On Sun, Jun 23, 2024 at 2:59 AM Xi Ruoyao <xry111@xxxxxxxxxxx> wrote:
>
> On Sat, 2024-06-22 at 15:41 -0700, Linus Torvalds wrote:
>
> > I do think that we should make AT_EMPTY_PATH with a NULL path
> > "JustWork(tm)", because the stupid "look if the pathname is empty" is
> > horrible.
> >
> > But moving that check into getname() is *NOT* the right answer,
> > because by the time you get to getname(), you have already lost.
>
> Oops. I'll try to get around of getname() too...
>
> > So the short-cut in vfs_fstatat() to never get a pathname is
> > disgusting - people should have used 'fstat()' - but it's _important_
> > disgusting.
>
> The problem is we don't have fstat() for LoongArch, and it'll be
> unusable on all 32-bit arch after 2037.
>
> And Arnd hates the idea adding fstat() for LoongArch because there would
> be one more 32-bit arch broken in 2037.
>
> Or should we just add something like "fstat_2037()"?
>
In that case fstat is out of the question, but no problem.
It was suggested to make AT_EMPTY_PATH + NULL pathname do the right
thing and have the syscalls short-circuit as needed.
for statx it would look like this (except you are going to have
implement do_statx_by_fd):
diff --git a/fs/stat.c b/fs/stat.c
index 16aa1f5ceec4..0afe72b320cc 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -710,6 +710,9 @@ SYSCALL_DEFINE5(statx,
int ret;
struct filename *name;
+ if (flags == AT_EMPTY_PATH && filename == NULL)
+ return do_statx_by_fd(...);
+
name = getname_flags(filename, getname_statx_lookup_flags(flags));
ret = do_statx(dfd, name, flags, mask, buffer);
putname(name);
and so on
Personally I would prefer if fstatx was added instead, fwiw most
massaging in the area will be the same regardless.
--
Mateusz Guzik <mjguzik gmail.com>
