On Fri, 31 Jan 2025 at 00:32, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> This commit lifts definition(s) of QSTR() into linux/dcache.h,
> converts it to compound literal (all bcachefs users are fine
> with that) and converts assorted open-coded instances to using
> that.
Looks fine to me. I do wonder if the cast to 'struct qstr' should be
part of QSTR_INIT, so that you can use that the same way when you
already know the length.
We have code like this in fs/overlayfs/namei.c:
*name = (struct qstr) QSTR_INIT(n, s - n);
in bcachefs has
return (struct qstr) QSTR_INIT(d.v->d_name, bch2_dirent_name_bytes(d));
So both of them would seem to want to have that cast as part of the
QSTR_INIT() thing.
Or maybe we could just make QSTR() itself more powerful, and do
something like this:
#define QSTR_INIT(n, l, ...) { { { .len = l } }, .name = n }
#define QSTR(a, ...) (struct qstr) QSTR_INIT(a , ## __VA_ARGS__, strlen(a))
which allows you to write either "QSTR(str)" or "QSTR(str, len)", and
defaults to using 'strlen()' when no length is given.
Because if we have heper macros, let's make them _helpful_.
Side note: you missed a few places in the core VFS code that could
also use this new cleanup:
struct qstr this = QSTR_INIT("pts", 3);
...
child = d_hash_and_lookup(parent, &this);
can now be just
child = d_hash_and_lookup(parent, &QSTR("pts"));
but sadly a few more are static initializers and can't use 'strlen()'.
Linus
