Re: [PATCH] fs: Rename mapping private members

[Al Viro <viro@zeniv.linux.org.uk>]

On Fri, Nov 17, 2023 at 10:13:32PM +0000, Matthew Wilcox wrote:
> On Fri, Nov 17, 2023 at 02:04:37PM -0800, Darrick J. Wong wrote:
> > On Fri, Nov 17, 2023 at 09:58:23PM +0000, Matthew Wilcox (Oracle) wrote:
> > > It is hard to find where mapping->private_lock, mapping->private_list and
> > > mapping->private_data are used, due to private_XXX being a relatively
> > > common name for variables and structure members in the kernel.  To fit
> > > with other members of struct address_space, rename them all to have an
> > > i_ prefix.  Tested with an allmodconfig build.
> > 
> > /me wonders if the prefix ought to be "as_" for address space instead of
> > inode.  Even though inode begat address_space, they're not the same
> > anymore.
> 
> It'd be the first thing in fs.h to ase an as_ prefix.  Right now, we
> have i_pages, i_mmap_writable, i_mmap, i_mmap_rwsem.  We have a_ops
> (which differs from f_op, i_op, s_op, dq_op, s_qcop in being plural!).
> Everything else doesn't have anything close to a meaningful prefix --
> host, invalidate_lock, gfp_mask, nr_thps, nrpages, writeback_index,
> flags, wb_err.
> 
> So i_ was the most common prefix, but if we wanted to go with a different
> prefix, we could go with a_.  Maybe we'll rename a_ops to a_op at
> some point.

Um...  One obvious note: there is only one point in the cycle where such
renaming can be done - rc1.  And it has to be announced and agreed upon
in the previous cycle.

IMO we need to figure out a policy for that kind of stuff; I _think_
that ->d_subdirs/->d_child conversion I have in my tree does not
quite reach the threshold for that (relatively small footprint),
but the thing you are suggesting is almost certainly crosses it.