[PATCH 1/1] dibs: Re-apply lost patch

[PATCH 1/1] dibs: Re-apply lost patch

[Steffen Jaeckel]

While merging the dibs layer, Matt [1] noticed that the changes which were
done in [2] conflicted and were missing. He subsequently fixed this in the
merge commit of his own tree, but the changes never made it upstream.

This commit re-introduces the changes.

[1] https://lore.kernel.org/netdev/74368a5c-48ac-4f8e-a198-40ec1ed3cf5f@kernel.org/
[2] a35c04de2565d ("net/smc: fix warning in smc_rx_splice() when calling get_page()")

Fixes: cc21191b584c ("dibs: Move data path to dibs layer")
Signed-off-by: Steffen Jaeckel <sjaeckel@suse.de>
---
 drivers/dibs/dibs_loopback.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/dibs/dibs_loopback.c b/drivers/dibs/dibs_loopback.c
index b3fd0f8100d4..aa029e29c6b2 100644
--- a/drivers/dibs/dibs_loopback.c
+++ b/drivers/dibs/dibs_loopback.c
@@ -12,6 +12,7 @@
 #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>
@@ -49,6 +50,7 @@ static int dibs_lo_register_dmb(struct dibs_dev *dibs, struct dibs_dmb *dmb,
 {
 	struct dibs_lo_dmb_node *dmb_node, *tmp_node;
 	struct dibs_lo_dev *ldev;
+	struct folio *folio;
 	unsigned long flags;
 	int sba_idx, rc;
 
@@ -70,13 +72,16 @@ static int dibs_lo_register_dmb(struct dibs_dev *dibs, struct dibs_dmb *dmb,
 
 	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);
 
@@ -122,7 +127,7 @@ static void __dibs_lo_unregister_dmb(struct dibs_lo_dev *ldev,
 	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))
-- 
2.52.0

Re: [PATCH 1/1] dibs: Re-apply lost patch

[Matthieu Baerts]

Hi Steffen,

On 27/01/2026 17:16, Steffen Jaeckel wrote:
> While merging the dibs layer, Matt [1] noticed that the changes which were
> done in [2] conflicted and were missing. He subsequently fixed this in the
> merge commit of his own tree, but the changes never made it upstream.
> 
> This commit re-introduces the changes.
> 
> [1] https://lore.kernel.org/netdev/74368a5c-48ac-4f8e-a198-40ec1ed3cf5f@kernel.org/
> [2] a35c04de2565d ("net/smc: fix warning in smc_rx_splice() when calling get_page()")

Thank you for the follow-up.

On which tree is this patch based on? Because I don't see the missing
resolution on net-next and even in Linus tree, see commit 203e3beb73e5
("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net") or
check the file in Linus tree:


https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/dibs/dibs_loopback.c

Am I missing something?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: [PATCH 1/1] dibs: Re-apply lost patch

[Steffen Jaeckel]

Hi Matt,

On 2026-01-27 17:53, Matthieu Baerts wrote:
> [...] see commit 203e3beb73e5
> ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")[...]

sorry for the noise, I missed that merge commit and didn't look at the 
current state.

Cheers
Steffen
-- 
Steffen Jaeckel                       Kernel Network Engineer
sjaeckel@suse.de
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: J. Jaser, A. McDonald, W. Knoblich