tree 4812193c6be29f41d3de3ae74705e95a9566546c
parent f8d7e1877e5121841bc9a4d284a04dbc13f45bea
author Al Viro <viro@zeniv.linux.org.uk> 1275882558 -0400
committer Al Viro <viro@zeniv.linux.org.uk> 1281386895 -0400

try to get rid of races in hostfs open()

In case of mode mismatch, do *not* blindly close the descriptor
another openers might be using right now.  Open the underlying
file with currently sufficient mode, then
	* if current mode has grown so that it's sufficient for
us now, just close our new fd
	* if current mode has grown and our fd is *not* enough
to cover it, close and repeat.
	* otherwise, install our fd if the file hadn't been
opened at all or dup2() our fd over the current one (and close
our fd).
Critical section is protected by mutex; yes, system-wide.  All
we do under it is a bunch of comparison and maybe an overwriting
dup2() on host.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>