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    Subject[ 064/153] svcrpc: make svc_age_temp_xprts enqueue under sv_lock
    3.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "J. Bruce Fields" <bfields@redhat.com>

    commit e75bafbff2270993926abcc31358361db74a9bc2 upstream.

    svc_age_temp_xprts expires xprts in a two-step process: first it takes
    the sv_lock and moves the xprts to expire off their server-wide list
    (sv_tempsocks or sv_permsocks) to a local list. Then it drops the
    sv_lock and enqueues and puts each one.

    I see no reason for this: svc_xprt_enqueue() will take sp_lock, but the
    sv_lock and sp_lock are not otherwise nested anywhere (and documentation
    at the top of this file claims it's correct to nest these with sp_lock
    inside.)

    Tested-by: Jason Tibbitts <tibbs@math.uh.edu>
    Tested-by: Paweł Sikora <pawel.sikora@agmk.net>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/sunrpc/svc_xprt.c | 15 ++-------------
    1 file changed, 2 insertions(+), 13 deletions(-)

    --- a/net/sunrpc/svc_xprt.c
    +++ b/net/sunrpc/svc_xprt.c
    @@ -816,7 +816,6 @@ static void svc_age_temp_xprts(unsigned
    struct svc_serv *serv = (struct svc_serv *)closure;
    struct svc_xprt *xprt;
    struct list_head *le, *next;
    - LIST_HEAD(to_be_aged);

    dprintk("svc_age_temp_xprts\n");

    @@ -837,25 +836,15 @@ static void svc_age_temp_xprts(unsigned
    if (atomic_read(&xprt->xpt_ref.refcount) > 1 ||
    test_bit(XPT_BUSY, &xprt->xpt_flags))
    continue;
    - svc_xprt_get(xprt);
    - list_move(le, &to_be_aged);
    + list_del_init(le);
    set_bit(XPT_CLOSE, &xprt->xpt_flags);
    set_bit(XPT_DETACHED, &xprt->xpt_flags);
    - }
    - spin_unlock_bh(&serv->sv_lock);
    -
    - while (!list_empty(&to_be_aged)) {
    - le = to_be_aged.next;
    - /* fiddling the xpt_list node is safe 'cos we're XPT_DETACHED */
    - list_del_init(le);
    - xprt = list_entry(le, struct svc_xprt, xpt_list);
    -
    dprintk("queuing xprt %p for closing\n", xprt);

    /* a thread will dequeue and close it soon */
    svc_xprt_enqueue(xprt);
    - svc_xprt_put(xprt);
    }
    + spin_unlock_bh(&serv->sv_lock);

    mod_timer(&serv->sv_temptimer, jiffies + svc_conn_age_period * HZ);
    }

    --
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