On Tue, Jun 25, 2024 at 11:00 PM Xi Ruoyao <xry111@xxxxxxxxxxx> wrote: > > On Tue, 2024-06-25 at 22:09 +0800, Huacai Chen wrote: > > On Tue, Jun 25, 2024 at 7:01 PM Mateusz Guzik <mjguzik@xxxxxxxxx> > > wrote: > > > > > > The newly used helper also checks for 0-sized buffers. > > > > > > This avoids path lookup code, lockref management, memory allocation > > > and > > > in case of NULL path userspace memory access (which can be quite > > > expensive with SMAP on x86_64). > > > > > > statx with AT_EMPTY_PATH paired with "" or NULL argument as > > > appropriate > > > issued on Sapphire Rapids (ops/s): > > > stock: 4231237 > > > 0-check: 5944063 (+40%) > > > NULL path: 6601619 (+11%/+56%) > > > > > > Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx> > > Hi, Ruoyao, > > > > I'm a bit confused. Ii this patch a replacement of your recent patch? > > Yes, both Linus and Christian hates introducing a new AT_ flag for this. > > This patch just makes statx(fd, NULL, AT_EMPTY_PATH, ...) behave like > statx(fd, "", AT_EMPTY_PATH, ...) instead. NULL avoids the performance > issue and it's also audit-able by seccomp BPF. To be honest, I still want to restore __ARCH_WANT_NEW_STAT. Because even if statx() becomes audit-able, it is still blacklisted now. Restoring __ARCH_WANT_NEW_STAT is a very small change that doesn't introduce any complexity, but it makes life easier. And I think libLoL also likes __ARCH_WANT_NEW_STAT, though it isn't an upstream project... Huacai > > -- > Xi Ruoyao <xry111@xxxxxxxxxxx> > School of Aerospace Science and Technology, Xidian University >
