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@xxxxxxxx>
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
> 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
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
