Commit:     9f81036c54ed1f860d2807c5a6aa4f2b30c21204
Parent:     518b1646f8a31904ca637b8df0c1e31c34a7a3c2
Author:     Michael S. Tsirkin <[EMAIL PROTECTED]>
AuthorDate: Mon May 21 19:06:54 2007 +0300
Committer:  Roland Dreier <[EMAIL PROTECTED]>
CommitDate: Mon May 21 13:41:29 2007 -0700

    IB/cm: Improve local id allocation
    The IB CM uses an idr for local id allocations, with a running counter
    as start_id.  This fails to generate distinct ids if
    1. An id is constantly created and destroyed
    2. A chunk of ids just beyond the current next_id value is occupied
    This in turn leads to an increased chance of connection request being
    mis-detected as a duplicate, sometimes for several retries, until
    next_id gets past the block of allocated ids. This has been observed
    in practice.
    As a fix, remember the last id allocated and start immediately above it.
    This also fixes a problem with the old code, where next_id might
    overflow and become negative.
    Signed-off-by: Michael S. Tsirkin <[EMAIL PROTECTED]>
    Acked-by: Sean Hefty <[EMAIL PROTECTED]>
    Signed-off-by: Roland Dreier <[EMAIL PROTECTED]>
 drivers/infiniband/core/cm.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
index eff591d..e840434 100644
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -306,7 +306,9 @@ static int cm_alloc_id(struct cm_id_private *cm_id_priv)
        do {
                spin_lock_irqsave(&cm.lock, flags);
                ret = idr_get_new_above(&cm.local_id_table, cm_id_priv,
-                                       next_id++, &id);
+                                       next_id, &id);
+               if (!ret)
+                       next_id = ((unsigned) id + 1) & MAX_ID_MASK;
                spin_unlock_irqrestore(&cm.lock, flags);
        } while( (ret == -EAGAIN) && idr_pre_get(&cm.local_id_table, 
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