glibc2.5-sync_file_range.patch

CentOS 5.8 kernels and headers support the sync_file_range() system call,
but glibc 2.5 doesn't provide the syscall stub.  It appears that this
problem is known but will never be fixed:

  https://bugzilla.redhat.com/show_bug.cgi?id=518581

  Bug 518581 - [RHEL5] glibc misses sync_file_range syscall interface 

  Status:       CLOSED CANTFIX 
  Last Closed:  2009-11-22 22:19:55

  Kirby Zhou 2009-08-20 23:37:55 EDT

  Description of problem:

  glibc misses sync_file_range syscall interface.  The header file and
  man page both say 'sync_file_range' should exist.  From man page,
  sync_file_range should exist sinc kernel-2.6.17

  Andreas Schwab 2009-08-21 03:24:24 EDT

  It has only been added to glibc 2.6, and cannot be backported due to
  ABI breakage.  You can always fall back to syscall(3).

  Ulrich Drepper 2009-11-22 22:19:55 EST

  As comment #1 says, no chance to backport this.

  See the syscall man page for instructions.

  Jon E 2010-03-19 10:32:37 EDT

  then why document it if it's broken and you're not going to fix it?
  .. might want to FTFM over at sync_file_range(2) - in the meantime -
  borrowing from glibc 2.6 .. any thoughts on this implementation for a
  hacky workaround for those still on your "ancient releases" .. (eg:
  RHEL5.3)?:

  #ifdef ULI_WONT_FIX_THIS_IN_GLIBC2.5
  #define NR_sync_file_range 277
  int sync_file_range (int fd, __off64_t from, __off64_t to, unsigned int flags)
  {
    return syscall (NR_sync_file_range, fd,
                           __LONG_LONG_PAIR ((long) (from >> 32), (long) from),
                           __LONG_LONG_PAIR ((long) (to >> 32), (long) to),
                           flags);
  }
  #endif

  assuming of course that you're on an x86_64 and include/asm-
  x86_64/unistd.h has the correct entry

  (fwiw - fio is starting to use this now)

Rather than attempting to provide an implementation using syscall(),
we take the more conservative route and ignore header support for
sync_file_range() flags when the glibc version is <= 2.5.

Upstream-Status: Inappropriate [everyone else builds on newer hosts :-)]

Signed-off-by: Donn Seeley <donn.seeley@windriver.com>
Signed-off-by: Lei Liu <lei.liu2@windriver.com>
---
 src/archives.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/src/archives.c
+++ b/src/archives.c
@@ -75,7 +75,7 @@
   /* Ignore the return code as it should be considered equivalent to an
    * asynchronous hint for the kernel, we are doing an fsync() later on
    * anyway. */
-#if defined(SYNC_FILE_RANGE_WRITE)
+#if defined(SYNC_FILE_RANGE_WRITE) && __GLIBC_PREREQ(2, 6)
   sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WRITE);
 #elif defined(HAVE_POSIX_FADVISE)
   posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
@@ -1179,7 +1179,7 @@
   return 0;
 }
 
-#if defined(SYNC_FILE_RANGE_WAIT_BEFORE)
+#if defined(SYNC_FILE_RANGE_WAIT_BEFORE) && __GLIBC_PREREQ(2, 6)
 static void
 tar_writeback_barrier(struct fileinlist *files, struct pkginfo *pkg)
 {