habanalabs: add put by handle method to memory manager

Putting object by its handle and not by object pointer is useful in
some finalization flows that do not have object pointer available.
It eliminates the need to first get the object and then perform
put twice.
Signed-off-by: Yuri Nudelman <ynudelman@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/habanalabs/common/habanalabs.h

@@ -3293,6 +3293,7 @@ int hl_mem_mgr_mmap(struct hl_mem_mgr *mmg, struct vm_area_struct *vma,
 		    void *args);
 struct hl_mmap_mem_buf *hl_mmap_mem_buf_get(struct hl_mem_mgr *mmg,
 						   u64 handle);
+int hl_mmap_mem_buf_put_handle(struct hl_mem_mgr *mmg, u64 handle);
 int hl_mmap_mem_buf_put(struct hl_mmap_mem_buf *buf);
 struct hl_mmap_mem_buf *
 hl_mmap_mem_buf_alloc(struct hl_mem_mgr *mmg,

drivers/misc/habanalabs/common/memory_mgr.c

@@ -14,8 +14,8 @@
  * @mmg: parent unifed memory manager
  * @handle: requested buffer handle
  *
- * @return Find the buffer in the store and return a pointer to its descriptor.
- *         Increase buffer refcount. If not found - return NULL.
+ * Find the buffer in the store and return a pointer to its descriptor.
+ * Increase buffer refcount. If not found - return NULL.
  */
 struct hl_mmap_mem_buf *hl_mmap_mem_buf_get(struct hl_mem_mgr *mmg, u64 handle)
 {
@@ -34,6 +34,23 @@ struct hl_mmap_mem_buf *hl_mmap_mem_buf_get(struct hl_mem_mgr *mmg, u64 handle)
 	return buf;
 }
 
+/**
+ * hl_mmap_mem_buf_destroy - destroy the unused buffer
+ *
+ * @buf: memory manager buffer descriptor
+ *
+ * Internal function, used as a final step of buffer release. Shall be invoked
+ * only when the buffer is no longer in use (removed from idr). Will call the
+ * release callback (if applicable), and free the memory.
+ */
+static void hl_mmap_mem_buf_destroy(struct hl_mmap_mem_buf *buf)
+{
+	if (buf->behavior->release)
+		buf->behavior->release(buf);
+
+	kfree(buf);
+}
+
 /**
  * hl_mmap_mem_buf_release - release buffer
  *
@@ -51,10 +68,23 @@ static void hl_mmap_mem_buf_release(struct kref *kref)
 	idr_remove(&buf->mmg->handles, lower_32_bits(buf->handle >> PAGE_SHIFT));
 	spin_unlock(&buf->mmg->lock);
 
-	if (buf->behavior->release)
-		buf->behavior->release(buf);
+	hl_mmap_mem_buf_destroy(buf);
+}
 
-	kfree(buf);
+/**
+ * hl_mmap_mem_buf_remove_idr_locked - remove handle from idr
+ *
+ * @kref: kref that reached 0.
+ *
+ * Internal function, used for kref put by handle. Assumes mmg lock is taken.
+ * Will remove the buffer from idr, without destroying it.
+ */
+static void hl_mmap_mem_buf_remove_idr_locked(struct kref *kref)
+{
+	struct hl_mmap_mem_buf *buf =
+		container_of(kref, struct hl_mmap_mem_buf, refcount);
+
+	idr_remove(&buf->mmg->handles, lower_32_bits(buf->handle >> PAGE_SHIFT));
 }
 
 /**
@@ -71,7 +101,41 @@ int hl_mmap_mem_buf_put(struct hl_mmap_mem_buf *buf)
 }
 
 /**
- * hl_mmap_mem_buf_alloc - allocate a new mappable buffer
+ * hl_mmap_mem_buf_put_handle - decrease the reference to the buffer with the
+ *                              given handle.
+ *
+ * @mmg: parent unifed memory manager
+ * @handle: requested buffer handle
+ *
+ * Decrease the reference to the buffer, and release it if it was the last one.
+ * Shall not be called from an interrupt context. Return -EINVAL if handle was
+ * not found, else return the put outcome (0 or 1).
+ */
+int hl_mmap_mem_buf_put_handle(struct hl_mem_mgr *mmg, u64 handle)
+{
+	struct hl_mmap_mem_buf *buf;
+
+	spin_lock(&mmg->lock);
+	buf = idr_find(&mmg->handles, lower_32_bits(handle >> PAGE_SHIFT));
+	if (!buf) {
+		spin_unlock(&mmg->lock);
+		dev_warn(mmg->dev,
+			 "Buff put failed, no match to handle %llu\n", handle);
+		return -EINVAL;
+	}
+
+	if (kref_put(&buf->refcount, hl_mmap_mem_buf_remove_idr_locked)) {
+		spin_unlock(&mmg->lock);
+		hl_mmap_mem_buf_destroy(buf);
+		return 1;
+	}
+
+	spin_unlock(&mmg->lock);
+	return 0;
+}
+
+/**
+ * @hl_mmap_mem_buf_alloc - allocate a new mappable buffer
  *
  * @mmg: parent unifed memory manager
  * @behavior: behavior object describing this buffer polymorphic behavior