Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1606 insertions, 0 deletions

diff --git a/src/libradosstriper/RadosStriperImpl.cc b/src/libradosstriper/RadosStriperImpl.cc
new file mode 100644
index 000000000..60fafd463
--- /dev/null
+++ b/src/libradosstriper/RadosStriperImpl.cc
@@ -0,0 +1,1606 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2014 Sebastien Ponce <sebastien.ponce@cern.ch>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#include <boost/algorithm/string/replace.hpp>
+
+#include "libradosstriper/RadosStriperImpl.h"
+
+#include <errno.h>
+
+#include <sstream>
+#include <iomanip>
+#include <algorithm>
+
+#include "include/types.h"
+#include "include/uuid.h"
+#include "include/ceph_fs.h"
+#include "common/dout.h"
+#include "common/strtol.h"
+#include "common/RefCountedObj.h"
+#include "osdc/Striper.h"
+#include "librados/AioCompletionImpl.h"
+#include <cls/lock/cls_lock_client.h>
+
+/*
+ * This file contents the actual implementation of the rados striped objects interface.
+ *
+ * Striped objects are stored in rados in a set of regular rados objects, after their
+ * content has been striped using the osdc/Striper interface.
+ *
+ * The external attributes of the striped object are mapped to the attributes of the
+ * first underlying object. This first object has a set of extra external attributes
+ * storing the layout of the striped object for future read back. These attributes are :
+ *  - striper.layout.object_size : the size of rados objects used.
+ *                                 Must be a multiple of striper.layout.stripe_unit
+ *  - striper.layout.stripe_unit : the size of a stripe unit
+ *  - striper.layout.stripe_count : the number of stripes used
+ *  - striper.size : total striped object size
+ *
+ * In general operations on striped objects are not atomic.
+ * However, a certain number of safety guards have been put to make the interface closer
+ * to atomicity :
+ *  - each data operation takes a shared lock on the first rados object for the
+ *    whole time of the operation
+ *  - the remove and trunc operations take an exclusive lock on the first rados object
+ *    for the whole time of the operation
+ * This makes sure that no removal/truncation of a striped object occurs while
+ * data operations are happening and vice versa. It thus makes sure that the layout
+ * of a striped object does not change during data operation, which is essential for
+ * data consistency.
+ *
+ * Still the writing to a striped object is not atomic. This means in particular that
+ * the size of an object may not be in sync with its content at all times.
+ * As the size is always guaranteed to be updated first and in an atomic way, and as
+ * sparse striped objects are supported (see below), what will typically happen is
+ * that a reader that comes too soon after a write will read 0s instead of the actual
+ * data.
+ *
+ * Note that remove handles the pieces of the striped object in reverse order,
+ * so that the head object is removed last, making the completion of the deletion atomic.
+ *
+ * Striped objects can be sparse, typically in case data was written at the end of the
+ * striped object only. In such a case, some rados objects constituing the striped object
+ * may be missing. Other can be partial (only the beginning will have data)
+ * When dealing with such sparse striped files, missing objects are detected and
+ * considered as full of 0s. They are however not created until real data is written
+ * to them.
+ *
+ * There are a number of missing features/improvements that could be implemented.
+ * Here are some ideas :
+ *    - implementation of missing entry points (compared to rados)
+ *      In particular : clone_range, sparse_read, exec, aio_flush_async, tmaps, omaps, ...
+ *
+ */
+
+#define dout_subsys ceph_subsys_rados
+#undef dout_prefix
+#define dout_prefix *_dout << "libradosstriper: "
+
+/// size of xattr buffer
+#define XATTR_BUFFER_SIZE 32
+
+/// names of the different xattr entries
+#define XATTR_LAYOUT_STRIPE_UNIT "striper.layout.stripe_unit"
+#define XATTR_LAYOUT_STRIPE_COUNT "striper.layout.stripe_count"
+#define XATTR_LAYOUT_OBJECT_SIZE "striper.layout.object_size"
+#define XATTR_SIZE "striper.size"
+#define LOCK_PREFIX "lock."
+
+/// name of the lock used on objects to ensure layout stability during IO
+#define RADOS_LOCK_NAME "striper.lock"
+
+/// format of the extension of rados objects created for a given striped object
+#define RADOS_OBJECT_EXTENSION_FORMAT ".%016llx"
+
+/// default object layout
+struct ceph_file_layout default_file_layout = {
+  init_le32(1<<22),	// fl_stripe_unit
+  init_le32(1),		// fl_stripe_count
+  init_le32(1<<22),	// fl_object_size
+  init_le32(0),		// fl_cas_hash
+  init_le32(0),		// fl_object_stripe_unit
+  init_le32(-1),	// fl_unused
+  init_le32(-1),	// fl_pg_pool
+};
+
+using libradosstriper::MultiAioCompletionImplPtr;
+
+namespace {
+
+///////////////////////// CompletionData /////////////////////////////
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous operations
+ */
+struct CompletionData : RefCountedObject {
+  /// complete method
+  void complete(int r);
+  /// striper to be used to handle the write completion
+  libradosstriper::RadosStriperImpl *m_striper;
+  /// striped object concerned by the write operation
+  std::string m_soid;
+  /// shared lock to be released at completion
+  std::string m_lockCookie;
+  /// completion handler
+  librados::IoCtxImpl::C_aio_Complete *m_ack;
+protected:
+  CompletionData(libradosstriper::RadosStriperImpl * striper,
+		 const std::string& soid,
+		 const std::string& lockCookie,
+		 librados::AioCompletionImpl *userCompletion = 0);
+  ~CompletionData() override;
+
+};
+
+CompletionData::CompletionData
+(libradosstriper::RadosStriperImpl* striper,
+ const std::string& soid,
+ const std::string& lockCookie,
+ librados::AioCompletionImpl *userCompletion) :
+  RefCountedObject(striper->cct()),
+  m_striper(striper), m_soid(soid), m_lockCookie(lockCookie), m_ack(0) {
+  m_striper->get();
+  if (userCompletion) {
+    m_ack = new librados::IoCtxImpl::C_aio_Complete(userCompletion);
+    userCompletion->io = striper->m_ioCtxImpl;
+  }
+}
+
+CompletionData::~CompletionData() {
+  if (m_ack) delete m_ack;
+  m_striper->put();
+}
+
+void CompletionData::complete(int r) {
+  if (m_ack) m_ack->finish(r);
+}
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous read operations
+ */
+struct ReadCompletionData : CompletionData {
+  /// bufferlist containing final result
+  bufferlist* m_bl;
+  /// extents that will be read
+  std::vector<ObjectExtent>* m_extents;
+  /// intermediate results
+  std::vector<bufferlist>* m_resultbl;
+  /// return code of read completion, to be remembered until unlocking happened
+  int m_readRc;
+  /// completion object for the unlocking of the striped object at the end of the read
+  librados::AioCompletion *m_unlockCompletion;
+  /// complete method for when reading is over
+  void complete_read(int r);
+  /// complete method for when object is unlocked
+  void complete_unlock(int r);
+
+private:
