Re: [PATCH v2] f2fs: another way to set large folio by remembering inode number

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 04/15, Darrick J. Wong wrote:
> On Wed, Apr 15, 2026 at 10:02:26PM +0000, Jaegeuk Kim wrote:
> > On 04/15, Matthew Wilcox wrote:
> > > On Wed, Apr 15, 2026 at 04:44:04PM +0000, Jaegeuk Kim wrote:
> > > > On 04/14, Christoph Hellwig wrote:
> > > > > Please add the relevant mailing lists when adding new user interfaces.
> > > > > 
> > > > > And I'm not sure hacks working around the proper large folio
> > > > > implementation are something that should be merged upstream.
> > > > 
> > > > Cc'ed linux-api and linux-fsdevel onto the patch thread with a proposal that
> > > > I'm not sure it's acceptable or not. 
> > > 
> > > You haven't sent a proposal.  This is a reply to a reply to a reply of a
> > > patch.  There's no justification for why f2fs is so special that it
> > > needs this.  What the hell is going on?  You know this is not the way to
> > > get code merged into Linux.
> > 
> > I added two ideas in that email. Have you even tried to understand?
> 
> You want to establish "user.fadvise" as an extended attribute containing
> a bitmask.  The sole bit defined in that attribute means "use large
> folios", but you also have to change the file mode and set the IMMUTABLE
> bit for it to actually do anything.

Partly yes. This path has nothing to do with IMMUTABLE bit, since I used to
activate the large folio with that bit, but hit a big pain which requires
clearing the bit whenever just deleting the file.

So, this gives a new way to activate the large folio by chmod(0400) and
setxattr("user.fadvise") only while providing quick inode eviction in order
to set mapping by iget, and allowing file deletion easily.

I feel the arguable points would be 1) the path to evict inode by calling
d_drop in release_file and returning 1 in drop_inode, 2) how to give the
hint between fadvise(FADV_LARGE_FOLIO) or setxattr(user.fadvise) by individual
file system.

> 
> Meanwhile, you can't actually persist any of the fadvise(2) advice
> flags, so the xattr name doesn't even make sense.  Maybe you meant to
> call it "user.madvise" since the closest thing I can think of is
> MADV_HUGEPAGE?
> 
> I've understood enough.  YUCK.

Thank you for taking the time to take a look.

> 
> --D