delete fallocate with punch_hole

Summary:
As discuss in this thread:
https://www.facebook.com/groups/rocksdb.dev/permalink/1218043868294125/

We remove fallocate with FALLOC_FL_PUNCH_HOLE because the recent bug on xfs in kernel 4.x+ that align file size to page size even with FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE.
Closes #2038

Differential Revision: D4779974

Pulled By: siying

fbshipit-source-id: 5f54625

HISTORY.md

@@ -15,6 +15,7 @@
 
 ### Bug Fixes
 * Fix the bug that iterator may skip keys
+* Remove calling fallocate with FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE flag to circumvent a kernel bug that changes file size after this call on XFS
 
 ## 5.2.0 (02/08/2017)
 ### Public API Change

util/io_posix.cc

@@ -751,29 +751,6 @@ Status PosixWritableFile::Close() {
     // but it will be nice to log these errors.
     int dummy __attribute__((unused));
     dummy = ftruncate(fd_, filesize_);
-#if defined(ROCKSDB_FALLOCATE_PRESENT) && !defined(TRAVIS)
-    // in some file systems, ftruncate only trims trailing space if the
-    // new file size is smaller than the current size. Calling fallocate
-    // with FALLOC_FL_PUNCH_HOLE flag to explicitly release these unused
-    // blocks. FALLOC_FL_PUNCH_HOLE is supported on at least the following
-    // filesystems:
-    //   XFS (since Linux 2.6.38)
-    //   ext4 (since Linux 3.0)
-    //   Btrfs (since Linux 3.7)
-    //   tmpfs (since Linux 3.5)
-    // We ignore error since failure of this operation does not affect
-    // correctness.
-    // TRAVIS - this code does not work on TRAVIS filesystems.
-    // the FALLOC_FL_KEEP_SIZE option is expected to not change the size
-    // of the file, but it does. Simple strace report will show that.
-    // While we work with Travis-CI team to figure out if this is a
-    // quirk of Docker/AUFS, we will comment this out.
-    IOSTATS_TIMER_GUARD(allocate_nanos);
-    if (allow_fallocate_) {
-      fallocate(fd_, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, filesize_,
-                block_size * last_allocated_block - filesize_);
-    }
-#endif
   }
 
   if (close(fd_) < 0) {