Date: Fri, 19 Jul 2013 13:30:25 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Andriy Gapon <avg@FreeBSD.org> Cc: freebsd-fs@FreeBSD.org, Adrian Chadd <adrian@FreeBSD.org> Subject: Re: Deadlock in nullfs/zfs somewhere Message-ID: <20130719103025.GJ5991@kib.kiev.ua> In-Reply-To: <51E91277.3070309@FreeBSD.org> References: <CAJ-VmokctCmV4%2By17uvqO9wXEyh0s%2BaXZ9nggvoAgP5%2BZHSgFA@mail.gmail.com> <51E59FD9.4020103@FreeBSD.org> <CAJ-VmokR8jJpdRc_kBJzhW4_R1pJnj3UPfsG5ANpq-kEGwCP9g@mail.gmail.com> <51E67F54.9080800@FreeBSD.org> <CAJ-Vmonk2HAzX38-mbL8hwxiUfL6JyJrMTq0dTBctW=P4dfyEQ@mail.gmail.com> <51E7B686.4090509@FreeBSD.org> <20130718112814.GA5991@kib.kiev.ua> <51E7F05A.5020609@FreeBSD.org> <20130718185215.GE5991@kib.kiev.ua> <51E91277.3070309@FreeBSD.org>
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--WHG05yakhlzm8Hk1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jul 19, 2013 at 01:18:31PM +0300, Andriy Gapon wrote: > on 18/07/2013 21:52 Konstantin Belousov said the following: > > There is VFS method VFS_SUSP_CLEAN, called when the suspension is > > lifted. UFS uses it to clean the back-queue of work which were > > not performed during the suspend, mostly inactivate the postponed > > inactive vnodes. ZFS probably does not need it, since it does > > not check for MNTK_SUSPEND, but if it starts care, there is a place > > to put the code. >=20 > I will keep this in mind. >=20 > > On the other hand, I believe that your patch is notoriously incomplete, > > because there should be a lot of threads which mutate ZFS mounts state > > and which do not call vn_start_write() around the mutations. I.e. > > all ZFS top-level code which calls into ZFS ops and which is not > > coming from VFS. >=20 > I agree. What I am trying to fix right now is VFS<->ZFS interaction. I = think > that ZFS<->ZFS should already be fine - it's protected by internal ZFS lo= cking. > OTOH, perhaps my understanding of what you said is incomplete or incorrec= t, > because VFS suspension mechanism is completely unknown to me yet. >=20 I think that you should satisfy the VFS invariants, and prevent mutators =66rom operating on the filesystem when MNTK_SUSPEND is set, for the case mutators are running outside the context where VFS could call vn_start_write() around. --WHG05yakhlzm8Hk1 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.20 (FreeBSD) iQIcBAEBAgAGBQJR6RVAAAoJEJDCuSvBvK1Bjq4P/2tWXpxKdyvuEJiqeer5wEsm DfErzv7U3fE9tDE0XNUgzDroXTWEQATJr3brdxUTpOvBVcQYKGWVR2jEAavZaWz9 YIH8tbat783yjiem0mvULlNRUJ7QRY12yPLMzetJkgmZAt3ocH4P6k+aHgqyisVu InzNL+Ekc1+0uD4AqEShuueQ2raypLUnY8B7FfAM6APcSO4ARvo8O8Z808hjXk4g cO8VGwvwwFxVT8j+7Woocs0pypRXyQkIhR6xVeBjst81VOzPdvvut8Ic9EH0nOdu 62YPkq4zwGQnyNLoYlWWYMYqNoA1D8AyzPpnmrT2PlVI6lZ3uBcRTRVIKxoQ37b9 h8zIrkHZK7f0o/f8X77VDVlFgzxQst637CjtDio+t9FKWYh5fG3DnR5kFqetXM6G uRuGjn2f2YLKfL2om2bYNdb0CQePdwhehnnegiIA/atAnPGHY6+YZTLi/CTD1Aal 3RwGChQuVsFecZuhlCdaEAeiWMCj+e2wuJEnkX5zzwrWc93t7QYUqBPMXLvYEcEy RwSlm2oN1HO3NX5q7vn9bWlRCyiYQILB4iGC5TIEM8RxYI46kQC8/+NVnIP5AC+n JzWd7cS99E8QdCBkr1DLmEa8H9dQMAtpJegeN6pILtzh56DmASFtXgcKo58PkIHj S8rrSKhnP9Cu5faDKVS2 =9m4K -----END PGP SIGNATURE----- --WHG05yakhlzm8Hk1--
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