Final forward port of PDQ performance patches

Change-Id: I4ef131b3cc7648d4571a4d854029efb1aff8b901
Signed-off-by: Peter Portante <peter.portante@redhat.com>
Reviewed-on: http://review.gluster.org/5305
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>

7 files changed, 928 insertions, 316 deletions

diff --git a/gluster/swift/common/DiskDir.py b/gluster/swift/common/DiskDir.py
index c1fb674..b4a8341 100644
--- a/gluster/swift/common/DiskDir.py
+++ b/gluster/swift/common/DiskDir.py
@@ -483,12 +483,6 @@ class DiskDir(DiskCommon):
         # within a directory implicitly.
         return
 
-    def empty(self):
-        try:
-            return dir_empty(self.datadir)
-        except FileOrDirNotFoundError:
-            return True
-
     def delete_db(self, timestamp):
         """
         Delete the container (directory) if empty.
diff --git a/gluster/swift/common/DiskFile.py b/gluster/swift/common/DiskFile.py
index 1ae5f7c..623248a 100644
--- a/gluster/swift/common/DiskFile.py
+++ b/gluster/swift/common/DiskFile.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2012 Red Hat, Inc.
+# Copyright (c) 2013 Red Hat, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,29 +15,241 @@
 
 import os
 import stat
+import fcntl
 import errno
 import random
+import logging
 from hashlib import md5
+from eventlet import sleep
 from contextlib import contextmanager
-from swift.common.utils import renamer
+from swift.common.utils import TRUE_VALUES, fallocate
 from swift.common.exceptions import DiskFileNotExist, DiskFileError
-from gluster.swift.common.exceptions import AlreadyExistsAsDir
-from gluster.swift.common.fs_utils import mkdirs, do_open, do_close, \
+from gluster.swift.common.exceptions import GlusterFileSystemOSError
+from gluster.swift.common.fs_utils import do_fstat, do_open, do_close, \
     do_unlink, do_chown, os_path, do_fsync, do_fchown, do_stat
 from gluster.swift.common.utils import read_metadata, write_metadata, \
-    validate_object, create_object_metadata, rmobjdir, dir_is_object
+    validate_object, create_object_metadata, rmobjdir, dir_is_object, \
+    get_object_metadata
 from gluster.swift.common.utils import X_CONTENT_LENGTH, X_CONTENT_TYPE, \
     X_TIMESTAMP, X_TYPE, X_OBJECT_TYPE, FILE, OBJECT, DIR_TYPE, \
     FILE_TYPE, DEFAULT_UID, DEFAULT_GID, DIR_NON_OBJECT, DIR_OBJECT
+from ConfigParser import ConfigParser, NoSectionError, NoOptionError
 
 from swift.obj.server import DiskFile
 
+# FIXME: Hopefully we'll be able to move to Python 2.7+ where O_CLOEXEC will
+# be back ported. See http://www.python.org/dev/peps/pep-0433/
+O_CLOEXEC = 02000000
 
 DEFAULT_DISK_CHUNK_SIZE = 65536
 # keep these lower-case
 DISALLOWED_HEADERS = set('content-length content-type deleted etag'.split())
 
 
+def _random_sleep():
+    sleep(random.uniform(0.5, 0.15))
+
+
+def _lock_parent(full_path):
+    parent_path, _ = full_path.rsplit(os.path.sep, 1)
+    try:
+        fd = os.open(parent_path, os.O_RDONLY | O_CLOEXEC)
+    except OSError as err:
+        if err.errno == errno.ENOENT:
+            # Cannot lock the parent because it does not exist, let the caller
+            # handle this situation.
+            return False
+        raise
+    else:
+        while True:
+            # Spin sleeping for 1/10th of a second until we get the lock.
+            # FIXME: Consider adding a final timeout just abort the operation.
+            try:
+                fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except IOError as err:
+                if err.errno == errno.EAGAIN:
+                    _random_sleep()
+                else:
+                    # Don't leak an open file on an exception
+                    os.close(fd)
+                    raise
+            except Exception:
+                # Don't leak an open file for any other exception
+                os.close(fd)
+                raise
+            else:
+                break
+        return fd
+
+
+def _make_directory_locked(full_path, uid, gid, metadata=None):
+    fd = _lock_parent(full_path)
+    if fd is False:
+        # Parent does not exist either, pass this situation on to the caller
+        # to handle.
+        return False, metadata
+    try:
+        # Check for directory existence
+        stats = do_stat(full_path)
+        if stats:
+            # It now exists, having acquired the lock of its parent directory,
+            # but verify it is actually a directory
+            is_dir = stat.S_ISDIR(stats.st_mode)
+            if not is_dir:
+                # It is not a directory!
+                raise DiskFileError("_make_directory_locked: non-directory"
+                                    " found at path %s when expecting a"
+                                    " directory", full_path)
+            return True, metadata
+
+        # We know the parent directory exists, and we have it locked, attempt
+        # the creation of the target directory.
+        return _make_directory_unlocked(full_path, uid, gid, metadata=metadata)
+    finally:
+        # We're done here, be sure to remove our lock and close our open FD.
+        try:
+            fcntl.flock(fd, fcntl.LOCK_UN)
+        except:
+            pass
+        os.close(fd)
+
+
+def _make_directory_unlocked(full_path, uid, gid, metadata=None):
+    """
+    Make a directory and change the owner ship as specified, and potentially
+    creating the object metadata if requested.
+    """
+    try:
+        os.mkdir(full_path)
+    except OSError as err:
+        if err.errno == errno.ENOENT:
+            # Tell the caller some directory of the parent path does not
+            # exist.
+            return False, metadata
+        elif err.errno == errno.EEXIST:
+            # Possible race, in that the caller invoked this method when it
+            # had previously determined the file did not exist.
+            #
+            # FIXME: When we are confident, remove this stat() call as it is
+            # not necessary.
+            try:
+                stats = os.stat(full_path)
+            except OSError as serr:
+                # FIXME: Ideally we'd want to return an appropriate error
+                # message and code in the PUT Object REST API response.
+                raise DiskFileError("_make_directory_unlocked: os.mkdir failed"
+                                    " because path %s already exists, and"
+                                    " a subsequent os.stat on that same"
+                                    " path failed (%s)" % (full_path,
+                                                           str(serr)))
+            else:
+                is_dir = stat.S_ISDIR(stats.st_mode)
+                if not is_dir:
+                    # FIXME: Ideally we'd want to return an appropriate error
+                    # message and code in the PUT Object REST API response.
+                    raise DiskFileError("_make_directory_unlocked: os.mkdir"
+                                        " failed on path %s because it already"
+                                        " exists but not as a directory" % (
+                                            full_path))
+            return True, metadata
+        elif err.errno == errno.ENOTDIR:
+            # FIXME: Ideally we'd want to return an appropriate error
+            # message and code in the PUT Object REST API response.
+            raise DiskFileError("_make_directory_unlocked: os.mkdir failed"
+                                " because some part of path %s is not in fact"
+                                " a directory" % (full_path))
+        elif err.errno == errno.EIO:
+            # Sometimes Fuse will return an EIO error when it does not know
+            # how to handle an unexpected, but transient situation. It is
+            # possible the directory now exists, stat() it to find out after a
+            # short period of time.
+            _random_sleep()
+            try:
+                stats = os.stat(full_path)
+            except OSError as serr:
+                if serr.errno == errno.ENOENT:
+                    errmsg = "_make_directory_unlocked: os.mkdir failed on" \
+                             " path %s (EIO), and a subsequent os.stat on" \
+                             " that same path did not find the file." % (
+                                 full_path,)
+                else:
+                    errmsg = "_make_directory_unlocked: os.mkdir failed on" \
+                             " path %s (%s), and a subsequent os.stat on" \
+                             " that same path failed as well (%s)" % (
+                                 full_path, str(err), str(serr))
+                raise DiskFileError(errmsg)
+            else:
+                # The directory at least exists now
+                is_dir = stat.S_ISDIR(stats.st_mode)
+                if is_dir:
+                    # Dump the stats to the log with the original exception.
+                    logging.warn("_make_directory_unlocked: os.mkdir initially"
+                                 " failed on path %s (%s) but a stat()"
+                                 " following that succeeded: %r" % (full_path,
+                                                                    str(err),
+                                                                    stats))
+                    # Assume another entity took care of the proper setup.
+                    return True, metadata
+                else:
+                    raise DiskFileError("_make_directory_unlocked: os.mkdir"
+                                        " initially failed on path %s (%s) but"
+                                        " now we see that it exists but is not"
+                                        " a directory (%r)" % (full_path,
+                                                               str(err),
+                                                               stats))
+        else:
+            # Some other potentially rare exception occurred that does not
+            # currently warrant a special log entry to help diagnose.
+            raise DiskFileError("_make_directory_unlocked: os.mkdir failed on"
+                                " path %s (%s)" % (full_path, str(err)))
+    else:
+        if metadata:
+            # We were asked to set the initial metadata for this object.
+            metadata_orig = get_object_metadata(full_path)
+            metadata_orig.update(metadata)
+            write_metadata(full_path, metadata_orig)
+            metadata = metadata_orig
+
+        # We created it, so we are reponsible for always setting the proper
+        # ownership.
+        do_chown(full_path, uid, gid)
+        return True, metadata
+
+
+_fs_conf = ConfigParser()
+if _fs_conf.read(os.path.join('/etc/swift', 'fs.conf')):
+    try:
+        _mkdir_locking = _fs_conf.get('DEFAULT', 'mkdir_locking', "no") \
+            in TRUE_VALUES
+    except (NoSectionError, NoOptionError):
+        _mkdir_locking = False
+    try:
+        _use_put_mount = _fs_conf.get('DEFAULT', 'use_put_mount', "no") \
+            in TRUE_VALUES
+    except (NoSectionError, NoOptionError):
+        _use_put_mount = False
+    try:
+        _relaxed_writes = _fs_conf.get('DEFAULT', 'relaxed_writes', "no") \
+            in TRUE_VALUES
+    except (NoSectionError, NoOptionError):
+        _relaxed_writes = False
+    try:
+        _preallocate = _fs_conf.get('DEFAULT', 'preallocate', "no") \
+            in TRUE_VALUES
+    except (NoSectionError, NoOptionError):
+        _preallocate = False
+else:
+    _mkdir_locking = False
+    _use_put_mount = False
+    _relaxed_writes = False
+    _preallocate = False
+
+if _mkdir_locking:
+    make_directory = _make_directory_locked
+else:
+    make_directory = _make_directory_unlocked
+
+
 def _adjust_metadata(metadata):
     # Fix up the metadata to ensure it has a proper value for the
     # Content-Type metadata, as well as an X_TYPE and X_OBJECT_TYPE
@@ -106,6 +318,11 @@ class Gluster_DiskFile(DiskFile):
         self.datadir = os.path.join(path, device, self.name)
         self.device_path = os.path.join(path, device)
         self._container_path = os.path.join(path, device, container)
+        if _use_put_mount:
+            self.put_datadir = os.path.join(self.device_path + '_PUT',
+                                            self.name)
+        else:
+            self.put_datadir = self.datadir
         self._is_dir = False
         self.tmppath = None
         self.logger = logger
@@ -123,15 +340,16 @@ class Gluster_DiskFile(DiskFile):
 
