Date: Tue, 07 Mar 2017 13:42:20 +0100 From: Harry Schmalzbauer <freebsd@omnilan.de> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: Konstantin Belousov <kostikbel@gmail.com>, FreeBSD Stable <freebsd-stable@freebsd.org>, Mark Johnston <markj@freebsd.org>, "kib@FreeBSD.org" <kib@freebsd.org> Subject: Re: unionfs bugs, a partial patch and some comments [Was: Re: 1-BETA3 Panic: __lockmgr_args: downgrade a recursed lockmgr nfs @ /usr/local/share/deploy-tools/RELENG_11/src/sys/fs/unionfs/union_vnops.c:1905] Message-ID: <58BEAAAC.4090303@omnilan.de> In-Reply-To: <YTXPR01MB018948D19A0A9BB5FAC3D5BADDE60@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM> References: <57A79E24.8000100@omnilan.de> <YQBPR01MB0401201977AEA8A803F27B23DD1A0@YQBPR01MB0401.CANPRD01.PROD.OUTLOOK.COM> <57A83C78.1070403@omnilan.de> <20160809060213.GA67664@raichu> <57A9A6C0.9060609@omnilan.de> <YTOPR01MB0412B2A08F1A3C1A3B2EB160DD1E0@YTOPR01MB0412.CANPRD01.PROD.OUTLOOK.COM>, <20160812123950.GO83214@kib.kiev.ua> <YTXPR01MB018919BE87B12E458144E218DD140@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM>, <57B8793E.4070004@omnilan.de> <YTXPR01MB018948D19A0A9BB5FAC3D5BADDE60@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM>
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Bezüglich Rick Macklem's Nachricht vom 05.09.2016 23:21 (localtime): > Harry Schmalzbauer <freebsd@omnilan.de> wrote: >>Bezüglich Rick Macklem's Nachricht vom 18.08.2016 02:03 (localtime): >>> Kostik wrote: >>> [stuff snipped] >>>> insmnque() performs the cleanup on its own, and that default cleanup > isnot suitable >for the situation. I think that insmntque1() would > betterfit your requirements, your >need to move the common code into a > helper.It seems that >unionfs_ins_cached_vnode() cleanup could reuse it. >>> <https://lists.freebsd.org>; >>> I've attached an updated patch (untested like the last one). This one > creates a >>> custom version insmntque_stddtr() that first calls unionfs_noderem() > and then >>> does the same stuff as insmntque_stddtr(). This looks like it does the > required >>> stuff (unionfs_noderem() is what the unionfs VOP_RECLAIM() does). >>> It switches the node back to using its own v_vnlock that is > exclusively locked, >>> among other things. >> >>Thanks a lot, today I gave it a try. >> >>With this patch, one reproducable panic can still be easily triggered: >> I have directory A unionfs_mounted under directory B. >>Then I mount_unionfs the same directory A below another directory C. >>panic: __lockmgr_args: downgrade a recursed lockmgr nfs @ >>/usr/local/share/deploy-tools/RELENG_11/src/sys/fs/unionfs/union_vnops.c:1905 >>Result is this backtrace, hardly helpful I guess: >> >>#1 0xffffffff80ae5fd9 in kern_reboot (howto=260) at >>/usr/local/share/deploy-tools/RELENG_11/src/sys/kern/kern_shutdown.c:366 >>#2 0xffffffff80ae658b in vpanic (fmt=<value optimized out>, ap=<value >>optimized out>) >> at >>/usr/local/share/deploy-tools/RELENG_11/src/sys/kern/kern_shutdown.c:759 >>#3 0xffffffff80ae63c3 in panic (fmt=0x0) at >>/usr/local/share/deploy-tools/RELENG_11/src/sys/kern/kern_shutdown.c:690 >>#4 0xffffffff80ab7ab7 in __lockmgr_args (lk=<value optimized out>, >>flags=<value optimized out>, ilk=<value optimized out>, wmesg=<value >>optimized out>, >> pri=<value optimized out>, timo=<value optimized out>, file=<value >>optimized out>, line=<value optimized out>) >> > at > /usr/local/share/deploy-tools/RELENG_11/src/sys/kern/kern_lock.c:992 >>#5 0xffffffff80ba510c in vop_stdlock (ap=<value optimized out>) at >>lockmgr.h:98 >>#6 0xffffffff8111932d in VOP_LOCK1_APV (vop=<value optimized out>, >>a=<value optimized out>) at vnode_if.c:2087 >>#7 0xffffffff80a18cfc in unionfs_lock (ap=0xfffffe007a3ba6a0) at >>vnode_if.h:859 >>#8 0xffffffff8111932d in VOP_LOCK1_APV (vop=<value optimized out>, >>a=<value