Message ID | 20200206030900.147032-3-leonardo@linux.ibm.com |
---|---|
State | Not Applicable |
Headers | show |
Series | Introduces new functions for tracking lockless pagetable walks | expand |
On Thu, 2020-02-06 at 00:08 -0300, Leonardo Bras wrote: > gup_pgd_range(addr, end, gup_flags, pages, &nr); > - local_irq_enable(); > + end_lockless_pgtbl_walk(IRQS_ENABLED); > ret = nr; > } > Just noticed IRQS_ENABLED is not available on other archs than ppc64. I will fix this for v7.
Hi Leonardo, Thank you for the patch! Yet something to improve: [auto build test ERROR on powerpc/next] [also build test ERROR on paulus-powerpc/kvm-ppc-next linus/master v5.5 next-20200206] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/Leonardo-Bras/Introduces-new-functions-for-tracking-lockless-pagetable-walks/20200207-071035 base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next config: i386-tinyconfig (attached as .config) compiler: gcc-7 (Debian 7.5.0-3) 7.5.0 reproduce: # save the attached .config to linux build tree make ARCH=i386 If you fix the issue, kindly add following tag Reported-by: kbuild test robot <lkp@intel.com> All errors (new ones prefixed by >>): mm/gup.c: In function 'get_user_pages_fast': >> mm/gup.c:2435:27: error: 'IRQS_ENABLED' undeclared (first use in this function); did you mean 'IS_ENABLED'? end_lockless_pgtbl_walk(IRQS_ENABLED); ^~~~~~~~~~~~ IS_ENABLED mm/gup.c:2435:27: note: each undeclared identifier is reported only once for each function it appears in vim +2435 mm/gup.c 2395 2396 /** 2397 * get_user_pages_fast() - pin user pages in memory 2398 * @start: starting user address 2399 * @nr_pages: number of pages from start to pin 2400 * @gup_flags: flags modifying pin behaviour 2401 * @pages: array that receives pointers to the pages pinned. 2402 * Should be at least nr_pages long. 2403 * 2404 * Attempt to pin user pages in memory without taking mm->mmap_sem. 2405 * If not successful, it will fall back to taking the lock and 2406 * calling get_user_pages(). 2407 * 2408 * Returns number of pages pinned. This may be fewer than the number 2409 * requested. If nr_pages is 0 or negative, returns 0. If no pages 2410 * were pinned, returns -errno. 2411 */ 2412 int get_user_pages_fast(unsigned long start, int nr_pages, 2413 unsigned int gup_flags, struct page **pages) 2414 { 2415 unsigned long addr, len, end; 2416 int nr = 0, ret = 0; 2417 2418 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM))) 2419 return -EINVAL; 2420 2421 start = untagged_addr(start) & PAGE_MASK; 2422 addr = start; 2423 len = (unsigned long) nr_pages << PAGE_SHIFT; 2424 end = start + len; 2425 2426 if (end <= start) 2427 return 0; 2428 if (unlikely(!access_ok((void __user *)start, len))) 2429 return -EFAULT; 2430 2431 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && 2432 gup_fast_permitted(start, end)) { 2433 begin_lockless_pgtbl_walk(); 2434 gup_pgd_range(addr, end, gup_flags, pages, &nr); > 2435 end_lockless_pgtbl_walk(IRQS_ENABLED); --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Hi Leonardo, Thank you for the patch! Yet something to improve: [auto build test ERROR on powerpc/next] [also build test ERROR on asm-generic/master paulus-powerpc/kvm-ppc-next linus/master v5.5 next-20200207] [cannot apply to kvm-ppc/kvm-ppc-next] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/Leonardo-Bras/Introduces-new-functions-for-tracking-lockless-pagetable-walks/20200207-071035 base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next config: mips-randconfig-a001-20200207 (attached as .config) compiler: mipsel-linux-gcc (GCC) 5.5.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree GCC_VERSION=5.5.0 make.cross ARCH=mips If you fix the issue, kindly add following tag Reported-by: kbuild test robot <lkp@intel.com> All errors (new ones prefixed by >>): mm/gup.c: In function 'get_user_pages_fast': >> mm/gup.c:2435:27: error: 'IRQS_ENABLED' undeclared (first use in this function) end_lockless_pgtbl_walk(IRQS_ENABLED); ^ mm/gup.c:2435:27: note: each undeclared identifier is reported only once for each function it appears in vim +/IRQS_ENABLED +2435 mm/gup.c 2395 2396 /** 2397 * get_user_pages_fast() - pin user pages in memory 2398 * @start: starting user address 2399 * @nr_pages: number of pages from start to pin 2400 * @gup_flags: flags modifying pin behaviour 2401 * @pages: array that receives pointers to the pages pinned. 2402 * Should be at least nr_pages long. 2403 * 2404 * Attempt to pin user pages in memory without taking mm->mmap_sem. 2405 * If not successful, it will fall back to taking the lock and 2406 * calling get_user_pages(). 