When unmounting and if there still have some caps or capsnaps flushing still not get the acks it will wait and dump them, but for the capsnaps they didn't initialize the ->ci, so when deferencing the ->ci we will see the kernel crash:
kernel: ceph: dump_cap_flushes: still waiting for cap flushes through 45572: kernel: ceph: 5000000008b:fffffffffffffffe Fw 23183 0 0 kernel: ceph: 5000000008a:fffffffffffffffe Fw 23184 0 0 kernel: ceph: 50000000089:fffffffffffffffe Fw 23185 0 0 kernel: ceph: 50000000084:fffffffffffffffe Fw 23189 0 0 kernel: ceph: 5000000007a:fffffffffffffffe Fw 23199 0 0 kernel: ceph: 50000000094:fffffffffffffffe Fw 23374 0 0 kernel: ceph: 50000000092:fffffffffffffffe Fw 23377 0 0 kernel: ceph: 50000000091:fffffffffffffffe Fw 23378 0 0 kernel: ceph: 5000000008e:fffffffffffffffe Fw 23380 0 0 kernel: ceph: 50000000087:fffffffffffffffe Fw 23382 0 0 kernel: ceph: 50000000086:fffffffffffffffe Fw 23383 0 0 kernel: ceph: 50000000083:fffffffffffffffe Fw 23384 0 0 kernel: ceph: 50000000082:fffffffffffffffe Fw 23385 0 0 kernel: ceph: 50000000081:fffffffffffffffe Fw 23386 0 0 kernel: ceph: 50000000080:fffffffffffffffe Fw 23387 0 0 kernel: ceph: 5000000007e:fffffffffffffffe Fw 23389 0 0 kernel: ceph: 5000000007b:fffffffffffffffe Fw 23392 0 0 kernel: BUG: kernel NULL pointer dereference, address: 0000000000000780 kernel: #PF: supervisor read access in kernel mode kernel: #PF: error_code(0x0000) - not-present page kernel: PGD 0 P4D 0 kernel: Oops: 0000 [#1] PREEMPT SMP PTI kernel: CPU: 3 PID: 46268 Comm: umount Tainted: G S 5.18.0-rc2-ceph-g1771083b2f18 #1 kernel: Hardware name: Supermicro SYS-5018R-WR/X10SRW-F, BIOS 2.0 12/17/2015 kernel: RIP: 0010:ceph_mdsc_sync.cold.64+0x77/0xc3 [ceph] kernel: RSP: 0018:ffffc90009c4fda8 EFLAGS: 00010212 kernel: RAX: 0000000000000000 RBX: ffff8881abf63000 RCX: 0000000000000000 kernel: RDX: 0000000000000000 RSI: ffffffff823932ad RDI: 0000000000000000 kernel: RBP: ffff8881abf634f0 R08: 0000000000005dc7 R09: c0000000ffffdfff kernel: R10: 0000000000000001 R11: ffffc90009c4fbc8 R12: 0000000000000001 kernel: R13: 000000000000b204 R14: ffffffffa0ab3598 R15: ffff88815d36a110 kernel: FS: 00007f50eb25e080(0000) GS:ffff88885fcc0000(0000) knlGS:0000000000000000 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 kernel: CR2: 0000000000000780 CR3: 0000000116ea2003 CR4: 00000000003706e0 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 kernel: Call Trace: kernel: <TASK> kernel: ? schedstat_stop+0x10/0x10 kernel: ceph_sync_fs+0x2c/0x100 [ceph] kernel: sync_filesystem+0x6d/0x90 kernel: generic_shutdown_super+0x22/0x120 kernel: kill_anon_super+0x14/0x30 kernel: ceph_kill_sb+0x36/0x90 [ceph] kernel: deactivate_locked_super+0x29/0x60 kernel: cleanup_mnt+0xb8/0x140 kernel: task_work_run+0x6d/0xb0 kernel: exit_to_user_mode_prepare+0x226/0x230 kernel: syscall_exit_to_user_mode+0x25/0x60 kernel: do_syscall_64+0x40/0x80 kernel: entry_SYSCALL_64_after_hwframe+0x44/0xae
Cc: stable@vger.kernel.org https://tracker.ceph.com/issues/55332 Signed-off-by: Xiubo Li xiubli@redhat.com --- fs/ceph/mds_client.c | 5 +++-- fs/ceph/snap.c | 1 + 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 46a13ea9d284..e8c87dea0551 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -2001,10 +2001,11 @@ static void dump_cap_flushes(struct ceph_mds_client *mdsc, u64 want_tid) list_for_each_entry(cf, &mdsc->cap_flush_list, g_list) { if (cf->tid > want_tid) break; - pr_info("%llx:%llx %s %llu %llu %d\n", + pr_info("%llx:%llx %s %llu %llu %d%s\n", ceph_vinop(&cf->ci->vfs_inode), ceph_cap_string(cf->caps), cf->tid, - cf->ci->i_last_cap_flush_ack, cf->wake); + cf->ci->i_last_cap_flush_ack, cf->wake, + cf->is_capsnap ? " is_capsnap" : ""); } spin_unlock(&mdsc->cap_dirty_lock); } diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index 322ee5add942..db1433ce666e 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -585,6 +585,7 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci, ceph_cap_string(dirty), capsnap->need_flush ? "" : "no_flush"); ihold(inode);
+ capsnap->cap_flush.ci = ci; capsnap->follows = old_snapc->seq; capsnap->issued = __ceph_caps_issued(ci, NULL); capsnap->dirty = dirty;