Date: Mon, 9 May 2011 20:27:49 +0000 (UTC) From: Max Laier <mlaier@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r221714 - head/sys/vm Message-ID: <201105092027.p49KRnkJ011953@svn.freebsd.org>
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Author: mlaier Date: Mon May 9 20:27:49 2011 New Revision: 221714 URL: http://svn.freebsd.org/changeset/base/221714 Log: Another long standing vm bug found at Isilon: Fix a race between vm_object_collapse and vm_fault. Reviewed by: alc@ MFC after: 3 days Modified: head/sys/vm/vm_object.c Modified: head/sys/vm/vm_object.c ============================================================================== --- head/sys/vm/vm_object.c Mon May 9 20:20:43 2011 (r221713) +++ head/sys/vm/vm_object.c Mon May 9 20:27:49 2011 (r221714) @@ -1468,6 +1468,24 @@ vm_object_backing_scan(vm_object_t objec pp = vm_page_lookup(object, new_pindex); if ( + (op & OBSC_COLLAPSE_NOWAIT) != 0 && + (pp != NULL && pp->valid == 0) + ) { + /* + * The page in the parent is not (yet) valid. + * We don't know anything about the state of + * the original page. It might be mapped, + * so we must avoid the next if here. + * + * This is due to a race in vm_fault() where + * we must unbusy the original (backing_obj) + * page before we can (re)lock the parent. + * Hence we can get here. + */ + p = next; + continue; + } + if ( pp != NULL || vm_pager_has_page(object, new_pindex, NULL, NULL) ) {
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