+  FRIEND_MAKE_REF(ReadCompletionData);
+  ReadCompletionData(libradosstriper::RadosStriperImpl * striper,
+		     const std::string& soid,
+		     const std::string& lockCookie,
+		     librados::AioCompletionImpl *userCompletion,
+		     bufferlist* bl,
+		     std::vector<ObjectExtent>* extents,
+		     std::vector<bufferlist>* resultbl);
+  ~ReadCompletionData() override;
+};
+
+ReadCompletionData::ReadCompletionData
+(libradosstriper::RadosStriperImpl* striper,
+ const std::string& soid,
+ const std::string& lockCookie,
+ librados::AioCompletionImpl *userCompletion,
+ bufferlist* bl,
+ std::vector<ObjectExtent>* extents,
+ std::vector<bufferlist>* resultbl) :
+  CompletionData(striper, soid, lockCookie, userCompletion),
+  m_bl(bl), m_extents(extents), m_resultbl(resultbl), m_readRc(0),
+  m_unlockCompletion(0) {}
+
+ReadCompletionData::~ReadCompletionData() {
+  m_unlockCompletion->release();
+  delete m_extents;
+  delete m_resultbl;
+}
+
+void ReadCompletionData::complete_read(int r) {
+  // gather data into final buffer
+  Striper::StripedReadResult readResult;
+  vector<bufferlist>::iterator bit = m_resultbl->begin();
+  for (vector<ObjectExtent>::iterator eit = m_extents->begin();
+       eit != m_extents->end();
+       ++eit, ++bit) {
+    readResult.add_partial_result(m_striper->cct(), *bit, eit->buffer_extents);
+  }
+  m_bl->clear();
+  readResult.assemble_result(m_striper->cct(), *m_bl, true);
+  // Remember return code
+  m_readRc = r;
+}
+
+void ReadCompletionData::complete_unlock(int r) {
+  // call parent's completion method
+  // Note that we ignore the return code of the unlock as we cannot do much about it
+  CompletionData::complete(m_readRc?m_readRc:m_bl->length());
+}
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous write operations
+ */
+struct WriteCompletionData : CompletionData {
+  /// safe completion handler
+  librados::IoCtxImpl::C_aio_Complete *m_safe;
+  /// completion object for the unlocking of the striped object at the end of the write
+  librados::AioCompletion *m_unlockCompletion;
+  /// return code of write completion, to be remembered until unlocking happened
+  int m_writeRc;
+  /// complete method for when writing is over
+  void complete_write(int r);
+  /// complete method for when object is unlocked
+  void complete_unlock(int r);
+  /// safe method
+  void safe(int r);
+private:
+  FRIEND_MAKE_REF(WriteCompletionData);
+  /// constructor
+  WriteCompletionData(libradosstriper::RadosStriperImpl * striper,
+		      const std::string& soid,
+		      const std::string& lockCookie,
+		      librados::AioCompletionImpl *userCompletion);
+  /// destructor
+  ~WriteCompletionData() override;
+};
+
+WriteCompletionData::WriteCompletionData
+(libradosstriper::RadosStriperImpl* striper,
+ const std::string& soid,
+ const std::string& lockCookie,
+ librados::AioCompletionImpl *userCompletion) :
+  CompletionData(striper, soid, lockCookie, userCompletion),
+  m_safe(0), m_unlockCompletion(0), m_writeRc(0) {
+  if (userCompletion) {
+    m_safe = new librados::IoCtxImpl::C_aio_Complete(userCompletion);
+  }
+}
+
+WriteCompletionData::~WriteCompletionData() {
+  m_unlockCompletion->release();
+  if (m_safe) delete m_safe;
+}
+
+void WriteCompletionData::complete_unlock(int r) {
+  // call parent's completion method
+  // Note that we ignore the return code of the unlock as we cannot do much about it
+  CompletionData::complete(m_writeRc);
+}
+
+void WriteCompletionData::complete_write(int r) {
+  // Remember return code
+  m_writeRc = r;
+}
+
+void WriteCompletionData::safe(int r) {
+  if (m_safe) m_safe->finish(r);
+}
+
+struct RemoveCompletionData : CompletionData {
+  /// removal flags
+  int flags;
+
+private:
+  FRIEND_MAKE_REF(RemoveCompletionData);
+  /**
+   * constructor
+   * note that the constructed object will take ownership of the lock
+   */
+  RemoveCompletionData(libradosstriper::RadosStriperImpl * striper,
+		       const std::string& soid,
+		       const std::string& lockCookie,
+		       librados::AioCompletionImpl *userCompletion,
+		       int flags = 0) :
+  CompletionData(striper, soid, lockCookie, userCompletion), flags(flags) {}
+};
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous truncate operations
+ */
+struct TruncateCompletionData : RefCountedObject {
+  /// striper to be used
+  libradosstriper::RadosStriperImpl *m_striper;
+  /// striped object concerned by the truncate operation
+  std::string m_soid;
+  /// the final size of the truncated object
+  uint64_t m_size;
+
+private:
+  FRIEND_MAKE_REF(TruncateCompletionData);
+  /// constructor
+  TruncateCompletionData(libradosstriper::RadosStriperImpl* striper,
+			 const std::string& soid,
+			 uint64_t size) :
+    RefCountedObject(striper->cct()),
+    m_striper(striper), m_soid(soid), m_size(size) {
+    m_striper->get();
+  }
+  /// destructor
+  ~TruncateCompletionData() override {
+    m_striper->put();
+  }
+};
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous read operations of a Rados File
+ */
+struct RadosReadCompletionData : RefCountedObject {
+  /// the multi asynch io completion object to be used
+  MultiAioCompletionImplPtr m_multiAioCompl;
+  /// the expected number of bytes
+  uint64_t m_expectedBytes;
+  /// the bufferlist object where data have been written
+  bufferlist *m_bl;
+
+private:
+  FRIEND_MAKE_REF(RadosReadCompletionData);
+  /// constructor
+  RadosReadCompletionData(MultiAioCompletionImplPtr multiAioCompl,
+			  uint64_t expectedBytes,
+			  bufferlist *bl,
+			  CephContext *context) :
+    RefCountedObject(context),
+    m_multiAioCompl(multiAioCompl), m_expectedBytes(expectedBytes), m_bl(bl) {}
+};
+
+/**
+ * struct handling (most of) the data needed to pass to the call back
+ * function in asynchronous stat operations.
+ * Inherited by the actual type for adding time information in different
+ * versions (time_t or struct timespec)
+ */
+struct BasicStatCompletionData : CompletionData {
+  // MultiAioCompletionImpl used to handle the double aysnc
+  // call in the back (stat + getxattr)
+  libradosstriper::MultiAioCompletionImpl *m_multiCompletion;
+  // where to store the size of first objct
+  // this will be ignored but we need a place to store it when
+  // async stat is called
+  uint64_t m_objectSize;
+  // where to store the file size
+  uint64_t *m_psize;
+  /// the bufferlist object used for the getxattr call
+  bufferlist m_bl;
+  /// return code of the stat
+  int m_statRC;
+  /// return code of the getxattr
+  int m_getxattrRC;
+
+protected:
+  /// constructor
+  BasicStatCompletionData(libradosstriper::RadosStriperImpl* striper,
+			  const std::string& soid,
+			  librados::AioCompletionImpl *userCompletion,
+			  libradosstriper::MultiAioCompletionImpl *multiCompletion,
+			  uint64_t *psize) :
+    CompletionData(striper, soid, "", userCompletion),
+    m_multiCompletion(multiCompletion), m_psize(psize),
+    m_statRC(0), m_getxattrRC(0) {};
+
+};
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous stat operations.
+ * Simple templated extension of BasicStatCompletionData.
