diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index 4a892d8..dbd8f76 100644
--- a/arch/powerpc/mm/mmu_context_book3s64.c
+++ b/arch/powerpc/mm/mmu_context_book3s64.c
@@ -26,48 +26,16 @@
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
 
-static DEFINE_SPINLOCK(mmu_context_lock);
 static DEFINE_IDA(mmu_context_ida);
 
 static int alloc_context_id(int min_id, int max_id)
 {
-	int index, err;
-
-again:
-	if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
-		return -ENOMEM;
-
-	spin_lock(&mmu_context_lock);
-	err = ida_get_new_above(&mmu_context_ida, min_id, &index);
-	spin_unlock(&mmu_context_lock);
-
-	if (err == -EAGAIN)
-		goto again;
-	else if (err)
-		return err;
-
-	if (index > max_id) {
-		spin_lock(&mmu_context_lock);
-		ida_remove(&mmu_context_ida, index);
-		spin_unlock(&mmu_context_lock);
-		return -ENOMEM;
-	}
-
-	return index;
+	return ida_alloc_range(&mmu_context_ida, min_id, max_id, GFP_KERNEL);
 }
 
 void hash__reserve_context_id(int id)
 {
-	int rc, result = 0;
-
-	do {
-		if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
-			break;
-
-		spin_lock(&mmu_context_lock);
-		rc = ida_get_new_above(&mmu_context_ida, id, &result);
-		spin_unlock(&mmu_context_lock);
-	} while (rc == -EAGAIN);
+	int result = ida_alloc_range(&mmu_context_ida, id, id, GFP_KERNEL);
 
 	WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result);
 }
@@ -172,9 +140,7 @@
 
 void __destroy_context(int context_id)
 {
-	spin_lock(&mmu_context_lock);
-	ida_remove(&mmu_context_ida, context_id);
-	spin_unlock(&mmu_context_lock);
+	ida_free(&mmu_context_ida, context_id);
 }
 EXPORT_SYMBOL_GPL(__destroy_context);
 
@@ -182,13 +148,11 @@
 {
 	int index, context_id;
 
-	spin_lock(&mmu_context_lock);
 	for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
 		context_id = ctx->extended_id[index];
 		if (context_id)
-			ida_remove(&mmu_context_ida, context_id);
+			ida_free(&mmu_context_ida, context_id);
 	}
-	spin_unlock(&mmu_context_lock);
 }
 
 static void pte_frag_destroy(void *pte_frag)
diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index ff9f488..e59e0e6 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -515,35 +515,17 @@
 	return 0;
 }
 
-static DEFINE_SPINLOCK(vas_ida_lock);
-
 static void vas_release_window_id(struct ida *ida, int winid)
 {
-	spin_lock(&vas_ida_lock);
-	ida_remove(ida, winid);
-	spin_unlock(&vas_ida_lock);
+	ida_free(ida, winid);
 }
 
 static int vas_assign_window_id(struct ida *ida)
 {
-	int rc, winid;
+	int winid = ida_alloc_max(ida, VAS_WINDOWS_PER_CHIP - 1, GFP_KERNEL);
 
-	do {
-		rc = ida_pre_get(ida, GFP_KERNEL);
-		if (!rc)
-			return -EAGAIN;
-
-		spin_lock(&vas_ida_lock);
-		rc = ida_get_new(ida, &winid);
-		spin_unlock(&vas_ida_lock);
-	} while (rc == -EAGAIN);
-
-	if (rc)
-		return rc;
-
-	if (winid > VAS_WINDOWS_PER_CHIP) {
-		pr_err("Too many (%d) open windows\n", winid);
-		vas_release_window_id(ida, winid);
+	if (winid == -ENOSPC) {
+		pr_err("Too many (%d) open windows\n", VAS_WINDOWS_PER_CHIP);
 		return -EAGAIN;
 	}
 
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index db253cd..d0666f5c 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -118,7 +118,6 @@
 
 static u32 cpu_use[NR_CPUS];
 
-static DEFINE_SPINLOCK(rssd_index_lock);
 static DEFINE_IDA(rssd_index_ida);
 
 static int mtip_block_initialize(struct driver_data *dd);
@@ -3767,20 +3766,10 @@
 		goto alloc_disk_error;
 	}
 
-	/* Generate the disk name, implemented same as in sd.c */
-	do {
-		if (!ida_pre_get(&rssd_index_ida, GFP_KERNEL)) {
-			rv = -ENOMEM;
-			goto ida_get_error;
-		}
-
-		spin_lock(&rssd_index_lock);
-		rv = ida_get_new(&rssd_index_ida, &index);
-		spin_unlock(&rssd_index_lock);
-	} while (rv == -EAGAIN);
-
-	if (rv)
+	rv = ida_alloc(&rssd_index_ida, GFP_KERNEL);
+	if (rv < 0)
 		goto ida_get_error;
+	index = rv;
 
 	rv = rssd_disk_name_format("rssd",
 				index,
@@ -3922,9 +3911,7 @@
 block_queue_alloc_tag_error:
 	mtip_hw_debugfs_exit(dd);
 disk_index_error:
-	spin_lock(&rssd_index_lock);
-	ida_remove(&rssd_index_ida, index);
-	spin_unlock(&rssd_index_lock);
+	ida_free(&rssd_index_ida, index);
 
 ida_get_error:
 	put_disk(dd->disk);
@@ -4012,9 +3999,7 @@
 	}
 	dd->disk  = NULL;
 
-	spin_lock(&rssd_index_lock);
-	ida_remove(&rssd_index_ida, dd->index);
-	spin_unlock(&rssd_index_lock);
+	ida_free(&rssd_index_ida, dd->index);
 
 	/* De-initialize the protocol layer. */
 	mtip_hw_exit(dd);
@@ -4054,9 +4039,7 @@
 		dd->queue = NULL;
 	}
 
-	spin_lock(&rssd_index_lock);
-	ida_remove(&rssd_index_ida, dd->index);
-	spin_unlock(&rssd_index_lock);
+	ida_free(&rssd_index_ida, dd->index);
 	return 0;
 }
 
diff --git a/drivers/block/rsxx/core.c b/drivers/block/rsxx/core.c
index b7d7191..f2c631c 100644
--- a/drivers/block/rsxx/core.c
+++ b/drivers/block/rsxx/core.c
@@ -58,7 +58,6 @@
 			     "until the card startup has completed.");
 
 static DEFINE_IDA(rsxx_disk_ida);
-static DEFINE_SPINLOCK(rsxx_ida_lock);
 
 /* --------------------Debugfs Setup ------------------- */
 
@@ -771,19 +770,10 @@
 	card->dev = dev;
 	pci_set_drvdata(dev, card);
 
-	do {
-		if (!ida_pre_get(&rsxx_disk_ida, GFP_KERNEL)) {
-			st = -ENOMEM;
-			goto failed_ida_get;
-		}
-
-		spin_lock(&rsxx_ida_lock);
-		st = ida_get_new(&rsxx_disk_ida, &card->disk_id);
-		spin_unlock(&rsxx_ida_lock);
-	} while (st == -EAGAIN);
-
-	if (st)
+	st = ida_alloc(&rsxx_disk_ida, GFP_KERNEL);
+	if (st < 0)
 		goto failed_ida_get;
+	card->disk_id = st;
 
 	st = pci_enable_device(dev);
 	if (st)
@@ -985,9 +975,7 @@
 failed_dma_mask:
 	pci_disable_device(dev);
 failed_enable:
-	spin_lock(&rsxx_ida_lock);
-	ida_remove(&rsxx_disk_ida, card->disk_id);
-	spin_unlock(&rsxx_ida_lock);
+	ida_free(&rsxx_disk_ida, card->disk_id);
 failed_ida_get:
 	kfree(card);
 
@@ -1050,6 +1038,7 @@
 	pci_disable_device(dev);
 	pci_release_regions(dev);
 
+	ida_free(&rsxx_disk_ida, card->disk_id);
 	kfree(card);
 }
 
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 272bed6..f1a441ab 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -161,9 +161,7 @@
 
 	chan_dev = container_of(dev, typeof(*chan_dev), device);
 	if (atomic_dec_and_test(chan_dev->idr_ref)) {
-		mutex_lock(&dma_list_mutex);
-		ida_remove(&dma_ida, chan_dev->dev_id);
-		mutex_unlock(&dma_list_mutex);
+		ida_free(&dma_ida, chan_dev->dev_id);
 		kfree(chan_dev->idr_ref);
 	}
 	kfree(chan_dev);
@@ -898,17 +896,12 @@
 
 static int get_dma_id(struct dma_device *device)
 {
-	int rc;
+	int rc = ida_alloc(&dma_ida, GFP_KERNEL);
 
