From 6dd29b3df975582ef429b5b93c899e6575785940 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sun, 23 Apr 2017 11:37:17 +0200 Subject: Revert "x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation" This reverts commit 2947ba054a4dabbd82848728d765346886050029. Dan Williams reported dax-pmem kernel warnings with the following signature: WARNING: CPU: 8 PID: 245 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1f5/0x200 percpu ref (dax_pmem_percpu_release [dax_pmem]) <= 0 (0) after switching to atomic ... and bisected it to this commit, which suggests possible memory corruption caused by the x86 fast-GUP conversion. He also pointed out: " This is similar to the backtrace when we were not properly handling pud faults and was fixed with this commit: 220ced1676c4 "mm: fix get_user_pages() vs device-dax pud mappings" I've found some missing _devmap checks in the generic get_user_pages_fast() path, but this does not fix the regression [...] " So given that there are known bugs, and a pretty robust looking bisection points to this commit suggesting that are unknown bugs in the conversion as well, revert it for the time being - we'll re-try in v4.13. Reported-by: Dan Williams Cc: Andrew Morton Cc: Borislav Petkov Cc: Catalin Marinas Cc: Kirill A. Shutemov Cc: Linus Torvalds Cc: Michal Hocko Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: aneesh.kumar@linux.vnet.ibm.com Cc: dann.frazier@canonical.com Cc: dave.hansen@intel.com Cc: steve.capper@linaro.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/arm64/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/arm64/Kconfig') diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index af62bf79721a..3741859765cf 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -205,7 +205,7 @@ config GENERIC_CALIBRATE_DELAY config ZONE_DMA def_bool y -config HAVE_GENERIC_GUP +config HAVE_GENERIC_RCU_GUP def_bool y config ARCH_DMA_ADDR_T_64BIT -- cgit v1.2.3