1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * DMA-BUF sysfs statistics. 4 * 5 * Copyright (C) 2021 Google LLC. 6 */ 7 8 #include <linux/dma-buf.h> 9 #include <linux/dma-resv.h> 10 #include <linux/kobject.h> 11 #include <linux/printk.h> 12 #include <linux/slab.h> 13 #include <linux/sysfs.h> 14 15 #include "dma-buf-sysfs-stats.h" 16 17 #define to_dma_buf_entry_from_kobj(x) container_of(x, struct dma_buf_sysfs_entry, kobj) 18 19 /** 20 * DOC: overview 21 * 22 * ``/sys/kernel/debug/dma_buf/bufinfo`` provides an overview of every DMA-BUF 23 * in the system. However, since debugfs is not safe to be mounted in 24 * production, procfs and sysfs can be used to gather DMA-BUF statistics on 25 * production systems. 26 * 27 * The ``/proc/<pid>/fdinfo/<fd>`` files in procfs can be used to gather 28 * information about DMA-BUF fds. Detailed documentation about the interface 29 * is present in Documentation/filesystems/proc.rst. 30 * 31 * Unfortunately, the existing procfs interfaces can only provide information 32 * about the DMA-BUFs for which processes hold fds or have the buffers mmapped 33 * into their address space. This necessitated the creation of the DMA-BUF sysfs 34 * statistics interface to provide per-buffer information on production systems. 35 * 36 * The interface at ``/sys/kernel/dma-buf/buffers`` exposes information about 37 * every DMA-BUF when ``CONFIG_DMABUF_SYSFS_STATS`` is enabled. 38 * 39 * The following stats are exposed by the interface: 40 * 41 * * ``/sys/kernel/dmabuf/buffers/<inode_number>/exporter_name`` 42 * * ``/sys/kernel/dmabuf/buffers/<inode_number>/size`` 43 * 44 * The information in the interface can also be used to derive per-exporter 45 * statistics. The data from the interface can be gathered on error conditions 46 * or other important events to provide a snapshot of DMA-BUF usage. 47 * It can also be collected periodically by telemetry to monitor various metrics. 48 * 49 * Detailed documentation about the interface is present in 50 * Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers. 51 */ 52 53 struct dma_buf_stats_attribute { 54 struct attribute attr; 55 ssize_t (*show)(struct dma_buf *dmabuf, 56 struct dma_buf_stats_attribute *attr, char *buf); 57 }; 58 #define to_dma_buf_stats_attr(x) container_of(x, struct dma_buf_stats_attribute, attr) 59 60 static ssize_t dma_buf_stats_attribute_show(struct kobject *kobj, 61 struct attribute *attr, 62 char *buf) 63 { 64 struct dma_buf_stats_attribute *attribute; 65 struct dma_buf_sysfs_entry *sysfs_entry; 66 struct dma_buf *dmabuf; 67 68 attribute = to_dma_buf_stats_attr(attr); 69 sysfs_entry = to_dma_buf_entry_from_kobj(kobj); 70 dmabuf = sysfs_entry->dmabuf; 71 72 if (!dmabuf || !attribute->show) 73 return -EIO; 74 75 return attribute->show(dmabuf, attribute, buf); 76 } 77 78 static const struct sysfs_ops dma_buf_stats_sysfs_ops = { 79 .show = dma_buf_stats_attribute_show, 80 }; 81 82 static ssize_t exporter_name_show(struct dma_buf *dmabuf, 83 struct dma_buf_stats_attribute *attr, 84 char *buf) 85 { 86 return sysfs_emit(buf, "%s\n", dmabuf->exp_name); 87 } 88 89 static ssize_t size_show(struct dma_buf *dmabuf, 90 struct dma_buf_stats_attribute *attr, 91 char *buf) 92 { 93 return sysfs_emit(buf, "%zu\n", dmabuf->size); 94 } 95 96 static struct dma_buf_stats_attribute exporter_name_attribute = 97 __ATTR_RO(exporter_name); 98 static struct dma_buf_stats_attribute size_attribute = __ATTR_RO(size); 99 100 static struct attribute *dma_buf_stats_default_attrs[] = { 101 &exporter_name_attribute.attr, 102 &size_attribute.attr, 103 NULL, 104 }; 105 ATTRIBUTE_GROUPS(dma_buf_stats_default); 106 107 static void dma_buf_sysfs_release(struct kobject *kobj) 108 { 109 struct dma_buf_sysfs_entry *sysfs_entry; 110 111 sysfs_entry = to_dma_buf_entry_from_kobj(kobj); 112 kfree(sysfs_entry); 113 } 114 115 static const struct kobj_type dma_buf_ktype = { 116 .sysfs_ops = &dma_buf_stats_sysfs_ops, 117 .release = dma_buf_sysfs_release, 118 .default_groups = dma_buf_stats_default_groups, 119 }; 120 121 void dma_buf_stats_teardown(struct dma_buf *dmabuf) 122 { 123 struct dma_buf_sysfs_entry *sysfs_entry; 124 125 sysfs_entry = dmabuf->sysfs_entry; 126 if (!sysfs_entry) 127 return; 128 129 kobject_del(&sysfs_entry->kobj); 130 kobject_put(&sysfs_entry->kobj); 131 } 132 133 134 /* Statistics files do not need to send uevents. */ 135 static int dmabuf_sysfs_uevent_filter(const struct kobject *kobj) 136 { 137 return 0; 138 } 139 140 static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { 141 .filter = dmabuf_sysfs_uevent_filter, 142 }; 143 144 static struct kset *dma_buf_stats_kset; 145 static struct kset *dma_buf_per_buffer_stats_kset; 146 int dma_buf_init_sysfs_statistics(void) 147 { 148 dma_buf_stats_kset = kset_create_and_add("dmabuf", 149 &dmabuf_sysfs_no_uevent_ops, 150 kernel_kobj); 151 if (!dma_buf_stats_kset) 152 return -ENOMEM; 153 154 dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers", 155 &dmabuf_sysfs_no_uevent_ops, 156 &dma_buf_stats_kset->kobj); 157 if (!dma_buf_per_buffer_stats_kset) { 158 kset_unregister(dma_buf_stats_kset); 159 return -ENOMEM; 160 } 161 162 return 0; 163 } 164 165 void dma_buf_uninit_sysfs_statistics(void) 166 { 167 kset_unregister(dma_buf_per_buffer_stats_kset); 168 kset_unregister(dma_buf_stats_kset); 169 } 170 171 int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file) 172 { 173 struct dma_buf_sysfs_entry *sysfs_entry; 174 int ret; 175 176 if (!dmabuf->exp_name) { 177 pr_err("exporter name must not be empty if stats needed\n"); 178 return -EINVAL; 179 } 180 181 sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL); 182 if (!sysfs_entry) 183 return -ENOMEM; 184 185 sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset; 186 sysfs_entry->dmabuf = dmabuf; 187 188 dmabuf->sysfs_entry = sysfs_entry; 189 190 /* create the directory for buffer stats */ 191 ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL, 192 "%lu", file_inode(file)->i_ino); 193 if (ret) 194 goto err_sysfs_dmabuf; 195 196 return 0; 197 198 err_sysfs_dmabuf: 199 kobject_put(&sysfs_entry->kobj); 200 dmabuf->sysfs_entry = NULL; 201 return ret; 202 } 203