         # Don't store a value for data_file until we know it exists.
         self.data_file = None
-        data_file = os.path.join(self.datadir, self._obj)
+        data_file = os.path.join(self.put_datadir, self._obj)
 
         try:
             stats = do_stat(data_file)
-        except OSError as ose:
-            if ose.errno == errno.ENOENT or ose.errno == errno.ENOTDIR:
+        except OSError as err:
+            if err.errno == errno.ENOTDIR:
+                return
+        else:
+            if not stats:
                 return
-            else:
-                raise
 
         self.data_file = data_file
         self._is_dir = stat.S_ISDIR(stats.st_mode)
@@ -162,8 +380,9 @@ class Gluster_DiskFile(DiskFile):
         :param verify_file: Defaults to True. If false, will not check
                             file to see if it needs quarantining.
         """
-        #Marker directory
+        # Marker directory
         if self._is_dir:
+            assert not self.fp
             return
         if self.fp:
             do_close(self.fp)
@@ -178,20 +397,61 @@ class Gluster_DiskFile(DiskFile):
         """
         return not self.data_file
 
-    def _create_dir_object(self, dir_path):
-        stats = None
-        try:
-            stats = do_stat(dir_path)
-        except OSError:
-            pass
+    def _create_dir_object(self, dir_path, metadata=None):
+        """
+        Create a directory object at the specified path. No check is made to
+        see if the directory object already exists, that is left to the
+        caller (this avoids a potentially duplicate stat() system call).
+
+        The "dir_path" must be relative to its container, self._container_path.
+
+        The "metadata" object is an optional set of metadata to apply to the
+        newly created directory object. If not present, no initial metadata is
+        applied.
+
+        The algorithm used is as follows:
 
-        if not stats:
-            mkdirs(dir_path)
-            do_chown(dir_path, self.uid, self.gid)
-            create_object_metadata(dir_path)
-        elif not stat.S_ISDIR(stats.st_mode):
-            raise DiskFileError("Cannot overwrite "
-                                "file %s with a directory" % dir_path)
+          1. An attempt is made to create the directory, assuming the parent
+             directory already exists
+
+             * Directory creation races are detected, returning success in
+               those cases
+
+          2. If the directory creation fails because some part of the path to
+             the directory does not exist, then a search back up the path is
+             performed to find the first existing ancestor directory, and then
+             the missing parents are successively created, finally creating
+             the target directory
+        """
+        full_path = os.path.join(self._container_path, dir_path)
+        cur_path = full_path
+        stack = []
+        while True:
+            md = None if cur_path != full_path else metadata
+            ret, newmd = make_directory(cur_path, self.uid, self.gid, md)
+            if ret:
+                break
+            # Some path of the parent did not exist, so loop around and
+            # create that, pushing this parent on the stack.
+            if os.path.sep not in cur_path:
+                raise DiskFileError("DiskFile._create_dir_object(): failed to"
+                                    " create directory path while exhausting"
+                                    " path elements to create: %s" % full_path)
+            cur_path, child = cur_path.rsplit(os.path.sep, 1)
+            assert child
+            stack.append(child)
+
+        child = stack.pop() if stack else None
+        while child:
+            cur_path = os.path.join(cur_path, child)
+            md = None if cur_path != full_path else metadata
+            ret, newmd = make_directory(cur_path, self.uid, self.gid, md)
+            if not ret:
+                raise DiskFileError("DiskFile._create_dir_object(): failed to"
+                                    " create directory path to target, %s,"
+                                    " on subpath: %s" % (full_path, cur_path))
+            child = stack.pop() if stack else None
+        return True, newmd
 
     def put_metadata(self, metadata, tombstone=False):
         """
@@ -227,39 +487,112 @@ class Gluster_DiskFile(DiskFile):
 
         if dir_is_object(metadata):
             if not self.data_file:
-                self.data_file = os.path.join(self.datadir, self._obj)
-                self._create_dir_object(self.data_file)
-            self.put_metadata(metadata)
+                # Does not exist, create it
+                data_file = os.path.join(self._obj_path, self._obj)
+                _, self.metadata = self._create_dir_object(data_file, metadata)
+                self.data_file = os.path.join(self._container_path, data_file)
+            elif not self.is_dir:
+                # Exists, but as a file
+                raise DiskFileError('DiskFile.put(): directory creation failed'
+                                    ' since the target, %s, already exists as'
+                                    ' a file' % self.data_file)
             return
 
