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[209.85.220.65]) by mx.google.com with SMTPS id m6sor971311pfm.141.2018.03.28.02.14.07 for (Google Transport Security); Wed, 28 Mar 2018 02:14:07 -0700 (PDT) Date: Wed, 28 Mar 2018 17:13:57 +0800 From: Wei Yang Subject: Re: [PATCH v2 1/5] mm: page_alloc: remain memblock_next_valid_pfn() when CONFIG_HAVE_ARCH_PFN_VALID is enable Message-ID: <20180328091357.GA97260@WeideMacBook-Pro.local> Reply-To: Wei Yang References: <1521894282-6454-1-git-send-email-hejianet@gmail.com> <1521894282-6454-2-git-send-email-hejianet@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1521894282-6454-2-git-send-email-hejianet@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jia He Cc: Andrew Morton , Michal Hocko , Catalin Marinas , Mel Gorman , Will Deacon , Mark Rutland , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Pavel Tatashin , Daniel Jordan , AKASHI Takahiro , Gioh Kim , Steven Sistare , Daniel Vacek , Eugeniu Rosca , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, James Morse , Ard Biesheuvel , Steve Capper , x86@kernel.org, Greg Kroah-Hartman , Kate Stewart , Philippe Ombredanne , Johannes Weiner , Kemi Wang , Petr Tesarik , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Jia He On Sat, Mar 24, 2018 at 05:24:38AM -0700, Jia He wrote: >Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns >where possible") optimized the loop in memmap_init_zone(). But it causes >possible panic bug. So Daniel Vacek reverted it later. > Why this has a bug? Do you have some link about it? If the audience could know the potential risk, it would be helpful to review the code and decide whether to take it back. >But memblock_next_valid_pfn is valid when CONFIG_HAVE_ARCH_PFN_VALID is >enabled. And as verified by Eugeniu Rosca, arm can benifit from this >commit. So remain the memblock_next_valid_pfn. > >Signed-off-by: Jia He >--- > include/linux/memblock.h | 4 ++++ > mm/memblock.c | 29 +++++++++++++++++++++++++++++ > mm/page_alloc.c | 11 ++++++++++- > 3 files changed, 43 insertions(+), 1 deletion(-) > >diff --git a/include/linux/memblock.h b/include/linux/memblock.h >index 0257aee..efbbe4b 100644 >--- a/include/linux/memblock.h >+++ b/include/linux/memblock.h >@@ -203,6 +203,10 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn, > i >= 0; __next_mem_pfn_range(&i, nid, p_start, p_end, p_nid)) > #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */ > >+#ifdef CONFIG_HAVE_ARCH_PFN_VALID >+unsigned long memblock_next_valid_pfn(unsigned long pfn); >+#endif >+ > /** > * for_each_free_mem_range - iterate through free memblock areas > * @i: u64 used as loop variable >diff --git a/mm/memblock.c b/mm/memblock.c >index ba7c878..bea5a9c 100644 >--- a/mm/memblock.c >+++ b/mm/memblock.c >@@ -1102,6 +1102,35 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid, > *out_nid = r->nid; > } > >+#ifdef CONFIG_HAVE_ARCH_PFN_VALID >+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn) >+{ >+ struct memblock_type *type = &memblock.memory; >+ unsigned int right = type->cnt; >+ unsigned int mid, left = 0; >+ phys_addr_t addr = PFN_PHYS(++pfn); >+ >+ do { >+ mid = (right + left) / 2; >+ >+ if (addr < type->regions[mid].base) >+ right = mid; >+ else if (addr >= (type->regions[mid].base + >+ type->regions[mid].size)) >+ left = mid + 1; >+ else { >+ /* addr is within the region, so pfn is valid */ >+ return pfn; >+ } >+ } while (left < right); >+ >+ if (right == type->cnt) >+ return -1UL; >+ else >+ return PHYS_PFN(type->regions[right].base); >+} >+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/ >+ > /** > * memblock_set_node - set node ID on memblock regions > * @base: base of area to set node ID for >diff --git a/mm/page_alloc.c b/mm/page_alloc.c >index c19f5ac..2a967f7 100644 >--- a/mm/page_alloc.c >+++ b/mm/page_alloc.c >@@ -5483,8 +5483,17 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > if (context != MEMMAP_EARLY) > goto not_early; > >- if (!early_pfn_valid(pfn)) >+ if (!early_pfn_valid(pfn)) { >+#if (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID) In commit b92df1de5d28, it use CONFIG_HAVE_MEMBLOCK_NODE_MAP. Not get the point of your change. >+ /* >+ * Skip to the pfn preceding the next valid one (or >+ * end_pfn), such that we hit a valid pfn (or end_pfn) >+ * on our next iteration of the loop. >+ */ >+ pfn = memblock_next_valid_pfn(pfn) - 1; >+#endif > continue; >+ } > if (!early_pfn_in_nid(pfn, nid)) > continue; > if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised)) >-- >2.7.4 -- Wei Yang Help you, Help me