On Mon, 11 Aug 2014 12:47:48 -0400
Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
> On Mon, Aug 11, 2014 at 11:35 AM, Jeff Layton
> <jeff.layton@xxxxxxxxxxxxxxx> wrote:
> > On Mon, 11 Aug 2014 08:09:24 -0700
> > Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> >
> >>
> >> I managed to hit a similar but different issue with your patch applied (note
> >> the slab poisoning pattern in rax):
> >>
> >> generic/089 409s ...[ 399.057379] general protection fault: 0000 [#1]
> >> SMP
> >> [ 399.059137] Modules linked in:
> >> [ 399.060089] CPU: 2 PID: 4367 Comm: kworker/2:2 Not tainted 3.16.0-rc6+ #1153
> >> [ 399.060617] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> >> [ 399.060617] Workqueue: nfsiod free_lock_state_work
> >> [ 399.060617] task: ffff88007ab68810 ti: ffff88007c3b4000 task.ti: ffff88007c3b4000
> >> [ 399.060617] RIP: 0010:[<ffffffff8134e5bb>] [<ffffffff8134e5bb>] nfs41_free_lock_state+0x2b/0x70
> >> [ 399.060617] RSP: 0018:ffff88007c3b7d18 EFLAGS: 00010286
> >> [ 399.060617] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88007cdd3800 RCX: 0000000000000000
> >> [ 399.060617] RDX: ffffffff81e04c60 RSI: ffff88007cdd39a0 RDI: ffff880079e5a000
> >> [ 399.060617] RBP: ffff88007c3b7d38 R08: ffffffff832df6d0 R09: 000001c90f100000
> >> [ 399.060617] R10: 0000000000000000 R11: 00000000000656f0 R12: ffff880079e5a000
> >> [ 399.060617] R13: ffff88007fd18b00 R14: ffff88007cdd39c0 R15: 0000000000000000
> >> [ 399.060617] FS: 0000000000000000(0000) GS:ffff88007fd00000(0000) knlGS:0000000000000000
> >> [ 399.060617] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> >> [ 399.060617] CR2: 00007f5ac2f56800 CR3: 000000007a95b000 CR4: 00000000000006e0
> >> [ 399.060617] Stack:
> >> [ 399.060617] 000000007fd13240 ffff88007a8f7800 ffff88007fd13240 ffff88007fd18b00
> >> [ 399.060617] ffff88007c3b7d58 ffffffff813621ae ffff88007cdd39c0 ffff88007a4d0c40
> >> [ 399.060617] ffff88007c3b7dd8 ffffffff810cc877 ffffffff810cc80d ffff88007fd13258
> >> [ 399.060617] Call Trace:
> >> [ 399.060617] [<ffffffff813621ae>] free_lock_state_work+0x2e/0x40
> >> [ 399.060617] [<ffffffff810cc877>] process_one_work+0x1c7/0x490
> >> [ 399.060617] [<ffffffff810cc80d>] ? process_one_work+0x15d/0x490
> >> [ 399.060617] [<ffffffff810cd569>] worker_thread+0x119/0x4f0
> >> [ 399.060617] [<ffffffff810fbbad>] ? trace_hardirqs_on+0xd/0x10
> >> [ 399.060617] [<ffffffff810cd450>] ? init_pwq+0x190/0x190
> >> [ 399.060617] [<ffffffff810d3c6f>] kthread+0xdf/0x100
> >> [ 399.060617] [<ffffffff810d3b90>] ? __init_kthread_worker+0x70/0x70
> >> [ 399.060617] [<ffffffff81d9873c>] ret_from_fork+0x7c/0xb0
> >> [ 399.060617] [<ffffffff810d3b90>] ? __init_kthread_worker+0x70/0x70
> >>
> >> (gdb) l *(nfs41_free_lock_state+0x2b)
> >> 0xffffffff8134e5bb is in nfs41_free_lock_state (fs/nfs/nfs4proc.c:8313).