-        # Check if directory already exists.
         if self._is_dir:
             # A pre-existing directory already exists on the file
             # system, perhaps gratuitously created when another
             # object was created, or created externally to Swift
             # REST API servicing (UFO use case).
-            msg = 'File object exists as a directory: %s' % self.data_file
-            raise AlreadyExistsAsDir(msg)
+            raise DiskFileError('DiskFile.put(): file creation failed since'
+                                ' the target, %s, already exists as a'
+                                ' directory' % self.data_file)
+
+        # Write out metadata before fsync() to ensure it is also forced to
+        # disk.
+        write_metadata(fd, metadata)
+
+        if not _relaxed_writes:
+            do_fsync(fd)
+            if X_CONTENT_LENGTH in metadata:
+                # Don't bother doing this before fsync in case the OS gets any
+                # ideas to issue partial writes.
+                fsize = int(metadata[X_CONTENT_LENGTH])
+                self.drop_cache(fd, 0, fsize)
+
+        # At this point we know that the object's full directory path exists,
+        # so we can just rename it directly without using Swift's
+        # swift.common.utils.renamer(), which makes the directory path and
+        # adds extra stat() calls.
+        data_file = os.path.join(self.put_datadir, self._obj)
+        while True:
+            try:
+                os.rename(self.tmppath, data_file)
+            except OSError as err:
+                if err.errno in (errno.ENOENT, errno.EIO):
+                    # FIXME: Why either of these two error conditions is
+                    # happening is unknown at this point. This might be a FUSE
+                    # issue of some sort or a possible race condition. So
+                    # let's sleep on it, and double check the environment
+                    # after a good nap.
+                    _random_sleep()
+                    # Tease out why this error occurred. The man page for
+                    # rename reads:
+                    #   "The link named by tmppath does not exist; or, a
+                    #    directory component in data_file does not exist;
+                    #    or, tmppath or data_file is an empty string."
+                    assert len(self.tmppath) > 0 and len(data_file) > 0
+                    tpstats = do_stat(self.tmppath)
+                    tfstats = do_fstat(fd)
+                    assert tfstats
+                    if not tpstats or tfstats.st_ino != tpstats.st_ino:
+                        # Temporary file name conflict
+                        raise DiskFileError('DiskFile.put(): temporary file,'
+                                            ' %s, was already renamed'
+                                            ' (targeted for %s)' % (
+                                                self.tmppath, data_file))
+                    else:
+                        # Data file target name now has a bad path!
+                        dfstats = do_stat(self.put_datadir)
+                        if not dfstats:
+                            raise DiskFileError('DiskFile.put(): path to'
+                                                ' object, %s, no longer exists'
+                                                ' (targeted for %s)' % (
+                                                    self.put_datadir,
+                                                    data_file))
+                        else:
+                            is_dir = stat.S_ISDIR(dfstats.st_mode)
+                            if not is_dir:
+                                raise DiskFileError('DiskFile.put(): path to'
+                                                    ' object, %s, no longer a'
+                                                    ' directory (targeted for'
+                                                    ' %s)' % (self.put_datadir,
+                                                              data_file))
+                            else:
+                                # Let's retry since everything looks okay
+                                logging.warn("DiskFile.put(): os.rename('%s',"
+                                             "'%s') initially failed (%s) but"
+                                             " a stat('%s') following that"
+                                             " succeeded: %r" % (
+                                                 self.tmppath, data_file,
+                                                 str(err), self.put_datadir,
+                                                 dfstats))
+                                continue
+                else:
+                    raise GlusterFileSystemOSError(
+                        err.errno, "%s, os.rename('%s', '%s')" % (
+                            err.strerror, self.tmppath, data_file))
+            else:
+                # Success!
+                break
+
+        # Avoid the unlink() system call as part of the mkstemp context cleanup
+        self.tmppath = None
 
-        write_metadata(self.tmppath, metadata)
-        if X_CONTENT_LENGTH in metadata:
-            self.drop_cache(fd, 0, int(metadata[X_CONTENT_LENGTH]))
-        do_fsync(fd)
-        if self._obj_path:
-            dir_objs = self._obj_path.split('/')
-            assert len(dir_objs) >= 1
-            tmp_path = self._container_path
-            for dir_name in dir_objs:
-                tmp_path = os.path.join(tmp_path, dir_name)
-                self._create_dir_object(tmp_path)
-
-        do_fchown(fd, self.uid, self.gid)
-        newpath = os.path.join(self.datadir, self._obj)
-        renamer(self.tmppath, newpath)
         self.metadata = metadata
-        self.data_file = newpath
         self.filter_metadata()
-        return
+
+        # Mark that it actually exists now
+        self.data_file = os.path.join(self.datadir, self._obj)
 
     def unlinkold(self, timestamp):
         """
@@ -313,7 +646,7 @@ class Gluster_DiskFile(DiskFile):
     def get_data_file_size(self):
         """
         Returns the os_path.getsize for the file.  Raises an exception if this
-        file does not match the Content-Length stored in the metadata. Or if
+        file does not match the Content-Length stored in the metadata, or if
         self.data_file does not exist.
 
         :returns: file size as an int
@@ -346,33 +679,94 @@ class Gluster_DiskFile(DiskFile):
             self.metadata.pop(X_OBJECT_TYPE)
 