+ * The template parameter is the type of the time information
+ * (used with time_t for stat and struct timespec for stat2)
+ */
+template<class TimeType>
+struct StatCompletionData : BasicStatCompletionData {
+  // where to store the file time
+  TimeType *m_pmtime;
+private:
+  FRIEND_MAKE_REF(StatCompletionData);
+  /// constructor
+  StatCompletionData<TimeType>(libradosstriper::RadosStriperImpl* striper,
+		     const std::string& soid,
+		     librados::AioCompletionImpl *userCompletion,
+		     libradosstriper::MultiAioCompletionImpl *multiCompletion,
+		     uint64_t *psize,
+		     TimeType *pmtime) :
+    BasicStatCompletionData(striper, soid, userCompletion, multiCompletion, psize),
+    m_pmtime(pmtime) {};
+};
+
+/**
+ * struct handling the data needed to pass to the call back
+ * function in asynchronous remove operations of a Rados File
+ */
+struct RadosRemoveCompletionData : RefCountedObject {
+  /// the multi asynch io completion object to be used
+  MultiAioCompletionImplPtr m_multiAioCompl;
+private:
+  FRIEND_MAKE_REF(RadosRemoveCompletionData);
+  /// constructor
+  RadosRemoveCompletionData(MultiAioCompletionImplPtr multiAioCompl,
+			    CephContext *context) :
+    RefCountedObject(context),
+    m_multiAioCompl(multiAioCompl) {};
+};
+
+
+} // namespace {
+
+///////////////////////// constructor /////////////////////////////
+
+libradosstriper::RadosStriperImpl::RadosStriperImpl(librados::IoCtx& ioctx, librados::IoCtxImpl *ioctx_impl) :
+  m_refCnt(0), m_radosCluster(ioctx), m_ioCtx(ioctx), m_ioCtxImpl(ioctx_impl),
+  m_layout(default_file_layout) {}
+
+///////////////////////// layout /////////////////////////////
+
+int libradosstriper::RadosStriperImpl::setObjectLayoutStripeUnit
+(unsigned int stripe_unit)
+{
+  /* stripe unit must be non-zero, 64k increment */
+  if (!stripe_unit || (stripe_unit & (CEPH_MIN_STRIPE_UNIT-1)))
+    return -EINVAL;
+  m_layout.fl_stripe_unit = stripe_unit;
+  return 0;
+}
+
+int libradosstriper::RadosStriperImpl::setObjectLayoutStripeCount
+(unsigned int stripe_count)
+{
+  /* stripe count must be non-zero */
+  if (!stripe_count)
+    return -EINVAL;
+  m_layout.fl_stripe_count = stripe_count;
+  return 0;
+}
+
+int libradosstriper::RadosStriperImpl::setObjectLayoutObjectSize
+(unsigned int object_size)
+{
+  /* object size must be non-zero, 64k increment */
+  if (!object_size || (object_size & (CEPH_MIN_STRIPE_UNIT-1)))
+    return -EINVAL;
+  /* object size must be a multiple of stripe unit */
+  if (object_size < m_layout.fl_stripe_unit ||
+      object_size % m_layout.fl_stripe_unit)
+    return -EINVAL;
+  m_layout.fl_object_size = object_size;
+  return 0;
+}
+
+///////////////////////// xattrs /////////////////////////////
+
+int libradosstriper::RadosStriperImpl::getxattr(const object_t& soid,
+                                                const char *name,
+                                                bufferlist& bl)
+{
+  std::string firstObjOid = getObjectId(soid, 0);
+  return m_ioCtx.getxattr(firstObjOid, name, bl);
+}
+
+int libradosstriper::RadosStriperImpl::setxattr(const object_t& soid,
+                                                const char *name,
+                                                bufferlist& bl)
+{
+  std::string firstObjOid = getObjectId(soid, 0);
+  return m_ioCtx.setxattr(firstObjOid, name, bl);
+}
+
+int libradosstriper::RadosStriperImpl::getxattrs(const object_t& soid,
+                                                 map<string, bufferlist>& attrset)
+{
+  std::string firstObjOid = getObjectId(soid, 0);
+  int rc = m_ioCtx.getxattrs(firstObjOid, attrset);
+  if (rc) return rc;
+  // cleanup internal attributes dedicated to striping and locking
+  attrset.erase(XATTR_LAYOUT_STRIPE_UNIT);
+  attrset.erase(XATTR_LAYOUT_STRIPE_COUNT);
+  attrset.erase(XATTR_LAYOUT_OBJECT_SIZE);
+  attrset.erase(XATTR_SIZE);
+  attrset.erase(std::string(LOCK_PREFIX) + RADOS_LOCK_NAME);
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::rmxattr(const object_t& soid,
+                                               const char *name)
+{
+  std::string firstObjOid = getObjectId(soid, 0);
+  return m_ioCtx.rmxattr(firstObjOid, name);
+}
+
+///////////////////////// io /////////////////////////////
+
+int libradosstriper::RadosStriperImpl::write(const std::string& soid,
+					     const bufferlist& bl,
+					     size_t len,
+					     uint64_t off) 
+{
+  // open the object. This will create it if needed, retrieve its layout
+  // and size and take a shared lock on it
+  ceph_file_layout layout;
+  std::string lockCookie;
+  int rc = createAndOpenStripedObject(soid, &layout, len+off, &lockCookie, true);
+  if (rc) return rc;
+  return write_in_open_object(soid, layout, lockCookie, bl, len, off);
+}
+
+int libradosstriper::RadosStriperImpl::append(const std::string& soid,
+					      const bufferlist& bl,
+					      size_t len) 
+{
+  // open the object. This will create it if needed, retrieve its layout
+  // and size and take a shared lock on it
+  ceph_file_layout layout;
+  uint64_t size = len;
+  std::string lockCookie;
+  int rc = openStripedObjectForWrite(soid, &layout, &size, &lockCookie, false);
+  if (rc) return rc;
+  return write_in_open_object(soid, layout, lockCookie, bl, len, size);
+}
+
+int libradosstriper::RadosStriperImpl::write_full(const std::string& soid,
+						  const bufferlist& bl) 
+{
+  int rc = trunc(soid, 0);
+  if (rc && rc != -ENOENT) return rc; // ENOENT is obviously ok
+  return write(soid, bl, bl.length(), 0);
+}
+
+int libradosstriper::RadosStriperImpl::read(const std::string& soid,
+					    bufferlist* bl,
+					    size_t len,
+					    uint64_t off)
+{
+  // create a completion object
+  librados::AioCompletionImpl c;
+  // call asynchronous method
+  int rc = aio_read(soid, &c, bl, len, off);
+  // and wait for completion
+  if (!rc) {
+    // wait for completion
+    c.wait_for_complete_and_cb();
+    // return result
+    rc = c.get_return_value();
+  }
+  return rc;
+}
+
+///////////////////////// asynchronous io /////////////////////////////
+
+int libradosstriper::RadosStriperImpl::aio_write(const std::string& soid,
+						 librados::AioCompletionImpl *c,
+						 const bufferlist& bl,
+						 size_t len,
+						 uint64_t off)
+{
+  ceph_file_layout layout;
+  std::string lockCookie;
+  int rc = createAndOpenStripedObject(soid, &layout, len+off, &lockCookie, true);
+  if (rc) return rc;
+  return aio_write_in_open_object(soid, c, layout, lockCookie, bl, len, off);
+}
+
+int libradosstriper::RadosStriperImpl::aio_append(const std::string& soid,
+						  librados::AioCompletionImpl *c,
+						  const bufferlist& bl,
+						  size_t len)
+{
+  ceph_file_layout layout;
+  uint64_t size = len;
+  std::string lockCookie;
+  int rc = openStripedObjectForWrite(soid, &layout, &size, &lockCookie, false);
+  if (rc) return rc;
+  // create a completion object
+  return aio_write_in_open_object(soid, c, layout, lockCookie, bl, len, size);
+}
+
+int libradosstriper::RadosStriperImpl::aio_write_full(const std::string& soid,
+						      librados::AioCompletionImpl *c,
+						      const bufferlist& bl)
+{
+  int rc = trunc(soid, 0);
+  if (rc) return rc;
+  return aio_write(soid, c, bl, bl.length(), 0);
+}
+
+static void rados_read_aio_unlock_complete(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = ceph::ref_t<ReadCompletionData>(static_cast<ReadCompletionData*>(arg), false);
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  cdata->complete_unlock(comp->rval);
+}
+
+static void striper_read_aio_req_complete(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = static_cast<ReadCompletionData*>(arg);
+  // launch the async unlocking of the object
+  cdata->m_striper->aio_unlockObject(cdata->m_soid, cdata->m_lockCookie, cdata->m_unlockCompletion);
+  // complete the read part in parallel
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  cdata->complete_read(comp->rval);
+}
+
+static void rados_req_read_complete(rados_completion_t c, void *arg)
+{
+  auto data = static_cast<RadosReadCompletionData*>(arg);
+  int rc = rados_aio_get_return_value(c);
+  // We need to handle the case of sparse files here
+  if (rc == -ENOENT) {
+    // the object did not exist at all. This can happen for sparse files.
+    // we consider we've read 0 bytes and it will fall into next case
+    rc = 0;
+  }
+  ssize_t nread = rc;
+  if (rc >= 0 && (((uint64_t)rc) < data->m_expectedBytes)) {
+    // only partial data were present in the object (or the object did not
+    // even exist if we've gone through previous case).
