Date: 24 Sep 1998 22:29:15 -0400 From: "Robert V. Baron" <rvb@cs.cmu.edu> To: Luoqi Chen <luoqi@watermarkgroup.com> Cc: committers@FreeBSD.ORG, dillon@backplane.com Subject: Re: Having some serious file write / mmap inconsistancy problems Message-ID: <yzsu31x7wn8.fsf@sicily.odyssey.cs.cmu.edu> In-Reply-To: Luoqi Chen's message of Thu, 24 Sep 1998 14:37:15 -0400 (EDT) References: <199809241837.OAA26496@lor.watermarkgroup.com>
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I have a possibly similar possibly different problem that could be explained (I think) with this sort of an inconsistency. I have a file system (Coda). Its vnodes contain Coda state but also contain the vnode of a cache file (typically ufs). So when you do open/close you open both vnodes and when you do read/write on a Coda vnode, you reapply the operation to the ufs vnode. So now consider copying a file from somewhere (say even coda) into coda. The copy will diff the same. But cmp different (cmp uses mmap). ALso you can not execute the file because the data is garbled (maping again). Again diff works fine. Ok so somehow I've managed to separate the object from the vnode (more on that later). But I lied/simplified before; sometimes the copies cmp and execute fine. What I don't totally understand at all, is that if I do several copies in a row. Some will work and some will not and it seems to be in runs. This sounds like a perfect opporunity of losing some dirty bits. NOTE: There is an added complexity here, because we're probably mapping the object associated with the Coda vnode (not the ufs vnode). So having two objects involved might be my problem. But I really can not understand why it would be intermittent.
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