From: Baoquan He <bhe@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, richardw.yang@linux.intel.com,
osalvador@suse.de, dan.j.williams@intel.com, mhocko@suse.com,
rppt@linux.ibm.com, robin.murphy@arm.com
Subject: Re: [PATCH v2 3/7] mm/sparse.c: introduce a new function clear_subsection_map()
Date: Tue, 3 Mar 2020 16:22:04 +0800 [thread overview]
Message-ID: <20200303082204.GA4433@MiWiFi-R3L-srv> (raw)
In-Reply-To: <1346f0c2-7b1f-6feb-5e9b-2854fd0022ba@redhat.com>
On 03/02/20 at 04:43pm, David Hildenbrand wrote:
> On 01.03.20 06:20, Baoquan He wrote:
> > On 02/28/20 at 03:36pm, David Hildenbrand wrote:
> >> On 20.02.20 05:33, Baoquan He wrote:
> >>> Wrap the codes which clear subsection map of one memory region from
> >>> section_deactivate() into clear_subsection_map().
> >>>
> >>> Signed-off-by: Baoquan He <bhe@redhat.com>
> >>> ---
> >>> mm/sparse.c | 46 ++++++++++++++++++++++++++++++++++++++--------
> >>> 1 file changed, 38 insertions(+), 8 deletions(-)
> >>>
> >>> diff --git a/mm/sparse.c b/mm/sparse.c
> >>> index 977b47acd38d..df857ee9330c 100644
> >>> --- a/mm/sparse.c
> >>> +++ b/mm/sparse.c
> >>> @@ -726,14 +726,25 @@ static void free_map_bootmem(struct page *memmap)
> >>> }
> >>> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
> >>>
> >>> -static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> >>> - struct vmem_altmap *altmap)
> >>> +/**
> >>> + * clear_subsection_map - Clear subsection map of one memory region
> >>> + *
> >>> + * @pfn - start pfn of the memory range
> >>> + * @nr_pages - number of pfns to add in the region
> >>> + *
> >>> + * This is only intended for hotplug, and clear the related subsection
> >>> + * map inside one section.
> >>> + *
> >>> + * Return:
> >>> + * * -EINVAL - Section already deactived.
> >>> + * * 0 - Subsection map is emptied.
> >>> + * * 1 - Subsection map is not empty.
> >>> + */
> >>
> >> Less verbose please (in my preference: none and simplify return handling)
> >>
> >>> +static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
> >>> {
> >>> DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> >>> DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
> >>> struct mem_section *ms = __pfn_to_section(pfn);
> >>> - bool section_is_early = early_section(ms);
> >>> - struct page *memmap = NULL;
> >>> unsigned long *subsection_map = ms->usage
> >>> ? &ms->usage->subsection_map[0] : NULL;
> >>>
> >>> @@ -744,8 +755,28 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> >>> if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
> >>> "section already deactivated (%#lx + %ld)\n",
> >>> pfn, nr_pages))
> >>> - return;
> >>> + return -EINVAL;
> >>> +
> >>> + bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
> >>>
> >>> + if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
> >>> + return 0;
> >>> +
> >>
> >> Can we please just have a
> >>
> >> subsection_map_empty() instead and handle that in the caller?
> >> (you can then always return true in the !VMEMMAP variant)
> >
> > I don't follow. Could you be more specific? or pseudo code please?
> >
> > The old code has to handle below case in which subsection_map has been
> > cleared. And I introduce clear_subsection_map() to encapsulate all
> > subsection map realted code so that !VMEMMAP won't have to see it any
> > more.
> >
>
> Something like this on top would be easier to understand IMHO
>
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index dc79b00ddaaa..be5c80e9cfee 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -726,20 +726,6 @@ static void free_map_bootmem(struct page *memmap)
> }
> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
>
> -/**
> - * clear_subsection_map - Clear subsection map of one memory region
> - *
> - * @pfn - start pfn of the memory range
> - * @nr_pages - number of pfns to add in the region
> - *
> - * This is only intended for hotplug, and clear the related subsection
> - * map inside one section.
> - *
> - * Return:
> - * * -EINVAL - Section already deactived.
> - * * 0 - Subsection map is emptied.
> - * * 1 - Subsection map is not empty.