> >> 8308 nfs41_free_lock_state(struct nfs_server *server, struct
> >> nfs4_lock_state *lsp)
> >> 8309 {
> >> 8310 struct rpc_task *task;
> >> 8311 struct rpc_cred *cred = lsp->ls_state->owner->so_cred;
> >> 8312
> >> 8313 task = _nfs41_free_stateid(server, &lsp->ls_stateid,
> >> cred, false);
> >> 8314 nfs4_free_lock_state(server, lsp);
> >> 8315 if (IS_ERR(task))
> >> 8316 return;
> >> 8317 rpc_put_task(task);
> >>
> >
> > Oof -- right. Same problem, just in a different spot. So there, we need
> > the openowner. We don't have a pointer directly to that, so we're
> > probably best off just holding a reference to the open stateid, and
> > pinning the superblock too.
> >
> > Maybe something like this instead? I'm also running xfstests on a VM
> > now to see if I can reproduce this and verify the fix:
> >
> > ---------------------[snip]-----------------------
> >
> > [PATCH] nfs: pin superblock and open state when running free_lock_state operations
> >
> > Christoph reported seeing this oops when running xfstests on a v4.1 client:
> >
> > generic/089 242s ...[ 2187.041239] general protection fault: 0000 [#1] SMP
> > [ 2187.042899] Modules linked in:
> > [ 2187.044000] CPU: 0 PID: 11913 Comm: kworker/0:1 Not tainted 3.16.0-rc6+ #1151
> > [ 2187.044287] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> > [ 2187.044287] Workqueue: nfsiod free_lock_state_work
> > [ 2187.044287] task: ffff880072b50cd0 ti: ffff88007a4ec000 task.ti: ffff88007a4ec000
> > [ 2187.044287] RIP: 0010:[<ffffffff81361ca6>] [<ffffffff81361ca6>] free_lock_state_work+0x16/0x30
> > [ 2187.044287] RSP: 0018:ffff88007a4efd58 EFLAGS: 00010296
> > [ 2187.044287] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88007a947ac0 RCX: 8000000000000000
> > [ 2187.044287] RDX: ffffffff826af9e0 RSI: ffff88007b093c00 RDI: ffff88007b093db8
> > [ 2187.044287] RBP: ffff88007a4efd58 R08: ffffffff832d3e10 R09: 000001c40efc0000
> > [ 2187.044287] R10: 0000000000000000 R11: 0000000000059e30 R12: ffff88007fc13240
> > [ 2187.044287] R13: ffff88007fc18b00 R14: ffff88007b093db8 R15: 0000000000000000
> > [ 2187.044287] FS: 0000000000000000(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
> > [ 2187.044287] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > [ 2187.044287] CR2: 00007f93ec33fb80 CR3: 0000000079dc2000 CR4: 00000000000006f0
> > [ 2187.044287] Stack:
> > [ 2187.044287] ffff88007a4efdd8 ffffffff810cc877 ffffffff810cc80d ffff88007fc13258
> > [ 2187.044287] 000000007a947af0 0000000000000000 ffffffff8353ccc8 ffffffff82b6f3d0
> > [ 2187.044287] 0000000000000000 ffffffff82267679 ffff88007a4efdd8 ffff88007fc13240
> > [ 2187.044287] Call Trace:
> > [ 2187.044287] [<ffffffff810cc877>] process_one_work+0x1c7/0x490
> > [ 2187.044287] [<ffffffff810cc80d>] ? process_one_work+0x15d/0x490
> > [ 2187.044287] [<ffffffff810cd569>] worker_thread+0x119/0x4f0
> > [ 2187.044287] [<ffffffff810fbbad>] ? trace_hardirqs_on+0xd/0x10
> > [ 2187.044287] [<ffffffff810cd450>] ? init_pwq+0x190/0x190
> > [ 2187.044287] [<ffffffff810d3c6f>] kthread+0xdf/0x100
> > [ 2187.044287] [<ffffffff810d3b90>] ? __init_kthread_worker+0x70/0x70
> > [ 2187.044287] [<ffffffff81d9873c>] ret_from_fork+0x7c/0xb0
> > [ 2187.044287] [<ffffffff810d3b90>] ? __init_kthread_worker+0x70/0x70
> > [ 2187.044287] Code: 0f 1f 44 00 00 31 c0 5d c3 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 8d b7 48 fe ff ff 48 8b 87 58 fe ff ff 48 89 e5 48 8b 40 30 <48> 8b 00 48 8b 10 48 89 c7 48 8b 92 90 03 00 00 ff 52 28 5d c3
> > [ 2187.044287] RIP [<ffffffff81361ca6>] free_lock_state_work+0x16/0x30
> > [ 2187.044287] RSP <ffff88007a4efd58>
> > [ 2187.103626] ---[ end trace 0f11326d28e5d8fa ]---
> >
> > It appears that the lock state outlived the open state with which it
> > was associated.
