nfsd: Don't release the callback slot unless it was actually held
authorTrond Myklebust <trondmy@gmail.com>
Fri, 5 Apr 2019 15:54:37 +0000 (08:54 -0700)
committerJ. Bruce Fields <bfields@redhat.com>
Mon, 8 Apr 2019 16:43:15 +0000 (12:43 -0400)
commite6abc8caa6deb14be2a206253f7e1c5e37e9515b
treee3eea6085be977aed5822ab9ad06b13b6e697f48
parent3c86794ac0e6582eea7733619d58ea150198502f
nfsd: Don't release the callback slot unless it was actually held

If there are multiple callbacks queued, waiting for the callback
slot when the callback gets shut down, then they all currently
end up acting as if they hold the slot, and call
nfsd4_cb_sequence_done() resulting in interesting side-effects.

In addition, the 'retry_nowait' path in nfsd4_cb_sequence_done()
causes a loop back to nfsd4_cb_prepare() without first freeing the
slot, which causes a deadlock when nfsd41_cb_get_slot() gets called
a second time.

This patch therefore adds a boolean to track whether or not the
callback did pick up the slot, so that it can do the right thing
in these 2 cases.

Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
fs/nfsd/nfs4callback.c
fs/nfsd/state.h