+    // This is typical of sparse file and we need to complete with 0s.
+    unsigned int lenOfZeros = data->m_expectedBytes-rc;
+    unsigned int existingDataToZero = min(data->m_bl->length()-rc, lenOfZeros);
+    if (existingDataToZero > 0) {
+      data->m_bl->zero(rc, existingDataToZero);
+    }
+    if (lenOfZeros > existingDataToZero) {
+      ceph::bufferptr zeros(ceph::buffer::create(lenOfZeros-existingDataToZero));
+      zeros.zero();
+      data->m_bl->push_back(zeros);
+    }
+    nread = data->m_expectedBytes;
+  }
+  auto multi_aio_comp = data->m_multiAioCompl;
+  multi_aio_comp->complete_request(nread);
+  multi_aio_comp->safe_request(rc);
+}
+
+int libradosstriper::RadosStriperImpl::aio_read(const std::string& soid,
+						librados::AioCompletionImpl *c,
+						bufferlist* bl,
+						size_t len,
+						uint64_t off)
+{
+  // open the object. This will retrieve its layout and size
+  // and take a shared lock on it
+  ceph_file_layout layout;
+  uint64_t size;
+  std::string lockCookie;
+  int rc = openStripedObjectForRead(soid, &layout, &size, &lockCookie);
+  if (rc) return rc;
+  // find out the actual number of bytes we can read
+  uint64_t read_len;
+  if (off >= size) {
+    // nothing to read ! We are done.
+    read_len = 0;
+  } else {
+    read_len = min(len, (size_t)(size-off));
+  }
+  // get list of extents to be read from
+  vector<ObjectExtent> *extents = new vector<ObjectExtent>();
+  if (read_len > 0) {
+    std::string format = soid;
+    boost::replace_all(format, "%", "%%");
+    format += RADOS_OBJECT_EXTENSION_FORMAT;
+    file_layout_t l;
+    l.from_legacy(layout);
+    Striper::file_to_extents(cct(), format.c_str(), &l, off, read_len,
+			     0, *extents);
+  }
+
+  // create a completion object and transfer ownership of extents and resultbl
+  vector<bufferlist> *resultbl = new vector<bufferlist>(extents->size());
+  auto cdata = ceph::make_ref<ReadCompletionData>(this, soid, lockCookie, c, bl, extents, resultbl);
+  c->is_read = true;
+  c->io = m_ioCtxImpl;
+  // create a completion for the unlocking of the striped object at the end of the read
+  librados::AioCompletion *unlock_completion =
+    librados::Rados::aio_create_completion(cdata->get() /* create ref! */, rados_read_aio_unlock_complete);
+  cdata->m_unlockCompletion = unlock_completion;
+  // create the multiCompletion object handling the reads
+  MultiAioCompletionImplPtr nc{new libradosstriper::MultiAioCompletionImpl,
+			       false};
+  nc->set_complete_callback(cdata.get(), striper_read_aio_req_complete);
+  // go through the extents
+  int r = 0, i = 0;
+  for (vector<ObjectExtent>::iterator p = extents->begin(); p != extents->end(); ++p) {
+    // create a buffer list describing where to place data read from current extend
+    bufferlist *oid_bl = &((*resultbl)[i++]);
+    for (vector<pair<uint64_t,uint64_t> >::iterator q = p->buffer_extents.begin();
+        q != p->buffer_extents.end();
+        ++q) {
+      bufferlist buffer_bl;
+      buffer_bl.substr_of(*bl, q->first, q->second);
+      oid_bl->append(buffer_bl);
+    }
+    // read all extends of a given object in one go
+    nc->add_request();
+    // we need 2 references on data as both rados_req_read_safe and rados_req_read_complete
+    // will release one
+    auto data = ceph::make_ref<RadosReadCompletionData>(nc, p->length, oid_bl, cct());
+    librados::AioCompletion *rados_completion =
+      librados::Rados::aio_create_completion(data.detach(), rados_req_read_complete);
+    r = m_ioCtx.aio_read(p->oid.name, rados_completion, oid_bl, p->length, p->offset);
+    rados_completion->release();
+    if (r < 0)
+      break;
+  }
+  nc->finish_adding_requests();
+  return r;
+}
+
+int libradosstriper::RadosStriperImpl::aio_read(const std::string& soid,
+						librados::AioCompletionImpl *c,
+						char* buf,
+						size_t len,
+						uint64_t off)
+{
+  // create a buffer list and store it inside the completion object
+  c->bl.clear();
+  c->bl.push_back(buffer::create_static(len, buf));
+  // call the bufferlist version of this method
+  return aio_read(soid, c, &c->bl, len, off);
+}
+
+int libradosstriper::RadosStriperImpl::aio_flush() 
+{
+  int ret;
+  // pass to the rados level
+  ret = m_ioCtx.aio_flush();
+  if (ret < 0)
+    return ret;
+  //wait all CompletionData are released
+  std::unique_lock l{lock};
+  cond.wait(l, [this] {return m_refCnt <= 1;});
+  return ret;
+}
+
+///////////////////////// stat and deletion /////////////////////////////
+
+int libradosstriper::RadosStriperImpl::stat(const std::string& soid, uint64_t *psize, time_t *pmtime)
+{
+  // create a completion object
+  librados::AioCompletionImpl c;
+  // call asynchronous version of stat
+  int rc = aio_stat(soid, &c, psize, pmtime);
+  if (rc == 0) {
+    // wait for completion of the remove
+    c.wait_for_complete();
+    // get result
+    rc = c.get_return_value();
+  }
+  return rc;
+}
+
+static void striper_stat_aio_stat_complete(rados_completion_t c, void *arg) {
+  auto data = ceph::ref_t<BasicStatCompletionData>(static_cast<BasicStatCompletionData*>(arg), false);
+  int rc = rados_aio_get_return_value(c);
+  if (rc == -ENOENT) {
+    // remember this has failed
+    data->m_statRC = rc;
+  }
+  data->m_multiCompletion->complete_request(rc);
+}
+
+static void striper_stat_aio_getxattr_complete(rados_completion_t c, void *arg) {
+  auto data = ceph::ref_t<BasicStatCompletionData>(static_cast<BasicStatCompletionData*>(arg), false);
+  int rc = rados_aio_get_return_value(c);
+  // We need to handle the case of sparse files here
+  if (rc < 0) {
+    // remember this has failed
+    data->m_getxattrRC = rc;
+  } else {
+    // this intermediate string allows to add a null terminator before calling strtol
+    std::string err;
+    std::string strsize(data->m_bl.c_str(), data->m_bl.length());
+    *data->m_psize = strict_strtoll(strsize.c_str(), 10, &err);
+    if (!err.empty()) {
+      lderr(data->m_striper->cct()) << XATTR_SIZE << " : " << err << dendl;
+      data->m_getxattrRC = -EINVAL;
+    }
+    rc = 0;
+  }
+  data->m_multiCompletion->complete_request(rc);
+}
+
+static void striper_stat_aio_req_complete(rados_striper_multi_completion_t c,
+					  void *arg) {
+  auto data = ceph::ref_t<BasicStatCompletionData>(static_cast<BasicStatCompletionData*>(arg), false);
+  if (data->m_statRC) {
+    data->complete(data->m_statRC);
+  } else {
+    if (data->m_getxattrRC < 0) {
+      data->complete(data->m_getxattrRC);
+    } else {
+      data->complete(0);
+    }
+  }
+}
+
+template<class TimeType>
+int libradosstriper::RadosStriperImpl::aio_generic_stat
+(const std::string& soid,
+ librados::AioCompletionImpl *c,
+ uint64_t *psize,
+ TimeType *pmtime,
+ typename libradosstriper::RadosStriperImpl::StatFunction<TimeType>::Type statFunction)
+{
+  // use a MultiAioCompletion object for dealing with the fact
+  // that we'll do 2 asynchronous calls in parallel
+  MultiAioCompletionImplPtr multi_completion{
+    new libradosstriper::MultiAioCompletionImpl, false};
+  // Data object used for passing context to asynchronous calls
+  std::string firstObjOid = getObjectId(soid, 0);
+  auto cdata = ceph::make_ref<StatCompletionData<TimeType>>(this, firstObjOid, c, multi_completion.get(), psize, pmtime);
