3 files changed, 29 insertions, 7 deletions
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 29afe27711..9053df1789 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -462,6 +462,13 @@
 # define __ASSUME_SET_ROBUST_LIST	1
 #endif
 
+/* Pessimistically assume that 2.6.18 introduced real handling of
+   large numbers of requests to readv and writev and that we don't
+   need a fallback.  It likely worked for much longer.  */
+#if __LINUX_KERNEL_VERSION >= 0x020612
+# define __ASSUME_COMPLETE_READV_WRITEV	1
+#endif
+
 /* Support for PI futexes was added in 2.6.18.  */
 #if __LINUX_KERNEL_VERSION >= 0x020612
 # define __ASSUME_FUTEX_LOCK_PI	1
diff --git a/sysdeps/unix/sysv/linux/readv.c b/sysdeps/unix/sysv/linux/readv.c
index 250c00a075..d12fa49373 100644
--- a/sysdeps/unix/sysv/linux/readv.c
+++ b/sysdeps/unix/sysv/linux/readv.c
@@ -1,5 +1,5 @@
 /* readv supports all Linux kernels >= 2.0.
-   Copyright (C) 1997,1998,2000,2002,2003 Free Software Foundation, Inc.
+   Copyright (C) 1997,1998,2000,2002,2003,2009 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
@@ -25,6 +25,7 @@
 #include <sysdep-cancel.h>
 #include <sys/syscall.h>
 #include <bp-checks.h>
+#include <kernel-features.h>
 
 static ssize_t __atomic_readv_replacement (int, __const struct iovec *,
 					   int) internal_function;
@@ -45,10 +46,14 @@ do_readv (int fd, const struct iovec *vector, int count)
 
   bytes_read = INLINE_SYSCALL (readv, 3, fd, CHECK_N (vector, count), count);
 
+#ifdef __ASSUME_COMPLETE_READV_WRITEV
+  return bytes_read;
+#else
   if (bytes_read >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
     return bytes_read;
 
   return __atomic_readv_replacement (fd, vector, count);
+#endif
 }
 
 
@@ -72,5 +77,7 @@ __libc_readv (fd, vector, count)
 strong_alias (__libc_readv, __readv)
 weak_alias (__libc_readv, readv)
 
-#define __libc_readv static internal_function __atomic_readv_replacement
-#include <sysdeps/posix/readv.c>
+#ifndef __ASSUME_COMPLETE_READV_WRITEV
+# define __libc_readv static internal_function __atomic_readv_replacement
+# include <sysdeps/posix/readv.c>
+#endif
diff --git a/sysdeps/unix/sysv/linux/writev.c b/sysdeps/unix/sysv/linux/writev.c
index 05978665fa..398a841bb3 100644
--- a/sysdeps/unix/sysv/linux/writev.c
+++ b/sysdeps/unix/sysv/linux/writev.c
@@ -1,5 +1,5 @@
 /* writev supports all Linux kernels >= 2.0.
-   Copyright (C) 1997, 1998, 2000, 2002, 2003 Free Software Foundation, Inc.
+   Copyright (C) 1997,1998,2000,2002,2003,2009 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
@@ -25,6 +25,7 @@
 #include <sysdep-cancel.h>
 #include <sys/syscall.h>
 #include <bp-checks.h>
+#include <kernel-features.h>
 
 static ssize_t __atomic_writev_replacement (int, const struct iovec *,
 					    int) internal_function;
@@ -43,12 +44,17 @@ do_writev (int fd, const struct iovec *vector, int count)
 {
   ssize_t bytes_written;
 
-  bytes_written = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count), count);
+  bytes_written = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count),
+				  count);
 
+#ifdef __ASSUME_COMPLETE_READV_WRITEV
+  return bytes_written;
+#else
   if (bytes_written >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
     return bytes_written;
 
   return __atomic_writev_replacement (fd, vector, count);
+#endif
 }
 
 ssize_t
@@ -71,5 +77,7 @@ __libc_writev (fd, vector, count)
 strong_alias (__libc_writev, __writev)
 weak_alias (__libc_writev, writev)
 
-#define __libc_writev static internal_function __atomic_writev_replacement
-#include <sysdeps/posix/writev.c>
+#ifndef __ASSUME_COMPLETE_READV_WRITEV
+# define __libc_writev static internal_function __atomic_writev_replacement
+# include <sysdeps/posix/writev.c>
+#endif