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

[Christoph Hellwig]

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.