     @contextmanager
-    def mkstemp(self):
-        """Contextmanager to make a temporary file."""
-
-        # Creating intermidiate directories and corresponding metadata.
-        # For optimization, check if the subdirectory already exists,
-        # if exists, then it means that it also has its metadata.
-        # Not checking for container, since the container should already
-        # exist for the call to come here.
-        if not os_path.exists(self.datadir):
-            path = self._container_path
-            subdir_list = self._obj_path.split(os.path.sep)
-            for i in range(len(subdir_list)):
-                path = os.path.join(path, subdir_list[i])
-                if not os_path.exists(path):
-                    self._create_dir_object(path)
-
-        tmpfile = '.' + self._obj + '.' + md5(self._obj +
-                  str(random.random())).hexdigest()
-
-        self.tmppath = os.path.join(self.datadir, tmpfile)
-        fd = do_open(self.tmppath, os.O_RDWR | os.O_CREAT | os.O_EXCL)
+    def mkstemp(self, size=None):
+        """
+        Contextmanager to make a temporary file, optionally of a specified
+        initial size.
+
+        For Gluster, we first optimistically create the temporary file using
+        the "rsync-friendly" .NAME.random naming. If we find that some path to
+        the file does not exist, we then create that path and then create the
+        temporary file again. If we get file name conflict, we'll retry using
+        different random suffixes 1,000 times before giving up.
+        """
+        data_file = os.path.join(self.put_datadir, self._obj)
+
+        # Assume the full directory path exists to the file already, and
+        # construct the proper name for the temporary file.
+        for i in range(0, 1000):
+            tmpfile = '.' + self._obj + '.' + md5(self._obj +
+                      str(random.random())).hexdigest()
+            tmppath = os.path.join(self.put_datadir, tmpfile)
+            try:
+                fd = do_open(tmppath,
+                             os.O_WRONLY | os.O_CREAT | os.O_EXCL | O_CLOEXEC)
+            except GlusterFileSystemOSError as gerr:
+                if gerr.errno == errno.EEXIST:
+                    # Retry with a different random number.
+                    continue
+                if gerr.errno == errno.EIO:
+                    # FIXME: Possible FUSE issue or race condition, let's
+                    # sleep on it and retry the operation.
+                    _random_sleep()
+                    logging.warn("DiskFile.mkstemp(): %s ... retrying in"
+                                 " 0.1 secs", gerr)
+                    continue
+                if gerr.errno != errno.ENOENT:
+                    # FIXME: Other cases we should handle?
+                    raise
+                if not self._obj_path:
+                    # No directory hierarchy and the create failed telling us
+                    # the container or volume directory does not exist. This
+                    # could be a FUSE issue or some race condition, so let's
+                    # sleep a bit and retry.
+                    _random_sleep()
+                    logging.warn("DiskFile.mkstemp(): %s ... retrying in"
+                                 " 0.1 secs", gerr)
+                    continue
+                if i != 0:
+                    # Got ENOENT after previously making the path. This could
+                    # also be a FUSE issue or some race condition, nap and
+                    # retry.
+                    _random_sleep()
+                    logging.warn("DiskFile.mkstemp(): %s ... retrying in"
+                                 " 0.1 secs" % gerr)
+                    continue
+                # It looks like the path to the object does not already exist
+                self._create_dir_object(self._obj_path)
+                continue
+            else:
+                break
+        else:
+            # We failed after 1,000 attempts to create the temporary file.
+            raise DiskFileError('DiskFile.mkstemp(): failed to successfully'
+                                ' create a temporary file without running'
+                                ' into a name conflict after 1,000 attempts'
+                                ' for: %s' % (data_file,))
+
+        self.tmppath = tmppath
+
         try:
+            # Ensure it is properly owned before we make it available.
+            do_fchown(fd, self.uid, self.gid)
+            if _preallocate and size:
+                # For XFS, fallocate() turns off speculative pre-allocation
+                # until a write is issued either to the last block of the file
+                # before the EOF or beyond the EOF. This means that we are
+                # less likely to fragment free space with pre-allocated
+                # extents that get truncated back to the known file size.
+                # However, this call also turns holes into allocated but
+                # unwritten extents, so that allocation occurs before the
+                # write, not during XFS writeback. This effectively defeats
+                # any allocation optimizations the filesystem can make at
+                # writeback time.
+                fallocate(fd, size)
             yield fd
         finally:
             try:
                 do_close(fd)
             except OSError:
                 pass
-            tmppath, self.tmppath = self.tmppath, None
-            do_unlink(tmppath)
+            if self.tmppath:
+                tmppath, self.tmppath = self.tmppath, None
+                do_unlink(tmppath)
diff --git a/gluster/swift/common/Glusterfs.py b/gluster/swift/common/Glusterfs.py
index 4506ef4..d1b456a 100644
--- a/gluster/swift/common/Glusterfs.py
+++ b/gluster/swift/common/Glusterfs.py
@@ -18,10 +18,13 @@ import fcntl
 import time
 import errno
 import logging
+import urllib
 
 from ConfigParser import ConfigParser, NoSectionError, NoOptionError
 from swift.common.utils import TRUE_VALUES, search_tree
-from gluster.swift.common.fs_utils import mkdirs
+from gluster.swift.common.fs_utils import do_ismount
+from gluster.swift.common.exceptions import GlusterfsException, \
+    FailureToMountError
 
 #
 # Read the fs.conf file once at startup (module load)
@@ -32,6 +35,8 @@ OBJECT_ONLY = True
 RUN_DIR = '/var/run/swift'
 SWIFT_DIR = '/etc/swift'
 _do_getsize = False
+_allow_mount_per_server = False
+
 if _fs_conf.read(os.path.join(SWIFT_DIR, 'fs.conf')):
     try:
         MOUNT_IP = _fs_conf.get('DEFAULT', 'mount_ip', MOUNT_IP)
@@ -55,6 +60,14 @@ if _fs_conf.read(os.path.join(SWIFT_DIR, 'fs.conf')):
     except (NoSectionError, NoOptionError):
         pass
 
+    try:
+        _allow_mount_per_server = _fs_conf.get('DEFAULT',
+                                               'allow_mount_per_server',
+                                               _allow_mount_per_server
+                                               ) in TRUE_VALUES
+    except (NoSectionError, NoOptionError):
+        pass
+
 NAME = 'glusterfs'
 
 
@@ -70,7 +83,97 @@ def _busy_wait(full_mount_path):
     return False
 
 
+def _get_unique_id():
+    # Each individual server will attempt to get a free lock file
+    # sequentially numbered, storing the pid of the holder of that
+    # file, That number represents the numbered mount point to use
+    # for its operations.
+    if not _allow_mount_per_server:
+        return 0
+    try:
+        os.mkdir(RUN_DIR)
+    except OSError as err:
+        if err.errno == errno.EEXIST:
+            pass
+    unique_id = 0
+    lock_file_template = os.path.join(RUN_DIR,
+                                      'swift.object-server-%03d.lock')
+    for i in range(1, 201):
+        lock_file = lock_file_template % i
+        fd = os.open(lock_file, os.O_CREAT | os.O_RDWR)
+        try:
+            fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        except IOError as ex:
+            os.close(fd)
+            if ex.errno in (errno.EACCES, errno.EAGAIN):
+                # This means that some other process has it locked, so they
+                # own the lock.
+                continue
+            raise
+        except:
+            os.close(fd)
+            raise
+        else:
+            # We got the lock, write our PID into it, but don't close the
+            # file, it will be closed when our process exists
+            os.lseek(fd, 0, os.SEEK_SET)
+            pid = str(os.getpid()) + '\n'
+            os.write(fd, pid)
+            unique_id = i
+            break
+    return unique_id
+
+
+_unique_id = None
+
+
+def _get_drive_mount_point_name(drive):
+    """
+    Get the GlusterFS mount point name to use for this worker for the target
+    drive name.
+
+    If unique is False, then we just map the drive directly to the mount point
+    name. If unique is True, then we determine a unique mount point name that
+    maps to our server PID.
+    """
+    if not _allow_mount_per_server:
+        # One-to-one mapping of drive to mount point name
+        mount_point = drive
+    else:
+        global _unique_id
+        if _unique_id is None:
+            _unique_id = _get_unique_id()
+        mount_point = ("%s_%03d" % (drive, _unique_id)) \
+            if _unique_id else drive
+    return mount_point
+
+
 def mount(root, drive):
+    """
+    Verify that the path to the device is a mount point and mounted.  This
+    allows us to fast fail on drives that have been unmounted because of
+    issues, and also prevents us for accidentally filling up the root
+    partition.
+
+    This method effectively replaces the swift.common.constraints.check_mount
+    method in behavior, adding the ability to auto-mount the volume, which is
+    dubious (FIXME).
+
+    :param root:  base path where the devices are mounted
+    :param drive: drive name to be checked
+    :returns: True if it is a valid mounted device, False otherwise
+    """
+    if not (urllib.quote_plus(drive) == drive):
+        return False
+
+    mount_point = _get_drive_mount_point_name(drive)
+    full_mount_path = os.path.join(root, mount_point)
+    if do_ismount(full_mount_path):
+        # Don't bother checking volume if it is already a mount point. Allows
+        # us to use local file systems for unit tests and some functional test
+        # environments to isolate behaviors from GlusterFS itself.
+        return True
+
     # FIXME: Possible thundering herd problem here
 
     el = _get_export_list()
@@ -81,15 +184,34 @@ def mount(root, drive):
         logging.error('No export found in %r matching drive, %s', el, drive)
         return False
 
