Add file:allocate/3 operation

This operation allows pre-allocation of space for files.
It succeeds only on systems that support such operation.

The POSIX standard defines the optional system call
posix_fallocate() to implement this feature. However,
some systems implement more specific functions to
accomplish the same operation.

On Linux, if the more specific function fallocate() is
implemented, it is used instead of posix_fallocate(),
falling back to posix_fallocate() if the fallocate()
call failed (it's only supported for the ext4, ocfs2,
xfs and btrfs file systems at the moment).

On Mac OS X it uses the specific fcntl() operation
F_PREALLOCATE, falling back to posix_fallocate() if
it's available (at the moment Mac OS X doesn't provide
posix_fallocate()).

On any other UNIX system, it uses posix_fallocate() if it's
available. Any other system not providing this system call
or any function to pre-allocate space for files, this operation
always fails with the ENOTSUP POSIX error.

1 files changed, 36 insertions, 1 deletions

diff --git a/erts/configure.in b/erts/configure.in
index 3256b0cb59..be9a753f7f 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -1075,8 +1075,43 @@ fi
 
 AC_SUBST(ERTS_BUILD_SMP_EMU)
 
-AC_CHECK_FUNCS([posix_fadvise])
+AC_CHECK_FUNCS([posix_fadvise, fallocate])
+AC_CHECK_HEADERS([linux/falloc.h])
 
+dnl * Old glibcs have broken posix_fallocate(). Make sure not to use it.
+dnl * It may also be broken in AIX.
+AC_CACHE_CHECK([whether posix_fallocate() works],i_cv_posix_fallocate_works,[
+    AC_TRY_RUN([
+        #if !defined(__sun) && !defined(__sun__)
+        #define _XOPEN_SOURCE 600
+        #endif
+        #include <stdio.h>
+        #include <stdlib.h>
+        #include <fcntl.h>
+        #include <unistd.h>
+        #if defined(__GLIBC__) && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 7))
+            possibly broken posix_fallocate
+        #endif
+        int main() {
+            int fd = creat("conftest.temp", 0600);
+            int ret;
+            if (-1 == fd) {
+               perror("creat()");
+               return 2;
+            }
+            ret = posix_fallocate(fd, 1024, 1024) < 0 ? 1 : 0;
+            unlink("conftest.temp");
+            return ret;
+        }
+    ], [
+        i_cv_posix_fallocate_works=yes
+    ], [
+        i_cv_posix_fallocate_works=no
+    ])
+])
+if test $i_cv_posix_fallocate_works = yes; then
+   AC_DEFINE(HAVE_POSIX_FALLOCATE,, Define if you have a working posix_fallocate())
+fi
 
 #
 # Figure out if the emulator should use threads. The default is set above