Messages in this thread | | | Date | Fri, 6 Aug 2021 15:22:19 +0200 | From | Greg KH <> | Subject | Re: [PATCH v9 1/5] cpumask: introduce cpumap_print_list/bitmask_to_buf to support large bitmask and list |
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On Fri, Aug 06, 2021 at 11:02:47PM +1200, Barry Song wrote: > From: Tian Tao <tiantao6@hisilicon.com> > > The existing cpumap_print_to_pagebuf() is used by cpu topology and other > drivers to export hexadecimal bitmask and decimal list to userspace by > sysfs ABI. > > Right now, those drivers are using a normal attribute for this kind of > ABIs. A normal attribute typically has show entry as below: > > static ssize_t example_dev_show(struct device *dev, > struct device_attribute *attr, char *buf) > { > ... > return cpumap_print_to_pagebuf(true, buf, &pmu_mmdc->cpu); > } > show entry of attribute has no offset and count parameters and this > means the file is limited to one page only. > > cpumap_print_to_pagebuf() API works terribly well for this kind of > normal attribute with buf parameter and without offset, count: > > static inline ssize_t > cpumap_print_to_pagebuf(bool list, char *buf, const struct cpumask *mask) > { > return bitmap_print_to_pagebuf(list, buf, cpumask_bits(mask), > nr_cpu_ids); > } > > The problem is once we have many cpus, we have a chance to make bitmask > or list more than one page. Especially for list, it could be as complex > as 0,3,5,7,9,...... We have no simple way to know it exact size. > > It turns out bin_attribute is a way to break this limit. bin_attribute > has show entry as below: > static ssize_t > example_bin_attribute_show(struct file *filp, struct kobject *kobj, > struct bin_attribute *attr, char *buf, > loff_t offset, size_t count) > { > ... > } > > With the new offset and count parameters, this makes sysfs ABI be able > to support file size more than one page. For example, offset could be > >= 4096. > > This patch introduces cpumap_print_bitmask/list_to_buf() and their bitmap > infrastructure bitmap_print_bitmask/list_to_buf() so that those drivers > can move to bin_attribute to support large bitmask and list. At the same > time, we have to pass those corresponding parameters such as offset, count > from bin_attribute to this new API. > > Signed-off-by: Tian Tao <tiantao6@hisilicon.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Cc: Randy Dunlap <rdunlap@infradead.org> > Cc: Stefano Brivio <sbrivio@redhat.com> > Cc: Alexander Gordeev <agordeev@linux.ibm.com> > Cc: "Ma, Jianpeng" <jianpeng.ma@intel.com> > Cc: Yury Norov <yury.norov@gmail.com> > Cc: Valentin Schneider <valentin.schneider@arm.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Daniel Bristot de Oliveira <bristot@redhat.com> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > --- > include/linux/bitmap.h | 6 +++ > include/linux/cpumask.h | 38 +++++++++++++++ > lib/bitmap.c | 103 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 147 insertions(+) > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h > index a36cfcec4e77..37f36dad18bd 100644 > --- a/include/linux/bitmap.h > +++ b/include/linux/bitmap.h > @@ -227,6 +227,12 @@ unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int ord, un > int bitmap_print_to_pagebuf(bool list, char *buf, > const unsigned long *maskp, int nmaskbits); > > +extern int bitmap_print_bitmask_to_buf(char *buf, const unsigned long *maskp, > + int nmaskbits, loff_t off, size_t count); > + > +extern int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp, > + int nmaskbits, loff_t off, size_t count); > +
Why are you adding bitmap_print_list_to_buf() when no one uses it in this patch series?
Did I miss it somewhere?
thanks,
greg k-h
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