mariadb/mysys/my_delete.c

/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */

#include "mysys_priv.h"
#include "mysys_err.h"
#include <my_sys.h>

#ifdef _WIN32
#include <direct.h> /* rmdir */
static int my_win_unlink(const char *name);
#endif

CREATE_NOSYMLINK_FUNCTION(
  unlink_nosymlinks(const char *pathname),
  unlinkat(dfd, filename, 0),
  unlink(pathname)
);

int my_delete(const char *name, myf MyFlags)
{
  int err;
  DBUG_ENTER("my_delete");
  DBUG_PRINT("my",("name %s MyFlags %lu", name, MyFlags));

#ifdef _WIN32
  err = my_win_unlink(name);
#else
  if (MyFlags & MY_NOSYMLINKS)
    err= unlink_nosymlinks(name);
  else
    err= unlink(name);
#endif

  if ((MyFlags & MY_IGNORE_ENOENT) && errno == ENOENT)
    DBUG_RETURN(0);

  if (err)
  {
    my_errno= errno;
    if (MyFlags & (MY_FAE+MY_WME))
      my_error(EE_DELETE, MYF(ME_BELL), name, errno);
  }
  else if ((MyFlags & MY_SYNC_DIR) && my_sync_dir_by_file(name, MyFlags))
    err= -1;
  DBUG_RETURN(err);
} /* my_delete */


#if defined (_WIN32)

/* 
  Delete file.

  The function also makes best effort to minimize number of errors, 
  where another program (or thread in the current program) has the the same file
  open.

  We're using several tricks to prevent the errors, such as

  - Windows 10 "posix semantics" delete

  - Avoid the error by using CreateFile() with FILE_FLAG_DELETE_ON_CLOSE, instead
  of DeleteFile()

  - If file which is deleted (delete on close) but has not entirely gone,
  because it is still opened by some app, an attempt to trcreate file with the 
  same name would  result in yet another error. The workaround here is renaming 
  a file to unique name.

  Symbolic link are deleted without renaming. Directories are not deleted.
*/
#include <my_rdtsc.h>

static int my_win_unlink(const char *name)
{
  HANDLE handle= INVALID_HANDLE_VALUE;
  DWORD attributes;
  uint last_error;
  char unique_filename[MAX_PATH + 35];
  unsigned long long tsc; /* time stamp counter, for unique filename*/
  int retries;
  DBUG_ENTER("my_win_unlink");

  DBUG_INJECT_FILE_SHARING_VIOLATION(name);

  for (retries= FILE_SHARING_VIOLATION_RETRIES; ; retries--)
  {
    attributes= GetFileAttributes(name);
    if (attributes == INVALID_FILE_ATTRIBUTES)
    {
      last_error= GetLastError();
      DBUG_PRINT("error",
                 ("GetFileAttributes(%s) failed with %u\n", name, last_error));
      goto error;
    }

    if (attributes & FILE_ATTRIBUTE_DIRECTORY)
    {
      DBUG_PRINT("error", ("can't remove %s - it is a directory\n", name));
      errno= EINVAL;
      DBUG_RETURN(-1);
    }

    if (attributes & FILE_ATTRIBUTE_REPARSE_POINT)
    {
      /* Symbolic link. Delete link, the not target */
      if (!DeleteFile(name))
      {
        last_error= GetLastError();
        DBUG_PRINT("error",
                   ("DeleteFile(%s) failed with %u\n", name, last_error));
        goto error;
      }
      DBUG_RETURN(0);
    }

    /*
      Try Windows 10 method, delete with "posix semantics" (file is not
      visible, and creating a file with the same name won't fail, even if it
      the file was open)
    */
    handle= CreateFile(name, DELETE,
                       FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
                       NULL, OPEN_EXISTING, 0, NULL);
    if (handle != INVALID_HANDLE_VALUE)
    {
      /* 0x3 = FILE_DISPOSITION_FLAG_DELETE | FILE_DISPOSITION_FLAG_POSIX_SEMANTICS */
      struct {DWORD _Flags;} disp= {0x3};
      BOOL ok= SetFileInformationByHandle(
          handle, (FILE_INFO_BY_HANDLE_CLASS) 21, &disp, sizeof(disp));
      CloseHandle(handle);
      if (ok)
        DBUG_RETURN(0);
    }

    handle= CreateFile(name, DELETE, 0, NULL, OPEN_EXISTING,
                       FILE_FLAG_DELETE_ON_CLOSE, NULL);
    if (handle != INVALID_HANDLE_VALUE)
    {
      /*
        We opened file without sharing flags (exclusive), no one else has this
        file opened, thus it is safe to close handle to remove it. No renaming
        is necessary.
      */
      CloseHandle(handle);
      DBUG_RETURN(0);
    }

    /*
       Can't open file exclusively, hence the file must be already opened by
       someone else. Open it for delete (with all FILE_SHARE flags set),
       rename to unique name, close.
    */
    handle= CreateFile(name, DELETE,
                       FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
                       NULL, OPEN_EXISTING, FILE_FLAG_DELETE_ON_CLOSE, NULL);
    if (handle == INVALID_HANDLE_VALUE)
    {
      last_error= GetLastError();
      DBUG_PRINT(
          "error",
          ("CreateFile(%s) with FILE_FLAG_DELETE_ON_CLOSE failed with %u\n",
           name, last_error));
      goto error;
    }

    tsc= my_timer_cycles();
    my_snprintf(unique_filename, sizeof(unique_filename), "%s.%llx.deleted",
                name, tsc);
    if (!MoveFile(name, unique_filename))
    {
      DBUG_PRINT("warning",
                 ("moving %s to unique filename failed, error %lu\n", name,
                  GetLastError()));
    }
    CloseHandle(handle);
    DBUG_RETURN(0);

error:
    if (last_error != ERROR_SHARING_VIOLATION || retries == 0)
    {
      my_osmaperr(last_error);
      DBUG_RETURN(-1);
    }
    DBUG_CLEAR_FILE_SHARING_VIOLATION();
    Sleep(FILE_SHARING_VIOLATION_DELAY_MS);
  }
}
#endif

/*
   Remove directory recursively.
*/
int my_rmtree(const char *dir, myf MyFlags)
{
  char path[FN_REFLEN];
  char sep[] = { FN_LIBCHAR, 0 };
  int err = 0;
  size_t i;

  MY_DIR *dir_info = my_dir(dir, MYF(MY_DONT_SORT | MY_WANT_STAT));
  if (!dir_info)
    return 1;

  for (i = 0; i < dir_info->number_of_files; i++)
  {
    FILEINFO *file = dir_info->dir_entry + i;
    /* Skip "." and ".." */
    if (!strcmp(file->name, ".") || !strcmp(file->name, ".."))
      continue;

    strxnmov(path, sizeof(path), dir, sep, file->name, NULL);

    if (!MY_S_ISDIR(file->mystat->st_mode))
    {
      err = my_delete(path, MyFlags);
#ifdef _WIN32
      /*
        On Windows, check and possible reset readonly attribute.
        my_delete(), or DeleteFile does not remove these files.
      */
      if (err)
      {
        DWORD attr = GetFileAttributes(path);
        if (attr != INVALID_FILE_ATTRIBUTES &&
          (attr & FILE_ATTRIBUTE_READONLY))
        {
          SetFileAttributes(path, attr &~FILE_ATTRIBUTE_READONLY);
          err = my_delete(path, MyFlags);
        }
      }
#endif
    }
    else
      err = my_rmtree(path, MyFlags);

    if (err)
      break;
  }

  my_dirend(dir_info);

  if (!err)
    err = rmdir(dir);

  return err;
}