LocalFileSystem Class Reference

#include <LocalFileSystem.h>

Classes
struct	FSInfo
	Information about file systems on this node. More...

Public Member Functions
std::string	findCachePath (const std::vector< std::string > &paths, double minFreeSpace)
bool	isLocalPath (const std::string &path)
	LocalFileSystem (void)
	~LocalFileSystem (void)

Private Member Functions
FSInfo *	findMount (const char *path, struct statfs *sfs, struct stat *s)
FSInfo *	initFSInfo (void *p)
int	initFSList (void)
	LocalFileSystem (LocalFileSystem &)
void	operator= (LocalFileSystem &)
int	readFSTypes (void)
int	statFSInfo (FSInfo *i)

Private Attributes
std::vector< FSInfo * >	fs_
std::vector< std::string >	fstypes_

Detailed Description

Definition at line 10 of file LocalFileSystem.h.

Constructor & Destructor Documentation

LocalFileSystem::LocalFileSystem

(

void

)

Initialise local file system status.

Definition at line 503 of file LocalFileSystem.cc.

References initFSList(), and readFSTypes().

{
  if (readFSTypes() < 0)
    return;

  if (initFSList() < 0)
    return;
}

LocalFileSystem::~LocalFileSystem

(

void

)

Free local file system status resources.

Definition at line 513 of file LocalFileSystem.cc.

References alignCSCRings::e, fs_, and i.

{
  for (size_t i = 0, e = fs_.size(); i < e; ++i)
    free(fs_[i]);
}

LocalFileSystem::LocalFileSystem ( LocalFileSystem &  )

private

Member Function Documentation

std::string LocalFileSystem::findCachePath	(	const std::vector< std::string > &	paths,
		double	minFreeSpace
	)

Find a writeable directory among paths which is known to be local and has at least minFreeSpace amount of free space in gigabytes.

The paths should contain list of relative or absolute candidate directories. If an entry starts with letter "$" then the value of that environment variable is used instead; if the value is $TMPDIR and the environment variable is empty, "/tmp" is used instead.

Returns the first path in paths which satisfies the criteria, expanded to environment variable value if appropriate, resolved to full absolute path. If no suitable path can be found, returns an empty string.

Does not throw exceptions. If any serious errors occur, the errors are reported as message logger warnings but the actual error is swallowed and the directory concerned is skipped. Non-existent and inaccessible directories are silently ignored without warning.

Definition at line 422 of file LocalFileSystem.cc.

References dtNoiseDBValidation_cfg::cerr, alignCSCRings::e, findMount(), LocalFileSystem::FSInfo::freespc, i, LocalFileSystem::FSInfo::local, m, AlCaHLTBitMon_ParallelJobs::p, cmsHarvester::path, query::result, and AlCaHLTBitMon_QueryRunRegistry::string.

Referenced by StorageFactory::setTempDir().

{
  struct stat s;
  struct statfs sfs;
  for (size_t i = 0, e = paths.size(); i < e; ++i)
  {
    char *fullpath;
    const char *inpath = paths[i].c_str();
    const char *path = inpath;

    if (*path == '$')
    {
      char *p = getenv(path+1);
      if (p && *p)
    path = p;
      else if (! strcmp(path, "$TMPDIR"))
    path = "/tmp";
    }

    if (! (fullpath = realpath(path, 0)))
      fullpath = strdup(path);

#if 0
    std::cerr /* edm::LogInfo("LocalFileSystem") */
      << "Checking if '" << fullpath << "', from '"
      << inpath << "' is valid cache path with "
      << minFreeSpace << " free space" << std::endl;
#endif

    if (lstat(fullpath, &s) < 0)
    {
      int nerr = errno;
      if (nerr != ENOENT && nerr != EACCES)
        edm::LogWarning("LocalFileSystem::findCachePath()")
      << "Cannot lstat('" << fullpath << "', from '"
      << inpath << "'): " << strerror(nerr) << " (error "
      << nerr << ")";
      free(fullpath);
      continue;
    }
    
    if (statfs(fullpath, &sfs) < 0)
    {
      int nerr = errno;
      edm::LogWarning("LocalFileSystem::findCachePath()")
    << "Cannot statfs('" << fullpath << "', from '"
    << inpath << "'): " << strerror(nerr) << " (error "
    << nerr << ")";
      free(fullpath);
      continue;
    }

    FSInfo *m = findMount(fullpath, &sfs, &s);
#if 0
    std::cerr /* edm::LogInfo("LocalFileSystem") */
      << "Candidate '" << fullpath << "': "
      << "found=" << (m ? 1 : 0)
      << " local=" << (m && m->local)
      << " free=" << (m ? m->freespc : 0)
      << " access=" << access(fullpath, W_OK)
      << std::endl;
#endif

    if (m
    && m->local
    && m->freespc >= minFreeSpace
    && access(fullpath, W_OK) == 0)
    {
      std::string result(fullpath);
      free(fullpath);
      return result;
    }

    free(fullpath);
  }

  return std::string();
}

LocalFileSystem::FSInfo * LocalFileSystem::findMount ( const char *  path, struct statfs *  sfs, struct stat *  s  )

private

Find the file system path was mounted from. The statfs() and stat() information for path should be in sfs and s, respectively.

