dma-buf/sync_file: refactor fence storage in struct sync_file

Create sync_file->fence to abstract the type of fence we are using for
each sync_file. If only one fence is present we use a normal struct fence
but if there is more fences to be added to the sync_file a fence_array
is created.

This change cleans up sync_file a bit. We don't need to have sync_file_cb
array anymore. Instead, as we always have  one fence, only one fence
callback is registered per sync_file.

v2: Comments from Chris Wilson and Christian König
	- Not using fence_ops anymore
	- fence_is_array() was created to differentiate fence from fence_array
	- fence_array_teardown() is now exported and used under fence_is_array()
	- struct sync_file lost num_fences member

v3: Comments from Chris Wilson and Christian König
	- struct sync_file lost status member in favor of fence_is_signaled()
	- drop use of fence_array_teardown()
	- use sizeof(*fence) to allocate only an array on fence pointers

v4: Comments from Chris Wilson
	- use sizeof(*fence) to reallocate array
	- fix typo in comments
	- protect num_fences sum against overflows
	- use array->base instead of casting the to struct fence

v5: fixes checkpatch warnings

v6: fix case where all fences are signaled.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

3 files changed, 129 insertions, 74 deletions

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 9aaa608dfe01..ac9c250af302 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -28,11 +28,11 @@
 
 static const struct file_operations sync_file_fops;
 
-static struct sync_file *sync_file_alloc(int size)
+static struct sync_file *sync_file_alloc(void)
 {
         struct sync_file *sync_file;
 
-        sync_file = kzalloc(size, GFP_KERNEL);
+        sync_file = kzalloc(sizeof(*sync_file), GFP_KERNEL);
         if (!sync_file)
                 return NULL;
 
@@ -45,6 +45,8 @@ static struct sync_file *sync_file_alloc(int size)
 
         init_waitqueue_head(&sync_file->wq);
 
+        INIT_LIST_HEAD(&sync_file->cb.node);
+
         return sync_file;
 
 err:
@@ -54,14 +56,11 @@ err:
 
 static void fence_check_cb_func(struct fence *f, struct fence_cb *cb)
 {
-        struct sync_file_cb *check;
         struct sync_file *sync_file;
 
-        check = container_of(cb, struct sync_file_cb, cb);
-        sync_file = check->sync_file;
+        sync_file = container_of(cb, struct sync_file, cb);
 
-        if (atomic_dec_and_test(&sync_file->status))
-                wake_up_all(&sync_file->wq);
+        wake_up_all(&sync_file->wq);
 }
 
 /**
@@ -76,22 +75,18 @@ struct sync_file *sync_file_create(struct fence *fence)
 {
         struct sync_file *sync_file;
 
-        sync_file = sync_file_alloc(offsetof(struct sync_file, cbs[1]));
+        sync_file = sync_file_alloc();
         if (!sync_file)
                 return NULL;
 
-        sync_file->num_fences = 1;
-        atomic_set(&sync_file->status, 1);
+        sync_file->fence = fence;
+
         snprintf(sync_file->name, sizeof(sync_file->name), "%s-%s%llu-%d",
                  fence->ops->get_driver_name(fence),
                  fence->ops->get_timeline_name(fence), fence->context,
                  fence->seqno);
 
-        sync_file->cbs[0].fence = fence;
-        sync_file->cbs[0].sync_file = sync_file;
-        if (fence_add_callback(fence, &sync_file->cbs[0].cb,
-                               fence_check_cb_func))
-                atomic_dec(&sync_file->status);
+        fence_add_callback(fence, &sync_file->cb, fence_check_cb_func);
 
         return sync_file;
 }
@@ -121,14 +116,49 @@ err:
         return NULL;
 }
 
-static void sync_file_add_pt(struct sync_file *sync_file, int *i,
-                             struct fence *fence)
+static int sync_file_set_fence(struct sync_file *sync_file,
+                               struct fence **fences, int num_fences)
 {
-        sync_file->cbs[*i].fence = fence;
-        sync_file->cbs[*i].sync_file = sync_file;
+        struct 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 fence_array creation.
+         */
+        if (num_fences == 1) {
+                sync_file->fence = fences[0];
+        } else {
+                array = fence_array_create(num_fences, fences,
+                                           fence_context_alloc(1), 1, false);
+                if (!array)
+                        return -ENOMEM;
+
+                sync_file->fence = &array->base;
+        }
 
