Am 30.05.22 um 18:00 schrieb Peter Xu:
On Mon, May 30, 2022 at 11:52:54AM -0400, Peter Xu wrote:On Mon, May 30, 2022 at 11:35:10AM +0200, Christian Borntraeger wrote:Am 29.05.22 um 22:33 schrieb Heiko Carstens: [...]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;Hmm, right after I replied I found "goto out" could be problematic, since all s390 callers of do_exception() will assume it an error condition (side note: "goto out_gmap" contains one step to clear "fault" to 0). I'll replace this with "return 0" instead if it looks good to both of you. I'll wait for a confirmation before reposting. Thanks,
Yes, that sounds good and thank you for double checking.
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