-	do {
-		if (!ida_pre_get(&dma_ida, GFP_KERNEL))
-			return -ENOMEM;
-		mutex_lock(&dma_list_mutex);
-		rc = ida_get_new(&dma_ida, &device->dev_id);
-		mutex_unlock(&dma_list_mutex);
-	} while (rc == -EAGAIN);
-
-	return rc;
+	if (rc < 0)
+		return rc;
+	device->dev_id = rc;
+	return 0;
 }
 
 /**
@@ -1092,9 +1085,7 @@
 err_out:
 	/* if we never registered a channel just release the idr */
 	if (atomic_read(idr_ref) == 0) {
-		mutex_lock(&dma_list_mutex);
-		ida_remove(&dma_ida, device->dev_id);
-		mutex_unlock(&dma_list_mutex);
+		ida_free(&dma_ida, device->dev_id);
 		kfree(idr_ref);
 		return rc;
 	}
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c b/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
index ddb1e93..b93c558 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
@@ -51,51 +51,34 @@
 {
 	struct vmwgfx_gmrid_man *gman =
 		(struct vmwgfx_gmrid_man *)man->priv;
-	int ret = 0;
 	int id;
 
 	mem->mm_node = NULL;
 
+	id = ida_alloc_max(&gman->gmr_ida, gman->max_gmr_ids - 1, GFP_KERNEL);
+	if (id < 0)
+		return id;
+
 	spin_lock(&gman->lock);
 
 	if (gman->max_gmr_pages > 0) {
 		gman->used_gmr_pages += bo->num_pages;
 		if (unlikely(gman->used_gmr_pages > gman->max_gmr_pages))
-			goto out_err_locked;
+			goto nospace;
 	}
 
-	do {
-		spin_unlock(&gman->lock);
-		if (unlikely(ida_pre_get(&gman->gmr_ida, GFP_KERNEL) == 0)) {
-			ret = -ENOMEM;
-			goto out_err;
-		}
-		spin_lock(&gman->lock);
-
-		ret = ida_get_new(&gman->gmr_ida, &id);
-		if (unlikely(ret == 0 && id >= gman->max_gmr_ids)) {
-			ida_remove(&gman->gmr_ida, id);
-			ret = 0;
-			goto out_err_locked;
-		}
-	} while (ret == -EAGAIN);
-
-	if (likely(ret == 0)) {
-		mem->mm_node = gman;
-		mem->start = id;
-		mem->num_pages = bo->num_pages;
-	} else
-		goto out_err_locked;
+	mem->mm_node = gman;
+	mem->start = id;
+	mem->num_pages = bo->num_pages;
 
 	spin_unlock(&gman->lock);
 	return 0;
 
-out_err:
-	spin_lock(&gman->lock);
-out_err_locked:
+nospace:
 	gman->used_gmr_pages -= bo->num_pages;
 	spin_unlock(&gman->lock);
-	return ret;
+	ida_free(&gman->gmr_ida, id);
+	return 0;
 }
 
 static void vmw_gmrid_man_put_node(struct ttm_mem_type_manager *man,
@@ -105,8 +88,8 @@
 		(struct vmwgfx_gmrid_man *)man->priv;
 
 	if (mem->mm_node) {
+		ida_free(&gman->gmr_ida, mem->start);
 		spin_lock(&gman->lock);
-		ida_remove(&gman->gmr_ida, mem->start);
 		gman->used_gmr_pages -= mem->num_pages;
 		spin_unlock(&gman->lock);
 		mem->mm_node = NULL;
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index fcdf3d5..3bae24b 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -585,18 +585,12 @@
 	entity->num_links = 0;
 	entity->num_backlinks = 0;
 
-	if (!ida_pre_get(&mdev->entity_internal_idx, GFP_KERNEL))
-		return -ENOMEM;
+	ret = ida_alloc_min(&mdev->entity_internal_idx, 1, GFP_KERNEL);
+	if (ret < 0)
+		return ret;
+	entity->internal_idx = ret;
 
 	mutex_lock(&mdev->graph_mutex);
-
-	ret = ida_get_new_above(&mdev->entity_internal_idx, 1,
-				&entity->internal_idx);
-	if (ret < 0) {
-		mutex_unlock(&mdev->graph_mutex);
-		return ret;
-	}
-
 	mdev->entity_internal_idx_max =
 		max(mdev->entity_internal_idx_max, entity->internal_idx);
 
@@ -642,7 +636,7 @@
 	struct media_interface *intf;
 	unsigned int i;
 
-	ida_simple_remove(&mdev->entity_internal_idx, entity->internal_idx);
+	ida_free(&mdev->entity_internal_idx, entity->internal_idx);
 
 	/* Remove all interface links pointing to this entity */
 	list_for_each_entry(intf, &mdev->interfaces, graph_obj.list) {
diff --git a/drivers/misc/cb710/core.c b/drivers/misc/cb710/core.c
index 4d4acf7..2c43fd0 100644
--- a/drivers/misc/cb710/core.c
+++ b/drivers/misc/cb710/core.c
@@ -16,7 +16,6 @@
 #include <linux/gfp.h>
 
 static DEFINE_IDA(cb710_ida);
-static DEFINE_SPINLOCK(cb710_ida_lock);
 
 void cb710_pci_update_config_reg(struct pci_dev *pdev,
 	int reg, uint32_t mask, uint32_t xor)
@@ -205,7 +204,6 @@
 	const struct pci_device_id *ent)
 {
 	struct cb710_chip *chip;
-	unsigned long flags;
 	u32 val;
 	int err;
 	int n = 0;
@@ -256,18 +254,10 @@
 	if (err)
 		return err;
 
-	do {
-		if (!ida_pre_get(&cb710_ida, GFP_KERNEL))
-			return -ENOMEM;
-
-		spin_lock_irqsave(&cb710_ida_lock, flags);
-		err = ida_get_new(&cb710_ida, &chip->platform_id);
-		spin_unlock_irqrestore(&cb710_ida_lock, flags);
-
-		if (err && err != -EAGAIN)
-			return err;
-	} while (err);
-
+	err = ida_alloc(&cb710_ida, GFP_KERNEL);
+	if (err < 0)
+		return err;
+	chip->platform_id = err;
 
 	dev_info(&pdev->dev, "id %d, IO 0x%p, IRQ %d\n",
 		chip->platform_id, chip->iobase, pdev->irq);
@@ -308,7 +298,6 @@
 static void cb710_remove_one(struct pci_dev *pdev)
 {
 	struct cb710_chip *chip = pci_get_drvdata(pdev);
-	unsigned long flags;
 
 	cb710_unregister_slot(chip, CB710_SLOT_SM);
 	cb710_unregister_slot(chip, CB710_SLOT_MS);
@@ -317,9 +306,7 @@
 	BUG_ON(atomic_read(&chip->slot_refs_count) != 0);
 #endif
 
-	spin_lock_irqsave(&cb710_ida_lock, flags);
-	ida_remove(&cb710_ida, chip->platform_id);
-	spin_unlock_irqrestore(&cb710_ida_lock, flags);
+	ida_free(&cb710_ida, chip->platform_id);
 }
 
 static const struct pci_device_id cb710_pci_tbl[] = {
diff --git a/drivers/scsi/osd/osd_uld.c b/drivers/scsi/osd/osd_uld.c
index 0e56f1e..eaf36cc 100644
--- a/drivers/scsi/osd/osd_uld.c
+++ b/drivers/scsi/osd/osd_uld.c
@@ -423,19 +423,11 @@
 	if (scsi_device->type != TYPE_OSD)
 		return -ENODEV;
 
-	do {
-		if (!ida_pre_get(&osd_minor_ida, GFP_KERNEL))
-			return -ENODEV;
-
-		error = ida_get_new(&osd_minor_ida, &minor);
-	} while (error == -EAGAIN);
-
-	if (error)
-		return error;
-	if (minor >= SCSI_OSD_MAX_MINOR) {
-		error = -EBUSY;
-		goto err_retract_minor;
-	}
+	minor = ida_alloc_max(&osd_minor_ida, SCSI_OSD_MAX_MINOR, GFP_KERNEL);
+	if (minor == -ENOSPC)
+		return -EBUSY;
+	if (minor < 0)
+		return -ENODEV;
 
 	error = -ENOMEM;
 	oud = kzalloc(sizeof(*oud), GFP_KERNEL);
@@ -499,7 +491,7 @@
 err_free_osd:
 	put_device(&oud->class_dev);
 err_retract_minor:
-	ida_remove(&osd_minor_ida, minor);
+	ida_free(&osd_minor_ida, minor);
 	return error;
 }
 
