[Linaro-mm-sig] Re: [PATCH 4/5] dma-buf: generalize dma_fence unwrap & merging v2

On Wed, May 04, 2022 at 02:22:55PM +0200, Christian König wrote:

Introduce a dma_fence_unwrap_merge() macro which allows to unwrap fences which potentially can be containers as well and then merge them back together into a flat dma_fence_array.

v2: rename the function, add some more comments about how the wrapper is used, move filtering of signaled fences into the unwrap iterator, add complex selftest which covers more cases.

Yeah this addresses everything. The only thing that leaves me puzzled is the unconditional dma_fence_put() in the testcases for the fences we stuff into containers, I thought we only need that for error cases but not the success. But I'm confused about that already in a previous patch.

Aside from that Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

Signed-off-by: Christian König christian.koenig@amd.com

drivers/dma-buf/dma-fence-unwrap.c | 99 +++++++++++++++++++++ drivers/dma-buf/st-dma-fence-unwrap.c | 109 +++++++++++++++++++++++ drivers/dma-buf/sync_file.c | 119 ++------------------------ include/linux/dma-fence-unwrap.h | 24 ++++++ 4 files changed, 238 insertions(+), 113 deletions(-)

diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c index 7b0b91086ded..4ed5ea8807d7 100644 --- a/drivers/dma-buf/dma-fence-unwrap.c +++ b/drivers/dma-buf/dma-fence-unwrap.c @@ -11,6 +11,7 @@ #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 * @@ -66,3 +67,101 @@ struct dma_fence *dma_fence_unwrap_next(struct dma_fence_unwrap *cursor) return tmp; } 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;
• unsigned int i;
• size_t count;
• count = 0;
• for (i = 0; i < num_fences; ++i) {

• dma_fence_unwrap_for_each(tmp, &iter[i], fences[i])
  

• 	++count;
  

• }
• if (count == 0)

• return dma_fence_get_stub();
  

• 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 = 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_get_stub();
  

• 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); diff --git a/drivers/dma-buf/st-dma-fence-unwrap.c b/drivers/dma-buf/st-dma-fence-unwrap.c index 59628add93f5..3a8aca651938 100644 --- a/drivers/dma-buf/st-dma-fence-unwrap.c +++ b/drivers/dma-buf/st-dma-fence-unwrap.c @@ -240,6 +240,113 @@ static int unwrap_chain_array(void *arg) return err; } +static int unwrap_merge(void *arg) +{

• struct dma_fence *fence, *f1, *f2, *f3;
• struct dma_fence_unwrap iter;
• int err = 0;
• f1 = mock_fence();
• if (!f1)

• return -ENOMEM;
  

• f2 = mock_fence();
• if (!f2) {

• err = -ENOMEM;
  

• goto error_put_f1;
  

• }
• f3 = dma_fence_unwrap_merge(f1, f2);
• if (!f3) {

• err = -ENOMEM;
  

• goto error_put_f2;
  

• }
• dma_fence_unwrap_for_each(fence, &iter, f3) {

• if (fence == f1) {
  

• 	dma_fence_put(f1);
  

• 	f1 = NULL;
  

• } else if (fence == f2) {
  

• 	dma_fence_put(f2);
  

• 	f2 = NULL;
  

• } else {
  

• 	pr_err("Unexpected fence!\n");
  

• 	err = -EINVAL;
  

• }
  

• }
• if (f1 || f2) {

• pr_err("Not all fences seen!\n");
  

• err = -EINVAL;
  

• }
• dma_fence_put(f3);

+error_put_f2:

• dma_fence_put(f2);

+error_put_f1:

• dma_fence_put(f1);
• return err;

+}

+static int unwrap_merge_complex(void *arg) +{

• struct dma_fence *fence, *f1, *f2, *f3, *f4, *f5;
• struct dma_fence_unwrap iter;
• int err = -ENOMEM;
• f1 = mock_fence();
• if (!f1)

• return -ENOMEM;
  

• f2 = mock_fence();
• if (!f2)

