Re: df bigger than ls?

Ben Myers
2012-03-09T01:55:58Z

On Fri, Mar 09, 2012 at 11:17:10AM +1100, Dave Chinner wrote:
> On Thu, Mar 08, 2012 at 10:23:48AM -0600, Ben Myers wrote:
> > On Thu, Mar 08, 2012 at 01:10:54PM +1100, Dave Chinner wrote:
> > > On Wed, Mar 07, 2012 at 12:04:26PM -0600, Eric Sandeen wrote:
> Alex and I discussed this problem briefly awhile ago. What is the best
> > way to lose when you hit ENOSPC (project quotas) or EDQUOT in
> > xfs_iomap_write_delay? You want to be fair; one user hitting his quota
> > shouldn't be able to steal some other user's block reservations unless
> > you really are near ENOSPC for the entire filesystem.
> >
> > I suggested something like... track inodes with preallocated block
> > reservations in LRU order and by dquot, so that the poor fella who is at
> > EDQUOT will first clean up the preallocations that resulted in quota
> > being enforced, try again, and then work on preallocations of other
> > users only if it can help in his situation. IIRC Alex shut me down when
> > he heard LRU. ;)
>
> And I agree with Alex. Nothing additional needs to be tracked on top
> of inodes with speculative prealloc. Just the search filter would
> need to be different (i.e. only select inodes with a specific dquot
> attached).

Yeah, maybe not. A single list of inodes with speculative prealloc does
seem a good place to start. Later maybe you would not want to
scan/filter through all of them and we could add additional lists for
dquots. My suggestion of using LRU was because I think that the oldest
unused speculative preallocs should be the first to go. One chronic
over-quota user shouldn't be able to punish everyone else.

> > Now that block reservations count toward quotas the symptom will
> > probably be a little different.
>
> Block reservations have always counted towards quotas, it's just
> that they were never reported.

Aw. My mistake. ;)

-Ben