> - */
> static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
> {
> DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> @@ -758,11 +744,12 @@ static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
> return -EINVAL;
>
> bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
> + return 0;
> +}
>
> - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
> - return 0;
> -
> - return 1;
> +static bool is_subsection_map_empty(unsigned long pfn, unsigned long nr_pages)
> +{
> + return bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
> }
>
> static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> @@ -771,11 +758,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> struct mem_section *ms = __pfn_to_section(pfn);
> bool section_is_early = early_section(ms);
> struct page *memmap = NULL;
> - int rc;
> -
>
> - rc = clear_subsection_map(pfn, nr_pages);
> - if (IS_ERR_VALUE((unsigned long)rc))
> + if (unlikely(clear_subsection_map(pfn, nr_pages)))
> return;
> /*
> * There are 3 cases to handle across two configurations
> @@ -794,7 +778,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> *
> * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
> */
> - if (!rc) {
> + if (is_subsection_map_empty(pfn, nr_pages)) {
> unsigned long section_nr = pfn_to_section_nr(pfn);
Tried this way, it's not good in this patch. Since ms->usage might be
freed in this place.
if (!PageReserved(virt_to_page(ms->usage))) {
kfree(ms->usage);
ms->usage = NULL;
}
If have to introduce is_subsection_map_empty(), the code need be
adjusted a little bit. It may need be done in another separate patch to
adjust it. If you agree, I would like to keep this patch as is, later
I can refactor this on top of this patchset, or if anyone else post
patch to adjust it, I can help review.
>
> /*
> @@ -816,7 +800,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> else
> depopulate_section_memmap(pfn, nr_pages, altmap);
>
> - if (!rc)
> + if (is_subsection_map_empty(pfn, nr_pages))
> ms->section_mem_map = (unsigned long)NULL;
> }
>
>
> --
> Thanks,
>
> David / dhildenb
next prev parent reply other threads:[~2020-03-03 8:22 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-20 4:33 [PATCH v2 0/7] mm/hotplug: Only use subsection map in VMEMMAP case Baoquan He
2020-02-20 4:33 ` [PATCH v2 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case Baoquan He
2020-02-20 6:11 ` Wei Yang
2020-02-20 12:07 ` David Hildenbrand
2020-02-26 12:31 ` David Hildenbrand
2020-02-26 13:07 ` Baoquan He
2020-02-26 18:09 ` Dan Williams
2020-03-03 8:34 ` David Hildenbrand
2020-03-03 8:39 ` Baoquan He
2020-02-20 4:33 ` [PATCH v2 2/7] mm/sparse.c: introduce new function fill_subsection_map() Baoquan He
2020-02-20 6:14 ` Wei Yang
2020-02-28 14:27 ` David Hildenbrand
2020-03-01 4:59 ` Baoquan He
2020-02-20 4:33 ` [PATCH v2 3/7] mm/sparse.c: introduce a new function clear_subsection_map() Baoquan He
2020-02-20 6:15 ` Wei Yang
2020-02-28 14:36 ` David Hildenbrand
2020-03-01 5:20 ` Baoquan He
2020-03-02 15:43 ` David Hildenbrand
2020-03-03 1:53 ` Baoquan He
2020-03-03 8:22 ` Baoquan He [this message]
2020-03-03 8:33 ` David Hildenbrand
2020-03-03 8:38 ` Baoquan He
2020-02-20 4:33 ` [PATCH v2 4/7] mm/sparse.c: only use subsection map in VMEMMAP case Baoquan He
2020-02-20 6:17 ` Wei Yang
2020-02-25 9:57 ` Michal Hocko
2020-02-26 3:53 ` Baoquan He
2020-02-26 9:10 ` Michal Hocko
2020-02-28 7:25 ` Baoquan He
2020-02-20 4:33 ` [PATCH v2 5/7] mm/sparse.c: add code comment about sub-section hotplug Baoquan He
2020-02-20 4:33 ` [PATCH v2 6/7] mm/sparse.c: move subsection_map related codes together Baoquan He
2020-02-20 6:18 ` Wei Yang
2020-02-20 7:04 ` Baoquan He
2020-02-20 7:12 ` Wei Yang
2020-02-20 8:55 ` Baoquan He
2020-02-20 21:52 ` Wei Yang
2020-02-20 4:33 ` [PATCH v2 7/7] mm/sparse.c: Use __get_free_pages() instead in populate_section_memmap() Baoquan He
2020-02-20 10:38 ` [PATCH v2 0/7] mm/hotplug: Only use subsection map in VMEMMAP case Michal Hocko
2020-02-21 14:28 ` Baoquan He
2020-02-25 9:10 ` David Hildenbrand
2020-02-25 10:02 ` Michal Hocko
2020-02-26 3:42 ` Baoquan He
2020-02-26 9:14 ` Michal Hocko
2020-02-26 12:30 ` Baoquan He
2020-02-25 10:03 ` Michal Hocko
2020-02-26 3:44 ` Baoquan He
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