• goto error_put_f1;
  

• f3 = dma_fence_unwrap_merge(f1, f2);
• if (!f3)

• goto error_put_f2;
  

• /* The resulting array has the fences in reverse */
• f4 = dma_fence_unwrap_merge(f2, f1);
• if (!f4)

• goto error_put_f3;
  

• /* Signaled fences should be filtered, the two arrays merged. */
• f5 = dma_fence_unwrap_merge(f3, f4, dma_fence_get_stub());
• if (!f5)

• goto error_put_f4;
  

• err = 0;
• dma_fence_unwrap_for_each(fence, &iter, f5) {

• if (fence == f1) {
  

• 	dma_fence_put(f1);
  

• 	f1 = NULL;
  

• } else if (fence == f2) {
  

• 	dma_fence_put(f2);
  

• 	f2 = NULL;
  

• } else {
  

• 	pr_err("Unexpected fence!\n");
  

• 	err = -EINVAL;
  

• }
  

• }
• if (f1 || f2) {

• pr_err("Not all fences seen!\n");
  

• err = -EINVAL;
  

• }
• dma_fence_put(f5);

+error_put_f4:

• dma_fence_put(f4);

+error_put_f3:

• dma_fence_put(f3);

+error_put_f2:

• dma_fence_put(f2);

+error_put_f1:

• dma_fence_put(f1);
• return err;

+}

int dma_fence_unwrap(void) { static const struct subtest tests[] = { @@ -247,6 +354,8 @@ int dma_fence_unwrap(void) SUBTEST(unwrap_array), SUBTEST(unwrap_chain), SUBTEST(unwrap_chain_array),

• SUBTEST(unwrap_merge),
  

• SUBTEST(unwrap_merge_complex),
  

  };

return subtests(tests, NULL); diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c index 0fe564539166..3ebec19a8e02 100644 --- a/drivers/dma-buf/sync_file.c +++ b/drivers/dma-buf/sync_file.c @@ -146,50 +146,6 @@ char *sync_file_get_name(struct sync_file *sync_file, char *buf, int len) return buf; } -static int sync_file_set_fence(struct sync_file *sync_file,

• 	       struct dma_fence **fences, int num_fences)
  

-{

• struct dma_fence_array *array;
• /*

• * The reference for the fences in the new sync_file and held
  

• * in add_fence() during the merge procedure, so for num_fences == 1
  

• * we already own a new reference to the fence. For num_fence > 1
  

• * we own the reference of the dma_fence_array creation.
  

• */
  

• if (num_fences == 0) {

• sync_file->fence = dma_fence_get_stub();
  

• kfree(fences);
  

• } else if (num_fences == 1) {

• sync_file->fence = fences[0];
  

• kfree(fences);
  

• } else {

• array = dma_fence_array_create(num_fences, fences,
  

• 			       dma_fence_context_alloc(1),
  

• 			       1, false);
  

• if (!array)
  

• 	return -ENOMEM;
  

• sync_file->fence = &array->base;
  

• }
• return 0;

-}

-static void add_fence(struct dma_fence **fences,

•       int *i, struct dma_fence *fence)
  

-{

• fences[*i] = fence;
• if (!dma_fence_is_signaled(fence)) {

• dma_fence_get(fence);
  

• (*i)++;
  

• }

-}

/**

• sync_file_merge() - merge two sync_files
• @name: name of new fence

@@ -203,84 +159,21 @@ static void add_fence(struct dma_fence **fences, static struct sync_file *sync_file_merge(const char *name, struct sync_file *a, struct sync_file *b) {

• struct dma_fence *a_fence, *b_fence, **fences;
• struct dma_fence_unwrap a_iter, b_iter;
• unsigned int index, num_fences; struct sync_file *sync_file;

• struct dma_fence *fence;

sync_file = sync_file_alloc(); if (!sync_file) return NULL;

• num_fences = 0;
• dma_fence_unwrap_for_each(a_fence, &a_iter, a->fence)

• ++num_fences;
  

• dma_fence_unwrap_for_each(b_fence, &b_iter, b->fence)

• ++num_fences;
  

• if (num_fences > INT_MAX)

• goto err_free_sync_file;
  

• fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
• if (!fences)

• goto err_free_sync_file;
  

• /*

• * We can't guarantee that fences in both a and b are ordered, but it is
  

• * still quite likely.
  

