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Message-Id: <1357379377-30021-1-git-send-email-jcmvbkbc@gmail.com> Date: Sat, 5 Jan 2013 13:49:37 +0400 From: Max Filippov <jcmvbkbc@...il.com> To: linux-kernel@...r.kernel.org Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, Johannes Weiner <hannes@...xchg.org>, "David S. Miller" <davem@...emloft.net>, Tejun Heo <tj@...nel.org>, Joonsoo Kim <js1304@...il.com>, Max Filippov <jcmvbkbc@...il.com> Subject: [PATCH v3] mm: bootmem: fix free_all_bootmem_core with odd bitmap alignment Currently free_all_bootmem_core ignores that node_min_pfn may be not multiple of BITS_PER_LONG. E.g. commit 6dccdcbe "mm: bootmem: fix checking the bitmap when finally freeing bootmem" shifts vec by lower bits of start instead of lower bits of idx. Also if (IS_ALIGNED(start, BITS_PER_LONG) && vec == ~0UL) assumes that vec bit 0 corresponds to start pfn, which is only true when node_min_pfn is a multiple of BITS_PER_LONG. Also loop in the else clause can double-free pages (e.g. with node_min_pfn == start == 1, map[0] == ~0 on 32-bit machine page 32 will be double-freed). This bug causes the following message during xtensa kernel boot: [ 0.000000] bootmem::free_all_bootmem_core nid=0 start=1 end=8000 [ 0.000000] BUG: Bad page state in process swapper pfn:00001 [ 0.000000] page:d04bd020 count:0 mapcount:-127 mapping: (null) index:0x2 [ 0.000000] page flags: 0x0() [ 0.000000] [ 0.000000] Stack: 00000000 00000002 00000004 ffffffff d0193e44 ffffff81 00000000 00000002 [ 0.000000] 90038c66 d0193e90 d04bd020 000001a8 00000000 ffffffff 00000000 00000020 [ 0.000000] 90039a4c d0193eb0 d04bd020 00000001 d04b7b20 ffff8ad0 00000000 00000000 [ 0.000000] Call Trace: [ 0.000000] [<d0038bf8>] bad_page+0x8c/0x9c [ 0.000000] [<d0038c66>] free_pages_prepare+0x5e/0x88 [ 0.000000] [<d0039a4c>] free_hot_cold_page+0xc/0xa0 [ 0.000000] [<d0039b28>] __free_pages+0x24/0x38 [ 0.000000] [<d01b8230>] __free_pages_bootmem+0x54/0x56 [ 0.000000] [<d01b1667>] free_all_bootmem_core$part$11+0xeb/0x138 [ 0.000000] [<d01b179e>] free_all_bootmem+0x46/0x58 [ 0.000000] [<d01ae7a9>] mem_init+0x25/0xa4 [ 0.000000] [<d01ad13e>] start_kernel+0x11e/0x25c [ 0.000000] [<d01a9121>] should_never_return+0x0/0x3be7 The fix is the following: - always align vec so that its bit 0 corresponds to start - provide BITS_PER_LONG bits in vec, if those bits are available in the map - don't free pages past next start position in the else clause. Signed-off-by: Max Filippov <jcmvbkbc@...il.com> --- Arrrgh, I no longer send patches at 4am, sorry ): v1 didn't build, v2 else loop initialization was wrong. mm/bootmem.c | 24 ++++++++++++++++++------ 1 files changed, 18 insertions(+), 6 deletions(-) diff --git a/mm/bootmem.c b/mm/bootmem.c index 1324cd7..b93376c 100644 --- a/mm/bootmem.c +++ b/mm/bootmem.c @@ -185,10 +185,23 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata) while (start < end) { unsigned long *map, idx, vec; + unsigned shift; map = bdata->node_bootmem_map; idx = start - bdata->node_min_pfn; + shift = idx & (BITS_PER_LONG - 1); + /* + * vec holds at most BITS_PER_LONG map bits, + * bit 0 corresponds to start. + */ vec = ~map[idx / BITS_PER_LONG]; + + if (shift) { + vec >>= shift; + if (end - start >= BITS_PER_LONG) + vec |= ~map[idx / BITS_PER_LONG + 1] << + (BITS_PER_LONG - shift); + } /* * If we have a properly aligned and fully unreserved * BITS_PER_LONG block of pages in front of us, free @@ -201,19 +214,18 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata) count += BITS_PER_LONG; start += BITS_PER_LONG; } else { - unsigned long off = 0; + unsigned long cur = start; - vec >>= start & (BITS_PER_LONG - 1); - while (vec) { + start = ALIGN(start + 1, BITS_PER_LONG); + while (vec && cur != start) { if (vec & 1) { - page = pfn_to_page(start + off); + page = pfn_to_page(cur); __free_pages_bootmem(page, 0); count++; } vec >>= 1; - off++; + ++cur; } - start = ALIGN(start + 1, BITS_PER_LONG); } } -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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