IB/core: convert to idr_alloc()

Convert to the much saner new idr interface.

v2: Mike triggered WARN_ON() in idr_preload() because send_mad(),
    which may be used from non-process context, was calling
    idr_preload() unconditionally.  Preload iff @gfp_mask has
    __GFP_WAIT.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Reported-by: "Marciniszyn, Mike" <mike.marciniszyn@intel.com>
Cc: Roland Dreier <roland@kernel.org>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 2709ff5..5ca44cd 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -145,7 +145,6 @@
 static struct ucma_context *ucma_alloc_ctx(struct ucma_file *file)
 {
 	struct ucma_context *ctx;
-	int ret;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
@@ -156,17 +155,10 @@
 	INIT_LIST_HEAD(&ctx->mc_list);
 	ctx->file = file;
 
-	do {
-		ret = idr_pre_get(&ctx_idr, GFP_KERNEL);
-		if (!ret)
-			goto error;
-
-		mutex_lock(&mut);
-		ret = idr_get_new(&ctx_idr, ctx, &ctx->id);
-		mutex_unlock(&mut);
-	} while (ret == -EAGAIN);
-
-	if (ret)
+	mutex_lock(&mut);
+	ctx->id = idr_alloc(&ctx_idr, ctx, 0, 0, GFP_KERNEL);
+	mutex_unlock(&mut);
+	if (ctx->id < 0)
 		goto error;
 
 	list_add_tail(&ctx->list, &file->ctx_list);
@@ -180,23 +172,15 @@
 static struct ucma_multicast* ucma_alloc_multicast(struct ucma_context *ctx)
 {
 	struct ucma_multicast *mc;
-	int ret;
 
 	mc = kzalloc(sizeof(*mc), GFP_KERNEL);
 	if (!mc)
 		return NULL;
 
-	do {
-		ret = idr_pre_get(&multicast_idr, GFP_KERNEL);
-		if (!ret)
-			goto error;
-
-		mutex_lock(&mut);
-		ret = idr_get_new(&multicast_idr, mc, &mc->id);
-		mutex_unlock(&mut);
-	} while (ret == -EAGAIN);
-
-	if (ret)
+	mutex_lock(&mut);
+	mc->id = idr_alloc(&multicast_idr, mc, 0, 0, GFP_KERNEL);
+	mutex_unlock(&mut);
+	if (mc->id < 0)
 		goto error;
 
 	mc->ctx = ctx;