Date: Mon, 8 Feb 2010 17:41:58 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Attilio Rao <attilio@freebsd.org> Cc: bzeeb+freebsd+lor@zabbadoz.net, Bruce Cran <bruce@cran.org.uk>, freebsd-current@freebsd.org Subject: Re: LOR: vfs_mount.c (ufs) / msdosfs_vfsops.c (devfs) Message-ID: <20100208154158.GM9991@deviant.kiev.zoral.com.ua> In-Reply-To: <3bbf2fe11002080740q1da560c8r8c8d92a1053d021b@mail.gmail.com> References: <20100207160031.GA27434@muon.cran.org.uk> <201002080900.44745.jhb@freebsd.org> <20100208145354.GJ9991@deviant.kiev.zoral.com.ua> <3bbf2fe11002080701u35a3e419ke562735f4f00ce97@mail.gmail.com> <3bbf2fe11002080706k11275a9evbf8a7fa1b14b447f@mail.gmail.com> <20100208150818.GL9991@deviant.kiev.zoral.com.ua> <3bbf2fe11002080740q1da560c8r8c8d92a1053d021b@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
--YIwHDYD8sUXtBKvt Content-Type: text/plain; charset=koi8-r Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 08, 2010 at 04:40:29PM +0100, Attilio Rao wrote: > 2010/2/8 Kostik Belousov <kostikbel@gmail.com>: > > On Mon, Feb 08, 2010 at 04:06:56PM +0100, Attilio Rao wrote: > >> 2010/2/8 Attilio Rao <attilio@freebsd.org>: > >> > 2010/2/8 Kostik Belousov <kostikbel@gmail.com>: > >> >> On Mon, Feb 08, 2010 at 09:00:44AM -0500, John Baldwin wrote: > >> >>> On Sunday 07 February 2010 11:00:32 am Bruce Cran wrote: > >> >>> > Running -CURRENT from today, I unmounted the msdosfs filesystem = on my > >> >>> > phone and got the following LOR: > >> >>> > > >> >>> > lock order reversal: > >> >>> > =9A1st 0xffffff00c51279f8 ufs (ufs) @ /usr/src/sys/kern/vfs_moun= t.c:1204 > >> >>> > =9A2nd 0xffffff010b892278 devfs (devfs) @ > >> >>> > /usr/src/sys/modules/msdosfs/../../fs/msdosfs/msdosfs_vfsops.c:9= 44 > >> >>> > KDB: stack backtrace: > >> >>> > db_trace_self_wrapper() at db_trace_self_wrapper+0x2a > >> >>> > _witness_debugger() at witness_debugger+0x2e > >> >>> > witness_checkorder() at witness_checkorder+0x81e > >> >>> > __lockmgr_args() at __lockmgr_args+0xd11 > >> >>> > vop_stdlock() at vop_stdlock+0x39 > >> >>> > VOP_LOCK1_APV() VOP_LOCK1_APV+0x9b > >> >>> > _vn_lock() at _vn_lock+0x47 > >> >>> > msdosfs_sync() at msdosfs_sync+0x227 > >> >>> > dounmount() at dounmount+0x2ca > >> >>> > unmount() at unmount+0x216 > >> >>> > syscall() at syscall+0x2a2 > >> >>> > Xfast_syscall() at Xfast_syscall+0xe1 > >> >>> > --- syscall (22, FreeBSD ELF64, unmount), rip =3D 0x8006a1e3c, r= sp =3D > >> >>> > 0x7fffffffe3a8, rbp =3D 0x800c08010 --- > >> >>> > >> >>> This is due to holding a lock on the coveredvp vnode for most of u= nmount(2). > >> >>> Probably it should not be held for all of that. =9APerhaps it is s= afe to just > >> >>> keep the vnode referenced instead, or could the handling for cover= edvp just > >> >>> move to the end of the function where it is now vput? > >> >> > >> >> Among other things, holding vnode lock on covered vnode prevents pa= rallel > >> >> unmounts of the same mount point. > >> > > >> > Uhm, I think that this should be hanlded by MNTK_UNMOUNT already (and > >> > thus stopping forced unmounts too). > >> > >> In other words probabilly keeping coveredvnode held until MNTK_UNMOUNT > >> and then refcounting it should be fine. > > > > Actually, the coveredvp then might be reclaimed ? Failed unmount then > > cannot recover. >=20 > I thought on domount() we did holdcount the coveredvp for the time being? > If we don't, maybe we should. Hold or ref does not prevent reclaim. --YIwHDYD8sUXtBKvt Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAktwMMYACgkQC3+MBN1Mb4h18ACgjL1dQVuJqMoOvY6xdKOUKXaF 3uAAnRYk2ka8NvC2aWZFY4Qp1HYfM17O =YKn/ -----END PGP SIGNATURE----- --YIwHDYD8sUXtBKvt--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20100208154158.GM9991>