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Sun, 1 Mar 2020 05:20:34 +0000 (UTC) Received: from localhost (ovpn-12-59.pek2.redhat.com [10.72.12.59]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ED13F8C091; Sun, 1 Mar 2020 05:20:31 +0000 (UTC) Date: Sun, 1 Mar 2020 13:20:28 +0800 From: Baoquan He To: David Hildenbrand 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() Message-ID: <20200301052028.GN24216@MiWiFi-R3L-srv> References: <20200220043316.19668-1-bhe@redhat.com> <20200220043316.19668-4-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > > --- > > 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. if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION), "section already deactivated (%#lx + %ld)\n", pfn, nr_pages)) return; > > I dislike the "rc" handling in the caller. > > > + return 1; > > +} > > + > > +static void section_deactivate(unsigned long pfn, unsigned long nr_pages, > > + struct vmem_altmap *altmap) > > +{ > > + struct mem_section *ms = __pfn_to_section(pfn); > > + bool section_is_early = early_section(ms); > > + struct page *memmap = NULL; > > + int rc; > > + > > + > > one superfluous empty line > > > + rc = clear_subsection_map(pfn, nr_pages); > > + if (IS_ERR_VALUE((unsigned long)rc)) > > huh? "if (rc < 0)" ? or am I missing something? Both is fine to me, I have no preference, can change like this. > > > + return; > > /* > > * There are 3 cases to handle across two configurations > > * (SPARSEMEM_VMEMMAP={y,n}): > > @@ -763,8 +794,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, > > * > > * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified > > */ > > - bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION); > > - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) { > > + if (!rc) { > > unsigned long section_nr = pfn_to_section_nr(pfn); > > > > /* > > @@ -786,7 +816,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, > > else > > depopulate_section_memmap(pfn, nr_pages, altmap); > > > > - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) > > + if (!rc) > > I don't really like that handling. > > Either > > s/rc/section_empty/ > > or use a separate subsection_map_empty() > > > ms->section_mem_map = (unsigned long)NULL; > > } > > > > > > Thanks! > > -- > Thanks, > > David / dhildenb