Re: [PATCH v4] mm: Avoid unnecessary page fault retires on shared memory types
From: Heiko Carstens <hca@linux.ibm.com>
Date: 2022-05-30 17:07:51
Also in:
linux-alpha, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, lkml, sparclinux
r@linux.ibm.com>, linux-parisc@vger.kernel.org, Max Filippov [off-list ref], linux-kernel@vger.kernel.org, Johannes Berg [off-list ref], Dinh Nguyen [off-list ref], linux-riscv@lists.infradead.org, Palmer Dabbelt [off-list ref], Sven Schnelle [off-list ref], linux-alpha@vger.kernel.org, Ivan Kokshaysky [off-list ref], Andrew Morton [off-list ref], Thomas Bogendoerfer [off-list ref], linuxppc-dev@lists.ozlabs.org, "David S . Miller" [off-list ref] Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" [off-list ref] On Mon, May 30, 2022 at 12:00:52PM -0400, Peter Xu wrote:
On Mon, May 30, 2022 at 11:52:54AM -0400, Peter Xu wrote:quoted
On Mon, May 30, 2022 at 11:35:10AM +0200, Christian Borntraeger wrote:quoted
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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; + }
fault = 0; <----
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+ 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,
Right, that was stupid. Thanks for double checking! However could you please add "fault = 0" just in front of the goto out like above? I'd like to avoid having returns and gotos mixed.