Re: [PATCH 1/6] VFS: improve interface for lookup_one functions

[Christian Brauner <brauner@kernel.org>]

On Fri, Mar 28, 2025 at 12:18:16PM +1100, NeilBrown wrote:
> On Fri, 21 Mar 2025, David Howells wrote:
> > NeilBrown <neil@brown.name> wrote:
> > 
> > > Also the path component name is passed as "name" and "len" which are
> > > (confusingly?) separate by the "base".  In some cases the len in simply
> > > "strlen" and so passing a qstr using QSTR() would make the calling
> > > clearer.
> > > Other callers do pass separate name and len which are stored in a
> > > struct.  Sometimes these are already stored in a qstr, other times it
> > > easily could be.
> > > 
> > > So this patch changes these three functions to receive a 'struct qstr',
> > > and improves the documentation.
> > 
> > You did want 'struct qstr' not 'struct qstr *' right?  I think there are
> > arches where this will cause the compiler to skip a register argument or two
> > if it's the second argument or third argument - i386 for example.  Plus you
> > have an 8-byte alignment requirement because of the u64 in it that may suck if
> > passed through several layers of function.
> 
> I don't think it is passed through several layers - except where the
> intermediate are inlined.
> And gcc enforces 16 byte alignment of the stack on function calls for
> i386, so I don't think alignment will be an issue.
> 
> I thought 'struct qstr' would result in slightly cleaner calling.  But I
> cannot make a strong argument in favour of it so I'm willing to change
> if there are concerns.

Fwiw, I massaged the whole series to pass struct qstr * instead of
struct qstr. I just forgot to finish that rebase and push.
/me doing so now.