+  multi_completion->set_complete_callback(cdata->get() /* create ref! */, striper_stat_aio_req_complete);
+  // use a regular AioCompletion for the stat async call
+  librados::AioCompletion *stat_completion =
+    librados::Rados::aio_create_completion(cdata->get() /* create ref! */, striper_stat_aio_stat_complete);
+  multi_completion->add_safe_request();
+  object_t obj(firstObjOid);
+  int rc = (m_ioCtxImpl->*statFunction)(obj, stat_completion->pc,
+					&cdata->m_objectSize, cdata->m_pmtime);
+  stat_completion->release();
+  if (rc < 0) {
+    // nothing is really started so cancel everything
+    delete cdata.detach();
+    return rc;
+  }
+  // use a regular AioCompletion for the getxattr async call
+  librados::AioCompletion *getxattr_completion =
+    librados::Rados::aio_create_completion(cdata->get() /* create ref! */, striper_stat_aio_getxattr_complete);
+  multi_completion->add_safe_request();
+  // in parallel, get the pmsize from the first object asynchronously
+  rc = m_ioCtxImpl->aio_getxattr(obj, getxattr_completion->pc,
+				 XATTR_SIZE, cdata->m_bl);
+  getxattr_completion->release();
+  multi_completion->finish_adding_requests();
+  if (rc < 0) {
+    // the async stat is ongoing, so we need to go on
+    // we mark the getxattr as failed in the data object
+    cdata->m_getxattrRC = rc;
+    multi_completion->complete_request(rc);
+    return rc;
+  }
+  return 0;
+}
+
+int libradosstriper::RadosStriperImpl::aio_stat(const std::string& soid,
+						librados::AioCompletionImpl *c,
+						uint64_t *psize,
+						time_t *pmtime)
+{
+  return aio_generic_stat<time_t>(soid, c, psize, pmtime, &librados::IoCtxImpl::aio_stat);
+}
+
+int libradosstriper::RadosStriperImpl::stat2(const std::string& soid, uint64_t *psize, struct timespec *pts)
+{
+  // create a completion object
+  librados::AioCompletionImpl c;
+  // call asynchronous version of stat
+  int rc = aio_stat2(soid, &c, psize, pts);
+  if (rc == 0) {
+    // wait for completion of the remove
+    c.wait_for_complete_and_cb();
+    // get result
+    rc = c.get_return_value();
+  }
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::aio_stat2(const std::string& soid,
+						librados::AioCompletionImpl *c,
+						uint64_t *psize,
+						struct timespec *pts)
+{
+  return aio_generic_stat<struct timespec>(soid, c, psize, pts, &librados::IoCtxImpl::aio_stat2);
+}
+
+static void rados_req_remove_complete(rados_completion_t c, void *arg)
+{
+  auto cdata = static_cast<RadosRemoveCompletionData*>(arg);
+  int rc = rados_aio_get_return_value(c);
+  // in case the object did not exist, it means we had a sparse file, all is fine
+  if (rc == -ENOENT) {
+    rc = 0;
+  }
+  cdata->m_multiAioCompl->complete_request(rc);
+  cdata->m_multiAioCompl->safe_request(rc);
+}
+
+static void striper_remove_aio_req_complete(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = ceph::ref_t<RemoveCompletionData>(static_cast<RemoveCompletionData*>(arg), false);
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  ldout(cdata->m_striper->cct(), 10)
+    << "RadosStriperImpl : striper_remove_aio_req_complete called for "
+    << cdata->m_soid << dendl;
+  int rc = comp->rval;
+  if (rc == 0) {
+    // All went fine, synchronously remove first object
+    rc = cdata->m_striper->m_ioCtx.remove(cdata->m_striper->getObjectId(cdata->m_soid, 0),
+					  cdata->flags);
+  } else {
+    lderr(cdata->m_striper->cct())
+      << "RadosStriperImpl : deletion/truncation incomplete for " << cdata->m_soid
+      << ", as errors were encountered. The file is left present but it's content "
+      << " has been partially removed"
+      << dendl;
+  }
+  cdata->complete(rc);
+}
+
+int libradosstriper::RadosStriperImpl::remove(const std::string& soid, int flags)
+{
+  // create a completion object
+  librados::AioCompletionImpl c;
+  // call asynchronous version of remove
+  int rc = aio_remove(soid, &c, flags);
+  if (rc == 0) {
+    // wait for completion of the remove
+    c.wait_for_complete_and_cb();
+    // get result
+    rc = c.get_return_value();
+  }
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::aio_remove(const std::string& soid,
+						  librados::AioCompletionImpl *c,
+						  int flags)
+{
+  // the RemoveCompletionData object will lock the given soid for the duration
+  // of the removal
+  std::string lockCookie = getUUID();
+  int rc = m_ioCtx.lock_exclusive(getObjectId(soid, 0), RADOS_LOCK_NAME, lockCookie, "", 0, 0);
+  if (rc) return rc;
+  // create CompletionData for the async remove call
+  auto cdata = ceph::make_ref<RemoveCompletionData>(this, soid, lockCookie, c, flags);
+  MultiAioCompletionImplPtr multi_completion{
+    new libradosstriper::MultiAioCompletionImpl, false};
+  multi_completion->set_complete_callback(cdata->get() /* create ref! */, striper_remove_aio_req_complete);
+  // call asynchronous internal version of remove
+  ldout(cct(), 10)
+    << "RadosStriperImpl : Aio_remove starting for "
+    << soid << dendl;
+  rc = internal_aio_remove(soid, multi_completion);
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::internal_aio_remove(
+ const std::string& soid,
+ MultiAioCompletionImplPtr multi_completion,
+ int flags)
+{
+  std::string firstObjOid = getObjectId(soid, 0);
+  try {
+    // check size and get number of rados objects to delete
+    uint64_t nb_objects = 0;
+    bufferlist bl2;
+    int rc = getxattr(soid, XATTR_SIZE, bl2);
+    if (rc < 0) {
+      // no object size (or not able to get it)
+      // try to find the number of object "by hand"
+      uint64_t psize;
+      time_t pmtime;
+      while (!m_ioCtx.stat(getObjectId(soid, nb_objects), &psize, &pmtime)) {
+        nb_objects++;
+      }
+    } else {
+      // count total number of rados objects in the striped object
+      std::string err;
+      // this intermediate string allows to add a null terminator before calling strtol
+      std::string strsize(bl2.c_str(), bl2.length());
+      uint64_t size = strict_strtoll(strsize.c_str(), 10, &err);
+      if (!err.empty()) {
+        lderr(cct()) << XATTR_SIZE << " : " << err << dendl;
+        
+        return -EINVAL;
+      }
+      uint64_t object_size = m_layout.fl_object_size;
+      uint64_t su = m_layout.fl_stripe_unit;
+      uint64_t stripe_count = m_layout.fl_stripe_count;
+      uint64_t nb_complete_sets = size / (object_size*stripe_count);
+      uint64_t remaining_data = size % (object_size*stripe_count);
+      uint64_t remaining_stripe_units = (remaining_data + su -1) / su;
+      uint64_t remaining_objects = std::min(remaining_stripe_units, stripe_count);
+      nb_objects = nb_complete_sets * stripe_count + remaining_objects;
+    }
+    // delete rados objects in reverse order
+    // Note that we do not drop the first object. This one will only be dropped
+    // if all other removals have been successful, and this is done in the
+    // callback of the multi_completion object
+    int rcr = 0;
+    for (int i = nb_objects-1; i >= 1; i--) {
+      multi_completion->add_request();
+      auto data = ceph::make_ref<RadosRemoveCompletionData>(multi_completion, cct());
+      librados::AioCompletion *rados_completion =
+	librados::Rados::aio_create_completion(data->get() /* create ref! */,
+					       rados_req_remove_complete);
+      if (flags == 0) {
