[Bug-tar] [patch] O_NOATIME support

[Ian Turner]

Hello all,

Attached is a patch to add O_NOATIME support to GNU tar. This allows one 
to make backups without changing atime, mtime, or ctime on regular 
files. O_NOATIME requires kernel 2.6.8 or greater, along with 
appropriate system headers, but this patch will still compile without 
those things.

O_NOATIME doesn't work if you aren't the owner of the file in question 
(or root), if the file is on an unsupported filesystem (like NFS), or if 
the file is a symlink.

Because of these limitations, and because of the very different 
side-effects, I have added a new option --no-atime, rather than extend 
the existing --preserve-atime option. The option exists (as a no-op), 
even if configure did not find required system headers. --no-atime does 
not at present interact with --preserve-atime, because it is impossible 
at present to know if O_NOATIME is actually working, at least under 
certain circumstances.

Comments are appreciated. Let me know if you have any criticisms, or if 
there is something else I must to do get this patch into the distribution.

Cheers,

--Ian Turner