From: Xiubo Li xiubli@redhat.com
commit 409e873ea3c1fd3079909718bbeb06ac1ec7f38b upstream.
There is a race between capsnaps flush and removing the inode from 'mdsc->snap_flush_list' list:
== Thread A == == Thread B == ceph_queue_cap_snap() -> allocate 'capsnapA' ->ihold('&ci->vfs_inode') ->add 'capsnapA' to 'ci->i_cap_snaps' ->add 'ci' to 'mdsc->snap_flush_list' ... == Thread C == ceph_flush_snaps() ->__ceph_flush_snaps() ->__send_flush_snap() handle_cap_flushsnap_ack() ->iput('&ci->vfs_inode') this also will release 'ci' ... == Thread D == ceph_handle_snap() ->flush_snaps() ->iterate 'mdsc->snap_flush_list' ->get the stale 'ci' ->remove 'ci' from ->ihold(&ci->vfs_inode) this 'mdsc->snap_flush_list' will WARNING
To fix this we will increase the inode's i_count ref when adding 'ci' to the 'mdsc->snap_flush_list' list.
[ idryomov: need_put int -> bool ]
Cc: stable@vger.kernel.org Link: https://bugzilla.redhat.com/show_bug.cgi?id=2209299 Signed-off-by: Xiubo Li xiubli@redhat.com Reviewed-by: Milind Changire mchangir@redhat.com Reviewed-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ceph/caps.c | 6 ++++++ fs/ceph/snap.c | 4 +++- 2 files changed, 9 insertions(+), 1 deletion(-)
--- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1626,6 +1626,7 @@ void ceph_flush_snaps(struct ceph_inode_ struct inode *inode = &ci->netfs.inode; struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc; struct ceph_mds_session *session = NULL; + bool need_put = false; int mds;
dout("ceph_flush_snaps %p\n", inode); @@ -1670,8 +1671,13 @@ out: ceph_put_mds_session(session); /* we flushed them all; remove this inode from the queue */ spin_lock(&mdsc->snap_flush_lock); + if (!list_empty(&ci->i_snap_flush_item)) + need_put = true; list_del_init(&ci->i_snap_flush_item); spin_unlock(&mdsc->snap_flush_lock); + + if (need_put) + iput(inode); }
/* --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -693,8 +693,10 @@ int __ceph_finish_cap_snap(struct ceph_i capsnap->size);
spin_lock(&mdsc->snap_flush_lock); - if (list_empty(&ci->i_snap_flush_item)) + if (list_empty(&ci->i_snap_flush_item)) { + ihold(inode); list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list); + } spin_unlock(&mdsc->snap_flush_lock); return 1; /* caller may want to ceph_flush_snaps */ }