On Tue, Oct 18, 2005 at 05:13:35PM -0700, Andrew Morton wrote:
> Andrea Arcangeli <[email protected]> wrote:
> >
> > Hello,
> >
> > @@ -183,6 +183,7 @@ __sync_single_inode(struct inode *inode,
> > list_move(&inode->i_list, &inode_in_use);
> > } else {
> > list_move(&inode->i_list, &inode_unused);
> > + inodes_stat.nr_unused++;
> > }
> > }
> > wake_up_inode(inode);
> >
> > Are you sure the above diff is correct? It was added somewhere between
> > 2.6.5 and 2.6.8. I think it's wrong.
> >
> > The only way I can imagine the i_count to be zero in the above path, is
> > that I_WILL_FREE is set. And if I_WILL_FREE is set, then we must not
> > increase nr_unused. So I believe the above change is buggy and it will
> > definitely overstate the number of unused inodes and it should be backed
> > out.
>
> Well according to my assertion (below), the inode in __sync_single_inode()
> cannot have a zero refcount, so the whole if() statement is never executed.
generic_forget_inode->write_inode_now->__writeback_single_inode->
__sync_single_inode
We do have I_WILL_FREE, but i_count will be zero.
>
> The thinking behind that increment is that __sync_single_inode() has just
> taken a dirty, zero-refcount inode and has cleaned it. A dirty inode
> cannot have previously been on inode_unused, hence we now are newly moving
> it to inode_unused.
nr_unused doesn't seem to count the number of inodes on the unused list.
It is actually counting the number of inodes whose i_count is 0. See
generic_forget_inode and invalidate_list to see what I mean.
generic_forget_inode took care of incrementing the unused count when
i_count went to zero. So, I don't think we need to worry about the
unused count in __writeback_single_inode.
-chris
-
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