schrieb Attilio Rao am 27.10.2012 23:07 (localtime): > On Sat, Oct 27, 2012 at 9:46 PM, Attilio Rao <atti...@freebsd.org> wrote: >> On Sat, Sep 8, 2012 at 12:48 AM, Attilio Rao <atti...@freebsd.org> wrote: >>> On Thu, Sep 6, 2012 at 4:52 PM, Harald Schmalzbauer >>> <h.schmalzba...@omnilan.de> wrote: >>>> schrieb Attilio Rao am 09.08.2012 20:26 (localtime): >>>>> On 8/8/12, Harald Schmalzbauer <h.schmalzba...@omnilan.de> wrote: >>>>>> schrieb Pavel Polyakov am 06.03.2012 11:20 (localtime): >>>>>>>>> mount -t unionfs -o noatime /usr /mnt >>>>>>>>> >>>>>>>>> insmntque: mp-safe fs and non-locked vp: 0xfffffe01d96704f0 is not >>>>>>>>> exclusive locked but should be >>>>>>>>> KDB: enter: lock violation >>>>>>>> Pavel, >>>>>>>> can you give a spin to this patch?: >>>>>>>> http://www.freebsd.org/~attilio/unionfs_missing_insmntque_lock.patch >>>>>>>> >>>>>>>> I think that the unlocking is due at that point as the vnode lock can >>>>>>>> be switch later on. >>>>>>>> >>>>>>>> Let me know what you think about it and what the test does. >>>>>>> Thanks! >>>>>>> This patch fixes the problem with lock violation. Sorry I've tested it >>>>>>> so >>>>>>> late. >>>>>> Hello, >>>>>> >>>>>> this patch still applies cleanly to RELENG_9_1. Was there another fix >>>>>> for the issue or has it just not been PR-sent and thus forgotten? >>>>> Can you and Pavel try the attached patch? Unfortunately I had no time >>>>> to test it, I just made in 5 free mins from a non-FreeBSD workstation, >>>> Sorry, couldn't test earlier, but now I did: >>>> With this patch applied the machine hangs without debug kernel and the >>>> latter gives the following panic: >>>> System call nmount returning with the following locks held: >>>> exclusive lockmgr ufs (ufs) r = 0 (0xc5438278) locked @ >>>> src/sys/fs/unionfs/union_vnops.c:1938 >>>> panic: witness_warn >>>> cpuid = 0 >>>> KDB: stack backtrace: >>>> db_trace_self_wrapper(c0a04f7f,c0c112c4,d1de3bb4,c097aa8c,fc,...) at >>>> db_trace_self_wrapper+0x26 >>>> kdb_backtrace(c0a4965f,0,c09c2ede3c1c,0,...) at kdb_backtrace+0x2a >>>> witness_warn(2,0,c0a4ac34,c0a0990a,286,...) at witness_warn+0x1e4 >>>> syscall(d1de3d08) ar syscall+0x415 >>>> Xint0x80_syscall() at Xint0x80_syscall+0x21 >>>> --- syscall (0, FreeBSD ELF32, nosys), eip = 0x280b883f,esp = >>>> 0xbfbfe46c, ebp = 0xbfbfede8 --- >>>> KDB: enter: panic >>>> [ thread pid 86 tid 100054 ] >>>> Stopped ad kdb_enter+0x3a: movl $0,kdb_why >>>> db> bt >>>> Tracing pid 86 tid 100054 td 0xc541b000 >>>> kdb_enter(c0a00d16,c0a09130,0,0,0,...) at panix+0x190 >>>> witness_warn(2,0,x0a4ac34,c0a0990a,286,...) at witness_warn+0x1e4 >>>> syscall(d1de3d08) at syscall+0x415 >>>> Xint0x80_syscall() at Xint0x80_syscall+0x21 >>>> >>>> Hmm, I guess I forgot to install kernel debug symbols... >>>> Coming back if I have more >>> Unfortunately unionfs does very wrong things with the insmntque() locking. >>> It basically expects the vnode to return locked in the same way >>> requested by the precedent namei() (when that happens) but when you do >>> insmntque() you can only have an LK_EXCLUSIVE lock on the vnode. >> Hello, >> the following patch should workout the issues around unionfs_nodeget() a bit: >> http://www.freebsd.org/~attilio/unionfs_nodeget2.patch >> >> Unfortunately unionfs code is rather messy in the lookup path about >> locking requirements so follow what it needs to be done there is a bit >> difficult. >> I have no way to test this patch, so it is just test-compiled at the >> moment, but I would need that you also test lookup path (so directory >> "ls", find(1) on the whole unionfs volume, etc.) to validate it >> someway. > On a second thought, I think that locking in lookup (and also other > operations) is so fragile and difficult to follow that it makes all > vnops real locking landmines. > I think that the following patch fixes the insmntque insertion and > follows the old approach well enough to be committed separately: > http://www.freebsd.org/~attilio/unionfs_nodeget3.patch >
Unfortunately I have no idea about all those locking strategies and
implementations.
Applying unionfs_nodeget3.patch results in:
sys/fs/unionfs/union_subr.c: In function 'unionfs_nodeget':
sys/fs/unionfs/union_subr.c:332: error: expected statement
before ')' token
*** [union_subr.o] Error code 1
I guess there is a typo in this chunk:
@@ -317,11 +328,11 @@ unionfs_nodeget(struct mount *mp, struct vnode *up
vref(vp);
} else
*vpp = vp;
-
-unionfs_nodeget_out:
- if (lkflags & LK_TYPE_MASK)
- vn_lock(vp, lkflags | LK_RETRY);
-
+ if (lkflags & LK_TYPE_MASK) {
+ if (lkflags == LK_SHARED))
---------------------------------------- ^
+ vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
+ } else
+ VOP_UNLOCK(vp, LK_RELEASE);
return (0);
}
After removing the second right parenthesis kernel compiles.
But it still crashes:
panic: Lock (lockmgr) ufs not locked @ sys/kern/vfs_default.c:512
cpuid = 1
KDB: stack backtrace:
...
If you can use the bt info I'll transcribe - no serial console available :-(
Am I right that I should only apply _one_ unionfs-patchX.patch
(unionfs_nodeget3.patch in that case)?
Thanks,
-Harry
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