+        rcr = m_ioCtx.aio_remove(getObjectId(soid, i), rados_completion);
+      } else {
+        rcr = m_ioCtx.aio_remove(getObjectId(soid, i), rados_completion, flags);
+      }
+      rados_completion->release();
+      if (rcr < 0 and -ENOENT != rcr) {
+        lderr(cct()) << "RadosStriperImpl::remove : deletion incomplete for " << soid
+		     << ", as " << getObjectId(soid, i) << " could not be deleted (rc=" << rc << ")"
+		     << dendl;
+        break;
+      }
+    }
+    // we are over adding requests to the multi_completion object
+    multi_completion->finish_adding_requests();
+    // return
+    return rcr;
+  } catch (ErrorCode &e) {
+    // error caught when trying to take the exclusive lock
+    return e.m_code;
+  }
+
+}
+
+int libradosstriper::RadosStriperImpl::trunc(const std::string& soid, uint64_t size)
+{
+  // lock the object in exclusive mode
+  std::string firstObjOid = getObjectId(soid, 0);
+  librados::ObjectWriteOperation op;
+  op.assert_exists();
+  std::string lockCookie = RadosStriperImpl::getUUID();
+  utime_t dur = utime_t();
+  rados::cls::lock::lock(&op, RADOS_LOCK_NAME, ClsLockType::EXCLUSIVE, lockCookie, "", "", dur, 0);
+  int rc = m_ioCtx.operate(firstObjOid, &op);
+  if (rc) return rc;
+  // load layout and size
+  ceph_file_layout layout;
+  uint64_t original_size;
+  rc = internal_get_layout_and_size(firstObjOid, &layout, &original_size);
+  if (!rc) {
+    if (size < original_size) {
+      rc = truncate(soid, original_size, size, layout);
+    } else if (size > original_size) {
+      rc = grow(soid, original_size, size, layout);
+    }
+  }
+  // unlock object, ignore return code as we cannot do much
+  m_ioCtx.unlock(firstObjOid, RADOS_LOCK_NAME, lockCookie);
+  // final return
+  return rc;
+}
+
+
+///////////////////////// private helpers /////////////////////////////
+
+std::string libradosstriper::RadosStriperImpl::getObjectId(const object_t& soid,
+                                                           long long unsigned objectno)
+{
+  std::ostringstream s;
+  s << soid << '.' << std::setfill ('0') << std::setw(16) << std::hex << objectno;
+  return s.str();
+}
+
+void libradosstriper::RadosStriperImpl::unlockObject(const std::string& soid,
+						     const std::string& lockCookie)
+{
+  // unlock the shared lock on the first rados object
+  std::string firstObjOid = getObjectId(soid, 0);
+  m_ioCtx.unlock(firstObjOid, RADOS_LOCK_NAME, lockCookie);
+}
+
+void libradosstriper::RadosStriperImpl::aio_unlockObject(const std::string& soid,
+						         const std::string& lockCookie,
+                                                         librados::AioCompletion *c)
+{
+  // unlock the shared lock on the first rados object
+  std::string firstObjOid = getObjectId(soid, 0);
+  m_ioCtx.aio_unlock(firstObjOid, RADOS_LOCK_NAME, lockCookie, c);
+}
+
+static void rados_write_aio_unlock_complete(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = ceph::ref_t<WriteCompletionData>(static_cast<WriteCompletionData*>(arg), false);
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  cdata->complete_unlock(comp->rval);
+}
+
+static void striper_write_aio_req_complete(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = ceph::ref_t<WriteCompletionData>(static_cast<WriteCompletionData*>(arg), false);
+  // launch the async unlocking of the object
+  cdata->m_striper->aio_unlockObject(cdata->m_soid, cdata->m_lockCookie, cdata->m_unlockCompletion);
+  // complete the write part in parallel
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  cdata->complete_write(comp->rval);
+}
+
+static void striper_write_aio_req_safe(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = ceph::ref_t<WriteCompletionData>(static_cast<WriteCompletionData*>(arg), false);
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  cdata->safe(comp->rval);
+}
+
+int libradosstriper::RadosStriperImpl::write_in_open_object(const std::string& soid,
+							    const ceph_file_layout& layout,
+							    const std::string& lockCookie,
+							    const bufferlist& bl,
+							    size_t len,
+							    uint64_t off) {
+  // create a completion object to be passed to the callbacks of the multicompletion
+  // we need 3 references as striper_write_aio_req_complete will release two and
+  // striper_write_aio_req_safe will release one
+  auto cdata = ceph::make_ref<WriteCompletionData>(this, soid, lockCookie, nullptr);
+  // create a completion object for the unlocking of the striped object at the end of the write
+  librados::AioCompletion *unlock_completion =
+    librados::Rados::aio_create_completion(cdata->get() /* create ref! */, rados_write_aio_unlock_complete);
+  cdata->m_unlockCompletion = unlock_completion;
+  // create the multicompletion that will handle the write completion
+  MultiAioCompletionImplPtr c{new libradosstriper::MultiAioCompletionImpl,
+                              false};
+  c->set_complete_callback(cdata->get() /* create ref! */, striper_write_aio_req_complete);
+  c->set_safe_callback(cdata->get() /* create ref! */, striper_write_aio_req_safe);
+  // call the asynchronous API
+  int rc = internal_aio_write(soid, c, bl, len, off, layout);
+  if (!rc) {
+    // wait for completion and safety of data
+    c->wait_for_complete_and_cb();
+    c->wait_for_safe_and_cb();
+    // wait for the unlocking
+    unlock_completion->wait_for_complete();
+    // return result
+    rc = c->get_return_value();
+  }
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::aio_write_in_open_object(const std::string& soid,
+								librados::AioCompletionImpl *c,
+								const ceph_file_layout& layout,
+								const std::string& lockCookie,
+								const bufferlist& bl,
+								size_t len,
+								uint64_t off) {
+  // create a completion object to be passed to the callbacks of the multicompletion
+  // we need 3 references as striper_write_aio_req_complete will release two and
+  // striper_write_aio_req_safe will release one
+  auto cdata = ceph::make_ref<WriteCompletionData>(this, soid, lockCookie, c);
+  m_ioCtxImpl->get();
+  c->io = m_ioCtxImpl;
+  // create a completion object for the unlocking of the striped object at the end of the write
+  librados::AioCompletion *unlock_completion =
+    librados::Rados::aio_create_completion(cdata->get() /* create ref! */, rados_write_aio_unlock_complete);
+  cdata->m_unlockCompletion = unlock_completion;
+  // create the multicompletion that will handle the write completion
+  libradosstriper::MultiAioCompletionImplPtr nc{
+    new libradosstriper::MultiAioCompletionImpl, false};
+  nc->set_complete_callback(cdata->get() /* create ref! */, striper_write_aio_req_complete);
+  nc->set_safe_callback(cdata->get() /* create ref! */, striper_write_aio_req_safe);
+  // internal asynchronous API
+  int rc = internal_aio_write(soid, nc, bl, len, off, layout);
+  return rc;
+}
+
+static void rados_req_write_complete(rados_completion_t c, void *arg)
+{
+  auto comp = reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(arg);
+  comp->complete_request(rados_aio_get_return_value(c));
+  comp->safe_request(rados_aio_get_return_value(c));
+}
+
+int
+libradosstriper::RadosStriperImpl::internal_aio_write(const std::string& soid,
+						      libradosstriper::MultiAioCompletionImplPtr c,
+						      const bufferlist& bl,
