Re: VOP_GETATTR: locking protocol change proposal

[Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>]

yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi) wrote:
> >> 
> >> postgresql assumes instant lseek(SEEK_END) to get the size of
> >> their heap files.
> >> 
> >>    http://rhaas.blogspot.com/2011/11/linux-lseek-scalability.html
> >> 
> >> as fsync etc keeps the vnode lock during i/o, it might cause severe
> >> performance regression.
> > 
> > I wonder if it is worth having a separate VOP for that, which would
> > retrieve a subset of vattr without lock held.  There are potentially
> > more uses in the tree.
> 
> while it's good to have VOP_GETATTR take a mask to specify a set of
> requested attributes, i don't think it's worth to have a serparete VOP
> for this.  (PR/30250 is related)

OK, in such case the mask would also indicate whether there is a need
of locking.

> 
> IMO we should make unlocked VOP calls safe (against revoke and umount -f)
> and put VOP_GETATTR locking back into filesystem internal.

Agree.

-- 
Mindaugas