Date: Thu, 29 Sep 2011 17:40:43 +0200 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> Subject: Re: Need to force sync(2) before umounting UFS1 filesystems? Message-ID: <CAJ-FndDxsVYkPQfqiYfshh%2BkpCyfbGTL0m%2BoCN37qXyjAucM6g@mail.gmail.com> In-Reply-To: <201109291531.p8TFVRka077669@chez.mckusick.com> References: <CAJ-FndA=769o9_FgA0vXTKFbnxCSaJ_5XUiAsYpa3vCAQBLH7Q@mail.gmail.com> <201109291531.p8TFVRka077669@chez.mckusick.com>
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2011/9/29 Kirk McKusick <mckusick@mckusick.com>: >> Date: Thu, 29 Sep 2011 12:04:24 +0200 >> From: Attilio Rao <attilio@freebsd.org> >> To: Kirk McKusick <mckusick@mckusick.com> >> Cc: Garrett Cooper <yanegomi@gmail.com>, freebsd-fs@freebsd.org, >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 Xin LI <delphij@freebsd.org> >> Subject: Re: Need to force sync(2) before umounting UFS1 filesystems? >> >> 2011/9/29 Kirk McKusick <mckusick@mckusick.com>: >> > Hi Attilio, >> > >> > I have been looking into the problem described below and since you >> > appear to be the person that put in the change in question, I would >> > like to get you opinion on what (if anything) should be changed here. >> >> Kirk, >> please note that I didn't add/change anything wrt. that codepath. >> >> In the old code it was present a lockmgr() acquisition with LK_DRAIN >> and LK_NOWAIT. This means that if the lockmgr() lock on the struct >> mount was already held by any other consumer it was going to fallback >> in the codepath you outlined in the patch immediately, rather than >> just sleeping (and note that LK_NOWAIT was just passed in the case of >> a non-forced unmount). >> >> Said that, I don't really have an objection with making the forced >> unmount case as the default, but I still didn't go through the whole >> thread you outlined and I don't have any context on it, thus I'm not >> sure if this is the right approach or not. >> >> If you want to share more context on the problem you are trying to >> solve by switching that policy we may discuss this too, but in general >> I don't have a problem about adopting forced unmount policy on unmount >> for all the cases. >> >> Attilio >> -- >> Peace can only be achieved by understanding - A. Einstein > > 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 --=20 Peace can only be achieved by understanding - A. Einstein
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