-        if (!fence_add_callback(fence, &sync_file->cbs[*i].cb,
-                                fence_check_cb_func)) {
+        return 0;
+}
+
+static struct fence **get_fences(struct sync_file *sync_file, int *num_fences)
+{
+        if (fence_is_array(sync_file->fence)) {
+                struct fence_array *array = to_fence_array(sync_file->fence);
+
+                *num_fences = array->num_fences;
+                return array->fences;
+        }
+
+        *num_fences = 1;
+        return &sync_file->fence;
+}
+
+static void add_fence(struct fence **fences, int *i, struct fence *fence)
+{
+        fences[*i] = fence;
+
+        if (!fence_is_signaled(fence)) {
                 fence_get(fence);
                 (*i)++;
         }
@@ -147,16 +177,24 @@ static void sync_file_add_pt(struct sync_file *sync_file, int *i,
 static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
                                          struct sync_file *b)
 {
-        int num_fences = a->num_fences + b->num_fences;
         struct sync_file *sync_file;
-        int i, i_a, i_b;
-        unsigned long size = offsetof(struct sync_file, cbs[num_fences]);
+        struct fence **fences, **nfences, **a_fences, **b_fences;
+        int i, i_a, i_b, num_fences, a_num_fences, b_num_fences;
 
-        sync_file = sync_file_alloc(size);
+        sync_file = sync_file_alloc();
         if (!sync_file)
                 return NULL;
 
-        atomic_set(&sync_file->status, num_fences);
+        a_fences = get_fences(a, &a_num_fences);
+        b_fences = get_fences(b, &b_num_fences);
+        if (a_num_fences > INT_MAX - b_num_fences)
+                return NULL;
+
+        num_fences = a_num_fences + b_num_fences;
+
+        fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
+        if (!fences)
+                goto err;
 
         /*
          * Assume sync_file a and b are both ordered and have no
@@ -165,55 +203,73 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
          * If a sync_file can only be created with sync_file_merge
          * and sync_file_create, this is a reasonable assumption.
          */
-        for (i = i_a = i_b = 0; i_a < a->num_fences && i_b < b->num_fences; ) {
-                struct fence *pt_a = a->cbs[i_a].fence;
-                struct fence *pt_b = b->cbs[i_b].fence;
+        for (i = i_a = i_b = 0; i_a < a_num_fences && i_b < b_num_fences; ) {
+                struct fence *pt_a = a_fences[i_a];
+                struct fence *pt_b = b_fences[i_b];
 
                 if (pt_a->context < pt_b->context) {
-                        sync_file_add_pt(sync_file, &i, pt_a);
+                        add_fence(fences, &i, pt_a);
 
                         i_a++;
                 } else if (pt_a->context > pt_b->context) {
-                        sync_file_add_pt(sync_file, &i, pt_b);
+                        add_fence(fences, &i, pt_b);
 
                         i_b++;
                 } else {
                         if (pt_a->seqno - pt_b->seqno <= INT_MAX)
-                                sync_file_add_pt(sync_file, &i, pt_a);
+                                add_fence(fences, &i, pt_a);
                         else
-                                sync_file_add_pt(sync_file, &i, pt_b);
+                                add_fence(fences, &i, pt_b);
 
                         i_a++;
                         i_b++;
                 }
         }
 
-        for (; i_a < a->num_fences; i_a++)
-                sync_file_add_pt(sync_file, &i, a->cbs[i_a].fence);
+        for (; i_a < a_num_fences; i_a++)
+                add_fence(fences, &i, a_fences[i_a]);
+
+        for (; i_b < b_num_fences; i_b++)
+                add_fence(fences, &i, b_fences[i_b]);
+
+        if (i == 0) {
+                add_fence(fences, &i, a_fences[0]);
+                i++;
+        }
 
-        for (; i_b < b->num_fences; i_b++)
-                sync_file_add_pt(sync_file, &i, b->cbs[i_b].fence);
+        if (num_fences > i) {
+                nfences = krealloc(fences, i * sizeof(*fences),
+                                  GFP_KERNEL);
+                if (!nfences)
+                        goto err;
+
+                fences = nfences;
+        }
+
+        if (sync_file_set_fence(sync_file, fences, i) < 0) {
+                kfree(fences);
+                goto err;
+        }
 
-        if (num_fences > i)
-                atomic_sub(num_fences - i, &sync_file->status);
-        sync_file->num_fences = i;
+        fence_add_callback(sync_file->fence, &sync_file->cb,
+                           fence_check_cb_func);
 
         strlcpy(sync_file->name, name, sizeof(sync_file->name));
         return sync_file;
+
+err:
+        fput(sync_file->file);
+        return NULL;
+
 }
 
 static void sync_file_free(struct kref *kref)
 {
         struct sync_file *sync_file = container_of(kref, struct sync_file,
                                                      kref);
-        int i;
-
-        for (i = 0; i < sync_file->num_fences; ++i) {
-                fence_remove_callback(sync_file->cbs[i].fence,
-                                      &sync_file->cbs[i].cb);
-                fence_put(sync_file->cbs[i].fence);
-        }
 
+        fence_remove_callback(sync_file->fence, &sync_file->cb);
+        fence_put(sync_file->fence);
         kfree(sync_file);
 }
 