+						      size_t len,
+						      uint64_t off,
+						      const ceph_file_layout& layout)
+{
+  int r = 0;
+  // Do not try anything if we are called with empty buffer,
+  // file_to_extents would raise an exception
+  if (len > 0) {
+    // get list of extents to be written to
+    vector<ObjectExtent> extents;
+    std::string format = soid;
+    boost::replace_all(format, "%", "%%");
+    format += RADOS_OBJECT_EXTENSION_FORMAT;
+    file_layout_t l;
+    l.from_legacy(layout);
+    Striper::file_to_extents(cct(), format.c_str(), &l, off, len, 0, extents);
+    // go through the extents
+    for (vector<ObjectExtent>::iterator p = extents.begin(); p != extents.end(); ++p) {
+      // assemble pieces of a given object into a single buffer list
+      bufferlist oid_bl;
+      for (vector<pair<uint64_t,uint64_t> >::iterator q = p->buffer_extents.begin();
+	   q != p->buffer_extents.end();
+	   ++q) {
+        bufferlist buffer_bl;
+        buffer_bl.substr_of(bl, q->first, q->second);
+        oid_bl.append(buffer_bl);
+      }
+      // and write the object
+      c->add_request();
+      librados::AioCompletion *rados_completion =
+        librados::Rados::aio_create_completion(c.get(),
+					       rados_req_write_complete);
+      r = m_ioCtx.aio_write(p->oid.name, rados_completion, oid_bl,
+			    p->length, p->offset);
+      rados_completion->release();
+      if (r < 0)
+        break;
+    }
+  }
+  c->finish_adding_requests();
+  return r;
+}
+
+int libradosstriper::RadosStriperImpl::extract_uint32_attr
+(std::map<std::string, bufferlist> &attrs,
+ const std::string& key,
+ ceph_le32 *value)
+{
+  std::map<std::string, bufferlist>::iterator attrsIt = attrs.find(key);
+  if (attrsIt != attrs.end()) {
+    // this intermediate string allows to add a null terminator before calling strtol
+    std::string strvalue(attrsIt->second.c_str(), attrsIt->second.length());
+    std::string err;   
+    *value = strict_strtol(strvalue.c_str(), 10, &err);
+    if (!err.empty()) {
+      lderr(cct()) << key << " : " << err << dendl;
+      return -EINVAL;
+    }
+  } else {
+    return -ENOENT;
+  }
+  return 0;
+}
+
+int libradosstriper::RadosStriperImpl::extract_sizet_attr
+(std::map<std::string, bufferlist> &attrs,
+ const std::string& key,
+ size_t *value)
+{
+  std::map<std::string, bufferlist>::iterator attrsIt = attrs.find(key);
+  if (attrsIt != attrs.end()) {
+    // this intermediate string allows to add a null terminator before calling strtol
+    std::string strvalue(attrsIt->second.c_str(), attrsIt->second.length());
+    std::string err;   
+    *value = strict_strtoll(strvalue.c_str(), 10, &err);
+    if (!err.empty()) {
+      lderr(cct()) << key << " : " << err << dendl;
+      return -EINVAL;
+    }
+  } else {
+    return -ENOENT;
+  }
+  return 0;
+}
+
+int libradosstriper::RadosStriperImpl::internal_get_layout_and_size(
+  const std::string& oid,
+  ceph_file_layout *layout,
+  uint64_t *size)
+{
+  // get external attributes of the first rados object
+  std::map<std::string, bufferlist> attrs;
+  int rc = m_ioCtx.getxattrs(oid, attrs);
+  if (rc) return rc;
+  // deal with stripe_unit
+  rc = extract_uint32_attr(attrs, XATTR_LAYOUT_STRIPE_UNIT, &layout->fl_stripe_unit);
+  if (rc) return rc;
+  // deal with stripe_count
+  rc = extract_uint32_attr(attrs, XATTR_LAYOUT_STRIPE_COUNT, &layout->fl_stripe_count);
+  if (rc) return rc;
+  // deal with object_size
+  rc = extract_uint32_attr(attrs, XATTR_LAYOUT_OBJECT_SIZE, &layout->fl_object_size);
+  if (rc) return rc;
+  // deal with size
+  size_t ssize;
+  rc = extract_sizet_attr(attrs, XATTR_SIZE, &ssize);
+  if (rc) {
+    return rc;
+  }
+  *size = ssize;
+  // make valgrind happy by setting unused fl_pg_pool
+  layout->fl_pg_pool = 0;
+  return 0;
+}
+
+int libradosstriper::RadosStriperImpl::openStripedObjectForRead(
+  const std::string& soid,
+  ceph_file_layout *layout,
+  uint64_t *size,
+  std::string *lockCookie)
+{
+  // take a lock the first rados object, if it exists and gets its size
+  // check, lock and size reading must be atomic and are thus done within a single operation
+  librados::ObjectWriteOperation op;
+  op.assert_exists();
+  *lockCookie = getUUID();
+  utime_t dur = utime_t();
+  rados::cls::lock::lock(&op, RADOS_LOCK_NAME, ClsLockType::SHARED, *lockCookie, "Tag", "", dur, 0);
+  std::string firstObjOid = getObjectId(soid, 0);
+  int rc = m_ioCtx.operate(firstObjOid, &op);
+  if (rc) {
+    // error case (including -ENOENT)
+    return rc;
+  }
+  rc = internal_get_layout_and_size(firstObjOid, layout, size);
+  if (rc) {
+    unlockObject(soid, *lockCookie);
+    lderr(cct()) << "RadosStriperImpl::openStripedObjectForRead : "
+		 << "could not load layout and size for "
+		 << soid << " : rc = " << rc << dendl;
+  }
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::openStripedObjectForWrite(const std::string& soid,
+								 ceph_file_layout *layout,
+								 uint64_t *size,
+								 std::string *lockCookie,
+								 bool isFileSizeAbsolute)
+{
+  // take a lock the first rados object, if it exists
+  // check and lock must be atomic and are thus done within a single operation
+  librados::ObjectWriteOperation op;
+  op.assert_exists();
+  *lockCookie = getUUID();
+  utime_t dur = utime_t();
+  rados::cls::lock::lock(&op, RADOS_LOCK_NAME, ClsLockType::SHARED, *lockCookie, "Tag", "", dur, 0);
+  std::string firstObjOid = getObjectId(soid, 0);
+  int rc = m_ioCtx.operate(firstObjOid, &op);
+  if (rc) {
+    if (rc == -ENOENT) {
+      // object does not exist, delegate to createEmptyStripedObject
+      int rc = createAndOpenStripedObject(soid, layout, *size, lockCookie, isFileSizeAbsolute);
+      // return original size
+      *size = 0;
+      return rc; 
+    } else {
+      return rc;
+    }
+  }
+  // all fine
+  uint64_t curSize;
+  rc = internal_get_layout_and_size(firstObjOid, layout, &curSize);
+  if (rc) {
+    unlockObject(soid, *lockCookie);
+    lderr(cct()) << "RadosStriperImpl::openStripedObjectForWrite : "
+		   << "could not load layout and size for "
+		   << soid << " : rc = " << rc << dendl;
+    return rc;
+  }
+  // atomically update object size, only if smaller than current one
+  if (!isFileSizeAbsolute)
+    *size += curSize;
+  librados::ObjectWriteOperation writeOp;
+  writeOp.cmpxattr(XATTR_SIZE, LIBRADOS_CMPXATTR_OP_GT, *size);
+  std::ostringstream oss;
+  oss << *size;
+  bufferlist bl;
+  bl.append(oss.str());
+  writeOp.setxattr(XATTR_SIZE, bl);
+  rc = m_ioCtx.operate(firstObjOid, &writeOp);
+  // return current size
+  *size = curSize;
+  // handle case where objectsize is already bigger than size
+  if (-ECANCELED == rc) 
+    rc = 0;
+  if (rc) {
+    unlockObject(soid, *lockCookie);
+    lderr(cct()) << "RadosStriperImpl::openStripedObjectForWrite : "
+		   << "could not set new size for "
+		   << soid << " : rc = " << rc << dendl;
+  }
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::createAndOpenStripedObject(const std::string& soid,
+								  ceph_file_layout *layout,
+								  uint64_t size,
+								  std::string *lockCookie,
+								  bool isFileSizeAbsolute)
+{
+  // build atomic write operation
+  librados::ObjectWriteOperation writeOp;
+  writeOp.create(true);
+  // object_size
+  std::ostringstream oss_object_size;
