From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 383176B0261 for ; Thu, 5 Oct 2017 17:12:19 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id k7so11053088wre.5 for ; Thu, 05 Oct 2017 14:12:19 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id a11si206128edb.453.2017.10.05.14.12.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Oct 2017 14:12:17 -0700 (PDT) From: Pavel Tatashin Subject: [PATCH v10 05/10] mm: zero reserved and unavailable struct pages Date: Thu, 5 Oct 2017 17:11:19 -0400 Message-Id: <20171005211124.26524-6-pasha.tatashin@oracle.com> In-Reply-To: <20171005211124.26524-1-pasha.tatashin@oracle.com> References: <20171005211124.26524-1-pasha.tatashin@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, kasan-dev@googlegroups.com, borntraeger@de.ibm.com, heiko.carstens@de.ibm.com, davem@davemloft.net, willy@infradead.org, mhocko@kernel.org, ard.biesheuvel@linaro.org, mark.rutland@arm.com, will.deacon@arm.com, catalin.marinas@arm.com, sam@ravnborg.org, mgorman@techsingularity.net, steven.sistare@oracle.com, daniel.m.jordan@oracle.com, bob.picco@oracle.com Some memory is reserved but unavailable: not present in memblock.memory (because not backed by physical pages), but present in memblock.reserved. Such memory has backing struct pages, but they are not initialized by going through __init_single_page(). In some cases these struct pages are accessed even if they do not contain any data. One example is page_to_pfn() might access page->flags if this is where section information is stored (CONFIG_SPARSEMEM, SECTION_IN_PAGE_FLAGS). One example of such memory: trim_low_memory_range() unconditionally reserves from pfn 0, but e820__memblock_setup() might provide the exiting memory from pfn 1 (i.e. KVM). Since, struct pages are zeroed in __init_single_page(), and not during allocation time, we must zero such struct pages explicitly. The patch involves adding a new memblock iterator: for_each_resv_unavail_range(i, p_start, p_end) Which iterates through reserved && !memory lists, and we zero struct pages explicitly by calling mm_zero_struct_page(). Signed-off-by: Pavel Tatashin Reviewed-by: Steven Sistare Reviewed-by: Daniel Jordan Reviewed-by: Bob Picco --- include/linux/memblock.h | 16 ++++++++++++++++ include/linux/mm.h | 15 +++++++++++++++ mm/page_alloc.c | 38 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 69 insertions(+) diff --git a/include/linux/memblock.h b/include/linux/memblock.h index bae11c7e7bf3..ce8bfa5f3e9b 100644 --- a/include/linux/memblock.h +++ b/include/linux/memblock.h @@ -237,6 +237,22 @@ unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn); for_each_mem_range_rev(i, &memblock.memory, &memblock.reserved, \ nid, flags, p_start, p_end, p_nid) +/** + * for_each_resv_unavail_range - iterate through reserved and unavailable memory + * @i: u64 used as loop variable + * @flags: pick from blocks based on memory attributes + * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL + * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL + * + * Walks over unavailable but reserved (reserved && !memory) areas of memblock. + * Available as soon as memblock is initialized. + * Note: because this memory does not belong to any physical node, flags and + * nid arguments do not make sense and thus not exported as arguments. + */ +#define for_each_resv_unavail_range(i, p_start, p_end) \ + for_each_mem_range(i, &memblock.reserved, &memblock.memory, \ + NUMA_NO_NODE, MEMBLOCK_NONE, p_start, p_end, NULL) + static inline void memblock_set_region_flags(struct memblock_region *r, unsigned long flags) { diff --git a/include/linux/mm.h b/include/linux/mm.h index 065d99deb847..04c8b2e5aff4 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -94,6 +94,15 @@ extern int mmap_rnd_compat_bits __read_mostly; #define mm_forbids_zeropage(X) (0) #endif +/* + * On some architectures it is expensive to call memset() for small sizes. + * Those architectures should provide their own implementation of "struct page" + * zeroing by defining this macro in . + */ +#ifndef mm_zero_struct_page +#define mm_zero_struct_page(pp) ((void)memset((pp), 0, sizeof(struct page))) +#endif + /* * Default maximum number of active map areas, this limits the number of vmas * per mm struct. Users can overwrite this number by sysctl but there is a @@ -2001,6 +2010,12 @@ extern int __meminit __early_pfn_to_nid(unsigned long pfn, struct mminit_pfnnid_cache *state); #endif +#ifdef CONFIG_HAVE_MEMBLOCK +void zero_resv_unavail(void); +#else +static inline void zero_resv_unavail(void) {} +#endif + extern void set_dma_reserve(unsigned long new_dma_reserve); extern void memmap_init_zone(unsigned long, int, unsigned long, unsigned long, enum memmap_context); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 20b0bace2235..5f0013bbbe9d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6209,6 +6209,42 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size, free_area_init_core(pgdat); } +#ifdef CONFIG_HAVE_MEMBLOCK +/* + * Only struct pages that are backed by physical memory are zeroed and + * initialized by going through __init_single_page(). But, there are some + * struct pages which are reserved in memblock allocator and their fields + * may be accessed (for example page_to_pfn() on some configuration accesses + * flags). We must explicitly zero those struct pages. + */ +void __paginginit zero_resv_unavail(void) +{ + phys_addr_t start, end; + unsigned long pfn; + u64 i, pgcnt; + + /* Loop through ranges that are reserved, but do not have reported + * physical memory backing. + */ + pgcnt = 0; + for_each_resv_unavail_range(i, &start, &end) { + for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) { + mm_zero_struct_page(pfn_to_page(pfn)); + pgcnt++; + } + } + + /* + * Struct pages that do not have backing memory. This could be because + * firmware is using some of this memory, or for some other reasons. + * Once memblock is changed so such behaviour is not allowed: i.e. + * list of "reserved" memory must be a subset of list of "memory", then + * this code can be removed. + */ + pr_info("Reserved but unavailable: %lld pages", pgcnt); +} +#endif /* CONFIG_HAVE_MEMBLOCK */ + #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP #if MAX_NUMNODES > 1 @@ -6632,6 +6668,7 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn) node_set_state(nid, N_MEMORY); check_for_memory(pgdat, nid); } + zero_resv_unavail(); } static int __init cmdline_parse_core(char *p, unsigned long *core) @@ -6795,6 +6832,7 @@ void __init free_area_init(unsigned long *zones_size) { free_area_init_node(0, zones_size, __pa(PAGE_OFFSET) >> PAGE_SHIFT, NULL); + zero_resv_unavail(); } static int page_alloc_cpu_dead(unsigned int cpu) -- 2.14.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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