On Fri, Mar 13, 2020 at 06:28:44PM +0000, Al Viro wrote: > On Fri, Mar 13, 2020 at 08:59:01PM +1100, Aleksa Sarai wrote: > > On 2020-03-12, Stefan Metzmacher <metze@xxxxxxxxx> wrote: > > > Am 12.03.20 um 17:24 schrieb Linus Torvalds: > > > > But yes, if we have a major package like samba use it, then by all > > > > means let's add linkat2(). How many things are we talking about? We > > > > have a number of system calls that do *not* take flags, but do do > > > > pathname walking. I'm thinking things like "mkdirat()"?) > > > > > > I haven't looked them up in detail yet. > > > Jeremy can you provide a list? > > > > > > Do you think we could route some of them like mkdirat() and mknodat() > > > via openat2() instead of creating new syscalls? > > > > I have heard some folks asking for a way to create a directory and get a > > handle to it atomically -- so arguably this is something that could be > > inside openat2()'s feature set (O_MKDIR?). But I'm not sure how popular > > of an idea this is. > > For fuck sake, *NO*! > > We don't need any more multiplexors from hell. mkdir() and open() have > deeply different interpretation of pathnames (and anyone who asks for > e.g. traversals of dangling symlinks on mkdir() is insane). Don't try to > mix those; even O_TMPFILE had been a mistake. > > Folks, we'd paid very dearly for the atomic_open() merge. We are _still_ > paying for it - and keep finding bugs induced by the convoluted horrors > in that thing (see yesterday pull from vfs.git#fixes for the latest crop). > I hope to get into more or less sane shape (part - this cycle, with > followups in the next one), but the last thing we need is more complexity > in the area. Can we disentangle the laudable desire to keep kernel internals simple (which I completely agree with :-) from the desire to keep user-space interfaces simple ? Having some way of doing a mkdir() that returns an open fd on the new directory *is* a very useful thing for many applications, but I really don't care how the kernel implements it. We have so much Linux-specific code already that one more thing won't matter :-).
