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    Unexport do_add_mount() and add in follow_automount(), not ->d_automount() · ea5b778a
    David Howells 提交于
    Unexport do_add_mount() and make ->d_automount() return the vfsmount to be
    added rather than calling do_add_mount() itself.  follow_automount() will then
    do the addition.
    
    This slightly complicates things as ->d_automount() normally wants to add the
    new vfsmount to an expiration list and start an expiration timer.  The problem
    with that is that the vfsmount will be deleted if it has a refcount of 1 and
    the timer will not repeat if the expiration list is empty.
    
    To this end, we require the vfsmount to be returned from d_automount() with a
    refcount of (at least) 2.  One of these refs will be dropped unconditionally.
    In addition, follow_automount() must get a 3rd ref around the call to
    do_add_mount() lest it eat a ref and return an error, leaving the mount we
    have open to being expired as we would otherwise have only 1 ref on it.
    
    d_automount() should also add the the vfsmount to the expiration list (by
    calling mnt_set_expiry()) and start the expiration timer before returning, if
    this mechanism is to be used.  The vfsmount will be unlinked from the
    expiration list by follow_automount() if do_add_mount() fails.
    
    This patch also fixes the call to do_add_mount() for AFS to propagate the mount
    flags from the parent vfsmount.
    Signed-off-by: NDavid Howells <dhowells@redhat.com>
    Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
    ea5b778a
vfs.txt 45.5 KB