File: internal_statvfs.c

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/* Copyright (C) 1998-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <mntent.h>
#include <paths.h>
#include <stdbool.h>
#include <stdio_ext.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <sys/statvfs.h>
#include "linux_fsinfo.h"
#include <kernel-features.h>


/* Special internal-only bit value.  */
#define ST_VALID 0x0020


#ifndef STATFS
# define STATFS statfs
# define STATVFS statvfs
# define INTERNAL_STATVFS __internal_statvfs


# ifndef __ASSUME_STATFS_F_FLAGS
int
__statvfs_getflags (const char *name, int fstype, int fd)
{
  struct stat64 st;

  if ((fd < 0 ? stat64 (name, &st) : fstat64 (fd, &st)) < 0)
    return 0;

  const char *fsname = NULL;
  const char *fsname2 = NULL;
  const char *fsname3 = NULL;

  /* Map the filesystem type we got from the statfs call to a string.  */
  switch (fstype)
    {
    case EXT2_SUPER_MAGIC:
      fsname = "ext4";
      fsname2 = "ext3";
      fsname3 = "ext2";
      break;
    case DEVPTS_SUPER_MAGIC:
      fsname= "devpts";
      break;
    case SHMFS_SUPER_MAGIC:
      fsname = "tmpfs";
      break;
    case PROC_SUPER_MAGIC:
      fsname = "proc";
      break;
    case USBDEVFS_SUPER_MAGIC:
      fsname = "usbdevfs";
      break;
    case AUTOFS_SUPER_MAGIC:
      fsname = "autofs";
      break;
    case NFS_SUPER_MAGIC:
      fsname = "nfs";
      break;
    case SYSFS_MAGIC:
      fsname = "sysfs";
      break;
    case REISERFS_SUPER_MAGIC:
      fsname = "reiserfs";
      break;
    case XFS_SUPER_MAGIC:
      fsname = "xfs";
      break;
    case JFS_SUPER_MAGIC:
      fsname = "jfs";
      break;
    case HPFS_SUPER_MAGIC:
      fsname = "hpfs";
      break;
    case DEVFS_SUPER_MAGIC:
      fsname = "devfs";
      break;
    case ISOFS_SUPER_MAGIC:
      fsname = "iso9660";
      break;
    case MSDOS_SUPER_MAGIC:
      fsname = "msdos";
      break;
    case NTFS_SUPER_MAGIC:
      fsname = "ntfs";
      break;
    case LOGFS_MAGIC_U32:
      fsname = "logfs";
      break;
    case BTRFS_SUPER_MAGIC:
      fsname = "btrfs";
      break;
    case CGROUP_SUPER_MAGIC:
      fsname = "cgroup";
      break;
    case LUSTRE_SUPER_MAGIC:
      fsname = "lustre";
      break;
    case F2FS_SUPER_MAGIC:
      fsname = "f2fs";
      break;
    case EFIVARFS_MAGIC:
      fsname = "efivarfs";
      break;
    }

  FILE *mtab = __setmntent ("/proc/mounts", "r");
  if (mtab == NULL)
    mtab = __setmntent (_PATH_MOUNTED, "r");

  int result = 0;
  if (mtab != NULL)
    {
      bool success = false;
      struct mntent mntbuf;
      char tmpbuf[1024];

      /* No locking needed.  */
      (void) __fsetlocking (mtab, FSETLOCKING_BYCALLER);

    again:
      while (__getmntent_r (mtab, &mntbuf, tmpbuf, sizeof (tmpbuf)))
	{
	  /* In a first round we look for a given mount point, if
	     we have a name.  */
	  if (name != NULL && strcmp (name, mntbuf.mnt_dir) != 0)
	    continue;
	  /* We need to look at the entry only if the filesystem
	     name matches.  If we have a filesystem name.  */
	  else if (fsname != NULL
		   && strcmp (fsname, mntbuf.mnt_type) != 0
		   && (fsname2 == NULL
		       || strcmp (fsname2, mntbuf.mnt_type) != 0)
		   && (fsname3 == NULL
		       || strcmp (fsname3, mntbuf.mnt_type) != 0))
	    continue;

