Expose the debugfs list and mutex so they are usable for the creation of a BPF iterator for dmabufs without the need for CONFIG_DEBUG_FS. Rename the symbols so it's clear debugfs is not required, and that the list contains dmabufs and not some other type.

Signed-off-by: T.J. Mercier tjmercier@google.com --- v2: Make the DMA buffer list independent of CONFIG_DEBUG_FS per Christian König drivers/dma-buf/dma-buf.c | 40 +++++++++++++++------------------------ include/linux/dma-buf.h | 6 ++++-- 2 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 5baa83b85515..7260bdd77c75 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -35,35 +35,25 @@

static inline int is_dma_buf_file(struct file *);

-#if IS_ENABLED(CONFIG_DEBUG_FS) -static DEFINE_MUTEX(debugfs_list_mutex); -static LIST_HEAD(debugfs_list); +DEFINE_MUTEX(dmabuf_list_mutex); +LIST_HEAD(dmabuf_list);

-static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf) +static void __dma_buf_list_add(struct dma_buf *dmabuf) { - mutex_lock(&debugfs_list_mutex); - list_add(&dmabuf->list_node, &debugfs_list); - mutex_unlock(&debugfs_list_mutex); + mutex_lock(&dmabuf_list_mutex); + list_add(&dmabuf->list_node, &dmabuf_list); + mutex_unlock(&dmabuf_list_mutex); }

-static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf) +static void __dma_buf_list_del(struct dma_buf *dmabuf) { if (!dmabuf) return;

- mutex_lock(&debugfs_list_mutex); + mutex_lock(&dmabuf_list_mutex); list_del(&dmabuf->list_node); - mutex_unlock(&debugfs_list_mutex); + mutex_unlock(&dmabuf_list_mutex); } -#else -static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf) -{ -} - -static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf) -{ -} -#endif

static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) { @@ -115,7 +105,7 @@ static int dma_buf_file_release(struct inode *inode, struct file *file) if (!is_dma_buf_file(file)) return -EINVAL;

- __dma_buf_debugfs_list_del(file->private_data); + __dma_buf_list_del(file->private_data);

return 0; } @@ -689,7 +679,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) file->f_path.dentry->d_fsdata = dmabuf; dmabuf->file = file;

- __dma_buf_debugfs_list_add(dmabuf); + __dma_buf_list_add(dmabuf);

return dmabuf;

@@ -1630,7 +1620,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused) size_t size = 0; int ret;

- ret = mutex_lock_interruptible(&debugfs_list_mutex); + ret = mutex_lock_interruptible(&dmabuf_list_mutex);

if (ret) return ret; @@ -1639,7 +1629,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused) seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\tname\n", "size", "flags", "mode", "count", "ino");

- list_for_each_entry(buf_obj, &debugfs_list, list_node) { + list_for_each_entry(buf_obj, &dmabuf_list, list_node) {

ret = dma_resv_lock_interruptible(buf_obj->resv, NULL); if (ret) @@ -1676,11 +1666,11 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)

seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);

- mutex_unlock(&debugfs_list_mutex); + mutex_unlock(&dmabuf_list_mutex); return 0;

error_unlock: - mutex_unlock(&debugfs_list_mutex); + mutex_unlock(&dmabuf_list_mutex); return ret; }

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 36216d28d8bd..ebcd208272bf 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -18,6 +18,7 @@ #include <linux/err.h> #include <linux/scatterlist.h> #include <linux/list.h> +#include <linux/mutex.h> #include <linux/dma-mapping.h> #include <linux/fs.h> #include <linux/dma-fence.h> @@ -370,10 +371,8 @@ struct dma_buf { */ struct module *owner;

-#if IS_ENABLED(CONFIG_DEBUG_FS) /** @list_node: node for dma_buf accounting and debugging. */ struct list_head list_node; -#endif

/** @priv: exporter specific private data for this buffer object. */ void *priv; @@ -556,6 +555,9 @@ struct dma_buf_export_info { struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \ .owner = THIS_MODULE }

+extern struct list_head dmabuf_list; +extern struct mutex dmabuf_list_mutex; + /** * get_dma_buf - convenience wrapper for get_file. * @dmabuf: [in] pointer to dma_buf

The dmabuf iterator traverses the list of all DMA buffers.