@@ -514,7 +506,7 @@
 	}
 
 	cdev_device_del(&oud->cdev, &oud->class_dev);
-	ida_remove(&osd_minor_ida, oud->minor);
+	ida_free(&osd_minor_ida, oud->minor);
 	put_device(&oud->class_dev);
 
 	return 0;
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index a58cee7a..b79b366 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -123,7 +123,6 @@
 static void sd_print_sense_hdr(struct scsi_disk *, struct scsi_sense_hdr *);
 static void sd_print_result(const struct scsi_disk *, const char *, int);
 
-static DEFINE_SPINLOCK(sd_index_lock);
 static DEFINE_IDA(sd_index_ida);
 
 /* This semaphore is used to mediate the 0->1 reference get in the
@@ -3340,16 +3339,8 @@
 	if (!gd)
 		goto out_free;
 
-	do {
-		if (!ida_pre_get(&sd_index_ida, GFP_KERNEL))
-			goto out_put;
-
-		spin_lock(&sd_index_lock);
-		error = ida_get_new(&sd_index_ida, &index);
-		spin_unlock(&sd_index_lock);
-	} while (error == -EAGAIN);
-
-	if (error) {
+	index = ida_alloc(&sd_index_ida, GFP_KERNEL);
+	if (index < 0) {
 		sdev_printk(KERN_WARNING, sdp, "sd_probe: memory exhausted.\n");
 		goto out_put;
 	}
@@ -3393,9 +3384,7 @@
 	return 0;
 
  out_free_index:
-	spin_lock(&sd_index_lock);
-	ida_remove(&sd_index_ida, index);
-	spin_unlock(&sd_index_lock);
+	ida_free(&sd_index_ida, index);
  out_put:
 	put_disk(gd);
  out_free:
@@ -3460,9 +3449,7 @@
 	struct scsi_disk *sdkp = to_scsi_disk(dev);
 	struct gendisk *disk = sdkp->disk;
 	
-	spin_lock(&sd_index_lock);
-	ida_remove(&sd_index_ida, sdkp->index);
-	spin_unlock(&sd_index_lock);
+	ida_free(&sd_index_ida, sdkp->index);
 
 	disk->private_data = NULL;
 	put_disk(disk);
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 8e22379..94bad43 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -57,9 +57,8 @@
 static DEFINE_MUTEX(np_lock);
 
 static struct idr tiqn_idr;
-struct idr sess_idr;
+DEFINE_IDA(sess_ida);
 struct mutex auth_id_lock;
-spinlock_t sess_idr_lock;
 
 struct iscsit_global *iscsit_global;
 
@@ -700,9 +699,7 @@
 
 	spin_lock_init(&iscsit_global->ts_bitmap_lock);
 	mutex_init(&auth_id_lock);
-	spin_lock_init(&sess_idr_lock);
 	idr_init(&tiqn_idr);
-	idr_init(&sess_idr);
 
 	ret = target_register_template(&iscsi_ops);
 	if (ret)
@@ -4375,10 +4372,7 @@
 	pr_debug("Decremented number of active iSCSI Sessions on"
 		" iSCSI TPG: %hu to %u\n", tpg->tpgt, tpg->nsessions);
 
-	spin_lock(&sess_idr_lock);
-	idr_remove(&sess_idr, sess->session_index);
-	spin_unlock(&sess_idr_lock);
-
+	ida_free(&sess_ida, sess->session_index);
 	kfree(sess->sess_ops);
 	sess->sess_ops = NULL;
 	spin_unlock_bh(&se_tpg->session_lock);
diff --git a/drivers/target/iscsi/iscsi_target.h b/drivers/target/iscsi/iscsi_target.h
index 42de184..48bac0a 100644
--- a/drivers/target/iscsi/iscsi_target.h
+++ b/drivers/target/iscsi/iscsi_target.h
@@ -55,9 +55,7 @@
 extern struct kmem_cache *lio_qr_cache;
 extern struct kmem_cache *lio_r2t_cache;
 
-extern struct idr sess_idr;
+extern struct ida sess_ida;
 extern struct mutex auth_id_lock;
-extern spinlock_t sess_idr_lock;
-
 
 #endif   /*** ISCSI_TARGET_H ***/
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 923b1a9..9e74f8b 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -336,22 +336,15 @@
 	timer_setup(&sess->time2retain_timer,
 		    iscsit_handle_time2retain_timeout, 0);
 
-	idr_preload(GFP_KERNEL);
-	spin_lock_bh(&sess_idr_lock);
-	ret = idr_alloc(&sess_idr, NULL, 0, 0, GFP_NOWAIT);
-	if (ret >= 0)
-		sess->session_index = ret;
-	spin_unlock_bh(&sess_idr_lock);
-	idr_preload_end();
-
+	ret = ida_alloc(&sess_ida, GFP_KERNEL);
 	if (ret < 0) {
-		pr_err("idr_alloc() for sess_idr failed\n");
+		pr_err("Session ID allocation failed %d\n", ret);
 		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
 				ISCSI_LOGIN_STATUS_NO_RESOURCES);
-		kfree(sess);
-		return -ENOMEM;
+		goto free_sess;
 	}
 
+	sess->session_index = ret;
 	sess->creation_time = get_jiffies_64();
 	/*
 	 * The FFP CmdSN window values will be allocated from the TPG's
@@ -365,20 +358,26 @@
 				ISCSI_LOGIN_STATUS_NO_RESOURCES);
 		pr_err("Unable to allocate memory for"
 				" struct iscsi_sess_ops.\n");
-		kfree(sess);
-		return -ENOMEM;
+		goto free_id;
 	}
 
 	sess->se_sess = transport_alloc_session(TARGET_PROT_NORMAL);
 	if (IS_ERR(sess->se_sess)) {
 		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
 				ISCSI_LOGIN_STATUS_NO_RESOURCES);
-		kfree(sess->sess_ops);
-		kfree(sess);
-		return -ENOMEM;
+		goto free_ops;
 	}
 
 	return 0;
+
+free_ops:
+	kfree(sess->sess_ops);
+free_id:
+	ida_free(&sess_ida, sess->session_index);
+free_sess:
+	kfree(sess);
+	conn->sess = NULL;
+	return -ENOMEM;
 }
 
 static int iscsi_login_zero_tsih_s2(
@@ -1161,13 +1160,9 @@
 				   ISCSI_LOGIN_STATUS_INIT_ERR);
 	if (!zero_tsih || !conn->sess)
 		goto old_sess_out;
-	if (conn->sess->se_sess)
-		transport_free_session(conn->sess->se_sess);
-	if (conn->sess->session_index != 0) {
-		spin_lock_bh(&sess_idr_lock);
-		idr_remove(&sess_idr, conn->sess->session_index);
-		spin_unlock_bh(&sess_idr_lock);
-	}
+
+	transport_free_session(conn->sess->se_sess);
+	ida_free(&sess_ida, conn->sess->session_index);
 	kfree(conn->sess->sess_ops);
 	kfree(conn->sess);
 	conn->sess = NULL;
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index e072e95..c538145 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -46,7 +46,7 @@
 static int pty_reserve = NR_UNIX98_PTY_RESERVE;
 static int pty_limit_min;
 static int pty_limit_max = INT_MAX;
-static int pty_count;
+static atomic_t pty_count = ATOMIC_INIT(0);
 
 static struct ctl_table pty_table[] = {
 	{
@@ -93,8 +93,6 @@
 	{}
 };
 
-static DEFINE_MUTEX(allocated_ptys_lock);
-
 struct pts_mount_opts {
 	int setuid;
 	int setgid;
@@ -533,44 +531,25 @@
 
 int devpts_new_index(struct pts_fs_info *fsi)
 {
-	int index;
-	int ida_ret;
+	int index = -ENOSPC;
 
-retry:
-	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
-		return -ENOMEM;
+	if (atomic_inc_return(&pty_count) >= (pty_limit -
+			  (fsi->mount_opts.reserve ? 0 : pty_reserve)))
+		goto out;
 
