Date: Mon, 24 Jul 1995 15:11:49 +0100 (BST) From: Doug Rabson <dfr@render.com> To: Matt Dillon <dillon@blob.best.net> Cc: bugs@freebsd.org Subject: Re: brelse() panic in nfs_read()/nfs_bioread() Message-ID: <Pine.BSF.3.91.950724150529.12542F-100000@minnow.render.com> In-Reply-To: <199507240638.XAA02219@blob.best.net>
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On Sun, 23 Jul 1995, Matt Dillon wrote: > Here's another one. I traced it out a bit to try > to give you guys as much info as possible. I am keeping > the crash dump around (all 134MB of it) as well. > > The mount point for the vp in question is /var/log/www, > which is an NFS mount to some other machine. I printed > out the vp->v_data's nfsnode down below as well. > > I can't quite tell which file caused the error, but judging > by the data and the size of the file, I believe it is my > 30-minute WWW log. Every 30 minutes, this file is truncated > to 0 by a process on the NFS server. It is possible that this > truncation may be related to the crash, and it is possible > that it is not related. > > This is the first time we have gotten this particular panic. 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 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? Can you reproduce this? Can you reproduce it with VFS_BIO_DEBUG defined in vfs_bio.c? -- Doug Rabson, Microsoft RenderMorphics Ltd. Mail: dfr@render.com Phone: +44 171 251 4411 FAX: +44 171 251 0939
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