_r);
    }

    if (mail_transaction_log_file_mmap(file, reason_r) < 0)
      return -1;
    ret = mail_transaction_log_file_sync(file, &retry, reason_r);
  } while (retry);

  return ret;
}

int mail_transaction_log_file_map(struct mail_transaction_log_file *file,
          uoff_t start_offset, uoff_t end_offset,
          const char **reason_r)
{
  uoff_t map_start_offset = start_offset;
  size_t size;
  int ret;

  if (file->hdr.indexid == 0) {
    /* corrupted */
    *reason_r = "corrupted, indexid=0";
    return 0;
  }

  i_assert(start_offset >= file->hdr.hdr_size);
  i_assert(start_offset <= end_offset);
  i_assert(file->buffer == NULL || file->mmap_base != NULL ||
     file->sync_offset >= file->buffer_offset + file->buffer->used);

  if (file->locked_sync_offset_updated && file == file->log->head &&
      end_offset == UOFF_T_MAX) {
    /* we're not interested of going further than sync_offset */
    if (!log_file_map_check_offsets(file, start_offset,
            end_offset, reason_r))
      return 0;
    i_assert(start_offset <= file->sync_offset);
    end_offset = file->sync_offset;
  }

  if (file->buffer != NULL && file->buffer_offset <= start_offset) {
    /* see if we already have it */
    size = file->buffer->used;
    if (file->buffer_offset + size >= end_offset)
      return 1;
  }

  if (file->locked) {
    /* set this only when we've synced to end of file while locked
       (either end_offset=UOFF_T_MAX or we had to read anyway) */
    file->locked_sync_offset_updated = TRUE;
  }

  if (MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file)) {
    if (start_offset < file->buffer_offset || file->buffer == NULL) {
      /* we had moved the log to memory but failed to read
         the beginning of the log file */
      *reason_r = "Beginning of the log isn't available";
      return 0;
    }
    return log_file_map_check_offsets(file, start_offset,
              end_offset, reason_r) ? 1 : 0;
  }

  if (start_offset > file->sync_offset)
    mail_transaction_log_file_skip_to_head(file);
  if (start_offset > file->sync_offset) {
    /* although we could just skip over the unwanted data, we have
       to sync everything so that modseqs are calculated
       correctly */
    map_start_offset = file->sync_offset;
  }

  if ((file->log->index->flags & MAIL_INDEX_OPEN_FLAG_MMAP_DISABLE) == 0)
    ret = mail_transaction_log_file_map_mmap(file, map_start_offset, reason_r);
  else {
    mail_transaction_log_file_munmap(file);
    ret = mail_transaction_log_file_read(file, map_start_offset, FALSE, reason_r);
  }

  i_assert(file->buffer == NULL || file->mmap_base != NULL ||
     file->sync_offset >= file->buffer_offset + file->buffer->used);
  if (ret <= 0)
    return ret;

  i_assert(file->buffer != NULL);
  return log_file_map_check_offsets(file, start_offset, end_offset,
            reason_r) ? 1 : 0;
}

int mail_transaction_log_file_move_to_memory(struct mail_transaction_log_file *file)
{
  const char *error;
  buffer_t *buf;
  int ret = 0;

  if (MAIL_TRANSACTION_LOG_FILE_IN_MEMORY(file))
    return 0;

  if (file->mmap_base != NULL) {
    /* just copy to memory */
    i_assert(file->buffer_offset == 0);

    buf = buffer_create_dynamic(default_pool, file->mmap_size);
    buffer_append(buf, file->mmap_base, file->mmap_size);
    buffer_free(&file->buffer);
    file->buffer = buf;

    /* and lose the mmap */
    if (munmap(file->mmap_base, file->mmap_size) < 0)
      log_file_set_syscall_error(file, "munmap()");
    file->mmap_base = NULL;
  } else if (file->buffer_offset != 0) {
    /* we don't have the full log in the memory. read it. */
    ret = mail_transaction_log_file_read(file, 0, FALSE, &error);
    if (ret <= 0) {
      mail_index_set_error(file->log->index,
        "%s: Failed to read into memory: %s", file->filepath, error);
    }
  }
  file->last_size = 0;

  if (close(file->fd) < 0)
    log_file_set_syscall_error(file, "close()");
  file->fd = -1;

  i_free(file->filepath);
  file->filepath = i_strdup(file->log->filepath);
  return ret < 0 ? -1 : 0;
}

Coverage Report

Created: 2026-08-31 07:00