Re: fishy ->put_inode usage in ntfs

[Anton Altaparmakov <aia21@cam.ac.uk>]

On Thu, 2004-10-14 at 13:44, Matthew Wilcox wrote:
> On Thu, Oct 14, 2004 at 01:39:30PM +0100, Anton Altaparmakov wrote:
> > Hm, I can now see that there is a small race window here and this is
> > simply fixed by doing the setting to NULL of bmp_ino before doing the
> > iput() of bmp_ino.  Thanks for pointing this problem area out to!  (-:
> 
> If you're going to rely on ordering like this, you must at least use
> wmb() to ensure that neither the compiler nor the processor reorders
> your stores.

Am I right that if I surround the code with down/up(i_sem) this implies
a memory barrier so I do not need wmb()?  The relevant code now is:

bvi = NULL;
down(&vi->i_sem);
if (atomic_read(&vi->i_count) == 2) {
	bvi = ni->itype.index.bmp_ino;
	if (bvi)
		ni->itype.index.bmp_ino = NULL;
}
up(&vi->i_sem);
if (bvi)
	iput(bvi);

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/, http://www-stu.christs.cam.ac.uk/~aia21/