From owner-freebsd-bugs Mon Jul 24 09:18:51 1995 Return-Path: bugs-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.11/8.6.6) id JAA25554 for bugs-outgoing; Mon, 24 Jul 1995 09:18:51 -0700 Received: (from dyson@localhost) by freefall.cdrom.com (8.6.11/8.6.6) id JAA25545 ; Mon, 24 Jul 1995 09:18:50 -0700 From: John Dyson Message-Id: <199507241618.JAA25545@freefall.cdrom.com> Subject: Re: brelse() panic in nfs_read()/nfs_bioread() To: dfr@render.com (Doug Rabson) Date: Mon, 24 Jul 1995 09:18:50 -0700 (PDT) Cc: dillon@blob.best.net, bugs@freebsd.org In-Reply-To: from "Doug Rabson" at Jul 24, 95 05:16:19 pm X-Mailer: ELM [version 2.4 PL24] Content-Type: text Content-Length: 1225 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? > Yikes!!! All of the pages??!!?!? I am at my primary job right now and not able to dedicate lots of time to it, but I DO NOT expect that all of the pages would be bogus!?!?!? It sort-of defeats the purpose. Definitely going to look at it tonight... John dyson@root.com