Date: Tue, 12 Mar 2013 11:26:02 -0500 From: Alan Cox <alc@rice.edu> To: attilio@FreeBSD.org Cc: Alan Cox <alc@freebsd.org>, src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r248185 - user/attilio/vmcontention/sys/vm Message-ID: <513F571A.5070007@rice.edu> In-Reply-To: <CAJ-FndCU5T4K=sLMF0t0vrn_J=nhASgrtGH7%2BqbeBrZoXr1MmQ@mail.gmail.com> References: <201303120614.r2C6EWve058965@svn.freebsd.org> <CAJ-FndCU5T4K=sLMF0t0vrn_J=nhASgrtGH7%2BqbeBrZoXr1MmQ@mail.gmail.com>
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On 03/12/2013 07:04, Attilio Rao wrote: > On Tue, Mar 12, 2013 at 7:14 AM, Alan Cox <alc@freebsd.org> wrote: >> Author: alc >> Date: Tue Mar 12 06:14:31 2013 >> New Revision: 248185 >> URL: http://svnweb.freebsd.org/changeset/base/248185 >> >> Log: >> When transferring the page from one object to another, don't insert the >> page into its new object until the page's pindex has been updated. >> Otherwise, one code path within vm_radix_insert() may use the wrong >> pindex value. > This is just a style change really because the code already subtracts > offindxstart from current m->pindex when inserting. The pindex on the > page is then adjusted when the real subtraction happens. > IIRC, I did this way because of less diffs against -CURRENT, but the > code looks correct to me already in the older version. > No, as I say in the commit message, there is a path in vm_radix_insert() that uses "page->pindex" and not the "index" argument: /* * A new node is needed because the right insertion level is reached. * Setup the new intermediate node and add the 2 children: the * new object and the older edge. */ tmp2 = vm_radix_node_get(vm_radix_trimkey(page->pindex, clev - 1), 2, clev); Prior to this change, if we follow this path, then we are using the wrong "pindex" value at this point in vm_radix_insert().
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