diff --cc drivers/dibs/dibs_loopback.c
index 000000000000,b3fd0f8100d4..aa029e29c6b2
mode 000000,100644..100644
--- a/drivers/dibs/dibs_loopback.c
+++ b/drivers/dibs/dibs_loopback.c
@@@ -1,0 -1,356 +1,361 @@@
+ // SPDX-License-Identifier: GPL-2.0
+ /*
+  *  Functions for dibs loopback/loopback-ism device.
+  *
+  *  Copyright (c) 2024, Alibaba Inc.
+  *
+  *  Author: Wen Gu <guwen@linux.alibaba.com>
+  *          Tony Lu <tonylu@linux.alibaba.com>
+  *
+  */
+ 
+ #include <linux/bitops.h>
+ #include <linux/device.h>
+ #include <linux/dibs.h>
++#include <linux/mm.h>
+ #include <linux/slab.h>
+ #include <linux/spinlock.h>
+ #include <linux/types.h>
+ 
+ #include "dibs_loopback.h"
+ 
+ #define DIBS_LO_SUPPORT_NOCOPY	0x1
+ #define DIBS_DMA_ADDR_INVALID	(~(dma_addr_t)0)
+ 
+ static const char dibs_lo_dev_name[] = "lo";
+ /* global loopback device */
+ static struct dibs_lo_dev *lo_dev;
+ 
+ static u16 dibs_lo_get_fabric_id(struct dibs_dev *dibs)
+ {
+ 	return DIBS_LOOPBACK_FABRIC;
+ }
+ 
+ static int dibs_lo_query_rgid(struct dibs_dev *dibs, const uuid_t *rgid,
+ 			      u32 vid_valid, u32 vid)
+ {
+ 	/* rgid should be the same as lgid */
+ 	if (!uuid_equal(rgid, &dibs->gid))
+ 		return -ENETUNREACH;
+ 	return 0;
+ }
+ 
+ static int dibs_lo_max_dmbs(void)
+ {
+ 	return DIBS_LO_MAX_DMBS;
+ }
+ 
+ static int dibs_lo_register_dmb(struct dibs_dev *dibs, struct dibs_dmb *dmb,
+ 				struct dibs_client *client)
+ {
+ 	struct dibs_lo_dmb_node *dmb_node, *tmp_node;
+ 	struct dibs_lo_dev *ldev;
++	struct folio *folio;
+ 	unsigned long flags;
+ 	int sba_idx, rc;
+ 
+ 	ldev = dibs->drv_priv;
+ 	sba_idx = dmb->idx;
+ 	/* check space for new dmb */
+ 	for_each_clear_bit(sba_idx, ldev->sba_idx_mask, DIBS_LO_MAX_DMBS) {
+ 		if (!test_and_set_bit(sba_idx, ldev->sba_idx_mask))
+ 			break;
+ 	}
+ 	if (sba_idx == DIBS_LO_MAX_DMBS)
+ 		return -ENOSPC;
+ 
+ 	dmb_node = kzalloc(sizeof(*dmb_node), GFP_KERNEL);
+ 	if (!dmb_node) {
+ 		rc = -ENOMEM;
+ 		goto err_bit;
+ 	}
+ 
+ 	dmb_node->sba_idx = sba_idx;
+ 	dmb_node->len = dmb->dmb_len;
 -	dmb_node->cpu_addr = kzalloc(dmb_node->len, GFP_KERNEL |
 -				     __GFP_NOWARN | __GFP_NORETRY |
 -				     __GFP_NOMEMALLOC);
 -	if (!dmb_node->cpu_addr) {
++
++	/* not critical; fail under memory pressure and fallback to TCP */
++	folio = folio_alloc(GFP_KERNEL | __GFP_NOWARN | __GFP_NOMEMALLOC |
++			    __GFP_NORETRY | __GFP_ZERO,
++			    get_order(dmb_node->len));