-    # NOTE: root is typically the default value of /mnt/gluster-object
-    full_mount_path = os.path.join(root, drive)
-    if not os.path.isdir(full_mount_path):
-        mkdirs(full_mount_path)
+    try:
+        os.makedirs(full_mount_path)
+    except OSError as err:
+        if err.errno == errno.EEXIST:
+            pass
+        else:
+            logging.exception('Could not create mount path hierarchy:'
+                              ' %s' % full_mount_path)
+            return False
 
-    lck_file = os.path.join(RUN_DIR, '%s.lock' % drive)
+    mnt_cmd = 'mount -t glusterfs %s:%s %s' % (MOUNT_IP, export,
+                                               full_mount_path)
 
-    if not os.path.exists(RUN_DIR):
-        mkdirs(RUN_DIR)
+    if _allow_mount_per_server:
+        if os.system(mnt_cmd):
+            logging.exception('Mount failed %s' % (mnt_cmd))
+        return True
+
+    lck_file = os.path.join(RUN_DIR, '%s.lock' % mount_point)
+
+    try:
+        os.mkdir(RUN_DIR)
+    except OSError as err:
+        if err.errno == errno.EEXIST:
+            pass
+        else:
+            logging.exception('Could not create RUN_DIR: %s' % full_mount_path)
+            return False
 
     fd = os.open(lck_file, os.O_CREAT | os.O_RDWR)
     with os.fdopen(fd, 'r+b') as f:
@@ -100,12 +222,8 @@ def mount(root, drive):
                 # This means that some other process is mounting the
                 # filesystem, so wait for the mount process to complete
                 return _busy_wait(full_mount_path)
-            else:
-                raise ex
-        mnt_cmd = 'mount -t glusterfs %s:%s %s' % (MOUNT_IP, export,
-                                                   full_mount_path)
         if os.system(mnt_cmd) or not _busy_wait(full_mount_path):
-            logging.error('Mount failed %s: %s', NAME, mnt_cmd)
+            logging.error('Mount failed %s', mnt_cmd)
             return False
     return True
 
@@ -115,7 +233,8 @@ def unmount(full_mount_path):
 
     umnt_cmd = 'umount %s 2>> /dev/null' % full_mount_path
     if os.system(umnt_cmd):
-        logging.error('Unable to unmount %s %s' % (full_mount_path, NAME))
+        raise FailureToMountError(
+            'Unable to unmount %s' % (full_mount_path))
 
 
 def _get_export_list():
@@ -124,7 +243,8 @@ def _get_export_list():
     export_list = []
 
     if os.system(cmnd + ' >> /dev/null'):
-        logging.error('Getting volume info failed for %s', NAME)
+        logging.error('Getting volume info failed, make sure to have'
+                      ' passwordless ssh on %s', MOUNT_IP)
     else:
         fp = os.popen(cmnd)
         while True:
@@ -139,18 +259,25 @@ def _get_export_list():
 
 
 def get_mnt_point(vol_name, conf_dir=SWIFT_DIR, conf_file="object-server*"):
-    """Read the object-server's configuration file and return
-    the device value"""
+    """
+    Read the object-server's configuration file and return
+    the device value.
 
+    :param vol_name: target GlusterFS volume name
+    :param conf_dir: Swift configuration directory root
+    :param conf_file: configuration file name for which to search
+    :returns full path to given target volume name
+    :raises GlusterfsException if unable to fetch mount point root from
+            configuration files
+    """
     mnt_dir = ''
     conf_files = search_tree(conf_dir, conf_file, '.conf')
     if not conf_files:
-        raise Exception("Config file not found")
-
+        raise GlusterfsException("Config file, %s, in directory, %s, "
+                                 "not found" % (conf_file, conf_dir))
     _conf = ConfigParser()
     if _conf.read(conf_files[0]):
-        try:
-            mnt_dir = _conf.get('DEFAULT', 'devices', '')
-        except (NoSectionError, NoOptionError):
-            raise
+        mnt_dir = _conf.get('DEFAULT', 'devices', '')
         return os.path.join(mnt_dir, vol_name)
+    else:
+        raise GlusterfsException("Config file, %s, is empty" % conf_files[0])
diff --git a/gluster/swift/common/constraints.py b/gluster/swift/common/constraints.py
index ce1df31..9a4d57e 100644
--- a/gluster/swift/common/constraints.py
+++ b/gluster/swift/common/constraints.py
@@ -91,23 +91,8 @@ def gluster_check_object_creation(req, object_name):
 # Replace the original check object creation with ours
 swift.common.constraints.check_object_creation = gluster_check_object_creation
 
-# Save the original check mount
-__check_mount = swift.common.constraints.check_mount
-
-
-# Define our new one which invokes the original
-def gluster_check_mount(root, drive):
-    # FIXME: Potential performance optimization here to not call the original
-    # check mount which makes two stat calls. We could do what they do with
-    # just one.
-    if __check_mount(root, drive):
-        return True
-
-    return Glusterfs.mount(root, drive)
-
-
 # Replace the original check mount with ours
-swift.common.constraints.check_mount = gluster_check_mount
+swift.common.constraints.check_mount = Glusterfs.mount
 
 # Save the original Ring class
 __Ring = _ring.Ring
diff --git a/gluster/swift/common/exceptions.py b/gluster/swift/common/exceptions.py
index 75a95ec..ec74353 100644
--- a/gluster/swift/common/exceptions.py
+++ b/gluster/swift/common/exceptions.py
@@ -14,10 +14,22 @@
 # limitations under the License.
 
 
+class GlusterFileSystemOSError(OSError):
+    pass
+
+
+class GlusterFileSystemIOError(IOError):
+    pass
+
+
 class GlusterfsException(Exception):
     pass
 
 
+class FailureToMountError(GlusterfsException):
+    pass
+
+
 class FileOrDirNotFoundError(GlusterfsException):
     pass
 
@@ -28,3 +40,7 @@ class NotDirectoryError(GlusterfsException):
 
 class AlreadyExistsAsDir(GlusterfsException):
     pass
+
+
+class AlreadyExistsAsFile(GlusterfsException):
+    pass
diff --git a/gluster/swift/common/fs_utils.py b/gluster/swift/common/fs_utils.py
index 1f8415c..ea5c180 100644
--- a/gluster/swift/common/fs_utils.py
+++ b/gluster/swift/common/fs_utils.py
@@ -16,10 +16,13 @@
 import logging
 import os
 import errno
+import stat
+import random
 import os.path as os_path    # noqa
 from eventlet import tpool
+from eventlet import sleep
 from gluster.swift.common.exceptions import FileOrDirNotFoundError, \
-    NotDirectoryError
+    NotDirectoryError, GlusterFileSystemOSError, GlusterFileSystemIOError
 
 
 def do_walk(*args, **kwargs):
@@ -30,78 +33,191 @@ def do_write(fd, msg):
     try:
         cnt = os.write(fd, msg)
     except OSError as err:
-        logging.exception("Write failed, err: %s", str(err))
-        raise
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.write("%s", ...)' % (err.strerror, fd))
     return cnt
 