@@ -232,9 +288,9 @@ static unsigned int sync_file_poll(struct file *file, poll_table *wait)
 
         poll_wait(file, &sync_file->wq, wait);
 
-        status = atomic_read(&sync_file->status);
+        status = fence_is_signaled(sync_file->fence);
 
-        if (!status)
+        if (status)
                 return POLLIN;
         if (status < 0)
                 return POLLERR;
@@ -315,8 +371,9 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 {
         struct sync_file_info info;
         struct sync_fence_info *fence_info = NULL;
+        struct fence **fences;
         __u32 size;
-        int ret, i;
+        int num_fences, ret, i;
 
         if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
                 return -EFAULT;
@@ -324,6 +381,8 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
         if (info.flags || info.pad)
                 return -EINVAL;
 
+        fences = get_fences(sync_file, &num_fences);
+
         /*
          * Passing num_fences = 0 means that userspace doesn't want to
          * retrieve any sync_fence_info. If num_fences = 0 we skip filling
@@ -333,16 +392,16 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
         if (!info.num_fences)
                 goto no_fences;
 
-        if (info.num_fences < sync_file->num_fences)
+        if (info.num_fences < num_fences)
                 return -EINVAL;
 
-        size = sync_file->num_fences * sizeof(*fence_info);
+        size = num_fences * sizeof(*fence_info);
         fence_info = kzalloc(size, GFP_KERNEL);
         if (!fence_info)
                 return -ENOMEM;
 
-        for (i = 0; i < sync_file->num_fences; ++i)
-                sync_fill_fence_info(sync_file->cbs[i].fence, &fence_info[i]);
+        for (i = 0; i < num_fences; i++)
+                sync_fill_fence_info(fences[i], &fence_info[i]);
 
         if (copy_to_user(u64_to_user_ptr(info.sync_fence_info), fence_info,
                          size)) {
@@ -352,11 +411,8 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 
 no_fences:
         strlcpy(info.name, sync_file->name, sizeof(info.name));
-        info.status = atomic_read(&sync_file->status);
-        if (info.status >= 0)
-                info.status = !info.status;
-
-        info.num_fences = sync_file->num_fences;
+        info.status = fence_is_signaled(sync_file->fence);
+        info.num_fences = num_fences;
 
         if (copy_to_user((void __user *)arg, &info, sizeof(info)))
                 ret = -EFAULT;
diff --git a/drivers/staging/android/sync_debug.c b/drivers/staging/android/sync_debug.c
index 4c5a85595a85..961a94bf156c 100644
--- a/drivers/staging/android/sync_debug.c
+++ b/drivers/staging/android/sync_debug.c
@@ -135,10 +135,16 @@ static void sync_print_sync_file(struct seq_file *s,
         int i;
 
         seq_printf(s, "[%p] %s: %s\n", sync_file, sync_file->name,
-                   sync_status_str(atomic_read(&sync_file->status)));
+                   sync_status_str(!fence_is_signaled(sync_file->fence)));
 
-        for (i = 0; i < sync_file->num_fences; ++i)
-                sync_print_fence(s, sync_file->cbs[i].fence, true);
+        if (fence_is_array(sync_file->fence)) {
+                struct fence_array *array = to_fence_array(sync_file->fence);
+
+                for (i = 0; i < array->num_fences; ++i)
+                        sync_print_fence(s, array->fences[i], true);
+        } else {
+                sync_print_fence(s, sync_file->fence, true);
+        }
 }
 
 static int sync_debugfs_show(struct seq_file *s, void *unused)
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index c6ffe8b0725c..2efc5ec60575 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -19,12 +19,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/fence.h>
-
-struct sync_file_cb {
-        struct fence_cb cb;
-        struct fence *fence;
-        struct sync_file *sync_file;
-};
+#include <linux/fence-array.h>
 
 /**
  * struct sync_file - sync file to export to the userspace
@@ -32,10 +27,9 @@ struct sync_file_cb {
  * @kref:               reference count on fence.
  * @name:               name of sync_file.  Useful for debugging
  * @sync_file_list:     membership in global file list
- * @num_fences:         number of sync_pts in the fence
  * @wq:                 wait queue for fence signaling
- * @status:             0: signaled, >0:active, <0: error
- * @cbs:                sync_pts callback information
+ * @fence:              fence with the fences in the sync_file
+ * @cb:                 fence callback information
  */
 struct sync_file {
         struct file             *file;
@@ -44,12 +38,11 @@ struct sync_file {
 #ifdef CONFIG_DEBUG_FS
         struct list_head        sync_file_list;
 #endif
-        int num_fences;
 
         wait_queue_head_t       wq;
-        atomic_t                status;
 
-        struct sync_file_cb     cbs[];
+        struct fence            *fence;
+        struct fence_cb cb;
 };
 
 struct sync_file *sync_file_create(struct fence *fence);