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perf_counter: allow and require one-page mmap on counting counters 

A brainfart stopped single page mmap()s working. The rest of the code
should be perfectly fine with not having any data pages.

Reported-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <1237981712.7972.812.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-03-25 12:48:31 +01:00 committed by Ingo Molnar
parent 00f0ad73ac
commit 7730d86558
1 changed files with 5 additions and 1 deletions
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6
kernel/perf_counter.c
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@ -1369,7 +1369,11 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
vma_size = vma->vm_end - vma->vm_start;
nr_pages = (vma_size / PAGE_SIZE) - 1;
if (nr_pages == 0 || !is_power_of_2(nr_pages))
/*
* If we have data pages ensure they're a power-of-two number, so we
* can do bitmasks instead of modulo.
*/
if (nr_pages != 0 && !is_power_of_2(nr_pages))
return -EINVAL;
if (vma_size != PAGE_SIZE * (1 + nr_pages))