 
+def do_ismount(path):
+    """
+    Test whether a path is a mount point.
+
+    This is code hijacked from C Python 2.6.8, adapted to remove the extra
+    lstat() system call.
+    """
+    try:
+        s1 = os.lstat(path)
+    except os.error as err:
+        if err.errno == errno.ENOENT:
+            # It doesn't exist -- so not a mount point :-)
+            return False
+        else:
+            raise GlusterFileSystemOSError(
+                err.errno, '%s, os.lstat("%s")' % (err.strerror, path))
+
+    if stat.S_ISLNK(s1.st_mode):
+        # A symlink can never be a mount point
+        return False
+
+    try:
+        s2 = os.lstat(os.path.join(path, '..'))
+    except os.error as err:
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.lstat("%s")' % (err.strerror,
+                                               os.path.join(path, '..')))
+
+    dev1 = s1.st_dev
+    dev2 = s2.st_dev
+    if dev1 != dev2:
+        # path/.. on a different device as path
+        return True
+
+    ino1 = s1.st_ino
+    ino2 = s2.st_ino
+    if ino1 == ino2:
+        # path/.. is the same i-node as path
+        return True
+
+    return False
+
+
+def do_mkdir(path):
+    try:
+        os.mkdir(path)
+    except OSError as err:
+        if err.errno == errno.EEXIST:
+            logging.warn("fs_utils: os.mkdir - path %s already exists", path)
+        else:
+            raise GlusterFileSystemOSError(
+                err.errno, '%s, os.mkdir("%s")' % (err.strerror, path))
+
+
 def do_listdir(path):
     try:
         buf = os.listdir(path)
     except OSError as err:
-        logging.exception("Listdir failed on %s err: %s", path, err.strerror)
-        raise
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.listdir("%s")' % (err.strerror, path))
     return buf
 
 
+def dir_empty(path):
+    """
+    Return true if directory is empty (or does not exist), false otherwise.
+
+    :param path: Directory path
+    :returns: True/False
+    """
+    try:
+        files = do_listdir(path)
+        return not files
+    except GlusterFileSystemOSError as err:
+        if err.errno == errno.ENOENT:
+            raise FileOrDirNotFoundError()
+        if err.errno == errno.ENOTDIR:
+            raise NotDirectoryError()
+        raise
+
+
+def do_rmdir(path):
+    try:
+        os.rmdir(path)
+    except OSError as err:
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.rmdir("%s")' % (err.strerror, path))
+
+
 def do_chown(path, uid, gid):
     try:
         os.chown(path, uid, gid)
     except OSError as err:
-        logging.exception("Chown failed on %s err: %s", path, err.strerror)
-        raise
-    return True
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.chown("%s", %s, %s)' % (
+                err.strerror, path, uid, gid))
 
 
 def do_fchown(fd, uid, gid):
     try:
         os.fchown(fd, uid, gid)
     except OSError as err:
-        logging.exception("fchown failed on %d err: %s", fd, err.strerror)
-        raise
-    return True
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.fchown(%s, %s, %s)' % (
+                err.strerror, fd, uid, gid))
+
+
+_STAT_ATTEMPTS = 10
 
 
 def do_stat(path):
+    serr = None
+    for i in range(0, _STAT_ATTEMPTS):
+        try:
+            stats = os.stat(path)
+        except OSError as err:
+            if err.errno == errno.EIO:
+                # Retry EIO assuming it is a transient error from FUSE after a
+                # short random sleep
+                serr = err
+                sleep(random.uniform(0.001, 0.005))
+                continue
+            if err.errno == errno.ENOENT:
+                stats = None
+            else:
+                raise GlusterFileSystemOSError(
+                    err.errno, '%s, os.stat("%s")[%d attempts]' % (
+                        err.strerror, path, i))
+        if i > 0:
+            logging.warn("fs_utils.do_stat():"
+                         " os.stat('%s') retried %d times (%s)",
+                         path, i, 'success' if stats else 'failure')
+        return stats
+    else:
+        raise GlusterFileSystemOSError(
+            serr.errno, '%s, os.stat("%s")[%d attempts]' % (
+                serr.strerror, path, _STAT_ATTEMPTS))
+
+
+def do_fstat(fd):
     try:
-        #Check for fd.
-        if isinstance(path, int):
-            buf = os.fstat(path)
-        else:
-            buf = os.stat(path)
+        stats = os.fstat(fd)
     except OSError as err:
-        logging.exception("Stat failed on %s err: %s", path, err.strerror)
-        raise
-    return buf
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.fstat(%s)' % (err.strerror, fd))
+    return stats
 
 
-def do_open(path, mode):
-    if isinstance(mode, int):
+def do_open(path, flags, **kwargs):
+    if isinstance(flags, int):
         try:
-            fd = os.open(path, mode)
+            fd = os.open(path, flags, **kwargs)
         except OSError as err:
-            logging.exception("Open failed on %s err: %s", path, str(err))
-            raise
+            raise GlusterFileSystemOSError(
+                err.errno, '%s, os.open("%s", %x, %r)' % (
+                    err.strerror, path, flags, kwargs))
+        return fd
     else:
         try:
-            fd = open(path, mode)
+            fp = open(path, flags, **kwargs)
         except IOError as err:
-            logging.exception("Open failed on %s err: %s", path, str(err))
-            raise
-    return fd
+            raise GlusterFileSystemIOError(
+                err.errno, '%s, open("%s", %s, %r)' % (
+                    err.strerror, path, flags, kwargs))
+        return fp
 
 
 def do_close(fd):
-    #fd could be file or int type.
-    try:
-        if isinstance(fd, int):
-            os.close(fd)
-        else:
+    if isinstance(fd, file):
+        try:
             fd.close()
-    except OSError as err:
-        logging.exception("Close failed on %s err: %s", fd, err.strerror)
-        raise
-    return True
+        except IOError as err:
+            raise GlusterFileSystemIOError(
+                err.errno, '%s, os.close(%s)' % (err.strerror, fd))
+    else:
+        try:
+            os.close(fd)
+        except OSError as err:
+            raise GlusterFileSystemOSError(
+                err.errno, '%s, os.close(%s)' % (err.strerror, fd))
 
 
 def do_unlink(path, log=True):
@@ -109,21 +225,28 @@ def do_unlink(path, log=True):
         os.unlink(path)
     except OSError as err:
         if err.errno != errno.ENOENT:
-            if log:
-                logging.exception("Unlink failed on %s err: %s",
-                                  path, err.strerror)
-            raise
-    return True
+            raise GlusterFileSystemOSError(
+                err.errno, '%s, os.unlink("%s")' % (err.strerror, path))
+        elif log:
+            logging.warn("fs_utils: os.unlink failed on non-existent path: %s",
+                         path)
 
 
 def do_rename(old_path, new_path):
     try:
         os.rename(old_path, new_path)
     except OSError as err:
-        logging.exception("Rename failed on %s to %s  err: %s",
-                          old_path, new_path, err.strerror)
-        raise
-    return True
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.rename("%s", "%s")' % (
+                err.strerror, old_path, new_path))
+
+
+def do_fsync(fd):
+    try:
+        tpool.execute(os.fsync, fd)
+    except OSError as err:
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.fsync("%s")' % (err.strerror, fd))
 
 
 def mkdirs(path):
@@ -133,47 +256,10 @@ def mkdirs(path):
 