-	mutex_lock(&allocated_ptys_lock);
-	if (pty_count >= (pty_limit -
-			  (fsi->mount_opts.reserve ? 0 : pty_reserve))) {
-		mutex_unlock(&allocated_ptys_lock);
-		return -ENOSPC;
-	}
+	index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1,
+			GFP_KERNEL);
 
-	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
-	if (ida_ret < 0) {
-		mutex_unlock(&allocated_ptys_lock);
-		if (ida_ret == -EAGAIN)
-			goto retry;
-		return -EIO;
-	}
-
-	if (index >= fsi->mount_opts.max) {
-		ida_remove(&fsi->allocated_ptys, index);
-		mutex_unlock(&allocated_ptys_lock);
-		return -ENOSPC;
-	}
-	pty_count++;
-	mutex_unlock(&allocated_ptys_lock);
+out:
+	if (index < 0)
+		atomic_dec(&pty_count);
 	return index;
 }
 
 void devpts_kill_index(struct pts_fs_info *fsi, int idx)
 {
-	mutex_lock(&allocated_ptys_lock);
-	ida_remove(&fsi->allocated_ptys, idx);
-	pty_count--;
-	mutex_unlock(&allocated_ptys_lock);
+	ida_free(&fsi->allocated_ptys, idx);
+	atomic_dec(&pty_count);
 }
 
 /**
diff --git a/fs/namespace.c b/fs/namespace.c
index 725d693..9918655 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -61,9 +61,6 @@
 static u64 event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
-static DEFINE_SPINLOCK(mnt_id_lock);
-static int mnt_id_start = 0;
-static int mnt_group_start = 1;
 
 static struct hlist_head *mount_hashtable __read_mostly;
 static struct hlist_head *mountpoint_hashtable __read_mostly;
@@ -101,50 +98,30 @@
 
 static int mnt_alloc_id(struct mount *mnt)
 {
-	int res;
+	int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
 
-retry:
-	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
-	spin_lock(&mnt_id_lock);
-	res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
-	if (!res)
-		mnt_id_start = mnt->mnt_id + 1;
-	spin_unlock(&mnt_id_lock);
-	if (res == -EAGAIN)
-		goto retry;
-
-	return res;
+	if (res < 0)
+		return res;
+	mnt->mnt_id = res;
+	return 0;
 }
 
 static void mnt_free_id(struct mount *mnt)
 {
-	int id = mnt->mnt_id;
-	spin_lock(&mnt_id_lock);
-	ida_remove(&mnt_id_ida, id);
-	if (mnt_id_start > id)
-		mnt_id_start = id;
-	spin_unlock(&mnt_id_lock);
+	ida_free(&mnt_id_ida, mnt->mnt_id);
 }
 
 /*
  * Allocate a new peer group ID
- *
- * mnt_group_ida is protected by namespace_sem
  */
 static int mnt_alloc_group_id(struct mount *mnt)
 {
-	int res;
+	int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
 
-	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
-		return -ENOMEM;
-
-	res = ida_get_new_above(&mnt_group_ida,
-				mnt_group_start,
-				&mnt->mnt_group_id);
-	if (!res)
-		mnt_group_start = mnt->mnt_group_id + 1;
-
-	return res;
+	if (res < 0)
+		return res;
+	mnt->mnt_group_id = res;
+	return 0;
 }
 
 /*
@@ -152,10 +129,7 @@
  */
 void mnt_release_group_id(struct mount *mnt)
 {
-	int id = mnt->mnt_group_id;
-	ida_remove(&mnt_group_ida, id);
-	if (mnt_group_start > id)
-		mnt_group_start = id;
+	ida_free(&mnt_group_ida, mnt->mnt_group_id);
 	mnt->mnt_group_id = 0;
 }
 
diff --git a/fs/super.c b/fs/super.c
index 7429588..f3a8c00 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -981,58 +981,42 @@
 	}
 }
 
-/*
- * Unnamed block devices are dummy devices used by virtual
- * filesystems which don't use real block-devices.  -- jrs
- */
-
 static DEFINE_IDA(unnamed_dev_ida);
-static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
-/* Many userspace utilities consider an FSID of 0 invalid.
- * Always return at least 1 from get_anon_bdev.
- */
-static int unnamed_dev_start = 1;
 
+/**
+ * get_anon_bdev - Allocate a block device for filesystems which don't have one.
+ * @p: Pointer to a dev_t.
+ *
+ * Filesystems which don't use real block devices can call this function
+ * to allocate a virtual block device.
+ *
+ * Context: Any context.  Frequently called while holding sb_lock.
+ * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
+ * or -ENOMEM if memory allocation failed.
+ */
 int get_anon_bdev(dev_t *p)
 {
 	int dev;
-	int error;
 
- retry:
-	if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
-		return -ENOMEM;
-	spin_lock(&unnamed_dev_lock);
-	error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
-	if (!error)
-		unnamed_dev_start = dev + 1;
-	spin_unlock(&unnamed_dev_lock);
-	if (error == -EAGAIN)
-		/* We raced and lost with another CPU. */
-		goto retry;
-	else if (error)
-		return -EAGAIN;
+	/*
+	 * Many userspace utilities consider an FSID of 0 invalid.
+	 * Always return at least 1 from get_anon_bdev.
+	 */
+	dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
+			GFP_ATOMIC);
+	if (dev == -ENOSPC)
+		dev = -EMFILE;
+	if (dev < 0)
+		return dev;
 
-	if (dev >= (1 << MINORBITS)) {
-		spin_lock(&unnamed_dev_lock);
-		ida_remove(&unnamed_dev_ida, dev);
-		if (unnamed_dev_start > dev)
-			unnamed_dev_start = dev;
-		spin_unlock(&unnamed_dev_lock);
-		return -EMFILE;
-	}
-	*p = MKDEV(0, dev & MINORMASK);
+	*p = MKDEV(0, dev);
 	return 0;
 }
 EXPORT_SYMBOL(get_anon_bdev);
 
 void free_anon_bdev(dev_t dev)
 {
-	int slot = MINOR(dev);
-	spin_lock(&unnamed_dev_lock);
-	ida_remove(&unnamed_dev_ida, slot);
-	if (slot < unnamed_dev_start)
-		unnamed_dev_start = slot;
-	spin_unlock(&unnamed_dev_lock);
+	ida_free(&unnamed_dev_ida, MINOR(dev));
 }
 EXPORT_SYMBOL(free_anon_bdev);
 
@@ -1040,7 +1024,6 @@
 {
 	return get_anon_bdev(&s->s_dev);
 }
-
 EXPORT_SYMBOL(set_anon_super);
 
 void kill_anon_super(struct super_block *sb)
@@ -1049,7 +1032,6 @@
 	generic_shutdown_super(sb);
 	free_anon_bdev(dev);
 }
-
 EXPORT_SYMBOL(kill_anon_super);
 
 void kill_litter_super(struct super_block *sb)
@@ -1058,7 +1040,6 @@
 		d_genocide(sb->s_root);
 	kill_anon_super(sb);
 }
-
 EXPORT_SYMBOL(kill_litter_super);
 
 static int ns_test_super(struct super_block *sb, void *data)
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 3e8215b..3ec8628 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -236,34 +236,74 @@
 }
 #define DEFINE_IDA(name)	struct ida name = IDA_INIT(name)
 
-int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
-int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
-void ida_remove(struct ida *ida, int id);
+int ida_alloc_range(struct ida *, unsigned int min, unsigned int max, gfp_t);
+void ida_free(struct ida *, unsigned int id);
 void ida_destroy(struct ida *ida);
 
