Our QE folks are noticing the old leftover locks WARN popping up in RHEL7
(it's since been removed). While investigating upstream, I found I could
make this happen by locking, then closing and signaling a process in a loop:
#0 [ffff88007a4874a0] __schedule at ffffffff81736d8a
#1 [ffff88007a4874f0] schedule at ffffffff81737407
#2 [ffff88007a487510] do_exit at ffffffff8109e18f
#3 [ffff88007a487590] oops_end at ffffffff8101822e
#4 [ffff88007a4875c0] no_context at ffffffff81063b55
#5 [ffff88007a487630] __bad_area_nosemaphore at ffffffff81063e1b
#6 [ffff88007a487680] bad_area_nosemaphore at ffffffff81063fa3
#7 [ffff88007a487690] __do_page_fault at ffffffff81064251
#8 [ffff88007a4876f0] trace_do_page_fault at ffffffff81064677
#9 [ffff88007a487730] do_async_page_fault at ffffffff8105ed0e
#10 [ffff88007a487750] async_page_fault at ffffffff8173d078
[exception RIP: nfs4_put_lock_state+82]
RIP: ffffffffa02dd5b2 RSP: ffff88007a487808 RFLAGS: 00010207
RAX: 0000003fffffffff RBX: ffff8800351d2000 RCX: 0000000000000024
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000009
RBP: ffff88007a487818 R8: 0000000000000000 R9: 0000000000000000
R10: 000000000000028b R11: 0000000000aaaaaa R12: ffff88003675e240
R13: ffff88003504d5b0 R14: ffff88007a487b30 R15: ffff880035097c40
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#11 [ffff88007a487800] nfs4_put_lock_state at ffffffffa02dd59b [nfsv4]
#12 [ffff88007a487820] nfs4_fl_release_lock at ffffffffa02dd605 [nfsv4]
#13 [ffff88007a487830] locks_release_private at ffffffff81258548
#14 [ffff88007a487850] locks_free_lock at ffffffff81258dbb
#15 [ffff88007a487870] locks_dispose_list at ffffffff81258f68
#16 [ffff88007a4878a0] __posix_lock_file at ffffffff81259ab6
#17 [ffff88007a487930] posix_lock_inode_wait at ffffffff8125a02a
#18 [ffff88007a4879b0] do_vfs_lock at ffffffffa02c4687 [nfsv4]
#19 [ffff88007a4879c0] nfs4_proc_lock at ffffffffa02cc1a1 [nfsv4]
#20 [ffff88007a487a70] do_unlk at ffffffffa0273d9e [nfs]
#21 [ffff88007a487ac0] nfs_lock at ffffffffa0273fa9 [nfs]
#22 [ffff88007a487b10] vfs_lock_file at ffffffff8125a76e
#23 [ffff88007a487b20] locks_remove_posix at ffffffff8125a819
#24 [ffff88007a487c10] locks_remove_posix at ffffffff8125a878
#25 [ffff88007a487c20] filp_close at ffffffff812092a2
#26 [ffff88007a487c50] put_files_struct at ffffffff812290c5
#27 [ffff88007a487ca0] exit_files at ffffffff812291c1
#28 [ffff88007a487cc0] do_exit at ffffffff8109dc5f
#29 [ffff88007a487d40] do_group_exit at ffffffff8109e3b5
#30 [ffff88007a487d70] get_signal at ffffffff810a9504
#31 [ffff88007a487e00] do_signal at ffffffff81014447
#32 [ffff88007a487f30] do_notify_resume at ffffffff81014b0e
#33 [ffff88007a487f50] int_signal at ffffffff8173b2fc
The nfs4_lock_state->ls_state pointer is pointing to free memory.
I think what's happening here is that a signal is bumping us out of
do_unlk() waiting on the io_counter while we try to release locks on
__fput(). Since the lock is never released, it sticks around on the inode
until another lock replaces it, and when it is freed it wants some bits from
nfs4_state, but the nfs4_state was already cleaned up.
Probably we need to do a better job not bailing out of do_unlk on file
close, but while I work on that, something like the following keeps the
nfs4_state around for proper cleanup of the nfs4_lock_state:
Is this sane?
Ben
8<--------------------------------------------------------------------
>From cab3dd59aa1a04f3be28811dfb515afc4a9080a7 Mon Sep 17 00:00:00 2001
Message-Id: <cab3dd59aa1a04f3be28811dfb515afc4a9080a7.1437578183.git.bcodding@xxxxxxxxxx>
From: Benjamin Coddington <bcodding@xxxxxxxxxx>
Date: Wed, 22 Jul 2015 11:02:26 -0400
Subject: [PATCH] NFS: keep nfs4_state for nfs4_lock_state cleanup
If we fail to release a lock due to an error or signal on file close, we
might later free the lock if another lock replaces it. Hold a reference to
the nfs4_state to ensure it is not released before freeing the
nfs4_lock_state.
---
fs/nfs/nfs4state.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 605840d..f93b410 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -827,6 +827,7 @@ static struct nfs4_lock_state *nfs4_alloc_lock_state(struct nfs4_state *state, f
return NULL;
nfs4_init_seqid_counter(&lsp->ls_seqid);
atomic_set(&lsp->ls_count, 1);
+ atomic_inc(&state->count);
lsp->ls_state = state;
lsp->ls_owner = fl_owner;
lsp->ls_seqid.owner_id = ida_simple_get(&server->lockowner_id, 0, 0, GFP_NOFS);
@@ -903,6 +904,7 @@ void nfs4_put_lock_state(struct nfs4_lock_state *lsp)
clp->cl_mvops->free_lock_state(server, lsp);
} else
nfs4_free_lock_state(server, lsp);
+ nfs4_put_open_state(state);
}
static void nfs4_fl_copy_lock(struct file_lock *dst, struct file_lock *src)
--
1.7.1
--
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