DMA buffers are refcounted through their associated struct file. A reference is taken on each buffer as the list is iterated to ensure each buffer persists for the duration of the bpf program execution without holding the list mutex.

Signed-off-by: T.J. Mercier tjmercier@google.com --- kernel/bpf/Makefile | 3 + kernel/bpf/dmabuf_iter.c | 134 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 137 insertions(+) create mode 100644 kernel/bpf/dmabuf_iter.c

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 70502f038b92..3a335c50e6e3 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -53,6 +53,9 @@ obj-$(CONFIG_BPF_SYSCALL) += relo_core.o obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o +ifeq ($(CONFIG_DMA_SHARED_BUFFER),y) +obj-$(CONFIG_BPF_SYSCALL) += dmabuf_iter.o +endif

CFLAGS_REMOVE_percpu_freelist.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_bpf_lru_list.o = $(CC_FLAGS_FTRACE) diff --git a/kernel/bpf/dmabuf_iter.c b/kernel/bpf/dmabuf_iter.c new file mode 100644 index 000000000000..968762e11f73 --- /dev/null +++ b/kernel/bpf/dmabuf_iter.c @@ -0,0 +1,134 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2025 Google LLC */ +#include <linux/bpf.h> +#include <linux/btf_ids.h> +#include <linux/dma-buf.h> +#include <linux/kernel.h> +#include <linux/seq_file.h> + +BTF_ID_LIST_SINGLE(bpf_dmabuf_btf_id, struct, dma_buf) +DEFINE_BPF_ITER_FUNC(dmabuf, struct bpf_iter_meta *meta, struct dma_buf *dmabuf) + +static struct dma_buf *get_next_dmabuf(struct dma_buf *dmabuf) +{ + struct dma_buf *ret = NULL; + + /* + * Look for the first/next buffer we can obtain a reference to. + * + * The list mutex does not protect a dmabuf's refcount, so it can be + * zeroed while we are iterating. We cannot call get_dma_buf() since the + * caller of this program may not already own a reference to the buffer. + */ + mutex_lock(&dmabuf_list_mutex); + if (dmabuf) { + dma_buf_put(dmabuf); + list_for_each_entry_continue(dmabuf, &dmabuf_list, list_node) { + if (file_ref_get(&dmabuf->file->f_ref)) { + ret = dmabuf; + break; + } + } + } else { + list_for_each_entry(dmabuf, &dmabuf_list, list_node) { + if (file_ref_get(&dmabuf->file->f_ref)) { + ret = dmabuf; + break; + } + } + } + mutex_unlock(&dmabuf_list_mutex); + return ret; +} + +static void *dmabuf_iter_seq_start(struct seq_file *seq, loff_t *pos) +{ + if (*pos) + return NULL; + + return get_next_dmabuf(NULL); +} + +static void *dmabuf_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct dma_buf *dmabuf = v; + + ++*pos; + + return get_next_dmabuf(dmabuf); +} + +struct bpf_iter__dmabuf { + __bpf_md_ptr(struct bpf_iter_meta *, meta); + __bpf_md_ptr(struct dma_buf *, dmabuf); +}; + +static int __dmabuf_seq_show(struct seq_file *seq, void *v, bool in_stop) +{ + struct bpf_iter_meta meta = { + .seq = seq, + }; + struct bpf_iter__dmabuf ctx = { + .meta = &meta, + .dmabuf = v, + }; + struct bpf_prog *prog = bpf_iter_get_info(&meta, in_stop); + + if (prog) + return bpf_iter_run_prog(prog, &ctx); + + return 0; +} + +static int dmabuf_iter_seq_show(struct seq_file *seq, void *v) +{ + return __dmabuf_seq_show(seq, v, false); +} + +static void dmabuf_iter_seq_stop(struct seq_file *seq, void *v) +{ + struct dma_buf *dmabuf = v; + + if (dmabuf) + dma_buf_put(dmabuf); +} + +static const struct seq_operations dmabuf_iter_seq_ops = { + .start = dmabuf_iter_seq_start, + .next = dmabuf_iter_seq_next, + .stop = dmabuf_iter_seq_stop, + .show = dmabuf_iter_seq_show, +}; + +static void bpf_iter_dmabuf_show_fdinfo(const struct bpf_iter_aux_info *aux, + struct seq_file *seq) +{ + seq_puts(seq, "dmabuf iter\n"); +} + +static const struct bpf_iter_seq_info dmabuf_iter_seq_info = { + .seq_ops = &dmabuf_iter_seq_ops, + .init_seq_private = NULL, + .fini_seq_private = NULL, + .seq_priv_size = 0, +}; + +static struct bpf_iter_reg bpf_dmabuf_reg_info = { + .target = "dmabuf", + .feature = BPF_ITER_RESCHED, + .show_fdinfo = bpf_iter_dmabuf_show_fdinfo, + .ctx_arg_info_size = 1, + .ctx_arg_info = { + { offsetof(struct bpf_iter__dmabuf, dmabuf), + PTR_TO_BTF_ID_OR_NULL }, + }, + .seq_info = &dmabuf_iter_seq_info, +}; + +static int __init dmabuf_iter_init(void) +{ + bpf_dmabuf_reg_info.ctx_arg_info[0].btf_id = bpf_dmabuf_btf_id[0]; + return bpf_iter_reg_target(&bpf_dmabuf_reg_info); +} + +late_initcall(dmabuf_iter_init);

