on...@monstr.eu>, Thomas Bogendoerfer <tsbog...@alpha.franken.de>, linux-par...@vger.kernel.org, Max Filippov <jcmvb...@gmail.com>, linux-ker...@vger.kernel.org, Johannes Berg <johan...@sipsolutions.net>, Dinh Nguyen <dingu...@kernel.org>, linux-ri...@lists.infradead.org, Palmer Dabbelt <pal...@dabbelt.com>, Sven Schnelle <sv...@linux.ibm.com>, linux-al...@vger.kernel.org, Ivan Kokshaysky <i...@jurassic.park.msu.ru>, Andrew Morton <a...@linux-foundation.org>, linuxppc-dev@lists.ozlabs.org, "David S . Miller" <da...@davemloft.net> Errors-To: linuxppc-dev-bounces+archive=mail-archive....@lists.ozlabs.org Sender: "Linuxppc-dev" <linuxppc-dev-bounces+archive=mail-archive....@lists.ozlabs.org>
On Fri, May 27, 2022 at 03:39:36PM -0400, Peter Xu wrote: > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index e173b6187ad5..4608cc962ecf 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -433,6 +433,17 @@ static inline vm_fault_t do_exception(struct pt_regs > *regs, int access) > goto out_up; > goto out; > } > + > + /* The fault is fully completed (including releasing mmap lock) */ > + if (fault & VM_FAULT_COMPLETED) { > + /* > + * Gmap will need the mmap lock again, so retake it. TODO: > + * only conditionally take the lock when CONFIG_PGSTE set. > + */ > + mmap_read_lock(mm); > + goto out_gmap; > + } > + > if (unlikely(fault & VM_FAULT_ERROR)) > goto out_up; > Guess the patch below on top of your patch is what we want. Just for clarification: if gmap is not NULL then the process is a kvm process. So, depending on the workload, this optimization makes sense. diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index 4608cc962ecf..e1d40ca341b7 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -436,12 +436,11 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) /* The fault is fully completed (including releasing mmap lock) */ if (fault & VM_FAULT_COMPLETED) { - /* - * Gmap will need the mmap lock again, so retake it. TODO: - * only conditionally take the lock when CONFIG_PGSTE set. - */ - mmap_read_lock(mm); - goto out_gmap; + if (gmap) { + mmap_read_lock(mm); + goto out_gmap; + } + goto out; } if (unlikely(fault & VM_FAULT_ERROR))