Date: Wed, 2 Mar 2016 19:39:46 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Maxim Sobolev <sobomax@FreeBSD.org> Cc: Kirk McKusick <mckusick@mckusick.com>, peter@holm.cc, fs@freebsd.org Subject: Re: Process stuck in "vnread" Message-ID: <20160302173946.GL67250@kib.kiev.ua> In-Reply-To: <CAH7qZfvsjavZF1b%2BBP6%2B2itG8buqiObrqPVOBk7q7-9Z9%2BNS2Q@mail.gmail.com> References: <CAH7qZfs3EwT8jnKyodHxF_5nK18MeLSaB_F-qqOfwV0MJMD7Vg@mail.gmail.com> <20160302095339.GB67250@kib.kiev.ua> <CAH7qZfs4jCiP=ARaZjGGW1XVa63a-oOkaWtCO1L1-Hk%2Bema7OQ@mail.gmail.com> <20160302115707.GF67250@kib.kiev.ua> <CAH7qZfvsjavZF1b%2BBP6%2B2itG8buqiObrqPVOBk7q7-9Z9%2BNS2Q@mail.gmail.com>
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On Wed, Mar 02, 2016 at 09:06:37AM -0800, Maxim Sobolev wrote: > Konstantin, this is nullfs mounted over UFS and nullfs is pointing over to > the part of the ZFS tree. I am not sure if it's what you are talking about > or not. > > > storage/builder on /builder (zfs, local, nfsv4acls) > > md0 vnode 3200M /builder/tmp/sspicd_tmp.ufs > > /dev/md0 on /builder/mnt (ufs, asynchronous, local, noatime) > /builder/usr/ports-bitbucket on /builder/mnt/usr/ports (nullfs, local) > > So, stuck process refers to file effectively being copied over from > /builder/mnt/usr/local/share/automake-1.15/compile to > /builder/usr/ports-bitbucket/SOMETHING/./compile by the process chrooted > into /builder/mnt, and it could be either in the read path or in the write > path. However looking at the full kernel side of stack trace of that cp(1), > I'd say it's probably the latter, as this would have to traverse through > top level vfs/ufs first, to nullfs layer and then via zfs, none of the last > two is compiled in so that there is no proper traceback. The nullfs mount > is used to allow it accessing ZFS tree on the upper level, i.e. > /builder/usr. > > Unfortunately I cannot find a way to figure out specific system call that > cp got stuck in. Attempting to attach gdb causes gdb to hang in turn. So > unless somebody got any other ideas on how to get some useful post-mortem > debug out of this situation I'll have to restart the box soon to recover it. > > I will put your patch in and see if it helps. I'd also compile nullfs > statically, so at least if it hits again we have some post-mortem evidence > to work with. No, my patch would not help you. Your problem is hung ZFS.
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