Finds currently mounted file system that path is owned by, and returns the FSInfo object for it, or null if no matching live file system can be found. If the return value is non-null, then it is guaranteed path was on that file system.

A null return value is possible for certain paths which are not on any mounted file system (e.g. /dev or /selinux), or if the file system is unavailable or some other way dysfunctional, such as dead nfs mount or filesystem does not implement statfs().

Definition at line 317 of file LocalFileSystem.cc.

References dir, fs_, i, and statFSInfo().

Referenced by findCachePath(), and isLocalPath().

{
  FSInfo *best = 0;
  size_t bestlen = 0;
  size_t len = strlen(path);
  for (size_t i = 0; i < fs_.size(); ++i)
  {
    // First match simply against the file system path.  We don't
    // touch the file system until the path prefix matches.
    size_t fslen = strlen(fs_[i]->dir);
    if (! strncmp(fs_[i]->dir, path, fslen)
    && ((fslen == 1 && fs_[i]->dir[0] == '/')
        || len == fslen || path[fslen] == '/')
    && (! best || fslen > bestlen))
    {
      // Get the file system device and file system ids.
      if (statFSInfo(fs_[i]) < 0)
    return 0;

      // Check the path is on the same device / file system.  If this
      // fails, we found a better prefix match on path, but it's the
      // wrong device, so reset our idea of the best match: it can't
      // be the outer mount any more.  Not sure this is the right
      // thing to do with e.g. loop-back or union mounts.
      if (fs_[i]->dev != s->st_dev || fs_[i]->fstype != sfs->f_type)
      {
    best = 0;
    continue;
      }

      // OK this is better than anything else we found so far.
      best = fs_[i];
      bestlen = fslen;
    }
  }

  return best;
}

LocalFileSystem::FSInfo * LocalFileSystem::initFSInfo ( void *  arg )

private

Initialise file system description from /etc/mtab info.

This function saves the information from getmntent(), matching the file system type to the known local ones. It only remembers the information from /etc/mtab, so the dev and fstype attributes are not yet valid; call statFSInfo() to fill those in. This avoids touching irrelevant filesystems unnecessarily; the file system may not be fully functional, or partially offline, or just very slow.

Definition at line 140 of file LocalFileSystem.cc.

References LocalFileSystem::FSInfo::checked, LocalFileSystem::FSInfo::dev, LocalFileSystem::FSInfo::dir, LocalFileSystem::FSInfo::freespc, LocalFileSystem::FSInfo::fsname, LocalFileSystem::FSInfo::fstype, fstypes_, i, j, LocalFileSystem::FSInfo::local, m, AlCaHLTBitMon_ParallelJobs::p, and LocalFileSystem::FSInfo::type.

Referenced by initFSList().

{
#if BSD
  struct statfs *m = static_cast<struct statfs *>(arg);
  size_t infolen = sizeof(struct FSInfo);
  size_t fslen = strlen(m->f_mntfromname) + 1;
  size_t dirlen = strlen(m->f_mntonname) + 1;
  size_t typelen = strlen(m->f_fstypename) + 1;
  size_t totlen = infolen + fslen + dirlen + typelen;
  FSInfo *i = (FSInfo *) malloc(totlen);
  char *p = (char *) i;
  i->fsname = strncpy(p += infolen, m->f_mntfromname, fslen);
  i->type = strncpy(p += fslen, m->f_fstypename, typelen);
  i->dir = strncpy(p += typelen, m->f_mntonname, dirlen);
  i->dev = m->f_fsid.val[0];
  i->fstype = m->f_type;
  i->freespc = 0;
  if (m->f_bsize > 0)
  {
    i->freespc = m->f_bavail;
    i->freespc *= m->f_bsize;
    i->freespc /= 1024. * 1024. * 1024.;
  } 
  /* FIXME: This incorrectly says that mounted disk images are local,
     even if it was mounted from a network server. The alternative is
     to walk up the device tree using either a) process IORegistry to
     get the device tree, which lists devices for disk images, and from
     there translate volume uuid to a mount point; b) parse output from
     'hdiutil info -plist' to determine image-path / dev-entry map. */
  i->local = ((m->f_flags & MNT_LOCAL) ? 1 : 0);
  i->checked = 1;
  return i;