++	if (!folio) {
+ 		rc = -ENOMEM;
+ 		goto err_node;
+ 	}
++	dmb_node->cpu_addr = folio_address(folio);
+ 	dmb_node->dma_addr = DIBS_DMA_ADDR_INVALID;
+ 	refcount_set(&dmb_node->refcnt, 1);
+ 
+ again:
+ 	/* add new dmb into hash table */
+ 	get_random_bytes(&dmb_node->token, sizeof(dmb_node->token));
+ 	write_lock_bh(&ldev->dmb_ht_lock);
+ 	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_node->token) {
+ 		if (tmp_node->token == dmb_node->token) {
+ 			write_unlock_bh(&ldev->dmb_ht_lock);
+ 			goto again;
+ 		}
+ 	}
+ 	hash_add(ldev->dmb_ht, &dmb_node->list, dmb_node->token);
+ 	write_unlock_bh(&ldev->dmb_ht_lock);
+ 	atomic_inc(&ldev->dmb_cnt);
+ 
+ 	dmb->idx = dmb_node->sba_idx;
+ 	dmb->dmb_tok = dmb_node->token;
+ 	dmb->cpu_addr = dmb_node->cpu_addr;
+ 	dmb->dma_addr = dmb_node->dma_addr;
+ 	dmb->dmb_len = dmb_node->len;
+ 
+ 	spin_lock_irqsave(&dibs->lock, flags);
+ 	dibs->dmb_clientid_arr[sba_idx] = client->id;
+ 	spin_unlock_irqrestore(&dibs->lock, flags);
+ 
+ 	return 0;
+ 
+ err_node:
+ 	kfree(dmb_node);
+ err_bit:
+ 	clear_bit(sba_idx, ldev->sba_idx_mask);
+ 	return rc;
+ }
+ 
+ static void __dibs_lo_unregister_dmb(struct dibs_lo_dev *ldev,
+ 				     struct dibs_lo_dmb_node *dmb_node)
+ {
+ 	/* remove dmb from hash table */
+ 	write_lock_bh(&ldev->dmb_ht_lock);
+ 	hash_del(&dmb_node->list);
+ 	write_unlock_bh(&ldev->dmb_ht_lock);
+ 
+ 	clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
 -	kfree(dmb_node->cpu_addr);
++	folio_put(virt_to_folio(dmb_node->cpu_addr));
+ 	kfree(dmb_node);
+ 
+ 	if (atomic_dec_and_test(&ldev->dmb_cnt))
+ 		wake_up(&ldev->ldev_release);
+ }
+ 
+ static int dibs_lo_unregister_dmb(struct dibs_dev *dibs, struct dibs_dmb *dmb)
+ {
+ 	struct dibs_lo_dmb_node *dmb_node = NULL, *tmp_node;
+ 	struct dibs_lo_dev *ldev;
+ 	unsigned long flags;
+ 
+ 	ldev = dibs->drv_priv;
+ 
+ 	/* find dmb from hash table */
+ 	read_lock_bh(&ldev->dmb_ht_lock);
+ 	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb->dmb_tok) {
+ 		if (tmp_node->token == dmb->dmb_tok) {
+ 			dmb_node = tmp_node;
+ 			break;
+ 		}
+ 	}
+ 	read_unlock_bh(&ldev->dmb_ht_lock);
+ 	if (!dmb_node)
+ 		return -EINVAL;
+ 
+ 	if (refcount_dec_and_test(&dmb_node->refcnt)) {
+ 		spin_lock_irqsave(&dibs->lock, flags);
+ 		dibs->dmb_clientid_arr[dmb_node->sba_idx] = NO_DIBS_CLIENT;
+ 		spin_unlock_irqrestore(&dibs->lock, flags);
+ 
+ 		__dibs_lo_unregister_dmb(ldev, dmb_node);