-int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
-		   gfp_t gfp_mask);
-void ida_simple_remove(struct ida *ida, unsigned int id);
+/**
+ * ida_alloc() - Allocate an unused ID.
+ * @ida: IDA handle.
+ * @gfp: Memory allocation flags.
+ *
+ * Allocate an ID between 0 and %INT_MAX, inclusive.
+ *
+ * Context: Any context.
+ * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
+ * or %-ENOSPC if there are no free IDs.
+ */
+static inline int ida_alloc(struct ida *ida, gfp_t gfp)
+{
+	return ida_alloc_range(ida, 0, ~0, gfp);
+}
+
+/**
+ * ida_alloc_min() - Allocate an unused ID.
+ * @ida: IDA handle.
+ * @min: Lowest ID to allocate.
+ * @gfp: Memory allocation flags.
+ *
+ * Allocate an ID between @min and %INT_MAX, inclusive.
+ *
+ * Context: Any context.
+ * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
+ * or %-ENOSPC if there are no free IDs.
+ */
+static inline int ida_alloc_min(struct ida *ida, unsigned int min, gfp_t gfp)
+{
+	return ida_alloc_range(ida, min, ~0, gfp);
+}
+
+/**
+ * ida_alloc_max() - Allocate an unused ID.
+ * @ida: IDA handle.
+ * @max: Highest ID to allocate.
+ * @gfp: Memory allocation flags.
+ *
+ * Allocate an ID between 0 and @max, inclusive.
+ *
+ * Context: Any context.
+ * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
+ * or %-ENOSPC if there are no free IDs.
+ */
+static inline int ida_alloc_max(struct ida *ida, unsigned int max, gfp_t gfp)
+{
+	return ida_alloc_range(ida, 0, max, gfp);
+}
 
 static inline void ida_init(struct ida *ida)
 {
 	INIT_RADIX_TREE(&ida->ida_rt, IDR_RT_MARKER | GFP_NOWAIT);
 }
 
-/**
- * ida_get_new - allocate new ID
- * @ida:	idr handle
- * @p_id:	pointer to the allocated handle
- *
- * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
- */
-static inline int ida_get_new(struct ida *ida, int *p_id)
-{
-	return ida_get_new_above(ida, 0, p_id);
-}
+#define ida_simple_get(ida, start, end, gfp)	\
+			ida_alloc_range(ida, start, (end) - 1, gfp)
+#define ida_simple_remove(ida, id)	ida_free(ida, id)
 
 static inline bool ida_is_empty(const struct ida *ida)
 {
 	return radix_tree_empty(&ida->ida_rt);
 }
+
+/* in lib/radix-tree.c */
+int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 #endif /* __IDR_H__ */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3589765..6133167 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1833,6 +1833,9 @@
 	  This is intended to help people writing architecture-specific
 	  optimized versions.  If unsure, say N.
 
+config TEST_IDA
+	tristate "Perform selftest on IDA functions"
+
 config TEST_PARMAN
 	tristate "Perform selftest on priority array manager"
 	depends on PARMAN
diff --git a/lib/Makefile b/lib/Makefile
index 9baefb6..ca3f7eb 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -50,6 +50,7 @@
 obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
 obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
 obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o
+obj-$(CONFIG_TEST_IDA) += test_ida.o
 obj-$(CONFIG_TEST_KASAN) += test_kasan.o
 CFLAGS_test_kasan.o += -fno-builtin
 obj-$(CONFIG_TEST_UBSAN) += test_ubsan.o
diff --git a/lib/idr.c b/lib/idr.c
index ed9c169..fab2fd5 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -317,18 +317,12 @@
  * bit per ID, and so is more space efficient than an IDR.  To use an IDA,
  * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
  * then initialise it using ida_init()).  To allocate a new ID, call
- * ida_simple_get().  To free an ID, call ida_simple_remove().
+ * ida_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range().
+ * To free an ID, call ida_free().
  *
- * If you have more complex locking requirements, use a loop around
- * ida_pre_get() and ida_get_new() to allocate a new ID.  Then use
- * ida_remove() to free an ID.  You must make sure that ida_get_new() and
- * ida_remove() cannot be called at the same time as each other for the
- * same IDA.
- *
- * You can also use ida_get_new_above() if you need an ID to be allocated
- * above a particular number.  ida_destroy() can be used to dispose of an
- * IDA without needing to free the individual IDs in it.  You can use
- * ida_is_empty() to find out whether the IDA has any IDs currently allocated.
+ * ida_destroy() can be used to dispose of an IDA without needing to
+ * free the individual IDs in it.  You can use ida_is_empty() to find
+ * out whether the IDA has any IDs currently allocated.
  *
  * IDs are currently limited to the range [0-INT_MAX].  If this is an awkward
  * limitation, it should be quite straightforward to raise the maximum.
@@ -369,25 +363,7 @@
 
 #define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1)
 
-/**
- * ida_get_new_above - allocate new ID above or equal to a start id
- * @ida: ida handle
- * @start: id to start search at
- * @id: pointer to the allocated handle
- *
- * Allocate new ID above or equal to @start.  It should be called
- * with any required locks to ensure that concurrent calls to
- * ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
- * Consider using ida_simple_get() if you do not have complex locking
- * requirements.
- *
- * If memory is required, it will return %-EAGAIN, you should unlock
- * and go back to the ida_pre_get() call.  If the ida is full, it will
- * return %-ENOSPC.  On success, it will return 0.
- *
- * @id returns a value in the range @start ... %0x7fffffff.
- */
-int ida_get_new_above(struct ida *ida, int start, int *id)
+static int ida_get_new_above(struct ida *ida, int start)
 {
 	struct radix_tree_root *root = &ida->ida_rt;
 	void __rcu **slot;
@@ -426,8 +402,8 @@
 			if (ebit < BITS_PER_LONG) {
 				tmp |= 1UL << ebit;
 				rcu_assign_pointer(*slot, (void *)tmp);
-				*id = new + ebit - RADIX_TREE_EXCEPTIONAL_SHIFT;
-				return 0;
+				return new + ebit -
+					RADIX_TREE_EXCEPTIONAL_SHIFT;
 			}
 			bitmap = this_cpu_xchg(ida_bitmap, NULL);
 			if (!bitmap)
@@ -458,8 +434,7 @@
 						RADIX_TREE_EXCEPTIONAL_ENTRY);
 				radix_tree_iter_replace(root, &iter, slot,
 						bitmap);
-				*id = new;
-				return 0;
+				return new;
 			}
 			bitmap = this_cpu_xchg(ida_bitmap, NULL);
 			if (!bitmap)
@@ -468,20 +443,11 @@
 			radix_tree_iter_replace(root, &iter, slot, bitmap);
 		}
 
-		*id = new;
-		return 0;
+		return new;
 	}
 }
-EXPORT_SYMBOL(ida_get_new_above);
 
-/**
- * ida_remove - Free the given ID
- * @ida: ida handle
- * @id: ID to free
- *
- * This function should not be called at the same time as ida_get_new_above().
- */
-void ida_remove(struct ida *ida, int id)
+static void ida_remove(struct ida *ida, int id)
 {
 	unsigned long index = id / IDA_BITMAP_BITS;
 	unsigned offset = id % IDA_BITMAP_BITS;
@@ -518,99 +484,90 @@
 	}
 	return;
  err:
-	WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
+	WARN(1, "ida_free called for id=%d which is not allocated.\n", id);
 }
-EXPORT_SYMBOL(ida_remove);
 
 /**
- * ida_destroy - Free the contents of an ida
- * @ida: ida handle
+ * ida_destroy() - Free all IDs.
+ * @ida: IDA handle.
  *
- * Calling this function releases all resources associated with an IDA.  When
- * this call returns, the IDA is empty and can be reused or freed.  The caller
- * should not allow ida_remove() or ida_get_new_above() to be called at the
- * same time.
+ * Calling this function frees all IDs and releases all resources used
+ * by an IDA.  When this call returns, the IDA is empty and can be reused
+ * or freed.  If the IDA is already empty, there is no need to call this
+ * function.
+ *
+ * Context: Any context.
  */
 void ida_destroy(struct ida *ida)
 {
+	unsigned long flags;
 	struct radix_tree_iter iter;
 	void __rcu **slot;
 
+	xa_lock_irqsave(&ida->ida_rt, flags);
 	radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
 		struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
 		if (!radix_tree_exception(bitmap))
 			kfree(bitmap);
 		radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
 	}
+	xa_unlock_irqrestore(&ida->ida_rt, flags);
 }
 EXPORT_SYMBOL(ida_destroy);
 
