• Yan, Zheng's avatar
    ceph: fix security xattr deadlock · 315f2408
    Yan, Zheng authored
    When security is enabled, security module can call filesystem's
    getxattr/setxattr callbacks during d_instantiate(). For cephfs,
    d_instantiate() is usually called by MDS' dispatch thread, while
    handling MDS reply. If the MDS reply does not include xattrs and
    corresponding caps, getxattr/setxattr need to send a new request
    to MDS and waits for the reply. This makes MDS' dispatch sleep,
    nobody handles later MDS replies.
    
    The fix is make sure lookup/atomic_open reply include xattrs and
    corresponding caps. So getxattr can be handled by cached xattrs.
    This requires some modification to both MDS and request message.
    (Client tells MDS what caps it wants; MDS encodes proper caps in
    the reply)
    
    Smack security module may call setxattr during d_instantiate().
    Unlike getxattr, we can't force MDS to issue CEPH_CAP_XATTR_EXCL
    to us. So just make setxattr return error when called by MDS'
    dispatch thread.
    Signed-off-by: default avatarYan, Zheng <zyan@redhat.com>
    315f2408
ceph_fs.h 23.9 KB