     :param path: path to create
     """
-    if not os.path.isdir(path):
-        try:
-            os.makedirs(path)
-        except OSError as err:
-            if err.errno != errno.EEXIST:
-                logging.exception("Makedirs failed on %s err: %s",
-                                  path, err.strerror)
-                raise
-    return True
-
-
-def dir_empty(path):
-    """
-    Return true if directory/container is empty.
-    :param path: Directory path.
-    :returns: True/False.
-    """
-    if os.path.isdir(path):
-        files = do_listdir(path)
-        return not files
-    elif not os.path.exists(path):
-        raise FileOrDirNotFoundError()
-    raise NotDirectoryError()
-
-
-def rmdirs(path):
-    if not os.path.isdir(path):
-        return False
     try:
-        os.rmdir(path)
+        os.makedirs(path)
     except OSError as err:
-        if err.errno != errno.ENOENT:
-            logging.error("rmdirs failed on %s, err: %s", path, err.strerror)
-            return False
-    return True
-
-
-def do_fsync(fd):
-    try:
-        tpool.execute(os.fsync, fd)
-    except OSError as err:
-        logging.exception("fsync failed with err: %s", err.strerror)
-        raise
-    return True
+        if err.errno == errno.EEXIST and os.path.isdir(path):
+            return
+        raise GlusterFileSystemOSError(
+            err.errno, '%s, os.makedirs("%s")' % (err.strerror, path))
diff --git a/gluster/swift/common/utils.py b/gluster/swift/common/utils.py
index 5547ea4..6503644 100644
--- a/gluster/swift/common/utils.py
+++ b/gluster/swift/common/utils.py
@@ -24,9 +24,8 @@ from eventlet import sleep
 import cPickle as pickle
 from swift.common.utils import normalize_timestamp
 from gluster.swift.common.fs_utils import do_rename, do_fsync, os_path, \
-    do_stat, do_listdir, do_walk, dir_empty, rmdirs
+    do_stat, do_listdir, do_walk, do_rmdir
 from gluster.swift.common import Glusterfs
-from gluster.swift.common.exceptions import FileOrDirNotFoundError
 
 X_CONTENT_TYPE = 'Content-Type'
 X_CONTENT_LENGTH = 'Content-Length'
@@ -56,11 +55,23 @@ PICKLE_PROTOCOL = 2
 CHUNK_SIZE = 65536
 
 
-def read_metadata(path):
+class GlusterFileSystemOSError(OSError):
+    # Having our own class means the name will show up in the stack traces
+    # recorded in the log files.
+    pass
+
+
+class GlusterFileSystemIOError(IOError):
+    # Having our own class means the name will show up in the stack traces
+    # recorded in the log files.
+    pass
+
+
+def read_metadata(path_or_fd):
     """
     Helper function to read the pickled metadata from a File/Directory.
 
-    :param path: File/Directory to read metadata from.
+    :param path_or_fd: File/Directory path or fd from which to read metadata.
 
     :returns: dictionary of metadata
     """
@@ -69,7 +80,7 @@ def read_metadata(path):
     key = 0
     while metadata is None:
         try:
-            metadata_s += xattr.getxattr(path,
+            metadata_s += xattr.getxattr(path_or_fd,
                                          '%s%s' % (METADATA_KEY, (key or '')))
         except IOError as err:
             if err.errno == errno.ENODATA:
@@ -79,18 +90,17 @@ def read_metadata(path):
                     # unpickle operation, we consider the metadata lost, and
                     # drop the existing data so that the internal state can be
                     # recreated.
-                    clean_metadata(path)
+                    clean_metadata(path_or_fd)
                 # We either could not find any metadata key, or we could find
                 # some keys, but were not successful in performing the
                 # unpickling (missing keys perhaps)? Either way, just report
                 # to the caller we have no metadata.
                 metadata = {}
             else:
-                logging.exception("xattr.getxattr failed on %s key %s err: %s",
-                                  path, key, str(err))
                 # Note that we don't touch the keys on errors fetching the
                 # data since it could be a transient state.
-                raise
+                raise GlusterFileSystemIOError(
+                    err.errno, 'xattr.getxattr("%s", %s)' % (path_or_fd, key))
         else:
             try:
                 # If this key provides all or the remaining part of the pickle
@@ -109,38 +119,39 @@ def read_metadata(path):
     return metadata
 
 
-def write_metadata(path, metadata):
+def write_metadata(path_or_fd, metadata):
     """
     Helper function to write pickled metadata for a File/Directory.
 
-    :param path: File/Directory path to write the metadata
-    :param metadata: dictionary to metadata write
+    :param path_or_fd: File/Directory path or fd to write the metadata
+    :param metadata: dictionary of metadata write
     """
     assert isinstance(metadata, dict)
     metastr = pickle.dumps(metadata, PICKLE_PROTOCOL)
     key = 0
     while metastr:
         try:
-            xattr.setxattr(path,
+            xattr.setxattr(path_or_fd,
                            '%s%s' % (METADATA_KEY, key or ''),
                            metastr[:MAX_XATTR_SIZE])
         except IOError as err:
-            logging.exception("setxattr failed on %s key %s err: %s",
-                              path, key, str(err))
-            raise
+            raise GlusterFileSystemIOError(
+                err.errno,
+                'xattr.setxattr("%s", %s, metastr)' % (path_or_fd, key))
         metastr = metastr[MAX_XATTR_SIZE:]
         key += 1
 
 
-def clean_metadata(path):
+def clean_metadata(path_or_fd):
     key = 0
     while True:
         try:
-            xattr.removexattr(path, '%s%s' % (METADATA_KEY, (key or '')))
+            xattr.removexattr(path_or_fd, '%s%s' % (METADATA_KEY, (key or '')))
         except IOError as err:
             if err.errno == errno.ENODATA:
                 break
-            raise
+            raise GlusterFileSystemIOError(
+                err.errno, 'xattr.removexattr("%s", %s)' % (path_or_fd, key))
         key += 1
 
 
@@ -150,9 +161,9 @@ def check_user_xattr(path):
     try:
         xattr.setxattr(path, 'user.test.key1', 'value1')
     except IOError as err:
-        logging.exception("check_user_xattr: set failed on %s err: %s",
-                          path, str(err))
-        raise
+        raise GlusterFileSystemIOError(
+            err.errno,
+            'xattr.setxattr("%s", "user.test.key1", "value1")' % (path,))
     try:
         xattr.removexattr(path, 'user.test.key1')
     except IOError as err:
@@ -245,7 +256,7 @@ def _update_list(path, cont_path, src_list, reg_file=True, object_count=0,
 
         object_count += 1
 
-        if Glusterfs._do_getsize and reg_file:
+        if reg_file and Glusterfs._do_getsize:
             bytes_used += os_path.getsize(os.path.join(path, obj_name))
             sleep()
 
@@ -254,7 +265,6 @@ def _update_list(path, cont_path, src_list, reg_file=True, object_count=0,
 
 def update_list(path, cont_path, dirs=[], files=[], object_count=0,
                 bytes_used=0, obj_list=[]):
-
     if files:
         object_count, bytes_used = _update_list(path, cont_path, files, True,
                                                 object_count, bytes_used,
@@ -266,22 +276,13 @@ def update_list(path, cont_path, dirs=[], files=[], object_count=0,
     return object_count, bytes_used
 
