Re: [PATCH] kernfs: don't create a negative dentry if inactive node exists

[Ian Kent <raven@themaw.net>]

On Wed, 2021-09-29 at 08:05 +0200, Greg Kroah-Hartman wrote:
> On Wed, Sep 29, 2021 at 11:04:34AM +0800, Ian Kent wrote:
> > In kernfs_iop_lookup() a negative dentry is created if there's no
> > kernfs
> > node associated with the dentry or the node is inactive.
> > 
> > But inactive kernfs nodes are meant to be invisible to the VFS and
> > creating a negative dentry for these can have unexpected side
> > effects
> > when the node transitions to an active state.
> > 
> > The point of creating negative dentries is to avoid the expensive
> > alloc/free cycle that occurs if there are frequent lookups for
> > kernfs
> > attributes that don't exist. So kernfs nodes that are not yet
> > active
> > should not result in a negative dentry being created so when they
> > transition to an active state VFS lookups can create an associated
> > dentry is a natural way.
> > 
> > Signed-off-by: Ian Kent <raven@themaw.net>
> > ---
> >  fs/kernfs/dir.c |    9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> Does this fix a specific commit and need a "Fixes:" tag?

Oh, of course yes, apologies, my bad.
I re-post it.


Ian