Date: Mon, 24 Jul 1995 09:18:50 -0700 (PDT) From: John Dyson <dyson> To: dfr@render.com (Doug Rabson) Cc: dillon@blob.best.net, bugs@freebsd.org Subject: Re: brelse() panic in nfs_read()/nfs_bioread() Message-ID: <199507241618.JAA25545@freefall.cdrom.com> In-Reply-To: <Pine.BSF.3.91.950724171431.12542M-100000@minnow.render.com> from "Doug Rabson" at Jul 24, 95 05:16:19 pm
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> > 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
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