From: Xiubo Li <xiubli@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2209299
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
Reviewed-by: Milind Changire <mchangir@xxxxxxxxxx>
Reviewed-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -1437,6 +1437,7 @@ void ceph_flush_snaps(struct ceph_inode_
struct inode *inode = &ci->vfs_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);
@@ -1490,8 +1491,13 @@ out:
}
/* 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
@@ -623,8 +623,10 @@ 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 */
}
