From 9ad1f4f10ff7bfe32d0a37361640fe5c65e56699 Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@redhat.com>
Date: Fri, 6 Oct 2017 15:28:49 -0500
Subject: [PATCH] os/ObjectStore: 0-length zero does not change length of
 object

Signed-off-by: Sage Weil <sage@redhat.com>
---
 src/os/ObjectStore.h               |  7 +++
 src/test/objectstore/store_test.cc | 77 ++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/src/os/ObjectStore.h b/src/os/ObjectStore.h
index c43090a2e28..65df8ec08eb 100644
--- a/src/os/ObjectStore.h
+++ b/src/os/ObjectStore.h
@@ -1051,6 +1051,8 @@ public:
      * newly provided data. More sophisticated implementations of
      * ObjectStore will omit the untouched data and store it as a
      * "hole" in the file.
+     *
+     * Note that a 0-length write does not affect the size of the object.
      */
     void write(const coll_t& cid, const ghobject_t& oid, uint64_t off, uint64_t len,
 	       const bufferlist& write_data, uint32_t flags = 0) {
@@ -1076,6 +1078,11 @@ public:
      * zero out the indicated byte range within an object. Some
      * ObjectStore instances may optimize this to release the
      * underlying storage space.
+     *
+     * If the zero range extends beyond the end of the object, the object
+     * size is extended, just as if we were writing a buffer full of zeros.
+     * EXCEPT if the length is 0, in which case (just like a 0-length write)
+     * we do not adjust the object size.
      */
     void zero(const coll_t& cid, const ghobject_t& oid, uint64_t off, uint64_t len) {
       Op* _op = _get_next_op();
diff --git a/src/test/objectstore/store_test.cc b/src/test/objectstore/store_test.cc
index 5defd3e3bb8..3fffab0e569 100644
--- a/src/test/objectstore/store_test.cc
+++ b/src/test/objectstore/store_test.cc
@@ -2260,6 +2260,55 @@ TEST_P(StoreTest, MiscFragmentTests) {
 
 }
 
+TEST_P(StoreTest, ZeroVsObjectSize) {
+  ObjectStore::Sequencer osr("test");
+  int r;
+  coll_t cid;
+  struct stat stat;
+  ghobject_t hoid(hobject_t(sobject_t("foo", CEPH_NOSNAP)));
+  {
+    ObjectStore::Transaction t;
+    t.create_collection(cid, 0);
+    cerr << "Creating collection " << cid << std::endl;
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(r, 0);
+  }
+  bufferlist a;
+  a.append("stuff");
+  {
+    ObjectStore::Transaction t;
+    t.write(cid, hoid, 0, 5, a);
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(r, 0);
+  }
+  ASSERT_EQ(0, store->stat(cid, hoid, &stat));
+  ASSERT_EQ(5, stat.st_size);
+  {
+    ObjectStore::Transaction t;
+    t.zero(cid, hoid, 1, 2);
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(r, 0);
+  }
+  ASSERT_EQ(0, store->stat(cid, hoid, &stat));
+  ASSERT_EQ(5, stat.st_size);
+  {
+    ObjectStore::Transaction t;
+    t.zero(cid, hoid, 3, 200);
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(r, 0);
+  }
+  ASSERT_EQ(0, store->stat(cid, hoid, &stat));
+  ASSERT_EQ(203, stat.st_size);
+  {
+    ObjectStore::Transaction t;
+    t.zero(cid, hoid, 100000, 200);
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(r, 0);
+  }
+  ASSERT_EQ(0, store->stat(cid, hoid, &stat));
+  ASSERT_EQ(100200, stat.st_size);
+}
+
 TEST_P(StoreTest, ZeroLengthWrite) {
   ObjectStore::Sequencer osr("test");
   int r;
@@ -2289,6 +2338,34 @@ TEST_P(StoreTest, ZeroLengthWrite) {
   ASSERT_EQ(0, r);
 }
 
+TEST_P(StoreTest, ZeroLengthZero) {
+  ObjectStore::Sequencer osr("test");
+  int r;
+  coll_t cid;
+  ghobject_t hoid(hobject_t(sobject_t("foo", CEPH_NOSNAP)));
+  {
+    ObjectStore::Transaction t;
+    t.create_collection(cid, 0);
+    t.touch(cid, hoid);
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(0, r);
+  }
+  {
+    ObjectStore::Transaction t;
+    t.zero(cid, hoid, 1048576, 0);
+    r = apply_transaction(store, &osr, std::move(t));
+    ASSERT_EQ(0, r);
+  }
+  struct stat stat;
+  r = store->stat(cid, hoid, &stat);
+  ASSERT_EQ(0, r);
+  ASSERT_EQ(0, stat.st_size);
+
+  bufferlist newdata;
+  r = store->read(cid, hoid, 0, 1048576, newdata);
+  ASSERT_EQ(0, r);
+}
+
 TEST_P(StoreTest, SimpleAttrTest) {
   ObjectStore::Sequencer osr("test");
   int r;
-- 
2.39.5