This test creates a udmabuf, and a dmabuf from the system dmabuf heap, and uses a BPF program that prints dmabuf metadata with the new dmabuf_iter to verify they can be found.

Signed-off-by: T.J. Mercier tjmercier@google.com --- tools/testing/selftests/bpf/config | 3 + .../selftests/bpf/prog_tests/dmabuf_iter.c | 224 ++++++++++++++++++ .../testing/selftests/bpf/progs/dmabuf_iter.c | 53 +++++ 3 files changed, 280 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c create mode 100644 tools/testing/selftests/bpf/progs/dmabuf_iter.c

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config index c378d5d07e02..2bdff2f3285f 100644 --- a/tools/testing/selftests/bpf/config +++ b/tools/testing/selftests/bpf/config @@ -22,6 +22,8 @@ CONFIG_CRYPTO_AES=y CONFIG_DEBUG_INFO=y CONFIG_DEBUG_INFO_BTF=y CONFIG_DEBUG_INFO_DWARF4=y +CONFIG_DMABUF_HEAPS=y +CONFIG_DMABUF_HEAPS_SYSTEM=y CONFIG_DUMMY=y CONFIG_DYNAMIC_FTRACE=y CONFIG_FPROBE=y @@ -106,6 +108,7 @@ CONFIG_SECURITY=y CONFIG_SECURITYFS=y CONFIG_SYN_COOKIES=y CONFIG_TEST_BPF=m +CONFIG_UDMABUF=y CONFIG_USERFAULTFD=y CONFIG_VSOCKETS=y CONFIG_VXLAN=y diff --git a/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c new file mode 100644 index 000000000000..35745f4ce0f8 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c @@ -0,0 +1,224 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2025 Google */ + +#include <test_progs.h> +#include <bpf/libbpf.h> +#include <bpf/btf.h> +#include "dmabuf_iter.skel.h" + +#include <fcntl.h> +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/ioctl.h> +#include <sys/mman.h> +#include <unistd.h> + +#include <linux/dma-buf.h> +#include <linux/dma-heap.h> +#include <linux/udmabuf.h> + +static int memfd, udmabuf; +static const char udmabuf_test_buffer_name[DMA_BUF_NAME_LEN] = "udmabuf_test_buffer_for_iter"; +static size_t udmabuf_test_buffer_size; +static int sysheap_dmabuf; +static const char sysheap_test_buffer_name[DMA_BUF_NAME_LEN] = "sysheap_test_buffer_for_iter"; +static size_t sysheap_test_buffer_size; + +static int create_udmabuf(void) +{ + struct udmabuf_create create; + int dev_udmabuf; + + udmabuf_test_buffer_size = 10 * getpagesize(); + + if (!ASSERT_LE(sizeof(udmabuf_test_buffer_name), DMA_BUF_NAME_LEN, "NAMETOOLONG")) + return 1; + + memfd = memfd_create("memfd_test", MFD_ALLOW_SEALING); + if (!ASSERT_OK_FD(memfd, "memfd_create")) + return 1; + + if (!ASSERT_OK(ftruncate(memfd, udmabuf_test_buffer_size), "ftruncate")) + return 1; + + if (!ASSERT_OK(fcntl(memfd, F_ADD_SEALS, F_SEAL_SHRINK), "seal")) + return 1; + + dev_udmabuf = open("/dev/udmabuf", O_RDONLY); + if (!ASSERT_OK_FD(dev_udmabuf, "open udmabuf")) + return 1; + + create.memfd = memfd; + create.flags = UDMABUF_FLAGS_CLOEXEC; + create.offset = 0; + create.size = udmabuf_test_buffer_size; + + udmabuf = ioctl(dev_udmabuf, UDMABUF_CREATE, &create); + close(dev_udmabuf); + if (!ASSERT_OK_FD(udmabuf, "udmabuf_create")) + return 1; + + if (!ASSERT_OK(ioctl(udmabuf, DMA_BUF_SET_NAME_B, udmabuf_test_buffer_name), "name")) + return 1; + + return 0; +} + +static int create_sys_heap_dmabuf(void) +{ + sysheap_test_buffer_size = 20 * getpagesize(); + + struct dma_heap_allocation_data data = { + .len = sysheap_test_buffer_size, + .fd = 0, + .fd_flags = O_RDWR | O_CLOEXEC, + .heap_flags = 0, + }; + int heap_fd, ret; + + if (!ASSERT_LE(sizeof(sysheap_test_buffer_name), DMA_BUF_NAME_LEN, "NAMETOOLONG")) + return 1; + + heap_fd = open("/dev/dma_heap/system", O_RDONLY); + if (!ASSERT_OK_FD(heap_fd, "open dma heap")) + return 1; + + ret = ioctl(heap_fd, DMA_HEAP_IOCTL_ALLOC, &data); + close(heap_fd); + if (!ASSERT_OK(ret, "syheap alloc")) + return 1; + + sysheap_dmabuf = data.fd; + + if (!ASSERT_OK(ioctl(sysheap_dmabuf, DMA_BUF_SET_NAME_B, sysheap_test_buffer_name), "name")) + return 1; + + return 0; +} + +static int create_test_buffers(void) +{ + int ret; + + ret = create_udmabuf(); + if (ret) + return ret; + + return create_sys_heap_dmabuf(); +} + +static void destroy_test_buffers(void) +{ + close(udmabuf); + close(memfd); + close(sysheap_dmabuf); +} + +enum Fields { INODE, SIZE, NAME, EXPORTER, FIELD_COUNT }; +struct DmabufInfo { + unsigned long inode; + unsigned long size; + char name[DMA_BUF_NAME_LEN]; + char exporter[32]; +}; + +static bool check_dmabuf_info(const struct DmabufInfo *bufinfo, + unsigned long size, + const char *name, const char *exporter) +{ + return size == bufinfo->size && + !strcmp(name, bufinfo->name) && + !strcmp(exporter, bufinfo->exporter); +} + +static void subtest_dmabuf_iter_check_default_iter(struct dmabuf_iter *skel) +{ + bool found_test_sysheap_dmabuf = false; + bool found_test_udmabuf = false; + struct DmabufInfo bufinfo; + size_t linesize = 0; + char *line = NULL; + FILE *iter_file; + int iter_fd, f = INODE; + + iter_fd = bpf_iter_create(bpf_link__fd(skel->links.dmabuf_collector)); + ASSERT_OK_FD(iter_fd, "iter_create"); + + iter_file = fdopen(iter_fd, "r"); + ASSERT_OK_PTR(iter_file, "fdopen"); + + while (getline(&line, &linesize, iter_file) != -1) { + if (f % FIELD_COUNT == INODE) { + ASSERT_EQ(sscanf(line, "%ld", &bufinfo.inode), 1, + "read inode"); + } else if (f % FIELD_COUNT == SIZE) { + ASSERT_EQ(sscanf(line, "%ld", &bufinfo.size), 1, + "read size"); + } else if (f % FIELD_COUNT == NAME) { + ASSERT_EQ(sscanf(line, "%s", bufinfo.name), 1, + "read name"); + } else if (f % FIELD_COUNT == EXPORTER) { + ASSERT_EQ(sscanf(line, "%31s", bufinfo.exporter), 1, + "read exporter"); + + if (check_dmabuf_info(&bufinfo, + sysheap_test_buffer_size, + sysheap_test_buffer_name, + "system")) + found_test_sysheap_dmabuf = true; + else if (check_dmabuf_info(&bufinfo, + udmabuf_test_buffer_size, + udmabuf_test_buffer_name, + "udmabuf")) + found_test_udmabuf = true; + } + ++f; + } + + ASSERT_EQ(f % FIELD_COUNT, INODE, "number of fields"); + + ASSERT_TRUE(found_test_sysheap_dmabuf, "found_test_sysheap_dmabuf"); + ASSERT_TRUE(found_test_udmabuf, "found_test_udmabuf"); + + free(line); + fclose(iter_file); + close(iter_fd); +} + +void test_dmabuf_iter(void) +{ + struct dmabuf_iter *skel = NULL; + char buf[256]; + int iter_fd; + + skel = dmabuf_iter__open_and_load(); + if (!ASSERT_OK_PTR(skel, "dmabuf_iter__open_and_load")) + return; + + if (!ASSERT_OK(create_test_buffers(), "create_buffers")) + goto destroy; + + if (!ASSERT_OK(dmabuf_iter__attach(skel), "skel_attach")) + goto destroy; + + iter_fd = bpf_iter_create(bpf_link__fd(skel->links.dmabuf_collector)); + if (!ASSERT_OK_FD(iter_fd, "iter_create")) + goto destroy; + + while (read(iter_fd, buf, sizeof(buf)) > 0) + ; /* Read out all contents */ + + /* Next reads should return 0 */ + ASSERT_EQ(read(iter_fd, buf, sizeof(buf)), 0, "read"); + + if (test__start_subtest("default_iter")) + subtest_dmabuf_iter_check_default_iter(skel); + + close(iter_fd); + +destroy: + destroy_test_buffers(); + dmabuf_iter__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/dmabuf_iter.c b/tools/testing/selftests/bpf/progs/dmabuf_iter.c new file mode 100644 index 000000000000..6e80a53c4670 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/dmabuf_iter.c @@ -0,0 +1,53 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2025 Google LLC */ +#include <vmlinux.h> +#include <bpf/bpf_core_read.h> +#include <bpf/bpf_helpers.h> + +/* From uapi/linux/dma-buf.h */ +#define DMA_BUF_NAME_LEN 32 + +char _license[] SEC("license") = "GPL"; + +/** + * Fields output by this iterator are delimited by newlines. Convert any + * newlines in user-provided printed strings to spaces. + */ +static void sanitize_string(char *src, size_t size) +{ + for (char *c = src; c && (size_t)(c-src) < size; ++c) + if (*c == '\n') + *c = ' '; +} + +SEC("iter/dmabuf") +int dmabuf_collector(struct bpf_iter__dmabuf *ctx) +{ + const struct dma_buf *dmabuf = ctx->dmabuf; + struct seq_file *seq = ctx->meta->seq; + unsigned long inode = 0; + size_t size; + const char *pname, *exporter; + char name[DMA_BUF_NAME_LEN] = {'\0'}; + + if (!dmabuf) + return 0; + + if (BPF_CORE_READ_INTO(&inode, dmabuf, file, f_inode, i_ino) || + bpf_core_read(&size, sizeof(size), &dmabuf->size) || + bpf_core_read(&pname, sizeof(pname), &dmabuf->name) || + bpf_core_read(&exporter, sizeof(exporter), &dmabuf->exp_name)) + return 1; + + /* Buffers are not required to be named */ + if (pname) { + if (bpf_probe_read_kernel(name, sizeof(name), pname)) + return 1; + + /* Name strings can be provided by userspace */ + sanitize_string(name, sizeof(name)); + } + + BPF_SEQ_PRINTF(seq, "%lu\n%llu\n%s\n%s\n", inode, size, name, exporter); + return 0; +}

