only try to use fallocate if it's actually present on the system

build_tools/build_detect_platform

@@ -189,6 +189,18 @@ EOF
         COMMON_FLAGS="$COMMON_FLAGS -DROCKSDB_ATOMIC_PRESENT"
     fi
 
+    # Test whether fallocate is available
+    $CXX $CFLAGS -x c++ - -o /dev/null 2>/dev/null  <<EOF
+      #include <fcntl.h>
+      int main() {
+	int fd = open("/dev/null", 0);
+	fallocate(fd, 0, 0, 1024);
+      }
+EOF
+    if [ "$?" = 0 ]; then
+        COMMON_FLAGS="$PLATFORM_LDFLAGS -DROCKSDB_FALLOCATE_PRESENT"
+    fi
+
     # Test whether Snappy library is installed
     # http://code.google.com/p/snappy/
     $CXX $CFLAGS -x c++ - -o /dev/null 2>/dev/null  <<EOF

util/env_posix.cc

@@ -389,7 +389,7 @@ class PosixMmapFile : public WritableFile {
   }
 
   Status MapNewRegion() {
-#ifdef OS_LINUX
+#ifdef ROCKSDB_FALLOCATE_PRESENT
     assert(base_ == nullptr);
 
     TEST_KILL_RANDOM(rocksdb_kill_odds);
@@ -575,7 +575,7 @@ class PosixMmapFile : public WritableFile {
 #endif
   }
 
-#ifdef OS_LINUX
+#ifdef ROCKSDB_FALLOCATE_PRESENT
   virtual Status Allocate(off_t offset, off_t len) {
     TEST_KILL_RANDOM(rocksdb_kill_odds);
     if (!fallocate(fd_, FALLOC_FL_KEEP_SIZE, offset, len)) {
@@ -752,7 +752,7 @@ class PosixWritableFile : public WritableFile {
 #endif
   }
 
-#ifdef OS_LINUX
+#ifdef ROCKSDB_FALLOCATE_PRESENT
   virtual Status Allocate(off_t offset, off_t len) {
     TEST_KILL_RANDOM(rocksdb_kill_odds);
     if (!fallocate(fd_, FALLOC_FL_KEEP_SIZE, offset, len)) {
@@ -856,7 +856,7 @@ class PosixRandomRWFile : public RandomRWFile {
     return Status::OK();
   }
 
-#ifdef OS_LINUX
+#ifdef ROCKSDB_FALLOCATE_PRESENT
   virtual Status Allocate(off_t offset, off_t len) {
     if (!fallocate(fd_, FALLOC_FL_KEEP_SIZE, offset, len)) {
       return Status::OK();

util/posix_logger.h

@@ -111,7 +111,7 @@ class PosixLogger : public Logger {
       assert(p <= limit);
       const size_t write_size = p - base;
 
-#ifdef OS_LINUX
+#ifdef ROCKSDB_FALLOCATE_PRESENT
       // If this write would cross a boundary of kDebugLogChunkSize
       // space, pre-allocate more space to avoid overly large
       // allocations from filesystem allocsize options.