 /**
- * ida_simple_get - get a new id.
- * @ida: the (initialized) ida.
- * @start: the minimum id (inclusive, < 0x8000000)
- * @end: the maximum id (exclusive, < 0x8000000 or 0)
- * @gfp_mask: memory allocation flags
+ * ida_alloc_range() - Allocate an unused ID.
+ * @ida: IDA handle.
+ * @min: Lowest ID to allocate.
+ * @max: Highest ID to allocate.
+ * @gfp: Memory allocation flags.
  *
- * Allocates an id in the range start <= id < end, or returns -ENOSPC.
- * On memory allocation failure, returns -ENOMEM.
+ * Allocate an ID between @min and @max, inclusive.  The allocated ID will
+ * not exceed %INT_MAX, even if @max is larger.
  *
- * Compared to ida_get_new_above() this function does its own locking, and
- * should be used unless there are special requirements.
- *
- * Use ida_simple_remove() to get rid of an id.
+ * Context: Any context.
+ * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
+ * or %-ENOSPC if there are no free IDs.
  */
-int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
-		   gfp_t gfp_mask)
+int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
+			gfp_t gfp)
 {
-	int ret, id;
-	unsigned int max;
+	int id = 0;
 	unsigned long flags;
 
-	BUG_ON((int)start < 0);
-	BUG_ON((int)end < 0);
+	if ((int)min < 0)
+		return -ENOSPC;
 
-	if (end == 0)
-		max = 0x80000000;
-	else {
-		BUG_ON(end < start);
-		max = end - 1;
-	}
+	if ((int)max < 0)
+		max = INT_MAX;
 
 again:
-	if (!ida_pre_get(ida, gfp_mask))
-		return -ENOMEM;
-
 	xa_lock_irqsave(&ida->ida_rt, flags);
-	ret = ida_get_new_above(ida, start, &id);
-	if (!ret) {
-		if (id > max) {
-			ida_remove(ida, id);
-			ret = -ENOSPC;
-		} else {
-			ret = id;
-		}
+	id = ida_get_new_above(ida, min);
+	if (id > (int)max) {
+		ida_remove(ida, id);
+		id = -ENOSPC;
 	}
 	xa_unlock_irqrestore(&ida->ida_rt, flags);
 
-	if (unlikely(ret == -EAGAIN))
+	if (unlikely(id == -EAGAIN)) {
+		if (!ida_pre_get(ida, gfp))
+			return -ENOMEM;
 		goto again;
+	}
 
-	return ret;
+	return id;
 }
-EXPORT_SYMBOL(ida_simple_get);
+EXPORT_SYMBOL(ida_alloc_range);
 
 /**
- * ida_simple_remove - remove an allocated id.
- * @ida: the (initialized) ida.
- * @id: the id returned by ida_simple_get.
+ * ida_free() - Release an allocated ID.
+ * @ida: IDA handle.
+ * @id: Previously allocated ID.
  *
- * Use to release an id allocated with ida_simple_get().
- *
- * Compared to ida_remove() this function does its own locking, and should be
- * used unless there are special requirements.
+ * Context: Any context.
  */
-void ida_simple_remove(struct ida *ida, unsigned int id)
+void ida_free(struct ida *ida, unsigned int id)
 {
 	unsigned long flags;
 
@@ -619,4 +576,4 @@
 	ida_remove(ida, id);
 	xa_unlock_irqrestore(&ida->ida_rt, flags);
 }
-EXPORT_SYMBOL(ida_simple_remove);
+EXPORT_SYMBOL(ida_free);
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index a9e41ae..bc03ecc 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -120,7 +120,7 @@
 static inline unsigned long
 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
 {
-	return slot - parent->slots;
+	return parent ? slot - parent->slots : 0;
 }
 
 static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
@@ -2106,14 +2106,6 @@
 }
 EXPORT_SYMBOL(idr_preload);
 
-/**
- * ida_pre_get - reserve resources for ida allocation
- * @ida: ida handle
- * @gfp: memory allocation flags
- *
- * This function should be called before calling ida_get_new_above().  If it
- * is unable to allocate memory, it will return %0.  On success, it returns %1.
- */
 int ida_pre_get(struct ida *ida, gfp_t gfp)
 {
 	/*
@@ -2134,7 +2126,6 @@
 
 	return 1;
 }
-EXPORT_SYMBOL(ida_pre_get);
 
 void __rcu **idr_get_free(struct radix_tree_root *root,
 			      struct radix_tree_iter *iter, gfp_t gfp,
diff --git a/lib/test_ida.c b/lib/test_ida.c
new file mode 100644
index 0000000..2d1637d
--- /dev/null
+++ b/lib/test_ida.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * test_ida.c: Test the IDA API
+ * Copyright (c) 2016-2018 Microsoft Corporation
+ * Copyright (c) 2018 Oracle Corporation
+ * Author: Matthew Wilcox <willy@infradead.org>
+ */
+
+#include <linux/idr.h>
+#include <linux/module.h>
+
+static unsigned int tests_run;
+static unsigned int tests_passed;
+
+#ifdef __KERNEL__
+void ida_dump(struct ida *ida) { }
+#endif
+#define IDA_BUG_ON(ida, x) do {						\
+	tests_run++;							\
+	if (x) {							\
+		ida_dump(ida);						\
+		dump_stack();						\
+	} else {							\
+		tests_passed++;						\
+	}								\
+} while (0)
+
+/*
+ * Straightforward checks that allocating and freeing IDs work.
+ */
+static void ida_check_alloc(struct ida *ida)
+{
+	int i, id;
+
+	for (i = 0; i < 10000; i++)
+		IDA_BUG_ON(ida, ida_alloc(ida, GFP_KERNEL) != i);
+
+	ida_free(ida, 20);
+	ida_free(ida, 21);
+	for (i = 0; i < 3; i++) {
+		id = ida_alloc(ida, GFP_KERNEL);
+		IDA_BUG_ON(ida, id < 0);
+		if (i == 2)
+			IDA_BUG_ON(ida, id != 10000);
+	}
+
+	for (i = 0; i < 5000; i++)
+		ida_free(ida, i);
+
+	IDA_BUG_ON(ida, ida_alloc_min(ida, 5000, GFP_KERNEL) != 10001);
+	ida_destroy(ida);
+
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+}
+
+/* Destroy an IDA with a single entry at @base */
+static void ida_check_destroy_1(struct ida *ida, unsigned int base)
+{
+	IDA_BUG_ON(ida, ida_alloc_min(ida, base, GFP_KERNEL) != base);
+	IDA_BUG_ON(ida, ida_is_empty(ida));
+	ida_destroy(ida);
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+}
+
+/* Check that ida_destroy and ida_is_empty work */
+static void ida_check_destroy(struct ida *ida)
+{
+	/* Destroy an already-empty IDA */
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+	ida_destroy(ida);
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+
+	ida_check_destroy_1(ida, 0);
+	ida_check_destroy_1(ida, 1);
+	ida_check_destroy_1(ida, 1023);
+	ida_check_destroy_1(ida, 1024);
+	ida_check_destroy_1(ida, 12345678);
+}
+
+/*
+ * Check what happens when we fill a leaf and then delete it.  This may
+ * discover mishandling of IDR_FREE.
+ */
+static void ida_check_leaf(struct ida *ida, unsigned int base)
+{
+	unsigned long i;
+
+	for (i = 0; i < IDA_BITMAP_BITS; i++) {
+		IDA_BUG_ON(ida, ida_alloc_min(ida, base, GFP_KERNEL) !=
+				base + i);
+	}
+
+	ida_destroy(ida);
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+
+	IDA_BUG_ON(ida, ida_alloc(ida, GFP_KERNEL) != 0);
+	IDA_BUG_ON(ida, ida_is_empty(ida));
+	ida_free(ida, 0);
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+}
+
+/*
+ * Check allocations up to and slightly above the maximum allowed (2^31-1) ID.
+ * Allocating up to 2^31-1 should succeed, and then allocating the next one
+ * should fail.
+ */
+static void ida_check_max(struct ida *ida)
+{
+	unsigned long i, j;
+
+	for (j = 1; j < 65537; j *= 2) {
+		unsigned long base = (1UL << 31) - j;
+		for (i = 0; i < j; i++) {
+			IDA_BUG_ON(ida, ida_alloc_min(ida, base, GFP_KERNEL) !=
+					base + i);
+		}
+		IDA_BUG_ON(ida, ida_alloc_min(ida, base, GFP_KERNEL) !=
+				-ENOSPC);
+		ida_destroy(ida);
+		IDA_BUG_ON(ida, !ida_is_empty(ida));
+	}
+}
+
+/*
+ * Check handling of conversions between exceptional entries and full bitmaps.
+ */
+static void ida_check_conv(struct ida *ida)
+{
+	unsigned long i;
+
+	for (i = 0; i < IDA_BITMAP_BITS * 2; i += IDA_BITMAP_BITS) {
+		IDA_BUG_ON(ida, ida_alloc_min(ida, i + 1, GFP_KERNEL) != i + 1);
+		IDA_BUG_ON(ida, ida_alloc_min(ida, i + BITS_PER_LONG,
+					GFP_KERNEL) != i + BITS_PER_LONG);
+		ida_free(ida, i + 1);
+		ida_free(ida, i + BITS_PER_LONG);
+		IDA_BUG_ON(ida, !ida_is_empty(ida));
+	}
+
+	for (i = 0; i < IDA_BITMAP_BITS * 2; i++)
+		IDA_BUG_ON(ida, ida_alloc(ida, GFP_KERNEL) != i);
+	for (i = IDA_BITMAP_BITS * 2; i > 0; i--)
+		ida_free(ida, i - 1);
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+
+	for (i = 0; i < IDA_BITMAP_BITS + BITS_PER_LONG - 4; i++)
+		IDA_BUG_ON(ida, ida_alloc(ida, GFP_KERNEL) != i);
+	for (i = IDA_BITMAP_BITS + BITS_PER_LONG - 4; i > 0; i--)
+		ida_free(ida, i - 1);
+	IDA_BUG_ON(ida, !ida_is_empty(ida));
+}
+
+static int ida_checks(void)
+{
+	DEFINE_IDA(ida);
+
+	IDA_BUG_ON(&ida, !ida_is_empty(&ida));
+	ida_check_alloc(&ida);
+	ida_check_destroy(&ida);
+	ida_check_leaf(&ida, 0);
+	ida_check_leaf(&ida, 1024);
+	ida_check_leaf(&ida, 1024 * 64);
+	ida_check_max(&ida);
+	ida_check_conv(&ida);
+
+	printk("IDA: %u of %u tests passed\n", tests_passed, tests_run);
+	return (tests_run != tests_passed) ? 0 : -EINVAL;
+}
+
+static void ida_exit(void)
+{
+}
+
+module_init(ida_checks);
+module_exit(ida_exit);
+MODULE_AUTHOR("Matthew Wilcox <willy@infradead.org>");
+MODULE_LICENSE("GPL");
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 738871a..670c84b 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -1001,22 +1001,18 @@
 	int error;
 