I think Android is probably the only remaining user of the dmabuf sysfs files. The BPF infrastructure added earlier in this series will allow us to get the same information much more cheaply.

This patch is a RFC because I'd like to keep this for at least one more longterm stable release (6.18?) before actually removing it so that we can have one longterm stable kernel version that supports both options to facilitate a transition from the sysfs files to a BPF program.

Signed-off-by: T.J. Mercier tjmercier@google.com --- .../ABI/testing/sysfs-kernel-dmabuf-buffers | 24 --- Documentation/driver-api/dma-buf.rst | 5 - drivers/dma-buf/Kconfig | 15 -- drivers/dma-buf/Makefile | 1 - drivers/dma-buf/dma-buf-sysfs-stats.c | 202 ------------------ drivers/dma-buf/dma-buf-sysfs-stats.h | 35 --- drivers/dma-buf/dma-buf.c | 18 -- 7 files changed, 300 deletions(-) delete mode 100644 Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers delete mode 100644 drivers/dma-buf/dma-buf-sysfs-stats.c delete mode 100644 drivers/dma-buf/dma-buf-sysfs-stats.h

diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers b/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers deleted file mode 100644 index 5d3bc997dc64..000000000000 --- a/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers +++ /dev/null @@ -1,24 +0,0 @@ -What: /sys/kernel/dmabuf/buffers -Date: May 2021 -KernelVersion: v5.13 -Contact: Hridya Valsaraju hridya@google.com -Description: The /sys/kernel/dmabuf/buffers directory contains a - snapshot of the internal state of every DMA-BUF. - /sys/kernel/dmabuf/buffers/<inode_number> will contain the - statistics for the DMA-BUF with the unique inode number - <inode_number> -Users: kernel memory tuning/debugging tools - -What: /sys/kernel/dmabuf/buffers/<inode_number>/exporter_name -Date: May 2021 -KernelVersion: v5.13 -Contact: Hridya Valsaraju hridya@google.com -Description: This file is read-only and contains the name of the exporter of - the DMA-BUF. - -What: /sys/kernel/dmabuf/buffers/<inode_number>/size -Date: May 2021 -KernelVersion: v5.13 -Contact: Hridya Valsaraju hridya@google.com -Description: This file is read-only and specifies the size of the DMA-BUF in - bytes. diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst index 29abf1eebf9f..2f36c21d9948 100644 --- a/Documentation/driver-api/dma-buf.rst +++ b/Documentation/driver-api/dma-buf.rst @@ -125,11 +125,6 @@ Implicit Fence Poll Support .. kernel-doc:: drivers/dma-buf/dma-buf.c :doc: implicit fence polling

-DMA-BUF statistics -~~~~~~~~~~~~~~~~~~ -.. kernel-doc:: drivers/dma-buf/dma-buf-sysfs-stats.c - :doc: overview - DMA Buffer ioctls ~~~~~~~~~~~~~~~~~

diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig index fee04fdb0822..03e38c0d1fff 100644 --- a/drivers/dma-buf/Kconfig +++ b/drivers/dma-buf/Kconfig @@ -76,21 +76,6 @@ menuconfig DMABUF_HEAPS allows userspace to allocate dma-bufs that can be shared between drivers.