+ 	}
+ 	return 0;
+ }
+ 
+ static int dibs_lo_support_dmb_nocopy(struct dibs_dev *dibs)
+ {
+ 	return DIBS_LO_SUPPORT_NOCOPY;
+ }
+ 
+ static int dibs_lo_attach_dmb(struct dibs_dev *dibs, struct dibs_dmb *dmb)
+ {
+ 	struct dibs_lo_dmb_node *dmb_node = NULL, *tmp_node;
+ 	struct dibs_lo_dev *ldev;
+ 
+ 	ldev = dibs->drv_priv;
+ 
+ 	/* find dmb_node according to dmb->dmb_tok */
+ 	read_lock_bh(&ldev->dmb_ht_lock);
+ 	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb->dmb_tok) {
+ 		if (tmp_node->token == dmb->dmb_tok) {
+ 			dmb_node = tmp_node;
+ 			break;
+ 		}
+ 	}
+ 	if (!dmb_node) {
+ 		read_unlock_bh(&ldev->dmb_ht_lock);
+ 		return -EINVAL;
+ 	}
+ 	read_unlock_bh(&ldev->dmb_ht_lock);
+ 
+ 	if (!refcount_inc_not_zero(&dmb_node->refcnt))
+ 		/* the dmb is being unregistered, but has
+ 		 * not been removed from the hash table.
+ 		 */
+ 		return -EINVAL;
+ 
+ 	/* provide dmb information */
+ 	dmb->idx = dmb_node->sba_idx;
+ 	dmb->dmb_tok = dmb_node->token;
+ 	dmb->cpu_addr = dmb_node->cpu_addr;
+ 	dmb->dma_addr = dmb_node->dma_addr;
+ 	dmb->dmb_len = dmb_node->len;
+ 	return 0;
+ }
+ 
+ static int dibs_lo_detach_dmb(struct dibs_dev *dibs, u64 token)
+ {
+ 	struct dibs_lo_dmb_node *dmb_node = NULL, *tmp_node;
+ 	struct dibs_lo_dev *ldev;
+ 
+ 	ldev = dibs->drv_priv;
+ 
+ 	/* find dmb_node according to dmb->dmb_tok */
+ 	read_lock_bh(&ldev->dmb_ht_lock);
+ 	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, token) {
+ 		if (tmp_node->token == token) {
+ 			dmb_node = tmp_node;
+ 			break;
+ 		}
+ 	}
+ 	if (!dmb_node) {
+ 		read_unlock_bh(&ldev->dmb_ht_lock);
+ 		return -EINVAL;
+ 	}
+ 	read_unlock_bh(&ldev->dmb_ht_lock);
+ 
+ 	if (refcount_dec_and_test(&dmb_node->refcnt))
+ 		__dibs_lo_unregister_dmb(ldev, dmb_node);
+ 	return 0;
+ }
+ 
+ static int dibs_lo_move_data(struct dibs_dev *dibs, u64 dmb_tok,
+ 			     unsigned int idx, bool sf, unsigned int offset,
+ 			     void *data, unsigned int size)
+ {
+ 	struct dibs_lo_dmb_node *rmb_node = NULL, *tmp_node;
+ 	struct dibs_lo_dev *ldev;
+ 	u16 s_mask;
+ 	u8 client_id;
+ 	u32 sba_idx;
+ 
+ 	ldev = dibs->drv_priv;
+ 
+ 	read_lock_bh(&ldev->dmb_ht_lock);
+ 	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_tok) {
+ 		if (tmp_node->token == dmb_tok) {
+ 			rmb_node = tmp_node;
+ 			break;
+ 		}
+ 	}
+ 	if (!rmb_node) {
+ 		read_unlock_bh(&ldev->dmb_ht_lock);
+ 		return -EINVAL;
+ 	}
