[PATCH v2] dma-buf: remove unused dma-fence-unwrap.c (stable/linux-5.15.y only)

[PATCH v2] dma-buf: remove unused dma-fence-unwrap.c (stable/linux-5.15.y only)

[Tudor Ambarus]

The file drivers/dma-buf/dma-fence-unwrap.c was incorrectly added to
the 5.15.y stable branch in commit 4e82b9c11d3c ("dma-buf: add
dma_fence_timestamp helper") as a new file, but it was never enabled in
the Makefile, and its header include/linux/dma-fence-unwrap.h was not
present, making it uncompilable.

A full revert of commit 4e82b9c11d3c ("dma-buf: add dma_fence_timestamp
helper") is not desirable because that commit also introduced the valid
dma_fence_timestamp() helper and fixed legitimate timestamp race
windows in drivers/dma-buf/sync_file.c and
drivers/gpu/drm/scheduler/sched_main.c.

Since there are no users of dma-fence-unwrap in the 5.15.y branch,
remove the unused file to clean up the tree and avoid confusion.

Fixes: 4e82b9c11d3c ("dma-buf: add dma_fence_timestamp helper")
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
---
Changes in v2:
- add To: stable@vger.kernel.org
- Link to v1: https://lore.kernel.org/r/20260703-5-15-dma-fence-unwrap-v1-1-0cf644bc501f@linaro.org
---
 drivers/dma-buf/dma-fence-unwrap.c | 176 -------------------------------------
 1 file changed, 176 deletions(-)

diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c
deleted file mode 100644
index 628af51c81af..000000000000
--- a/drivers/dma-buf/dma-fence-unwrap.c
+++ /dev/null
@@ -1,176 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * dma-fence-util: misc functions for dma_fence objects
- *
- * Copyright (C) 2022 Advanced Micro Devices, Inc.
- * Authors:
- *	Christian König <christian.koenig@amd.com>
- */
-
-#include <linux/dma-fence.h>
-#include <linux/dma-fence-array.h>
-#include <linux/dma-fence-chain.h>
-#include <linux/dma-fence-unwrap.h>
-#include <linux/slab.h>
-
-/* Internal helper to start new array iteration, don't use directly */
-static struct dma_fence *
-__dma_fence_unwrap_array(struct dma_fence_unwrap *cursor)
-{
-	cursor->array = dma_fence_chain_contained(cursor->chain);
-	cursor->index = 0;
-	return dma_fence_array_first(cursor->array);
-}
-
-/**
- * dma_fence_unwrap_first - return the first fence from fence containers
- * @head: the entrypoint into the containers
- * @cursor: current position inside the containers
- *
- * Unwraps potential dma_fence_chain/dma_fence_array containers and return the
- * first fence.
- */
-struct dma_fence *dma_fence_unwrap_first(struct dma_fence *head,
-					 struct dma_fence_unwrap *cursor)
-{
-	cursor->chain = dma_fence_get(head);
-	return __dma_fence_unwrap_array(cursor);
-}
-EXPORT_SYMBOL_GPL(dma_fence_unwrap_first);
-
-/**
- * dma_fence_unwrap_next - return the next fence from a fence containers
- * @cursor: current position inside the containers
- *
- * Continue unwrapping the dma_fence_chain/dma_fence_array containers and return
- * the next fence from them.
- */
-struct dma_fence *dma_fence_unwrap_next(struct dma_fence_unwrap *cursor)
-{
-	struct dma_fence *tmp;
-
-	++cursor->index;
-	tmp = dma_fence_array_next(cursor->array, cursor->index);
-	if (tmp)
-		return tmp;
-
-	cursor->chain = dma_fence_chain_walk(cursor->chain);
-	return __dma_fence_unwrap_array(cursor);
-}
-EXPORT_SYMBOL_GPL(dma_fence_unwrap_next);
-
-/* Implementation for the dma_fence_merge() marco, don't use directly */
-struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,
-					   struct dma_fence **fences,
-					   struct dma_fence_unwrap *iter)
-{
-	struct dma_fence_array *result;
-	struct dma_fence *tmp, **array;
-	ktime_t timestamp;
-	unsigned int i;
-	size_t count;
-
-	count = 0;
-	timestamp = ns_to_ktime(0);
-	for (i = 0; i < num_fences; ++i) {
-		dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) {
-			if (!dma_fence_is_signaled(tmp)) {
-				++count;
-			} else {
-				ktime_t t = dma_fence_timestamp(tmp);
-
-				if (ktime_after(t, timestamp))
-					timestamp = t;
-			}
-		}
-	}
-
-	/*
-	 * If we couldn't find a pending fence just return a private signaled
-	 * fence with the timestamp of the last signaled one.
-	 */
-	if (count == 0)
-		return dma_fence_allocate_private_stub(timestamp);
-
-	array = kmalloc_array(count, sizeof(*array), GFP_KERNEL);
-	if (!array)
-		return NULL;
-
-	/*
-	 * This trashes the input fence array and uses it as position for the
-	 * following merge loop. This works because the dma_fence_merge()
-	 * wrapper macro is creating this temporary array on the stack together
-	 * with the iterators.
-	 */
-	for (i = 0; i < num_fences; ++i)
-		fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]);
-
-	count = 0;
-	do {
-		unsigned int sel;
-
-restart:
-		tmp = NULL;
-		for (i = 0; i < num_fences; ++i) {
-			struct dma_fence *next;
-
-			while (fences[i] && dma_fence_is_signaled(fences[i]))
-				fences[i] = dma_fence_unwrap_next(&iter[i]);
-
-			next = fences[i];
-			if (!next)
-				continue;
-
-			/*
-			 * We can't guarantee that inpute fences are ordered by
-			 * context, but it is still quite likely when this
-			 * function is used multiple times. So attempt to order
-			 * the fences by context as we pass over them and merge
-			 * fences with the same context.
-			 */
-			if (!tmp || tmp->context > next->context) {
-				tmp = next;
-				sel = i;
-
-			} else if (tmp->context < next->context) {
-				continue;
-
-			} else if (dma_fence_is_later(tmp, next)) {
-				fences[i] = dma_fence_unwrap_next(&iter[i]);
-				goto restart;
-			} else {
-				fences[sel] = dma_fence_unwrap_next(&iter[sel]);
-				goto restart;
-			}
-		}
-
-		if (tmp) {
-			array[count++] = dma_fence_get(tmp);
-			fences[sel] = dma_fence_unwrap_next(&iter[sel]);
-		}
-	} while (tmp);
-
-	if (count == 0) {
-		tmp = dma_fence_allocate_private_stub(ktime_get());
-		goto return_tmp;
-	}
-
-	if (count == 1) {
-		tmp = array[0];
-		goto return_tmp;
-	}
-
-	result = dma_fence_array_create(count, array,
-					dma_fence_context_alloc(1),
-					1, false);
-	if (!result) {
-		tmp = NULL;
-		goto return_tmp;
-	}
-	return &result->base;
-
-return_tmp:
-	kfree(array);
-	return tmp;
-}
-EXPORT_SYMBOL_GPL(__dma_fence_unwrap_merge);

---
base-commit: eceeec79dbc646d6dace49ed1ba2f656683d5537
change-id: 20260703-5-15-dma-fence-unwrap-0f4a6c03daf2

Best regards,
-- 
Tudor Ambarus <tudor.ambarus@linaro.org>

Re: [PATCH v2] dma-buf: remove unused dma-fence-unwrap.c (stable/linux-5.15.y only)

[Sasha Levin]

On Thu, 2026-07-03 at 14:28 +0000, Tudor Ambarus wrote:
> The file drivers/dma-buf/dma-fence-unwrap.c was incorrectly added to
> the 5.15.y stable branch in commit 4e82b9c11d3c ("dma-buf: add
> dma_fence_timestamp helper") as a new file, but it was never enabled in
> the Makefile, and its header include/linux/dma-fence-unwrap.h was not
> present, making it uncompilable.

Queued for 5.15.y, thanks.

-- 
Thanks,
Sasha