 
-class ContainerDetails(object):
-    def __init__(self, bytes_used, object_count, obj_list, dir_list):
-        self.bytes_used = bytes_used
-        self.object_count = object_count
-        self.obj_list = obj_list
-        self.dir_list = dir_list
-
-
-def _get_container_details_from_fs(cont_path):
+def get_container_details(cont_path):
     """
     get container details by traversing the filesystem
     """
     bytes_used = 0
     object_count = 0
     obj_list = []
-    dir_list = []
 
     if os_path.isdir(cont_path):
         for (path, dirs, files) in do_walk(cont_path):
@@ -289,36 +290,12 @@ def _get_container_details_from_fs(cont_path):
                                                    files, object_count,
                                                    bytes_used, obj_list)
 
-            dir_list.append((path, do_stat(path).st_mtime))
             sleep()
 
-    return ContainerDetails(bytes_used, object_count, obj_list, dir_list)
+    return obj_list, object_count, bytes_used
 
 
-def get_container_details(cont_path):
-    """
-    Return object_list, object_count and bytes_used.
-    """
-    cd = _get_container_details_from_fs(cont_path)
-
-    return cd.obj_list, cd.object_count, cd.bytes_used
-
-
-class AccountDetails(object):
-    """ A simple class to store the three pieces of information associated
-        with an account:
-
-        1. The last known modification time
-        2. The count of containers in the following list
-        3. The list of containers
-    """
-    def __init__(self, mtime, container_count, container_list):
-        self.mtime = mtime
-        self.container_count = container_count
-        self.container_list = container_list
-
-
-def _get_account_details_from_fs(acc_path):
+def get_account_details(acc_path):
     """
     Return container_list and container_count.
     """
@@ -326,35 +303,40 @@ def _get_account_details_from_fs(acc_path):
     container_count = 0
 
     acc_stats = do_stat(acc_path)
-    is_dir = stat.S_ISDIR(acc_stats.st_mode)
-    if is_dir:
-        for name in do_listdir(acc_path):
-            if name.lower() == TEMP_DIR \
-                    or name.lower() == ASYNCDIR \
-                    or not os_path.isdir(os.path.join(acc_path, name)):
-                continue
-            container_count += 1
-            container_list.append(name)
+    if acc_stats:
+        is_dir = stat.S_ISDIR(acc_stats.st_mode)
+        if is_dir:
+            for name in do_listdir(acc_path):
+                if name.lower() == TEMP_DIR \
+                        or name.lower() == ASYNCDIR \
+                        or not os_path.isdir(os.path.join(acc_path, name)):
+                    continue
+                container_count += 1
+                container_list.append(name)
 
-    return AccountDetails(acc_stats.st_mtime, container_count, container_list)
+    return container_list, container_count
 
 
-def get_account_details(acc_path):
-    """
-    Return container_list and container_count.
+def _get_etag(path):
     """
-    ad = _get_account_details_from_fs(acc_path)
+    FIXME: It would be great to have a translator that returns the md5sum() of
+    the file as an xattr that can be simply fetched.
 
-    return ad.container_list, ad.container_count
-
-
-def _get_etag(path):
+    Since we don't have that we should yield after each chunk read and
+    computed so that we don't consume the worker thread.
+    """
     etag = md5()
     with open(path, 'rb') as fp:
         while True:
             chunk = fp.read(CHUNK_SIZE)
             if chunk:
                 etag.update(chunk)
+                if len(chunk) >= CHUNK_SIZE:
+                    # It is likely that we have more data to be read from the
+                    # file. Yield the co-routine cooperatively to avoid
+                    # consuming the worker during md5sum() calculations on
+                    # large files.
+                    sleep()
             else:
                 break
     return etag.hexdigest()
@@ -364,14 +346,11 @@ def get_object_metadata(obj_path):
     """
     Return metadata of object.
     """
-    try:
-        stats = do_stat(obj_path)
-    except OSError as e:
-        if e.errno != errno.ENOENT:
-            raise
+    stats = do_stat(obj_path)
+    if not stats:
         metadata = {}
     else:
-        is_dir = (stats.st_mode & 0040000) != 0
+        is_dir = stat.S_ISDIR(stats.st_mode)
         metadata = {
             X_TYPE: OBJECT,
             X_TIMESTAMP: normalize_timestamp(stats.st_ctime),
@@ -444,12 +423,14 @@ def create_object_metadata(obj_path):
 
 def create_container_metadata(cont_path):
     metadata = get_container_metadata(cont_path)
-    return restore_metadata(cont_path, metadata)
+    rmd = restore_metadata(cont_path, metadata)
+    return rmd
 
 
 def create_account_metadata(acc_path):
     metadata = get_account_metadata(acc_path)
-    return restore_metadata(acc_path, metadata)
+    rmd = restore_metadata(acc_path, metadata)
+    return rmd
 
 
 def write_pickle(obj, dest, tmp=None, pickle_protocol=0):
@@ -498,42 +479,71 @@ def dir_is_object(metadata):
 
 def rmobjdir(dir_path):
     """
-    Removes the directory as long as there are
-    no objects stored in it.  This works for containers also.
+    Removes the directory as long as there are no objects stored in it. This
+    works for containers also.
     """
     try:
-        if dir_empty(dir_path):
-            rmdirs(dir_path)
-            return True
-    except FileOrDirNotFoundError:
-        # No such directory exists
-        return False
+        do_rmdir(dir_path)
+    except OSError as err:
+        if err.errno == errno.ENOENT:
+            # No such directory exists
+            return False
+        if err.errno != errno.ENOTEMPTY:
+            raise
+        # Handle this non-empty directories below.
+    else:
+        return True
 
+    # We have a directory that is not empty, walk it to see if it is filled
+    # with empty sub-directories that are not user created objects
+    # (gratuitously created as a result of other object creations).
     for (path, dirs, files) in do_walk(dir_path, topdown=False):
         for directory in dirs:
             fullpath = os.path.join(path, directory)
-            metadata = read_metadata(fullpath)
 
-            if not dir_is_object(metadata):
-                # Directory is not an object created by the caller
-                # so we can go ahead and delete it.
-                try:
-                    if dir_empty(fullpath):
-                        rmdirs(fullpath)
-                    else:
-                        # Non-object dir is not empty!
-                        return False
-                except FileOrDirNotFoundError:
-                    # No such dir!
-                    return False
+            try:
+                metadata = read_metadata(fullpath)
+            except OSError as err:
+                if err.errno == errno.ENOENT:
+                    # Ignore removal from another entity.
+                    continue
+                raise
             else:
-                # Wait, this is an object created by the caller
-                # We cannot delete
-                return False
-    rmdirs(dir_path)
-    return True
+                if dir_is_object(metadata):
+                    # Wait, this is an object created by the caller
+                    # We cannot delete
+                    return False
+
+            # Directory is not an object created by the caller
+            # so we can go ahead and delete it.
+            try:
+                do_rmdir(fullpath)
+            except OSError as err:
+                if err.errno == errno.ENOTEMPTY:
+                    # Directory is not empty, it might have objects in it
+                    return False
+                if err.errno == errno.ENOENT:
+                    # No such directory exists, already removed, ignore
+                    continue
+                raise
+
+    try:
+        do_rmdir(dir_path)
+    except OSError as err:
+        if err.errno == errno.ENOTEMPTY:
+            # Directory is not empty, race with object creation
+            return False
+        if err.errno == errno.ENOENT:
+            # No such directory exists, already removed, ignore
+            return True
+        raise
+    else:
+        return True
 
 
 # Over-ride Swift's utils.write_pickle with ours
+#
+# FIXME: Is this even invoked anymore given we don't perform container or
+# account updates?
 import swift.common.utils
 swift.common.utils.write_pickle = write_pickle