	  /* Find out about the device the current entry is for.  */
	  struct stat64 fsst;
	  if (stat64 (mntbuf.mnt_dir, &fsst) >= 0
	      && st.st_dev == fsst.st_dev)
	    {
	      /* Bingo, we found the entry for the device FD is on.
		 Now interpret the option string.  */
	      char *cp = mntbuf.mnt_opts;
	      char *opt;

	      while ((opt = strsep (&cp, ",")) != NULL)
		if (strcmp (opt, "ro") == 0)
		  result |= ST_RDONLY;
		else if (strcmp (opt, "nosuid") == 0)
		  result |= ST_NOSUID;
		else if (strcmp (opt, "noexec") == 0)
		  result |= ST_NOEXEC;
		else if (strcmp (opt, "nodev") == 0)
		  result |= ST_NODEV;
		else if (strcmp (opt, "sync") == 0)
		  result |= ST_SYNCHRONOUS;
		else if (strcmp (opt, "mand") == 0)
		  result |= ST_MANDLOCK;
		else if (strcmp (opt, "noatime") == 0)
		  result |= ST_NOATIME;
		else if (strcmp (opt, "nodiratime") == 0)
		  result |= ST_NODIRATIME;
		else if (strcmp (opt, "relatime") == 0)
		  result |= ST_RELATIME;

	      /* We can stop looking for more entries.  */
	      success = true;
	      break;
	    }
	}
      /* Maybe the kernel names for the filesystems changed or the
	 statvfs call got a name which was not the mount point.  Check
	 again, this time without checking for name matches first.  */
      if (! success && (name != NULL || fsname != NULL))
	{
	  if (name != NULL)
	    /* Try without a mount point name.  */
	    name = NULL;
	  else
	    {
	      /* Try without a filesystem name.  */
	      assert (fsname != NULL);
	      fsname = fsname2 = fsname3 = NULL;
	    }

	  /* It is not strictly allowed to use rewind here.  But
	     this code is part of the implementation so it is
	     acceptable.  */
	  rewind (mtab);

	  goto again;
	}

      /* Close the file.  */
      __endmntent (mtab);
    }

  return result;
}
# endif
#else
extern int __statvfs_getflags (const char *name, int fstype, int fd);
#endif


void
INTERNAL_STATVFS (const char *name, struct STATVFS *buf,
		  struct STATFS *fsbuf, int fd)
{
  /* Now fill in the fields we have information for.  */
  buf->f_bsize = fsbuf->f_bsize;
  /* Linux has the f_frsize size only in later version of the kernel.
     If the value is not filled in use f_bsize.  */
  buf->f_frsize = fsbuf->f_frsize ?: fsbuf->f_bsize;
  buf->f_blocks = fsbuf->f_blocks;
  buf->f_bfree = fsbuf->f_bfree;
  buf->f_bavail = fsbuf->f_bavail;
  buf->f_files = fsbuf->f_files;
  buf->f_ffree = fsbuf->f_ffree;
  if (sizeof (buf->f_fsid) == sizeof (fsbuf->f_fsid))
    /* The shifting uses 'unsigned long long int' even though the target
       field might only have 32 bits.  This is OK since the 'if' branch
       is not used in this case but the compiler would still generate
       warnings.  */
    buf->f_fsid = ((fsbuf->f_fsid.__val[0]
		    & ((1ULL << (8 * sizeof (fsbuf->f_fsid.__val[0]))) - 1))
		   | ((unsigned long long int) fsbuf->f_fsid.__val[1]
		      << (8 * (sizeof (buf->f_fsid)
			       - sizeof (fsbuf->f_fsid.__val[0])))));
  else
    /* We cannot help here.  The statvfs element is not large enough to
       contain both words of the statfs f_fsid field.  */
    buf->f_fsid = fsbuf->f_fsid.__val[0];
#ifdef _STATVFSBUF_F_UNUSED
  buf->__f_unused = 0;
#endif
  buf->f_namemax = fsbuf->f_namelen;
  memset (buf->__f_spare, '\0', sizeof (buf->__f_spare));

  /* What remains to do is to fill the fields f_favail and f_flag.  */

  /* XXX I have no idea how to compute f_favail.  Any idea???  */
  buf->f_favail = buf->f_ffree;

#ifndef __ASSUME_STATFS_F_FLAGS
  if ((fsbuf->f_flags & ST_VALID) == 0)
    /* Determining the flags is tricky.  We have to read /proc/mounts or
       the /etc/mtab file and search for the entry which matches the given
       file.  The way we can test for matching filesystem is using the
       device number.  */
    buf->f_flag = __statvfs_getflags (name, fsbuf->f_type, fd);
  else
#endif
    buf->f_flag = fsbuf->f_flags ^ ST_VALID;
}