On Sun, Apr 23, 2017 at 4:31 PM, Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote: > On Thu, Apr 20, 2017 at 02:46:51PM -0700, Dan Williams wrote: >> On Sat, Mar 18, 2017 at 2:52 AM, tip-bot for Kirill A. Shutemov >> <tipbot@xxxxxxxxx> wrote: >> > Commit-ID: 2947ba054a4dabbd82848728d765346886050029 >> > Gitweb: http://git.kernel.org/tip/2947ba054a4dabbd82848728d765346886050029 >> > Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> >> > AuthorDate: Fri, 17 Mar 2017 00:39:06 +0300 >> > Committer: Ingo Molnar <mingo@xxxxxxxxxx> >> > CommitDate: Sat, 18 Mar 2017 09:48:03 +0100 >> > >> > x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation >> > >> > This patch provides all required callbacks required by the generic >> > get_user_pages_fast() code and switches x86 over - and removes >> > the platform specific implementation. >> > >> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> >> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> > Cc: Aneesh Kumar K . V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> >> > Cc: Borislav Petkov <bp@xxxxxxxxx> >> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> >> > Cc: Dann Frazier <dann.frazier@xxxxxxxxxxxxx> >> > Cc: Dave Hansen <dave.hansen@xxxxxxxxx> >> > Cc: H. Peter Anvin <hpa@xxxxxxxxx> >> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> >> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> >> > Cc: Rik van Riel <riel@xxxxxxxxxx> >> > Cc: Steve Capper <steve.capper@xxxxxxxxxx> >> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >> > Cc: linux-arch@xxxxxxxxxxxxxxx >> > Cc: linux-mm@xxxxxxxxx >> > Link: http://lkml.kernel.org/r/20170316213906.89528-1-kirill.shutemov@xxxxxxxxxxxxxxx >> > [ Minor readability edits. ] >> > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> >> >> I'm still trying to spot the bug, but bisect points to this patch as >> the point at which my unit tests start failing with the following >> signature: >> >> [ 35.423841] WARNING: CPU: 8 PID: 245 at lib/percpu-refcount.c:155 >> percpu_ref_switch_to_atomic_rcu+0x1f5/0x200 > > Okay, I've tracked it down. The issue is triggered by replacment > get_page() with page_cache_get_speculative(). > > page_cache_get_speculative() doesn't have get_zone_device_page(). :-| > > And I think it's your bug, Dan: it's wrong to have > get_/put_zone_device_page() in get_/put_page(). I must be handled by > page_ref_* machinery to catch all cases where we manipulate with page > refcount. The page_ref conversion landed in 4.6 *after* the ZONE_DEVICE implementation that landed in 4.5, so there was a missed conversion of the zone-device reference counting to page_ref. > Back to the big picture: > > I hate that we need to have such additional code in page refcount > primitives. I worked hard to remove compound page ugliness from there and > now zone_device creeping in... > > Is it the only option? Not sure, I need to spend some time to understand what page_ref means to ZONE_DEVICE. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
