[OpenAFS-devel] osi_vfsops.c / afs_put_inode (LINUX) - editing bug?

[Jeffrey Altman]

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Rainer Toebbicke wrote:
> I'm slightly worried about afs/LINUX/osi_vfsops.c, function afs_put_inode.
> 
> 
> The code in 1.4.1-rc7 looks a bit odd:
> 
>     if (VREFCOUNT(vcp) == 2) {
>         if (VREFCOUNT(vcp) == 2)
>             afs_InactiveVCache(vcp, NULL);
> 
> The double-making-sure that VREFCOUNT(vcp) == 2 looks like an editing bug.
> 
> More seriously however, afs_InactiveVCache() through the subsequently
> called afs_InvalidateAllSegments() needs the vnode to be locked. I'm
> worried that given that this is an upcall from the kernel this might not
> always be the case, e.g. when invoked through afs_linux_lookup().
> 
> (Besides I still believe this function can be called with the global
> lock already held and thus deadlock, but this is another story.)

Searching through CVS you can find that the removal of the lock took
place in:

http://www.openafs.org/cgi-bin/cvsweb.cgi/openafs/src/afs/LINUX/osi_vfsops.c.diff?r1=1.40&r2=1.41

This was to fix ticket 20820.  At which point there was a VREFCOUNT test
followed by the acquisition of AFS_GLOCK() followed by another VREFCOUNT
test.

Then in

http://www.openafs.org/cgi-bin/cvsweb.cgi/openafs/src/afs/LINUX/osi_vfsops.c.diff?r1=1.41&r2=1.42

The AFS_GLOCK() was moved outside the initial VREFCOUNT test which
resulted in two identical tests being performed in a row.  This was
to fix 23318.

Chas will have to explain why the combination of these changes is what
is desired.

Jeffrey Altman








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