Date: Mon, 24 Jul 1995 17:16:19 +0100 (BST) From: Doug Rabson <dfr@render.com> To: John Dyson <dyson@freefall.cdrom.com> Cc: dillon@blob.best.net, bugs@freebsd.org Subject: Re: brelse() panic in nfs_read()/nfs_bioread() Message-ID: <Pine.BSF.3.91.950724171431.12542M-100000@minnow.render.com> In-Reply-To: <199507241559.IAA24492@freefall.cdrom.com>
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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? -- Doug Rabson, Microsoft RenderMorphics Ltd. Mail: dfr@render.com Phone: +44 171 251 4411 FAX: +44 171 251 0939
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