Date: Thu, 29 Sep 2011 08:59:38 -0700 From: Kirk McKusick <mckusick@mckusick.com> To: Attilio Rao <attilio@freebsd.org> Cc: Garrett Cooper <yanegomi@gmail.com>, freebsd-fs@freebsd.org, Xin LI <delphij@freebsd.org> Subject: Re: Need to force sync(2) before umounting UFS1 filesystems? Message-ID: <201109291559.p8TFxc63084067@chez.mckusick.com> In-Reply-To: <CAJ-FndDxsVYkPQfqiYfshh%2BkpCyfbGTL0m%2BoCN37qXyjAucM6g@mail.gmail.com>
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> Date: Thu, 29 Sep 2011 17:40:43 +0200 > Subject: Re: Need to force sync(2) before umounting UFS1 filesystems? > From: Attilio Rao <attilio@freebsd.org> > To: Kirk McKusick <mckusick@mckusick.com> > Cc: Garrett Cooper <yanegomi@gmail.com>, freebsd-fs@freebsd.org, > Xin LI <delphij@freebsd.org> > > 2011/9/29 Kirk McKusick <mckusick@mckusick.com>: > > > Thanks for providing a bit more of the history on this codepath. > > > > Since 9-stable has now been branched, I believe that the best path > > forward is to check this change into head and let it sit there for > > several months so that we can get some experience with it. If it > > causes folks problems we can back it out. If it does not cause > > problems, then we can MFC it to 9-stable. > > > > Does this seem like a reasonable approach? > > In general yes, but I'd like to understand why unmount should fail so > much with SU... do we do extended period with vfs_busy()'ed > filesystem? > > I need more context here, likely I'd need to look into the PRs too > before to give an informative answer. > > Attilio I am definitely not in a rush on this, so by all means take some time to look it over. The EBUSY unmount has been in its current state for several years, so I am fine with taking a few weeks to sort out the correct solution. Indeed, I am glad that Garrett has volunteered to do some more serious testing. If this general approach is not correct, I can put a hook in for just UFS so that it can have its historic behavior. As you have noted, the SU code has a lot of activity that gets done under the protection of vfs_busy. So it may be the only filesystem for which draining the vfs_busy lock during unmount is needed. Will you be at the EuroBSD conference next week? If so we can discuss this there. > Date: Thu, 29 Sep 2011 08:38:59 -0700 > Subject: Re: Need to force sync(2) before umounting UFS1 filesystems? > From: Garrett Cooper <yanegomi@gmail.com> > To: Kirk McKusick <mckusick@mckusick.com> > Cc: Attilio Rao <attilio@freebsd.org>, freebsd-fs@freebsd.org, > Xin LI <delphij@freebsd.org> > > > Does this seem like a reasonable approach? > > I'll give it a quick run through first on some machines this weekend, > with NFS, UFS, and ZFS. It seems like this could negatively affect a > number of users, so I want to make sure that it passes a smoke test > before committing directly to HEAD. > > Thanks! > -Garrett Thanks for doing these tests to help us find out if there are landmines in this change. Kirk McKusick
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