Messages in this thread | ![/](/images/icornerl.gif) | | From | David Howells <> | Subject | Re: [PATCH] Fix order_base_2(0) | Date | Thu, 15 Dec 2011 00:33:44 +0000 |
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Linus Torvalds <torvalds@linux-foundation.org> wrote:
> Does anybody actually *want* order_base_2(0)?
There aren't actually that many users:
| arch/mips/include/asm/mach-powertv/ioremap.h:#define _IOR_OFFSET_WIDTH(n) (1 << order_base_2(n))
Doesn't look like it should ever be 0. In fact, this looks like a case for using roundup_pow_of_two() directly.
| arch/powerpc/platforms/pseries/iommu.c: len = order_base_2(max_addr);
Not sure. Doesn't look likely, but can memory_hotplug_max() be 0 if hotplug is not supported?
| arch/x86/kvm/x86.c: return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU));
Constant 64. Can't be 0.
| fs/ext4/indirect.c: blk_bits = order_base_2(lblock);
lblock *could* perhaps be 0. Being negative is checked for, but not for it being 0.
| fs/ext4/mballoc.c: int blocksize_bits = order_base_2(size); | fs/jbd2/journal.c: int i = order_base_2(size) - 10;
Can't be 0.
| fs/jbd2/journal.c: int i = order_base_2(size) - 10;
Hmmm... Can jbd2_alloc() be given a 0 size? (Or jbd2_free() for that matter)
| mm/percpu-km.c: pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages)); | mm/percpu-km.c: __free_pages(chunk->data, order_base_2(nr_pages));
Can pcpu_group_sizes[0] be less than PAGE_SIZE?
I can't tell from a cursory inspection of pcpu_setup_first_chunk().
In fact, pcpu_create_chunk() could do order_base_2() then subtract PAGE_SHIFT rather than shifting and then taking the log.
David
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