s3: prefer posix_fallocate for doing "strict allocate"

posix_fallocate is more efficient than manual zero'ing the file. When
preallocation in kernel space is supported it's extremely fast. Support for
preallocation at fs layer via posix_fallocate and fallocate at kernel site
can be found in Linux kernel 2.6.23/glibc 2.10 with ext4, XFS and OCFS2. Other
systems that I know of which support fast preallocation in kernel space are
AIX 6.1 with JFS2 and recent Solaris versions with ZFS maybe UFS2, too.

People who have a system with preallocation in kernel space might want to set
"strict allocate = yes". This reduces file fragentation and it's also safer for
setups with quota being turned on.

As of today most systems still don't have preallocation in kernel space, and
that's why "strict allocate = no" will stay the default for now.

1 files changed, 1 insertions, 0 deletions

diff --git a/source3/include/proto.h b/source3/include/proto.h
index f0ce7a32f8..7013709fbb 100644
--- a/source3/include/proto.h
+++ b/source3/include/proto.h
@@ -932,6 +932,7 @@ int sys_fstat(int fd, SMB_STRUCT_STAT *sbuf,
 int sys_lstat(const char *fname,SMB_STRUCT_STAT *sbuf,
 	      bool fake_dir_create_times);
 int sys_ftruncate(int fd, SMB_OFF_T offset);
+int sys_posix_fallocate(int fd, SMB_OFF_T offset, SMB_OFF_T len);
 SMB_OFF_T sys_lseek(int fd, SMB_OFF_T offset, int whence);
 int sys_fseek(FILE *fp, SMB_OFF_T offset, int whence);
 SMB_OFF_T sys_ftell(FILE *fp);