From owner-freebsd-bugs Mon Jul 24 09:13:32 1995 Return-Path: bugs-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.11/8.6.6) id JAA25249 for bugs-outgoing; Mon, 24 Jul 1995 09:13:32 -0700 Received: from minnow.render.com (render.demon.co.uk [158.152.30.118]) by freefall.cdrom.com (8.6.11/8.6.6) with ESMTP id JAA25238 ; Mon, 24 Jul 1995 09:13:24 -0700 Received: (from dfr@localhost) by minnow.render.com (8.6.9/8.6.9) id RAA15320; Mon, 24 Jul 1995 17:16:21 +0100 Date: Mon, 24 Jul 1995 17:16:19 +0100 (BST) From: Doug Rabson To: John Dyson cc: dillon@blob.best.net, bugs@freebsd.org Subject: Re: brelse() panic in nfs_read()/nfs_bioread() In-Reply-To: <199507241559.IAA24492@freefall.cdrom.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: bugs-owner@freebsd.org Precedence: bulk On Mon, 24 Jul 1995, John Dyson wrote: > > > > I am mystified by this one. It looks as if the VM system has helpfully > > reallocated one of the pages associated with the buffer between starting > > the read and releasing the buffer. This should be impossible, as the > DG and I have been working this problem for the last few days. It is > indeed subtile... (Actually a similar one -- probably the same cause.) > > > pages are marked busy (vfs_busy_pages(bp, 0)) and the buffer is busy > > (B_BUSY is set). I don't really understand this bogus_page stuff; can > > someone explain it to me? > > > The bogus page stuff is used to keep modified pages that might have > lost their association with a buffer from being lost. > Why does vfs_busy_pages set all the pages in the buffer to bogus_page though? Does bp->b_addr still reference the original pages or does it reference the bogus_page? -- Doug Rabson, Microsoft RenderMorphics Ltd. Mail: dfr@render.com Phone: +44 171 251 4411 FAX: +44 171 251 0939