> >
> > Fix this by pinning down the open stateid and the superblock prior to
> > queueing the workqueue job, and then releasing putting those references
> > once the RPC task has been queued.
> >
> > Reported-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
> > ---
> > fs/nfs/nfs4state.c | 13 +++++++++----
> > 1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> > index a770c8e469a7..fb29c7cbe8e3 100644
> > --- a/fs/nfs/nfs4state.c
> > +++ b/fs/nfs/nfs4state.c
> > @@ -804,11 +804,14 @@ free_lock_state_work(struct work_struct *work)
> > {
> > struct nfs4_lock_state *lsp = container_of(work,
> > struct nfs4_lock_state, ls_release);
> > - struct nfs4_state *state = lsp->ls_state;
> > - struct nfs_server *server = state->owner->so_server;
> > + struct nfs4_state *osp = lsp->ls_state;
> > + struct super_block *sb = osp->inode->i_sb;
> > + struct nfs_server *server = NFS_SB(sb);
> > struct nfs_client *clp = server->nfs_client;
> >
> > clp->cl_mvops->free_lock_state(server, lsp);
> > + nfs4_put_open_state(osp);
> > + nfs_sb_deactive(sb);
> > }
> >
> > /*
> > @@ -896,9 +899,11 @@ void nfs4_put_lock_state(struct nfs4_lock_state *lsp)
> > if (list_empty(&state->lock_states))
> > clear_bit(LK_STATE_IN_USE, &state->flags);
> > spin_unlock(&state->state_lock);
> > - if (test_bit(NFS_LOCK_INITIALIZED, &lsp->ls_flags))
> > + if (test_bit(NFS_LOCK_INITIALIZED, &lsp->ls_flags)) {
> > + atomic_inc(&lsp->ls_state->count);
> > + nfs_sb_active(lsp->ls_state->inode->i_sb);
> > queue_work(nfsiod_workqueue, &lsp->ls_release);
> > - else {
> > + } else {
> > server = state->owner->so_server;
> > nfs4_free_lock_state(server, lsp);
> > }
> > --
> > 1.9.3
> >
>
> Can we step back a little? It looks to me as if we're working on a
> whole new range of symptoms that are a consequence of a set of locking
> rule changes for fl_release_private that were not well thought
> through.
> Prior to commit 72f98e72551fa, the locking rules for
> fl_release_private stated that it _does_ allow blocking.
> Nothing in commit 72f98e72551fa was done to change the code that did
> block, instead it just decreed that fl_release_private no longer
> allows blocking as if that magically makes thing work.
>
> This whole thing of doing an asynchronous call started because
> locks_delete_lock() is calling lock_free_lock() instead of just
> unlinking, and then deferring the actual freeing of the locks until
> we've dropped the spinlocks.
>
> It should be trivial to change locks_delete_lock() so that after
> calling locks_unlink_lock(), it adds to a private list that can then
> be drained at the end of flock_lock_file(), __posix_lock_file(), and
> locks_remove_file().
> The lease code looks like it may need to be special cased
> (lease_modify()), but that can just keep doing what it is currently
> doing until someone fixes it.
>
> Pretty please....
>
Ok. It's not quite that simple but it should be doable...
locks_release_private is also called by locks_copy_lock, and I don't
see a good way to defer that call. We might be able to just get rid of
it though, and just require a "pristine" lock be passed to
locks_copy_lock. It looks like that's already done in most cases anyway
(maybe all cases).
I've already been making some motions toward doing a lock pushdown in
the lease code anyway, so this may just give me a real reason to finish
that up...
--
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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