#else // ! BSD
  mntent *m = static_cast<mntent *>(arg);
  size_t infolen = sizeof(struct FSInfo);
  size_t fslen = strlen(m->mnt_fsname) + 1;
  size_t dirlen = strlen(m->mnt_dir) + 1;
  size_t typelen = strlen(m->mnt_type) + 1;
  size_t totlen = infolen + fslen + dirlen + typelen;
  FSInfo *i = (FSInfo *) malloc(totlen);
  char *p = (char *) i;
  i->fsname = strncpy(p += infolen, m->mnt_fsname, fslen);
  i->type = strncpy(p += fslen, m->mnt_type, typelen);
  i->dir = strncpy(p += typelen, m->mnt_dir, dirlen);
  i->dev = -1;
  i->fstype = -1;
  i->freespc = 0;
  i->local = 0;
  i->checked = 0;

  for (size_t j = 0; j < fstypes_.size() && ! i->local; ++j)
    if (fstypes_[j] == i->type)
      i->local = 1;
#endif // BSD

  return i;
}

int LocalFileSystem::initFSList ( void  )

private

Initialise the list of currently mounted file systems.

Reads /etc/mtab (or equivalent) to determine all currently mounted file systems, and initialises FSInfo structure for them. It does not yet call statFSInfo() on them, so the device and file type ids are not yet complete.

Definition at line 206 of file LocalFileSystem.cc.

References fs_, initFSInfo(), and m.

Referenced by LocalFileSystem().

{
#if BSD
  int rc;
  struct statfs *mtab = 0;
  if ((rc = getmntinfo(&mtab, MNT_NOWAIT)) < 0)
  {
    int nerr = errno;
    edm::LogWarning("LocalFileSystem::initFSList()")
      << "getmntinfo() failed: " << strerror(nerr)
      << " (error " << nerr << ")";
    return -1;
  }

  fs_.reserve(rc);
  for (int ix = 0; ix < rc; ++ix)
    fs_.push_back(initFSInfo(&mtab[ix]));

  free(mtab);
#else
  const char * const _PATH_MOUNTED_LINUX = "/proc/self/mounts";
  struct mntent *m;
  FILE *mtab = setmntent(_PATH_MOUNTED_LINUX, "r");
  if (! mtab)
  {
    int nerr = errno;
    edm::LogWarning("LocalFileSystem::initFSList()")
      << "Cannot read '" << _PATH_MOUNTED_LINUX << "': "
      << strerror(nerr) << " (error " << nerr << ")";
    return -1;
  }

  fs_.reserve(20);
  while ((m = getmntent(mtab)))
    fs_.push_back(initFSInfo(m));

  endmntent(mtab);
#endif

  return 0;
}

bool LocalFileSystem::isLocalPath

(

const std::string &

path

)

Determine if path is on a file system known to be local.

Returns true if the path is definitely known to be local. Returns false otherwise, including when it's not possible to determine anything about the path at all.

Does not throw exceptions. If any errors occur, the errors are reported as message logger warnings but the actual error is swallowed and the function simply returns false.

Definition at line 366 of file LocalFileSystem.cc.

References findMount(), LocalFileSystem::FSInfo::local, and m.

Referenced by StorageFactory::wrapNonLocalFile().

{
  struct stat s;
  struct statfs sfs;
  char *fullpath = realpath(path.c_str(), 0);

  if (! fullpath)
    fullpath = strdup(path.c_str());

  if (lstat(fullpath, &s) < 0)
  {
    int nerr = errno;
    edm::LogWarning("LocalFileSystem::isLocalPath()")
      << "Cannot lstat('" << fullpath << "' alias '"
      << path << "'): " << strerror(nerr) << " (error "
      << nerr << ")";
    free(fullpath);
    return false;
  }
    
  if (statfs(fullpath, &sfs) < 0)
  {
    int nerr = errno;
    edm::LogWarning("LocalFileSystem::isLocalPath()")
      << "Cannot statfs('" << fullpath << "' alias '"
      << path << "'): " << strerror(nerr) << " (error "
      << nerr << ")";
    free(fullpath);
    return false;
  }

  FSInfo *m = findMount(fullpath, &sfs, &s);
  free(fullpath);

  return m ? m->local : false;
}

void LocalFileSystem::operator= ( LocalFileSystem &  )

private

int LocalFileSystem::readFSTypes ( void  )

private

Read /proc/filesystems to determine which filesystems are local, meaning access latency is tolerably small, and operating system buffer cache will likely do a good job at caching file contents and accelerate many small file operations reasonably well.

