Date: Fri, 4 Mar 2016 16:23:28 +0100 From: Peter Holm <peter@holm.cc> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Maxim Sobolev <sobomax@sippysoft.com>, Kirk McKusick <mckusick@mckusick.com>, fs@freebsd.org Subject: Re: Process stuck in "vnread" Message-ID: <20160304152328.GA71951@x2.osted.lan> In-Reply-To: <20160302115707.GF67250@kib.kiev.ua> 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>
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On Wed, Mar 02, 2016 at 01:57:07PM +0200, Konstantin Belousov wrote: > On Wed, Mar 02, 2016 at 03:02:02AM -0800, Maxim Sobolev wrote: > > About the backtrace, indeed, looks like you are right and some portion of > > it is not decoded properly, as it's loaded as a kernel module. The setup is > > somewhat even more complicated, the /usr/ports is mounted via NULLFS, so in > > this command: > > > > cp /usr/local/share/automake-1.15/compile ./compile > > > > The target (i.e. ./compile) here is a path on ZFS that is exported via > > NULLFS, while the source is a file on UFS2->md->ZFS. This is probably the > > reason stack trace is incomplete, both zfs.ko and nullfs.ko are loaded as > > modules and the next few frames point towards those. Unfortunately I cannot > > beat kgdb to read symbols from those .ko's and decode them. > > Is nullfs mount put over ZFS only ? The backtrace you shown cannot > happen for ZFS, since ZFS has its own pager vop. In fact, I would > agree that the backtrace is reasonable for nullfs over UFS upper vnode. > The following patch should fix the 'paging while faulting on uiomove' > issue for nullfs over UFS. > > Peter, could you, please, test the patch ? It is purely nullfs change, > and the most interesting situation is the ups' deadlock, but the whole > set of nullfs tests would be good to check. > > diff --git a/sys/fs/nullfs/null_vfsops.c b/sys/fs/nullfs/null_vfsops.c > index 64e1e29..49bae28 100644 > --- a/sys/fs/nullfs/null_vfsops.c I have tested this patch with all of the nullfs scenarios I have, multiple times. I also tested the UPS' scenario on nullfs without finding any problems. - Peter
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