 	if (ops->id) {
-again:
-		error = ida_get_new_above(&net_generic_ids, MIN_PERNET_OPS_ID, ops->id);
-		if (error < 0) {
-			if (error == -EAGAIN) {
-				ida_pre_get(&net_generic_ids, GFP_KERNEL);
-				goto again;
-			}
+		error = ida_alloc_min(&net_generic_ids, MIN_PERNET_OPS_ID,
+				GFP_KERNEL);
+		if (error < 0)
 			return error;
-		}
+		*ops->id = error;
 		max_gen_ptrs = max(max_gen_ptrs, *ops->id + 1);
 	}
 	error = __register_pernet_operations(list, ops);
 	if (error) {
 		rcu_barrier();
 		if (ops->id)
-			ida_remove(&net_generic_ids, *ops->id);
+			ida_free(&net_generic_ids, *ops->id);
 	}
 
 	return error;
@@ -1027,7 +1023,7 @@
 	__unregister_pernet_operations(ops);
 	rcu_barrier();
 	if (ops->id)
-		ida_remove(&net_generic_ids, *ops->id);
+		ida_free(&net_generic_ids, *ops->id);
 }
 
 /**
diff --git a/tools/testing/radix-tree/Makefile b/tools/testing/radix-tree/Makefile
index db66f8a..37baecc 100644
--- a/tools/testing/radix-tree/Makefile
+++ b/tools/testing/radix-tree/Makefile
@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 
-CFLAGS += -I. -I../../include -g -O2 -Wall -D_LGPL_SOURCE -fsanitize=address
-LDFLAGS += -fsanitize=address
+CFLAGS += -I. -I../../include -g -Og -Wall -D_LGPL_SOURCE -fsanitize=address \
+	  -fsanitize=undefined
+LDFLAGS += -fsanitize=address -fsanitize=undefined
 LDLIBS+= -lpthread -lurcu
 TARGETS = main idr-test multiorder
 CORE_OFILES := radix-tree.o idr.o linux.o test.o find_bit.o
@@ -21,6 +22,7 @@
 
 main:	$(OFILES)
 
+idr-test.o: ../../../lib/test_ida.c
 idr-test: idr-test.o $(CORE_OFILES)
 
 multiorder: multiorder.o $(CORE_OFILES)
diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c
index ee820fc..321ba92 100644
--- a/tools/testing/radix-tree/idr-test.c
+++ b/tools/testing/radix-tree/idr-test.c
@@ -309,141 +309,61 @@
 	idr_u32_test(0);
 }
 
+#define module_init(x)
+#define module_exit(x)
+#define MODULE_AUTHOR(x)
+#define MODULE_LICENSE(x)
+#define dump_stack()    assert(0)
+void ida_dump(struct ida *);
+
+#include "../../../lib/test_ida.c"
+
 /*
  * Check that we get the correct error when we run out of memory doing
- * allocations.  To ensure we run out of memory, just "forget" to preload.
+ * allocations.  In userspace, GFP_NOWAIT will always fail an allocation.
  * The first test is for not having a bitmap available, and the second test
  * is for not being able to allocate a level of the radix tree.
  */
 void ida_check_nomem(void)
 {
 	DEFINE_IDA(ida);
-	int id, err;
-
-	err = ida_get_new_above(&ida, 256, &id);
-	assert(err == -EAGAIN);
-	err = ida_get_new_above(&ida, 1UL << 30, &id);
-	assert(err == -EAGAIN);
-}
-
-/*
- * Check what happens when we fill a leaf and then delete it.  This may
- * discover mishandling of IDR_FREE.
- */
-void ida_check_leaf(void)
-{
-	DEFINE_IDA(ida);
 	int id;
-	unsigned long i;
 
-	for (i = 0; i < IDA_BITMAP_BITS; i++) {
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		assert(!ida_get_new(&ida, &id));
-		assert(id == i);
-	}
-
-	ida_destroy(&ida);
-	assert(ida_is_empty(&ida));
-
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new(&ida, &id));
-	assert(id == 0);
-	ida_destroy(&ida);
-	assert(ida_is_empty(&ida));
+	id = ida_alloc_min(&ida, 256, GFP_NOWAIT);
+	IDA_BUG_ON(&ida, id != -ENOMEM);
+	id = ida_alloc_min(&ida, 1UL << 30, GFP_NOWAIT);
+	IDA_BUG_ON(&ida, id != -ENOMEM);
+	IDA_BUG_ON(&ida, !ida_is_empty(&ida));
 }
 
 /*
  * Check handling of conversions between exceptional entries and full bitmaps.
  */
-void ida_check_conv(void)
+void ida_check_conv_user(void)
 {
 	DEFINE_IDA(ida);
-	int id;
 	unsigned long i;
 
-	for (i = 0; i < IDA_BITMAP_BITS * 2; i += IDA_BITMAP_BITS) {
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		assert(!ida_get_new_above(&ida, i + 1, &id));
-		assert(id == i + 1);
-		assert(!ida_get_new_above(&ida, i + BITS_PER_LONG, &id));
-		assert(id == i + BITS_PER_LONG);
-		ida_remove(&ida, i + 1);
-		ida_remove(&ida, i + BITS_PER_LONG);
-		assert(ida_is_empty(&ida));
-	}
-
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-
-	for (i = 0; i < IDA_BITMAP_BITS * 2; i++) {
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		assert(!ida_get_new(&ida, &id));
-		assert(id == i);
-	}
-
-	for (i = IDA_BITMAP_BITS * 2; i > 0; i--) {
-		ida_remove(&ida, i - 1);
-	}
-	assert(ida_is_empty(&ida));
-
-	for (i = 0; i < IDA_BITMAP_BITS + BITS_PER_LONG - 4; i++) {
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		assert(!ida_get_new(&ida, &id));
-		assert(id == i);
-	}
-
-	for (i = IDA_BITMAP_BITS + BITS_PER_LONG - 4; i > 0; i--) {
-		ida_remove(&ida, i - 1);
-	}
-	assert(ida_is_empty(&ida));
-
 	radix_tree_cpu_dead(1);
 	for (i = 0; i < 1000000; i++) {
-		int err = ida_get_new(&ida, &id);
-		if (err == -EAGAIN) {
-			assert((i % IDA_BITMAP_BITS) == (BITS_PER_LONG - 2));
-			assert(ida_pre_get(&ida, GFP_KERNEL));
-			err = ida_get_new(&ida, &id);
+		int id = ida_alloc(&ida, GFP_NOWAIT);
+		if (id == -ENOMEM) {
+			IDA_BUG_ON(&ida, (i % IDA_BITMAP_BITS) !=
+					BITS_PER_LONG - 2);
+			id = ida_alloc(&ida, GFP_KERNEL);
 		} else {
-			assert((i % IDA_BITMAP_BITS) != (BITS_PER_LONG - 2));
+			IDA_BUG_ON(&ida, (i % IDA_BITMAP_BITS) ==
+					BITS_PER_LONG - 2);
 		}
-		assert(!err);
-		assert(id == i);
+		IDA_BUG_ON(&ida, id != i);
 	}
 	ida_destroy(&ida);
 }
 