• *
  

• * So attempt to order the fences as we pass over them and merge fences
  

• * with the same context.
  

• */
  

• index = 0;
• for (a_fence = dma_fence_unwrap_first(a->fence, &a_iter),

•     b_fence = dma_fence_unwrap_first(b->fence, &b_iter);
  

•     a_fence || b_fence; ) {
  

• if (!b_fence) {
  

• 	add_fence(fences, &index, a_fence);
  

• 	a_fence = dma_fence_unwrap_next(&a_iter);
  

• } else if (!a_fence) {
  

• 	add_fence(fences, &index, b_fence);
  

• 	b_fence = dma_fence_unwrap_next(&b_iter);
  

• } else if (a_fence->context < b_fence->context) {
  

• 	add_fence(fences, &index, a_fence);
  

• 	a_fence = dma_fence_unwrap_next(&a_iter);
  

• } else if (b_fence->context < a_fence->context) {
  

• 	add_fence(fences, &index, b_fence);
  

• 	b_fence = dma_fence_unwrap_next(&b_iter);
  

• } else if (__dma_fence_is_later(a_fence->seqno, b_fence->seqno,
  

• 				a_fence->ops)) {
  

• 	add_fence(fences, &index, a_fence);
  

• 	a_fence = dma_fence_unwrap_next(&a_iter);
  

• 	b_fence = dma_fence_unwrap_next(&b_iter);
  

• } else {
  

• 	add_fence(fences, &index, b_fence);
  

• 	a_fence = dma_fence_unwrap_next(&a_iter);
  

• 	b_fence = dma_fence_unwrap_next(&b_iter);
  

• }
  

• fence = dma_fence_unwrap_merge(a->fence, b->fence);
• if (!fence) {

• fput(sync_file->file);
  

• return NULL;
  

  }

• if (sync_file_set_fence(sync_file, fences, index) < 0)

• goto err_put_fences;
  

• sync_file->fence = fence; strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name)); return sync_file;

-err_put_fences:

• while (index)

• dma_fence_put(fences[--index]);
  

• kfree(fences);

-err_free_sync_file:

• fput(sync_file->file);
• return NULL;

} static int sync_file_release(struct inode *inode, struct file *file) diff --git a/include/linux/dma-fence-unwrap.h b/include/linux/dma-fence-unwrap.h index e9d114637294..43c8a9bbee88 100644 --- a/include/linux/dma-fence-unwrap.h +++ b/include/linux/dma-fence-unwrap.h @@ -48,4 +48,28 @@ struct dma_fence *dma_fence_unwrap_next(struct dma_fence_unwrap *cursor); for (fence = dma_fence_unwrap_first(head, cursor); fence; \ fence = dma_fence_unwrap_next(cursor)) +struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,

• 			   struct dma_fence **fences,
  

• 			   struct dma_fence_unwrap *cursors);
  

+/**

• • dma_fence_unwrap_merge - unwrap and merge fences
• • All fences given as parameters are unwrapped and merged back together as flat
• • dma_fence_array. Useful if multiple containers need to be merged together.
• • Implemented as a macro to allocate the necessary arrays on the stack and
• • account the stack frame size to the caller.
• • Returns NULL on memory allocation failure, a dma_fence object representing
• • all the given fences otherwise.
• */

+#define dma_fence_unwrap_merge(...) \

• ({ \

• struct dma_fence *__f[] = { __VA_ARGS__ };		\
  

• struct dma_fence_unwrap __c[ARRAY_SIZE(__f)];		\
  

• 							\
  

• __dma_fence_unwrap_merge(ARRAY_SIZE(__f), __f, __c);	\
  

• })

#endif

2.25.1