comparison mercurial/util.py @ 12938:bf826c0b9537 stable

opener: check hardlink count reporting (issue1866)

The Linux CIFS kernel driver (even in 2.6.36) suffers from a hardlink
count blindness bug (lstat() returning 1 in st_nlink when it is expected
to return >1), which causes repository corruption if Mercurial running
on Linux pushes or commits to a hardlinked repository stored on a Windows
share, if that share is mounted using the CIFS driver.

This patch works around issue1866 and improves the workaround done in
50523b4407f6 to fix issue761, by teaching the opener to lazily execute a
runtime check (new function checknlink) to see if the hardlink count
reported by nlinks() can be trusted.

Since nlinks() is also known to return varying count values (1 or >1)
depending on whether the file is open or not and depending on what client
and server software combination is being used for accessing and serving
the Windows share, we deliberately open the file before calling nlinks() in
order to have a stable precondition. Trying to depend on the precondition
"file closed" would be fragile, as the file could have been opened very
easily somewhere else in the program.

12937:6ff784de7c3a

        os.unlink(name)
        return True
    except (OSError, AttributeError):
        return False

def endswithsep(path):
    '''Check path ends with os.sep or os.altsep.'''
    return path.endswith(os.sep) or os.altsep and path.endswith(os.altsep)

def splitpath(path):

        if audit:
            self.auditor = path_auditor(base)
        else:
            self.auditor = always
        self.createmode = None

    @propertycache
    def _can_symlink(self):
        return checklink(self.base)

                if 'w' in mode:
                    st_mode = os.lstat(f).st_mode & 0777
                    os.unlink(f)
                    nlink = 0
                else:
                    nlink = nlinks(f)
            except OSError:
                nlink = 0
                if not os.path.isdir(dirname):
                    makedirs(dirname, self.createmode)
            if nlink > 1:
                rename(mktempcopy(f), f)
        fp = posixfile(f, mode)
        if nlink == 0:
            if st_mode is None:
                self._fixfilemode(f)
            else:

12938:bf826c0b9537

        os.unlink(name)
        return True
    except (OSError, AttributeError):
        return False

def checknlink(testfile):
    '''check whether hardlink count reporting works properly'''
    f = testfile + ".hgtmp"

    try:
        os_link(testfile, f)
    except OSError, inst:
        if inst.errno == errno.EINVAL:
            # FS doesn't support creating hardlinks
            return True
        return False

    try:
        # nlinks() may behave differently for files on Windows shares if
        # the file is open.
        fd = open(f)
        return nlinks(f) > 1
    finally:
        fd.close()
        os.unlink(f)

    return False

def endswithsep(path):
    '''Check path ends with os.sep or os.altsep.'''
    return path.endswith(os.sep) or os.altsep and path.endswith(os.altsep)

def splitpath(path):

        if audit:
            self.auditor = path_auditor(base)
        else:
            self.auditor = always
        self.createmode = None
        self._trustnlink = None

    @propertycache
    def _can_symlink(self):
        return checklink(self.base)

                if 'w' in mode:
                    st_mode = os.lstat(f).st_mode & 0777
                    os.unlink(f)
                    nlink = 0
                else:
                    # nlinks() may behave differently for files on Windows
                    # shares if the file is open.
                    fd = open(f)
                    nlink = nlinks(f)
                    fd.close()
            except (OSError, IOError):
                nlink = 0
                if not os.path.isdir(dirname):
                    makedirs(dirname, self.createmode)
            if nlink > 0:
                if self._trustnlink is None:
                    self._trustnlink = nlink > 1 or checknlink(f)
                if nlink > 1 or not self._trustnlink:
                    rename(mktempcopy(f), f)
        fp = posixfile(f, mode)
        if nlink == 0:
            if st_mode is None:
                self._fixfilemode(f)
            else: