Messages in this thread Patch in this message | | | From | Jerry <> | Subject | [PATCH] mm: negative left shift count when PAGE_SHIFT > 20 | Date | Fri, 19 Jul 2013 00:56:12 +0800 |
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When PAGE_SHIFT > 20, the result of "20 - PAGE_SHIFT" is negative. The calculating here will generate an unexpected result. In addition, if PAGE_SHIFT > 20, The memory size represented by numentries was already integral multiple of 1MB.
Signed-off-by: Jerry <uulinux@gmail.com> --- mm/page_alloc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b100255..cd41797 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5745,9 +5745,11 @@ void *__init alloc_large_system_hash(const char *tablename, if (!numentries) { /* round applicable memory size up to nearest megabyte */ numentries = nr_kernel_pages; - numentries += (1UL << (20 - PAGE_SHIFT)) - 1; - numentries >>= 20 - PAGE_SHIFT; - numentries <<= 20 - PAGE_SHIFT; + if (20 > PAGE_SHIFT) { + numentries += (1UL << (20 - PAGE_SHIFT)) - 1; + numentries >>= 20 - PAGE_SHIFT; + numentries <<= 20 - PAGE_SHIFT; + } /* limit to 1 bucket per 2^scale bytes of low memory */ if (scale > PAGE_SHIFT) -- 1.8.1.5
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