| Message ID | 20220315152946.12912-1-dossche.niels@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] ceph: get snap_rwsem read lock in handle_cap_export for ceph_add_cap | expand |
On Tue, 2022-03-15 at 16:29 +0100, Niels Dossche wrote: > ceph_add_cap says in its function documentation that the caller should > hold the read lock on the session snap_rwsem. Furthermore, not only > ceph_add_cap needs that lock, when it calls to ceph_lookup_snap_realm it > eventually calls ceph_get_snap_realm which states via lockdep that > snap_rwsem needs to be held. handle_cap_export calls ceph_add_cap > without that mdsc->snap_rwsem held. Thus, since ceph_get_snap_realm > and ceph_add_cap both need the lock, the common place to acquire that > lock is inside handle_cap_export. > > Signed-off-by: Niels Dossche <dossche.niels@gmail.com> > --- > fs/ceph/caps.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c > index b472cd066d1c..a23cf2a528bc 100644 > --- a/fs/ceph/caps.c > +++ b/fs/ceph/caps.c > @@ -3856,6 +3856,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, > dout("handle_cap_export inode %p ci %p mds%d mseq %d target %d\n", > inode, ci, mds, mseq, target); > retry: > + down_read(&mdsc->snap_rwsem); > spin_lock(&ci->i_ceph_lock); > cap = __get_cap_for_mds(ci, mds); > if (!cap || cap->cap_id != le64_to_cpu(ex->cap_id)) > @@ -3919,6 +3920,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, > } > > spin_unlock(&ci->i_ceph_lock); > + up_read(&mdsc->snap_rwsem); > mutex_unlock(&session->s_mutex); > > /* open target session */ > @@ -3944,6 +3946,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, > > out_unlock: > spin_unlock(&ci->i_ceph_lock); > + up_read(&mdsc->snap_rwsem); > mutex_unlock(&session->s_mutex); > if (tsession) { > mutex_unlock(&tsession->s_mutex); Looks good. Merged into testing branch. Thanks!
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index b472cd066d1c..a23cf2a528bc 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -3856,6 +3856,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, dout("handle_cap_export inode %p ci %p mds%d mseq %d target %d\n", inode, ci, mds, mseq, target); retry: + down_read(&mdsc->snap_rwsem); spin_lock(&ci->i_ceph_lock); cap = __get_cap_for_mds(ci, mds); if (!cap || cap->cap_id != le64_to_cpu(ex->cap_id)) @@ -3919,6 +3920,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, } spin_unlock(&ci->i_ceph_lock); + up_read(&mdsc->snap_rwsem); mutex_unlock(&session->s_mutex); /* open target session */ @@ -3944,6 +3946,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, out_unlock: spin_unlock(&ci->i_ceph_lock); + up_read(&mdsc->snap_rwsem); mutex_unlock(&session->s_mutex); if (tsession) { mutex_unlock(&tsession->s_mutex);
ceph_add_cap says in its function documentation that the caller should hold the read lock on the session snap_rwsem. Furthermore, not only ceph_add_cap needs that lock, when it calls to ceph_lookup_snap_realm it eventually calls ceph_get_snap_realm which states via lockdep that snap_rwsem needs to be held. handle_cap_export calls ceph_add_cap without that mdsc->snap_rwsem held. Thus, since ceph_get_snap_realm and ceph_add_cap both need the lock, the common place to acquire that lock is inside handle_cap_export. Signed-off-by: Niels Dossche <dossche.niels@gmail.com> --- fs/ceph/caps.c | 3 +++ 1 file changed, 3 insertions(+)