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-rw-r--r--drivers/dma-buf/dma-buf-sysfs-stats.c202
1 files changed, 202 insertions, 0 deletions
diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c
new file mode 100644
index 000000000..4b680e10c
--- /dev/null
+++ b/drivers/dma-buf/dma-buf-sysfs-stats.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * DMA-BUF sysfs statistics.
+ *
+ * Copyright (C) 2021 Google LLC.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/dma-resv.h>
+#include <linux/kobject.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include "dma-buf-sysfs-stats.h"
+
+#define to_dma_buf_entry_from_kobj(x) container_of(x, struct dma_buf_sysfs_entry, kobj)
+
+/**
+ * DOC: overview
+ *
+ * ``/sys/kernel/debug/dma_buf/bufinfo`` provides an overview of every DMA-BUF
+ * in the system. However, since debugfs is not safe to be mounted in
+ * production, procfs and sysfs can be used to gather DMA-BUF statistics on
+ * production systems.
+ *
+ * The ``/proc/<pid>/fdinfo/<fd>`` files in procfs can be used to gather
+ * information about DMA-BUF fds. Detailed documentation about the interface
+ * is present in Documentation/filesystems/proc.rst.
+ *
+ * Unfortunately, the existing procfs interfaces can only provide information
+ * about the DMA-BUFs for which processes hold fds or have the buffers mmapped
+ * into their address space. This necessitated the creation of the DMA-BUF sysfs
+ * statistics interface to provide per-buffer information on production systems.
+ *
+ * The interface at ``/sys/kernel/dma-buf/buffers`` exposes information about
+ * every DMA-BUF when ``CONFIG_DMABUF_SYSFS_STATS`` is enabled.
+ *
+ * The following stats are exposed by the interface:
+ *
+ * * ``/sys/kernel/dmabuf/buffers/<inode_number>/exporter_name``
+ * * ``/sys/kernel/dmabuf/buffers/<inode_number>/size``
+ *
+ * The information in the interface can also be used to derive per-exporter
+ * statistics. The data from the interface can be gathered on error conditions
+ * or other important events to provide a snapshot of DMA-BUF usage.
+ * It can also be collected periodically by telemetry to monitor various metrics.
+ *
+ * Detailed documentation about the interface is present in
+ * Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers.
+ */
+
+struct dma_buf_stats_attribute {
+ struct attribute attr;
+ ssize_t (*show)(struct dma_buf *dmabuf,
+ struct dma_buf_stats_attribute *attr, char *buf);
+};
+#define to_dma_buf_stats_attr(x) container_of(x, struct dma_buf_stats_attribute, attr)
+
+static ssize_t dma_buf_stats_attribute_show(struct kobject *kobj,
+ struct attribute *attr,
+ char *buf)
+{
+ struct dma_buf_stats_attribute *attribute;
+ struct dma_buf_sysfs_entry *sysfs_entry;
+ struct dma_buf *dmabuf;
+
+ attribute = to_dma_buf_stats_attr(attr);
+ sysfs_entry = to_dma_buf_entry_from_kobj(kobj);
+ dmabuf = sysfs_entry->dmabuf;
+
+ if (!dmabuf || !attribute->show)
+ return -EIO;
+
+ return attribute->show(dmabuf, attribute, buf);
+}
+
+static const struct sysfs_ops dma_buf_stats_sysfs_ops = {
+ .show = dma_buf_stats_attribute_show,
+};
+
+static ssize_t exporter_name_show(struct dma_buf *dmabuf,
+ struct dma_buf_stats_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "%s\n", dmabuf->exp_name);
+}
+
+static ssize_t size_show(struct dma_buf *dmabuf,
+ struct dma_buf_stats_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "%zu\n", dmabuf->size);
+}
+
+static struct dma_buf_stats_attribute exporter_name_attribute =
+ __ATTR_RO(exporter_name);
+static struct dma_buf_stats_attribute size_attribute = __ATTR_RO(size);
+
+static struct attribute *dma_buf_stats_default_attrs[] = {
+ &exporter_name_attribute.attr,
+ &size_attribute.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(dma_buf_stats_default);
+
+static void dma_buf_sysfs_release(struct kobject *kobj)
+{
+ struct dma_buf_sysfs_entry *sysfs_entry;
+
+ sysfs_entry = to_dma_buf_entry_from_kobj(kobj);
+ kfree(sysfs_entry);
+}
+
+static struct kobj_type dma_buf_ktype = {
+ .sysfs_ops = &dma_buf_stats_sysfs_ops,
+ .release = dma_buf_sysfs_release,
+ .default_groups = dma_buf_stats_default_groups,
+};
+
+void dma_buf_stats_teardown(struct dma_buf *dmabuf)
+{
+ struct dma_buf_sysfs_entry *sysfs_entry;
+
+ sysfs_entry = dmabuf->sysfs_entry;
+ if (!sysfs_entry)
+ return;
+
+ kobject_del(&sysfs_entry->kobj);
+ kobject_put(&sysfs_entry->kobj);
+}
+
+
+/* Statistics files do not need to send uevents. */
+static int dmabuf_sysfs_uevent_filter(struct kobject *kobj)
+{
+ return 0;
+}
+
+static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = {
+ .filter = dmabuf_sysfs_uevent_filter,
+};
+
+static struct kset *dma_buf_stats_kset;
+static struct kset *dma_buf_per_buffer_stats_kset;
+int dma_buf_init_sysfs_statistics(void)
+{
+ dma_buf_stats_kset = kset_create_and_add("dmabuf",
+ &dmabuf_sysfs_no_uevent_ops,
+ kernel_kobj);
+ if (!dma_buf_stats_kset)
+ return -ENOMEM;
+
+ dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers",
+ &dmabuf_sysfs_no_uevent_ops,
+ &dma_buf_stats_kset->kobj);
+ if (!dma_buf_per_buffer_stats_kset) {
+ kset_unregister(dma_buf_stats_kset);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+void dma_buf_uninit_sysfs_statistics(void)
+{
+ kset_unregister(dma_buf_per_buffer_stats_kset);
+ kset_unregister(dma_buf_stats_kset);
+}
+
+int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)
+{
+ struct dma_buf_sysfs_entry *sysfs_entry;
+ int ret;
+
+ if (!dmabuf->exp_name) {
+ pr_err("exporter name must not be empty if stats needed\n");
+ return -EINVAL;
+ }
+
+ sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL);
+ if (!sysfs_entry)
+ return -ENOMEM;
+
+ sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset;
+ sysfs_entry->dmabuf = dmabuf;
+
+ dmabuf->sysfs_entry = sysfs_entry;
+
+ /* create the directory for buffer stats */
+ ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL,
+ "%lu", file_inode(file)->i_ino);
+ if (ret)
+ goto err_sysfs_dmabuf;
+
+ return 0;
+
+err_sysfs_dmabuf:
+ kobject_put(&sysfs_entry->kobj);
+ dmabuf->sysfs_entry = NULL;
+ return ret;
+}