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SubjectRe: [patch V2 11/16] x86/ioperm: Share I/O bitmap if identical
On Tue, 12 Nov 2019, Peter Zijlstra wrote:
> On Mon, Nov 11, 2019 at 11:03:25PM +0100, Thomas Gleixner wrote:
> > @@ -59,8 +71,26 @@ long ksys_ioperm(unsigned long from, uns
> > return -ENOMEM;
> >
> > memset(iobm->bits, 0xff, sizeof(iobm->bits));
> > + refcount_set(&iobm->refcnt, 1);
> > + }
> > +
> > + /*
> > + * If the bitmap is not shared, then nothing can take a refcount as
> > + * current can obviously not fork at the same time. If it's shared
> > + * duplicate it and drop the refcount on the original one.
> > + */
> > + if (refcount_read(&iobm->refcnt) > 1) {
> > + iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
> > + if (!iobm)
> > + return -ENOMEM;
> > + io_bitmap_exit();
> refcount_set(&iobm->refcnd, 1);

Indeed.

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