| Message ID | 20200206030900.147032-3-leonardo@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | Introduces new functions for tracking lockless pagetable walks | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (530a1cfd52af0aba1af4b1c9a7bc66a202a459b1) |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 30 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
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
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? thanks,
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(-)