On Fri, Feb 17, 2017 at 09:34:07AM -0800, James Bottomley wrote:
> On Fri, 2017-02-17 at 02:55 +0000, Al Viro wrote:
> > On Thu, Feb 16, 2017 at 07:56:30AM -0800, James Bottomley wrote:
> >
> > > > Hi James,
> > > >
> > > > Should it be "return d_splice_alias()" so that if we find an
> > > > alias it is returned back to caller and passed in dentry can be
> > > > freed. Though I don't know in what cases alias can be found. And
> > > > if alias is found how do we make sure alias_dentry->d_fsdata is
> > > > pointing to new (real dentry).
> > >
> > > It probably should be for the sake of the pattern. In our case I
> > > don't think we can have any root aliases because the root dentry is
> > > always pinned in the cache, so cache lookup should always find it.
> >
> > What does that have to do with root dentry? The real reason why that
> > code works (FVerySVO) is that the damn thing allocates a new inode
> > every time. Including the hardlinks, BTW.
>
> Yes, this is a known characteristic of stacked filesystems. Is there
> some magic I don't know about that would make it easier to reflect hard
> links as aliases?
I think overlayfs had the same issue in the beginning and miklos fixed it.
commit 51f7e52dc943468c6929fa0a82d4afac3c8e9636
Author: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Date: Fri Jul 29 12:05:24 2016 +0200
ovl: share inode for hard link
Vivek
