Date: Thu, 25 Nov 2004 10:43:36 +1030 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Xin LI <delphij@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/vm vm_contig.c Message-ID: <20041125001336.GP43681@wantadilla.lemis.com> In-Reply-To: <200411241856.iAOIuDo5055072@repoman.freebsd.org> References: <200411241856.iAOIuDo5055072@repoman.freebsd.org>
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--KI6XeYrntNhU1GwB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wednesday, 24 November 2004 at 18:56:13 +0000, Xin LI wrote: > delphij 2004-11-24 18:56:13 UTC > > FreeBSD src repository > > Modified files: > sys/vm vm_contig.c > Log: > Try to close a potential, but serious race in our VM subsystem. > > Historically, our contigmalloc1() and contigmalloc2() assumes > that a page in PQ_CACHE can be unconditionally reused by busying > and freeing it. Unfortunatelly, when object happens to be not > NULL, the code will set m->object to NULL and disregard the fact > that the page is actually in the VM page bucket, resulting in > page bucket hash table corruption and finally, a filesystem > corruption, or a 'page not in hash' panic. > > This commit has borrowed the idea taken from DragonFlyBSD's fix > to the VM fix by Matthew Dillon[1]. This version of patch will > do the following checks: > > - When scanning pages in PQ_CACHE, check hold_count and > skip over pages that are held temporarily. > - For pages in PQ_CACHE and selected as candidate of being > freed, check if it is busy at that time. > > Note: It seems that this is might be unrelated to kern/72539. Nice log message! Thanks. Greg -- See complete headers for address and phone numbers. --KI6XeYrntNhU1GwB Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (FreeBSD) iD8DBQFBpSOwIubykFB6QiMRAuajAKCa25SklZiiNrqN7rfjz9sZWO9FaACfdxkL wXkqhVmDZs/OES6rS5Cq4Pc= =ikq5 -----END PGP SIGNATURE----- --KI6XeYrntNhU1GwB--
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