+ 	memcpy((char *)rmb_node->cpu_addr + offset, data, size);
+ 	sba_idx = rmb_node->sba_idx;
+ 	read_unlock_bh(&ldev->dmb_ht_lock);
+ 
+ 	if (!sf)
+ 		return 0;
+ 
+ 	spin_lock(&dibs->lock);
+ 	client_id = dibs->dmb_clientid_arr[sba_idx];
+ 	s_mask = ror16(0x1000, idx);
+ 	if (likely(client_id != NO_DIBS_CLIENT && dibs->subs[client_id]))
+ 		dibs->subs[client_id]->ops->handle_irq(dibs, sba_idx, s_mask);
+ 	spin_unlock(&dibs->lock);
+ 
+ 	return 0;
+ }
+ 
+ static const struct dibs_dev_ops dibs_lo_ops = {
+ 	.get_fabric_id = dibs_lo_get_fabric_id,
+ 	.query_remote_gid = dibs_lo_query_rgid,
+ 	.max_dmbs = dibs_lo_max_dmbs,
+ 	.register_dmb = dibs_lo_register_dmb,
+ 	.unregister_dmb = dibs_lo_unregister_dmb,
+ 	.move_data = dibs_lo_move_data,
+ 	.support_mmapped_rdmb = dibs_lo_support_dmb_nocopy,
+ 	.attach_dmb = dibs_lo_attach_dmb,
+ 	.detach_dmb = dibs_lo_detach_dmb,
+ };
+ 
+ static void dibs_lo_dev_init(struct dibs_lo_dev *ldev)
+ {
+ 	rwlock_init(&ldev->dmb_ht_lock);
+ 	hash_init(ldev->dmb_ht);
+ 	atomic_set(&ldev->dmb_cnt, 0);
+ 	init_waitqueue_head(&ldev->ldev_release);
+ }
+ 
+ static void dibs_lo_dev_exit(struct dibs_lo_dev *ldev)
+ {
+ 	if (atomic_read(&ldev->dmb_cnt))
+ 		wait_event(ldev->ldev_release, !atomic_read(&ldev->dmb_cnt));
+ }
+ 
+ static int dibs_lo_dev_probe(void)
+ {
+ 	struct dibs_lo_dev *ldev;
+ 	struct dibs_dev *dibs;
+ 	int ret;
+ 
+ 	ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
+ 	if (!ldev)
+ 		return -ENOMEM;
+ 
+ 	dibs = dibs_dev_alloc();
+ 	if (!dibs) {
+ 		kfree(ldev);
+ 		return -ENOMEM;
+ 	}
+ 
+ 	ldev->dibs = dibs;
+ 	dibs->drv_priv = ldev;
+ 	dibs_lo_dev_init(ldev);
+ 	uuid_gen(&dibs->gid);
+ 	dibs->ops = &dibs_lo_ops;
+ 
+ 	dibs->dev.parent = NULL;
+ 	dev_set_name(&dibs->dev, "%s", dibs_lo_dev_name);
+ 
+ 	ret = dibs_dev_add(dibs);
+ 	if (ret)
+ 		goto err_reg;
+ 	lo_dev = ldev;
+ 	return 0;
+ 
+ err_reg:
+ 	kfree(dibs->dmb_clientid_arr);
+ 	/* pairs with dibs_dev_alloc() */
+ 	put_device(&dibs->dev);
+ 	kfree(ldev);
+ 
+ 	return ret;
+ }
+ 
+ static void dibs_lo_dev_remove(void)
+ {
+ 	if (!lo_dev)
+ 		return;
+ 
+ 	dibs_dev_del(lo_dev->dibs);
+ 	dibs_lo_dev_exit(lo_dev);
+ 	/* pairs with dibs_dev_alloc() */
+ 	put_device(&lo_dev->dibs->dev);
+ 	kfree(lo_dev);
+ 	lo_dev = NULL;
+ }
+ 
+ int dibs_loopback_init(void)
+ {
+ 	return dibs_lo_dev_probe();
+ }
+ 
+ void dibs_loopback_exit(void)
+ {
+ 	dibs_lo_dev_remove();
+ }