The /proc list enumerates all filesystems known by the kernel, except a few special ones like /dev and /selinux. The ones marked as "nodev" have unstable device definition, meaning they are some way or another "virtual" file systems. This labeling is used by kernel nfsd to determine which file systems are safe for exporting without help (fixing fsid), and turns out to be close enough to list of file systems that we can consider to be high-speed local, minus a few exceptions. Everything else we consider "remote" or "slow" file systems where application should prefer massive bulk streaming I/O for better performance.

The exceptions to /proc/filesystems list: lustre and fuse file systems are forced to remote status. Everything else like NFS, AFS, GPFS and various cluster-based systems are already remote.

Definition at line 58 of file LocalFileSystem.cc.

References fstypes_, geometryCSVtoXML::line, and run_regression::ret.

Referenced by LocalFileSystem().

{
  int ret = 0;

#if __linux__
  static const char procfs[] = "/proc/filesystems";
  FILE *fs = fopen(procfs, "r");
  if (! fs)
  {
    int nerr = errno;
    edm::LogWarning("LocalFileSystem::readFSTypes()")
      << "Cannot read '" << procfs << "': "
      << strerror(nerr) << " (error " << nerr << ")";
    return -1;
  }

  ssize_t nread;
  int line = 0;
  while (! feof(fs))
  {
    char *type = 0;
    char *fstype = 0;
    size_t len = 0;
    ++line;

    if ((nread = getdelim(&type, &len, '\t', fs)) == -1 && ! feof(fs))
    {
      fprintf(stderr, "%s:%d: %s (%zd; 1)\n",
          procfs, line, strerror(errno), nread);
      free(type);
      ret = -1;
      break;
    }

    if ((nread = getdelim(&fstype, &len, '\n', fs)) == -1 && ! feof(fs))
    {
      fprintf(stderr, "%s:%d: %s (%zd; 2)\n",
          procfs, line, strerror(errno), nread);
      free(type);
      free(fstype);
      ret = -1;
      break;
    }

    if (feof (fs))
    {
      free(type);
      free(fstype);
      break;
    }
    
    if (! strcmp(type, "nodev\t")
    || ! strcmp(fstype, "lustre\n")
    || ! strncmp(fstype, "fuse", 4))
    {
      free(type);
      free(fstype);
      continue;
    }

    assert(nread >= 1);
    fstype[nread-1] = 0;
    fstypes_.push_back(fstype);
    free(fstype);
    free(type);
  }

  fclose(fs);
#endif // __linux__

  return ret;
}

int LocalFileSystem::statFSInfo ( FSInfo *  i )

private

Figure out file system device and type ids.

Calls stat() and statfs() on the file system to determine device and file system type ids. These are required to determine if two paths are actually on the same file system.

This function can be called any number of times. It only does the file system check the first time the function is called.

Definition at line 257 of file LocalFileSystem.cc.

References LocalFileSystem::FSInfo::checked, LocalFileSystem::FSInfo::dev, LocalFileSystem::FSInfo::dir, LocalFileSystem::FSInfo::freespc, LocalFileSystem::FSInfo::fstype, and run_regression::ret.

Referenced by findMount().

{
  int ret = 0;
  struct stat s;
  struct statfs sfs;

  if (! i->checked)
  {
    i->checked = 1;
    if (lstat(i->dir, &s) < 0)
    {
      int nerr = errno;
      if (nerr != ENOENT && nerr != EACCES)
        edm::LogWarning("LocalFileSystem::statFSInfo()")
      << "Cannot lstat('" << i->dir << "'): "
      << strerror(nerr) << " (error " << nerr << ")";
      return -1;
    }

    if (statfs(i->dir, &sfs) < 0)
    {
      int nerr = errno;
      edm::LogWarning("LocalFileSystem::statFSInfo()")
    << "Cannot statfs('" << i->dir << "'): "
    << strerror(nerr) << " (error " << nerr << ")";
      return -1;
    }

    i->dev = s.st_dev;
    i->fstype = sfs.f_type;
    if (sfs.f_bsize > 0)
    {
      i->freespc = sfs.f_bavail;
      i->freespc *= sfs.f_bsize;
      i->freespc /= 1024. * 1024. * 1024.;
    }
  }
  else if (i->fstype == -1)
  {
    errno = ENOENT;
    ret = -1;
  }

  return ret;
}

Member Data Documentation

std::vector<FSInfo *> LocalFileSystem::fs_

private

Definition at line 27 of file LocalFileSystem.h.

Referenced by findMount(), initFSList(), and ~LocalFileSystem().

std::vector<std::string> LocalFileSystem::fstypes_

private

Definition at line 28 of file LocalFileSystem.h.

Referenced by initFSInfo(), and readFSTypes().