-menuconfig DMABUF_SYSFS_STATS - bool "DMA-BUF sysfs statistics (DEPRECATED)" - depends on DMA_SHARED_BUFFER - help - Choose this option to enable DMA-BUF sysfs statistics - in location /sys/kernel/dmabuf/buffers. - - /sys/kernel/dmabuf/buffers/<inode_number> will contain - statistics for the DMA-BUF with the unique inode number - <inode_number>. - - This option is deprecated and should sooner or later be removed. - Android is the only user of this and it turned out that this resulted - in quite some performance problems. - source "drivers/dma-buf/heaps/Kconfig"

endmenu diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile index 70ec901edf2c..8ab2bfecb1c9 100644 --- a/drivers/dma-buf/Makefile +++ b/drivers/dma-buf/Makefile @@ -6,7 +6,6 @@ obj-$(CONFIG_DMABUF_HEAPS) += heaps/ obj-$(CONFIG_SYNC_FILE) += sync_file.o obj-$(CONFIG_SW_SYNC) += sw_sync.o sync_debug.o obj-$(CONFIG_UDMABUF) += udmabuf.o -obj-$(CONFIG_DMABUF_SYSFS_STATS) += dma-buf-sysfs-stats.o

dmabuf_selftests-y := \ selftest.o \ diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c deleted file mode 100644 index b5b62e40ccc1..000000000000 --- a/drivers/dma-buf/dma-buf-sysfs-stats.c +++ /dev/null @@ -1,202 +0,0 @@ -// 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/dmabuf/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 const 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(const 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; -} diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.h b/drivers/dma-buf/dma-buf-sysfs-stats.h deleted file mode 100644 index 7a8a995b75ba..000000000000 --- a/drivers/dma-buf/dma-buf-sysfs-stats.h +++ /dev/null @@ -1,35 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0-only */ -/* - * DMA-BUF sysfs statistics. - * - * Copyright (C) 2021 Google LLC. - */ - -#ifndef _DMA_BUF_SYSFS_STATS_H -#define _DMA_BUF_SYSFS_STATS_H - -#ifdef CONFIG_DMABUF_SYSFS_STATS - -int dma_buf_init_sysfs_statistics(void); -void dma_buf_uninit_sysfs_statistics(void); - -int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file); - -void dma_buf_stats_teardown(struct dma_buf *dmabuf); -#else - -static inline int dma_buf_init_sysfs_statistics(void) -{ - return 0; -} - -static inline void dma_buf_uninit_sysfs_statistics(void) {} - -static inline int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file) -{ - return 0; -} - -static inline void dma_buf_stats_teardown(struct dma_buf *dmabuf) {} -#endif -#endif // _DMA_BUF_SYSFS_STATS_H diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 7260bdd77c75..adc6a0c96641 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -31,8 +31,6 @@ #include <uapi/linux/dma-buf.h> #include <uapi/linux/magic.h>

-#include "dma-buf-sysfs-stats.h" - static inline int is_dma_buf_file(struct file *);

DEFINE_MUTEX(dmabuf_list_mutex); @@ -88,7 +86,6 @@ static void dma_buf_release(struct dentry *dentry) */ BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);

- dma_buf_stats_teardown(dmabuf); dmabuf->ops->release(dmabuf);

if (dmabuf->resv == (struct dma_resv *)&dmabuf[1]) @@ -671,10 +668,6 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) dmabuf->resv = resv; }

- ret = dma_buf_stats_setup(dmabuf, file); - if (ret) - goto err_dmabuf; - file->private_data = dmabuf; file->f_path.dentry->d_fsdata = dmabuf; dmabuf->file = file; @@ -683,10 +676,6 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)

return dmabuf;

-err_dmabuf: - if (!resv) - dma_resv_fini(dmabuf->resv); - kfree(dmabuf); err_file: fput(file); err_module: @@ -1717,12 +1706,6 @@ static inline void dma_buf_uninit_debugfs(void)

static int __init dma_buf_init(void) { - int ret; - - ret = dma_buf_init_sysfs_statistics(); - if (ret) - return ret; - dma_buf_mnt = kern_mount(&dma_buf_fs_type); if (IS_ERR(dma_buf_mnt)) return PTR_ERR(dma_buf_mnt); @@ -1736,6 +1719,5 @@ static void __exit dma_buf_deinit(void) { dma_buf_uninit_debugfs(); kern_unmount(dma_buf_mnt); - dma_buf_uninit_sysfs_statistics(); } __exitcall(dma_buf_deinit);