* misc/Makefile (routines): Add preadv, preadv64, pwritev, pwritev64.

* misc/Versions: Export preadv, preadv64, pwritev, pwritev64 for
	GLIBC_2.10.
	* misc/sys/uio.h: Declare preadv, preadv64, pwritev, pwritev64.
	* sysdeps/unix/sysv/linux/kernel-features.h: Add entries for preadv
	and pwritev.
	* misc/preadv.c: New file.
	* misc/preadv64.c: New file.
	* misc/pwritev.c: New file.
	* misc/pwritev64.c: New file.
	* sysdeps/posx/preadv.c: New file.
	* sysdeps/posx/preadv64.c: New file.
	* sysdeps/posx/pwritev.c: New file.
	* sysdeps/posx/pwritev64.c: New file.
	* sysdeps/unix/sysv/linux/preadv.c: New file.
	* sysdeps/unix/sysv/linux/preadv64.c: New file.
	* sysdeps/unix/sysv/linux/pwritev.c: New file.
	* sysdeps/unix/sysv/linux/pwritev64.c: New file.
	* sysdeps/unix/sysv/linux/wordsize-64/preadv64.c: New file.
	* sysdeps/unix/sysv/linux/wordsize-64/pwritev64.c: New file.

sysdeps/posix/pwritev.c

@@ -0,0 +1,108 @@
+/* Copyright (C) 2009 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <sys/param.h>
+#if __WORDSIZE == 64 && !defined PWRITEV
+/* Hide the pwritev64 declaration.  */
+# define pwritev64 __redirect_pwritev64
+#endif
+#include <sys/uio.h>
+#include <bits/wordsize.h>
+
+#ifndef PWRITEV
+# define PWRITEV pwritev
+# define PWRITE __pwrite
+# define OFF_T off_t
+#endif
+
+
+static void
+ifree (char **ptrp)
+{
+  free (*ptrp);
+}
+
+
+/* Read data from file descriptor FD at the given position OFFSET
+   without change the file pointer, and put the result in the buffers
+   described by VECTOR, which is a vector of COUNT 'struct iovec's.
+   The buffers are filled in the order specified.  Operates just like
+   'read' (see <unistd.h>) except that data are put in VECTOR instead
+   of a contiguous buffer.  */
+ssize_t
+PWRITEV (int fd, const struct iovec *vector, int count, OFF_T offset)
+{
+  /* Find the total number of bytes to be read.  */
+  size_t bytes = 0;
+  for (int i = 0; i < count; ++i)
+    {
+      /* Check for ssize_t overflow.  */
+      if (SSIZE_MAX - bytes < vector[i].iov_len)
+	{
+	  __set_errno (EINVAL);
+	  return -1;
+	}
+      bytes += vector[i].iov_len;
+    }
+
+  /* Allocate a temporary buffer to hold the data.  We should normally
+     use alloca since it's faster and does not require synchronization
+     with other threads.  But we cannot if the amount of memory
+     required is too large.  */
+  char *buffer;
+  char *malloced_buffer __attribute__ ((__cleanup__ (ifree))) = NULL;
+  if (__libc_use_alloca (bytes))
+    buffer = (char *) __alloca (bytes);
+  else
+    {
+      malloced_buffer = buffer = (char *) malloc (bytes);
+      if (buffer == NULL)
+	return -1;
+    }
+
+  /* Read the data.  */
+  ssize_t bytes_read = PWRITE (fd, buffer, bytes, offset);
+  if (bytes_read <= 0)
+    return -1;
+
+  /* Copy the data from BUFFER into the memory specified by VECTOR.  */
+  bytes = bytes_read;
+  for (int i = 0; i < count; ++i)
+    {
+      size_t copy = MIN (vector[i].iov_len, bytes);
+
+      (void) memcpy ((void *) vector[i].iov_base, (void *) buffer, copy);
+
+      buffer += copy;
+      bytes -= copy;
+      if (bytes == 0)
+	break;
+    }
+
+  return bytes_read;
+}
+#if __WORDSIZE == 64 && defined pwritev64
+# undef pwritev64
+strong_alias (pwritev, pwritev64)
+#endif