-/*
- * Check allocations up to and slightly above the maximum allowed (2^31-1) ID.
- * Allocating up to 2^31-1 should succeed, and then allocating the next one
- * should fail.
- */
-void ida_check_max(void)
-{
-	DEFINE_IDA(ida);
-	int id, err;
-	unsigned long i, j;
-
-	for (j = 1; j < 65537; j *= 2) {
-		unsigned long base = (1UL << 31) - j;
-		for (i = 0; i < j; i++) {
-			assert(ida_pre_get(&ida, GFP_KERNEL));
-			assert(!ida_get_new_above(&ida, base, &id));
-			assert(id == base + i);
-		}
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		err = ida_get_new_above(&ida, base, &id);
-		assert(err == -ENOSPC);
-		ida_destroy(&ida);
-		assert(ida_is_empty(&ida));
-		rcu_barrier();
-	}
-}
-
 void ida_check_random(void)
 {
 	DEFINE_IDA(ida);
 	DECLARE_BITMAP(bitmap, 2048);
-	int id, err;
 	unsigned int i;
 	time_t s = time(NULL);
 
@@ -454,15 +374,11 @@
 		int bit = i & 2047;
 		if (test_bit(bit, bitmap)) {
 			__clear_bit(bit, bitmap);
-			ida_remove(&ida, bit);
+			ida_free(&ida, bit);
 		} else {
 			__set_bit(bit, bitmap);
-			do {
-				ida_pre_get(&ida, GFP_KERNEL);
-				err = ida_get_new_above(&ida, bit, &id);
-			} while (err == -EAGAIN);
-			assert(!err);
-			assert(id == bit);
+			IDA_BUG_ON(&ida, ida_alloc_min(&ida, bit, GFP_KERNEL)
+					!= bit);
 		}
 	}
 	ida_destroy(&ida);
@@ -488,71 +404,12 @@
 	ida_destroy(&ida);
 }
 
-void ida_checks(void)
+void user_ida_checks(void)
 {
-	DEFINE_IDA(ida);
-	int id;
-	unsigned long i;
-
 	radix_tree_cpu_dead(1);
+
 	ida_check_nomem();
-
-	for (i = 0; i < 10000; i++) {
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		assert(!ida_get_new(&ida, &id));
-		assert(id == i);
-	}
-
-	ida_remove(&ida, 20);
-	ida_remove(&ida, 21);
-	for (i = 0; i < 3; i++) {
-		assert(ida_pre_get(&ida, GFP_KERNEL));
-		assert(!ida_get_new(&ida, &id));
-		if (i == 2)
-			assert(id == 10000);
-	}
-
-	for (i = 0; i < 5000; i++)
-		ida_remove(&ida, i);
-
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new_above(&ida, 5000, &id));
-	assert(id == 10001);
-
-	ida_destroy(&ida);
-
-	assert(ida_is_empty(&ida));
-
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new_above(&ida, 1, &id));
-	assert(id == 1);
-
-	ida_remove(&ida, id);
-	assert(ida_is_empty(&ida));
-	ida_destroy(&ida);
-	assert(ida_is_empty(&ida));
-
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new_above(&ida, 1, &id));
-	ida_destroy(&ida);
-	assert(ida_is_empty(&ida));
-
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new_above(&ida, 1, &id));
-	assert(id == 1);
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new_above(&ida, 1025, &id));
-	assert(id == 1025);
-	assert(ida_pre_get(&ida, GFP_KERNEL));
-	assert(!ida_get_new_above(&ida, 10000, &id));
-	assert(id == 10000);
-	ida_remove(&ida, 1025);
-	ida_destroy(&ida);
-	assert(ida_is_empty(&ida));
-
-	ida_check_leaf();
-	ida_check_max();
-	ida_check_conv();
+	ida_check_conv_user();
 	ida_check_random();
 	ida_simple_get_remove_test();
 
@@ -582,12 +439,19 @@
 		pthread_join(threads[i], NULL);
 }
 
+void ida_tests(void)
+{
+	user_ida_checks();
+	ida_checks();
+	ida_exit();
+	ida_thread_tests();
+}
+
 int __weak main(void)
 {
 	radix_tree_init();
 	idr_checks();
-	ida_checks();
-	ida_thread_tests();
+	ida_tests();
 	radix_tree_cpu_dead(1);
 	rcu_barrier();
 	if (nr_allocated)
diff --git a/tools/testing/radix-tree/linux/xarray.h b/tools/testing/radix-tree/linux/xarray.h
new file mode 100644
index 0000000..df3812c
--- /dev/null
+++ b/tools/testing/radix-tree/linux/xarray.h
@@ -0,0 +1,2 @@
+#include "generated/map-shift.h"
+#include "../../../../include/linux/xarray.h"
diff --git a/tools/testing/radix-tree/main.c b/tools/testing/radix-tree/main.c
index 257f3f8..b741686 100644
--- a/tools/testing/radix-tree/main.c
+++ b/tools/testing/radix-tree/main.c
@@ -27,20 +27,22 @@
 		item_check_present(&tree, middle + idx);
 	item_check_absent(&tree, middle + up);
 
-	item_gang_check_present(&tree, middle - down,
-			up + down, chunk, hop);
-	item_full_scan(&tree, middle - down, down + up, chunk);
+	if (chunk > 0) {
+		item_gang_check_present(&tree, middle - down, up + down,
+				chunk, hop);
+		item_full_scan(&tree, middle - down, down + up, chunk);
+	}
 	item_kill_tree(&tree);
 }
 
 void gang_check(void)
 {
-	__gang_check(1 << 30, 128, 128, 35, 2);
-	__gang_check(1 << 31, 128, 128, 32, 32);
-	__gang_check(1 << 31, 128, 128, 32, 100);
-	__gang_check(1 << 31, 128, 128, 17, 7);
-	__gang_check(0xffff0000, 0, 65536, 17, 7);
-	__gang_check(0xfffffffe, 1, 1, 17, 7);
+	__gang_check(1UL << 30, 128, 128, 35, 2);
+	__gang_check(1UL << 31, 128, 128, 32, 32);
+	__gang_check(1UL << 31, 128, 128, 32, 100);
+	__gang_check(1UL << 31, 128, 128, 17, 7);
+	__gang_check(0xffff0000UL, 0, 65536, 17, 7);
+	__gang_check(0xfffffffeUL, 1, 1, 17, 7);
 }
 
 void __big_gang_check(void)
@@ -322,7 +324,7 @@
 	printv(2, "after dynamic_height_check: %d allocated, preempt %d\n",
 		nr_allocated, preempt_count);
 	idr_checks();
-	ida_checks();
+	ida_tests();
 	rcu_barrier();
 	printv(2, "after idr_checks: %d allocated, preempt %d\n",
 		nr_allocated, preempt_count);
@@ -369,7 +371,6 @@
 	iteration_test(0, 10 + 90 * long_run);
 	iteration_test(7, 10 + 90 * long_run);
 	single_thread_tests(long_run);
-	ida_thread_tests();
 
 	/* Free any remaining preallocated nodes */
 	radix_tree_cpu_dead(0);
diff --git a/tools/testing/radix-tree/test.h b/tools/testing/radix-tree/test.h
index 31f1d9b..92d901e 100644
--- a/tools/testing/radix-tree/test.h
+++ b/tools/testing/radix-tree/test.h
@@ -39,8 +39,7 @@
 void iteration_test(unsigned order, unsigned duration);
 void benchmark(void);
 void idr_checks(void);
-void ida_checks(void);
-void ida_thread_tests(void);
+void ida_tests(void);
 
 struct item *
 item_tag_set(struct radix_tree_root *root, unsigned long index, int tag);