2407 * 2408 * Returns number of pages pinned. This may be fewer than the number 2409 * requested. If nr_pages is 0 or negative, returns 0. If no pages 2410 * were pinned, returns -errno. 2411 */ 2412 int get_user_pages_fast(unsigned long start, int nr_pages, 2413 unsigned int gup_flags, struct page **pages) 2414 { 2415 unsigned long addr, len, end; 2416 int nr = 0, ret = 0; 2417 2418 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM))) 2419 return -EINVAL; 2420 2421 start = untagged_addr(start) & PAGE_MASK; 2422 addr = start; 2423 len = (unsigned long) nr_pages << PAGE_SHIFT; 2424 end = start + len; 2425 2426 if (end <= start) 2427 return 0; 2428 if (unlikely(!access_ok((void __user *)start, len))) 2429 return -EFAULT; 2430 2431 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && 2432 gup_fast_permitted(start, end)) { 2433 begin_lockless_pgtbl_walk(); 2434 gup_pgd_range(addr, end, gup_flags, pages, &nr); > 2435 end_lockless_pgtbl_walk(IRQS_ENABLED); --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org Intel Corporation
Hello John, comments inline; On Fri, 2020-02-07 at 14:54 -0800, John Hubbard wrote: > On 2/5/20 7:25 PM, Leonardo Bras wrote: > > On Thu, 2020-02-06 at 00:08 -0300, Leonardo Bras wrote: > > > gup_pgd_range(addr, end, gup_flags, pages, &nr); > > > - local_irq_enable(); > > > + end_lockless_pgtbl_walk(IRQS_ENABLED); > > > ret = nr; > > > } > > > > > > > Just noticed IRQS_ENABLED is not available on other archs than ppc64. > > I will fix this for v7. > > > > What's the fix going to look like, approximately? I am not sure what is the best approach yet. 1. On irq_mask == 0, always enable irq on end_lockless_pgtbl_walk(). Not sure how bat would that affect other archs. 2. Add another function like end_lockless_pgtbl_walk_irqen() that always enables IRQ. 3. Add another parameter in end_lockless_pgtbl_walk(), so that caller can choose ii IRQ must be enabled. Also, not sure if internal_get_user_pages_fast() can possibly be called with IRQ disabled, and then return with it enabled. Maybe just saving/restoring should be fine. Other suggestions are welcome. > > > thanks, Best regards, Leonardo Bras
Hello, On Thu, Feb 06, 2020 at 12:25:18AM -0300, Leonardo Bras wrote: > On Thu, 2020-02-06 at 00:08 -0300, Leonardo Bras wrote: > > gup_pgd_range(addr, end, gup_flags, pages, &nr); > > - local_irq_enable(); > > + end_lockless_pgtbl_walk(IRQS_ENABLED); > > ret = nr; > > } > > > > Just noticed IRQS_ENABLED is not available on other archs than ppc64. > I will fix this for v7. Has threre been v7? I cannot find it. Thanks Michal
Hi Michal, On 10/15/20 8:16 PM, Michal Suchánek wrote: > Hello, > > On Thu, Feb 06, 2020 at 12:25:18AM -0300, Leonardo Bras wrote: >> On Thu, 2020-02-06 at 00:08 -0300, Leonardo Bras wrote: >>> gup_pgd_range(addr, end, gup_flags, pages, &nr); >>> - local_irq_enable(); >>> + end_lockless_pgtbl_walk(IRQS_ENABLED); >>> ret = nr; >>> } >>> >> >> Just noticed IRQS_ENABLED is not available on other archs than ppc64. >> I will fix this for v7. > > Has threre been v7? > > I cannot find it. > > Thanks > > Michal > https://lore.kernel.org/linuxppc-dev/20200505071729.54912-1-aneesh.kumar@linux.ibm.com This series should help here. -aneesh
diff --git a/mm/gup.c b/mm/gup.c index 1b521e0ac1de..04e6f46993b6 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2369,7 +2369,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { unsigned long len, end; - unsigned long flags; + unsigned long irq_mask; int nr = 0; start = untagged_addr(start) & PAGE_MASK; @@ -2395,9 +2395,9 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) { - local_irq_save(flags); + irq_mask = begin_lockless_pgtbl_walk(); gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr); - local_irq_restore(flags); + end_lockless_pgtbl_walk(irq_mask); } return nr; @@ -2450,9 +2450,9 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) { - local_irq_disable(); + begin_lockless_pgtbl_walk(); gup_pgd_range(addr, end, gup_flags, pages, &nr); - local_irq_enable(); + end_lockless_pgtbl_walk(IRQS_ENABLED); ret = nr; }
As described, gup_pgd_range is a lockless pagetable walk. So, in order to track against THP split/collapse, it disables/enables irq around it. To make use of the new tracking functions, it replaces irq disable/enable by {begin,end}_lockless_pgtbl_walk(). As local_irq_{save,restore} is present inside {begin,end}_lockless_pgtbl_walk, there should be no change in the workings. Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com> --- mm/gup.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)