optimized out>) at vnode_if.c:2087 >>#9 0xffffffff80bc9b93 in _vn_lock (vp=<value optimized out>, >>flags=66560, file=<value optimized out>, line=<value optimized out>) at >>vnode_if.h:859 >>#10 0xffffffff80a18460 in unionfs_readdir (ap=<value optimized out>) at >>/usr/local/share/deploy-tools/RELENG_11/src/sys/fs/unionfs/union_vnops.c:1531 >>#11 0xffffffff81118ecf in VOP_READDIR_APV (vop=<value optimized out>, >>a=<value optimized out>) at vnode_if.c:1822 >>#12 0xffffffff80bc6e3b in kern_getdirentries (td=<value optimized out>, >>fd=<value optimized out>, buf=0x800c3d000 <Address 0x800c3d000 out of >>bounds>, >> count=<value optimized out>, basep=0xfffffe007a3ba980, residp=0x0) >>at vnode_if.h:758 >>#13 0xffffffff80bc6bf8 in sys_getdirentries (td=0x0, >>uap=0xfffffe007a3baa40) at >>/usr/local/share/deploy-tools/RELENG_11/src/sys/kern/vfs_syscalls.c:3940 >>#14 0xffffffff80fad6b8 in amd64_syscall (td=<value optimized out>, >>traced=0) at subr_syscall.c:135 >>#15 0xffffffff80f8feab in Xfast_syscall () at >>/usr/local/share/deploy-tools/RELENG_11/src/sys/amd64/amd64/exception.S:396 >>#16 0x0000000000452eea in ?? () >>Previous frame inner to this frame (corrupt stack? > Ok, I finally got around to looking at this and the panic() looks like a > pretty straightforward > bug in the unionfs code. > - In unionfs_readdir(), it does a vn_lock(..LK_UPGRADE) and then later > in the code > vn_lock(..LK_DOWNGRADE) if it did the upgrade. (At line#1531 as noted > in the backtrace.) > - In unionfs_lock(), it sets LK_CANRECURSE when it is the rootvp and > LK_EXCLUSIVE. > (So it allows recursive acquisition in this case.) > --> Then it would call vn_lock(..LK_DOWNGRADE), which would panic if it > has recursed. > > Now, I'll admit unionfs_lock() is too obscure for me to understand, but... > Is it necessary to vn_lock(..LK_DOWNGRADE) or can unionfs_readdir() just > return > with the vnode exclusively locked? > (It would be easy to change the code to avoid the > vn_lock(..LK_DOWNGRADE) call > when it has done the vn_lock(..LK_EXCLUSIVE) after > vn_lock(..LK_UPGRADE) fails.) > > rick > >>I ran your previous patch with for some time. >>Similarly, mounting one directory below a 2nd mountpount crashed the >>machine (forgot to config dumpdir, so can't compare backtrace with the >>current patch). >>Otherwise, at least with the previous patch, I haven't had any other >>panic for about one week. Something ufs related seems to have tightened the unionfs locking problem in stable/11. Now the machine instantaniously panics during boot after mounting root with Rick's latest patch. Unfortunately I don't have SWAP available on that machine (yet), but maybe shit is a hint for anybody. db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00982220e0 vpanic() at vpanic+0x186/frame 0xfffffe0098222160 kassert_panic() at kassert_panic+0x126/frame 0xfffffe00982221d0 witness_assert() at witness_assert+0x35a/frame 0xfffffe0098222230 __lockmgr_args() at __lockmgr_args+0x517/frame 0xfffffe00982222d0 vop_stdunlock() at vop_stdunlock+0x3b/frame 0xfffffe00982222f0 VOP_UNLOCK_APV() at VOP_UNLOCK_APV+0xe0/frame 0xfffffe0098222320 unionfs_unlock() at unionfs_unlock+0x112/frame 0xfffffe0098222390 VOP_UNLOCK_APV() at VOP_UNLOCK_APV+0xe0/frame 0xfffffe00982223c0 unionfs_nodeget() at unionfs_nodeget+0x3ef/frame 0xfffffe0098222470 unionfs_domount() at unionfs_domount+0x518/frame 0xfffffe00982226b0 vfs_donmount() at vfs_donmount+0xe37/frame 0xfffffe00982228f0 sys_nmount() at sys_nmount+0x72/frame 0xfffffe0098222930 amd64_syscall() at amd64_syscall+0x2f9/frame 0xfffffe0098222ab0 Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe0098222ab0 --- syscall (378, FreeBSD ELF64, sys_nmount), rip = 0x80086ecea, rsp = 0x7fffffffe318, rbp = 0x7fffffffeca0 --- -harry
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