Re: [PATCH V6 6/8] fs/xfs: Combine xfs_diflags_to_linux() and xfs_diflags_to_iflags()

[Ira Weiny]

On Thu, Apr 09, 2020 at 02:41:27PM +0200, Christoph Hellwig wrote:
> On Wed, Apr 08, 2020 at 05:22:03PM -0700, Ira Weiny wrote:
> > > You mean something like XFS_IDONTCACHE?
> > > 
> > > i.e. the functionality already exists in XFS to selectively evict an
> > > inode from cache when the last reference to it is dropped rather
> > > than let it go to the LRUs and hang around in memory.
> > > 
> > > That flag can be set when changing the on disk DAX flag, and we can
> > > tweak how it works so new cache hits don't clear it (as happens
> > > now). Hence the only thing that can prevent eviction are active
> > > references.
> > > 
> > > That means we'll still need to stop the application and drop_caches,
> > > because we need to close all the files and purge the dentries that
> > > hold references to the inode before it can be evicted.
> > 
> > That sounds like a great idea...
> > 
> > Jan?  Christoph?
> 
> Sounds ok.  Note that we could also pretty trivially lift
> XFS_IDONTCACHE to the VFS if we need to apply the same scheme to
> ext4.

Yes I have been slowing working on ext4 in the background.  So lifting
XXX_IDONTCACHE to VFS will be part of that series.

Thanks,
Ira