+  oss_object_size << m_layout.fl_object_size;
+  bufferlist bl_object_size;
+  bl_object_size.append(oss_object_size.str());
+  writeOp.setxattr(XATTR_LAYOUT_OBJECT_SIZE, bl_object_size);
+  // stripe unit
+  std::ostringstream oss_stripe_unit;
+  oss_stripe_unit << m_layout.fl_stripe_unit;
+  bufferlist bl_stripe_unit;
+  bl_stripe_unit.append(oss_stripe_unit.str());
+  writeOp.setxattr(XATTR_LAYOUT_STRIPE_UNIT, bl_stripe_unit);
+  // stripe count
+  std::ostringstream oss_stripe_count;
+  oss_stripe_count << m_layout.fl_stripe_count;
+  bufferlist bl_stripe_count;
+  bl_stripe_count.append(oss_stripe_count.str());
+  writeOp.setxattr(XATTR_LAYOUT_STRIPE_COUNT, bl_stripe_count);
+  // size
+  std::ostringstream oss_size;
+  oss_size << (isFileSizeAbsolute?size:0);
+  bufferlist bl_size;
+  bl_size.append(oss_size.str());
+  writeOp.setxattr(XATTR_SIZE, bl_size);
+  // effectively change attributes
+  std::string firstObjOid = getObjectId(soid, 0);
+  int rc = m_ioCtx.operate(firstObjOid, &writeOp);
+  // in case of error (but no EEXIST which would mean the object existed), return
+  if (rc && -EEXIST != rc) return rc;
+  // Otherwise open the object
+  uint64_t fileSize = size;
+  return openStripedObjectForWrite(soid, layout, &fileSize, lockCookie, isFileSizeAbsolute);
+}
+
+static void striper_truncate_aio_req_complete(rados_striper_multi_completion_t c, void *arg)
+{
+  auto cdata = ceph::ref_t<TruncateCompletionData>(static_cast<TruncateCompletionData*>(arg), false);
+  libradosstriper::MultiAioCompletionImpl *comp =
+    reinterpret_cast<libradosstriper::MultiAioCompletionImpl*>(c);
+  if (0 == comp->rval) {
+    // all went fine, change size in the external attributes
+    std::ostringstream oss;
+    oss << cdata->m_size;
+    bufferlist bl;
+    bl.append(oss.str());
+    cdata->m_striper->setxattr(cdata->m_soid, XATTR_SIZE, bl);
+  }
+}
+
+int libradosstriper::RadosStriperImpl::truncate(const std::string& soid,
+						uint64_t original_size,
+						uint64_t size,
+						ceph_file_layout &layout) 
+{
+  auto cdata = ceph::make_ref<TruncateCompletionData>(this, soid, size);
+  libradosstriper::MultiAioCompletionImplPtr multi_completion{
+    new libradosstriper::MultiAioCompletionImpl, false};
+  multi_completion->set_complete_callback(cdata->get() /* create ref! */, striper_truncate_aio_req_complete);
+  // call asynchrous version of truncate
+  int rc = aio_truncate(soid, multi_completion, original_size, size, layout);
+  // wait for completion of the truncation
+  multi_completion->finish_adding_requests();
+  multi_completion->wait_for_complete_and_cb();
+  // return result
+  if (rc == 0) {
+    rc = multi_completion->get_return_value();
+  }
+  return rc;
+}
+
+int libradosstriper::RadosStriperImpl::aio_truncate
+(const std::string& soid,
+ libradosstriper::MultiAioCompletionImplPtr multi_completion,
+ uint64_t original_size,
+ uint64_t size,
+ ceph_file_layout &layout)
+{
+  // handle the underlying rados objects. 3 cases here :
+  //  -- the objects belonging to object sets entirely located
+  //     before the truncation are unchanged
+  //  -- the objects belonging to the object set where the
+  //     truncation took place are truncated or removed
+  //  -- the objects belonging to object sets entirely located
+  //     after the truncation are removed
+  // Note that we do it backward and that we change the size in
+  // the external attributes only at the end. This make sure that
+  // no rados object stays behind if we remove the striped object
+  // after a truncation has failed
+  uint64_t trunc_objectsetno = size / layout.fl_object_size / layout.fl_stripe_count;
+  uint64_t last_objectsetno = original_size / layout.fl_object_size / layout.fl_stripe_count;
+  bool exists = false;
+  for (int64_t objectno = (last_objectsetno+1) * layout.fl_stripe_count-1;
+       objectno >= (int64_t)((trunc_objectsetno + 1) * layout.fl_stripe_count);
+       objectno--) {
+    // if no object existed so far, check object existence
+    if (!exists) {
+      uint64_t nb_full_object_set = objectno / layout.fl_stripe_count;
+      uint64_t object_index_in_set = objectno % layout.fl_stripe_count;
+      uint64_t set_start_off = nb_full_object_set * layout.fl_object_size * layout.fl_stripe_count;
+      uint64_t object_start_off = set_start_off + object_index_in_set * layout.fl_stripe_unit;
+      exists = (original_size > object_start_off);
+    }
+    if (exists) {
+      // remove asynchronously
+      multi_completion->add_request();
+      auto data = ceph::make_ref<RadosRemoveCompletionData>(multi_completion, cct());
+      librados::AioCompletion *rados_completion =
+	librados::Rados::aio_create_completion(data->get() /* create ref! */,
+					       rados_req_remove_complete);
+      int rc = m_ioCtx.aio_remove(getObjectId(soid, objectno), rados_completion);
+      rados_completion->release();
+      // in case the object did not exist, it means we had a sparse file, all is fine
+      if (rc && rc != -ENOENT) return rc;
+    }
+  }
+  for (int64_t objectno = ((trunc_objectsetno + 1) * layout.fl_stripe_count) -1;
+       objectno >= (int64_t)(trunc_objectsetno * layout.fl_stripe_count);
+       objectno--) {
+    // if no object existed so far, check object existence
+    if (!exists) {
+      uint64_t object_start_off = ((objectno / layout.fl_stripe_count) * layout.fl_object_size) +
+	((objectno % layout.fl_stripe_count) * layout.fl_stripe_unit);
+      exists = (original_size > object_start_off);
+    }
+    if (exists) {
+      // truncate
+      file_layout_t l;
+      l.from_legacy(layout);
+      uint64_t new_object_size = Striper::object_truncate_size(cct(), &l, objectno, size);
+      int rc;
+      if (new_object_size > 0 or 0 == objectno) {
+	// trunc is synchronous as there is no async version
+	// but note that only a single object will be truncated
+	// reducing the overload to a fixed amount
+	rc = m_ioCtx.trunc(getObjectId(soid, objectno), new_object_size);
+      } else {
+	// removes are asynchronous in order to speed up truncations of big files
+	multi_completion->add_request();
+	auto data = ceph::make_ref<RadosRemoveCompletionData>(multi_completion, cct());
+	librados::AioCompletion *rados_completion =
+	  librados::Rados::aio_create_completion(data->get() /* create ref! */,
+						 rados_req_remove_complete);
+	rc = m_ioCtx.aio_remove(getObjectId(soid, objectno), rados_completion);
+	rados_completion->release();
+      }
+      // in case the object did not exist, it means we had a sparse file, all is fine
+      if (rc && rc != -ENOENT) return rc;
+    }
+  }
+  return 0;
+}  
+
+int libradosstriper::RadosStriperImpl::grow(const std::string& soid,
+					    uint64_t original_size,
+					    uint64_t size,
+					    ceph_file_layout &layout) 
+{
+  // handle the underlying rados objects. As we support sparse objects,
+  // we only have to change the size in the external attributes
+  std::ostringstream oss;
+  oss << size;
+  bufferlist bl;
+  bl.append(oss.str());
+  int rc = m_ioCtx.setxattr(getObjectId(soid, 0), XATTR_SIZE, bl);
+  return rc;
+}  
+
+std::string libradosstriper::RadosStriperImpl::getUUID()
+{
+  struct uuid_d uuid;
+  uuid.generate_random();
+  char suuid[37];
+  uuid.print(suuid);
+  return std::string(suuid);
+}