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authorGreg Hackmann <ghackmann@google.com>2019-06-14 01:34:06 +0300
committerSumit Semwal <sumit.semwal@linaro.org>2019-06-14 12:30:50 +0300
commited63bb1d1f8469586006a9ca63c42344401aa2ab (patch)
tree577f34abf29a23010020204e50df5a758fe7684d /drivers/dma-buf
parent51e857af9f3f1ab78be10ff6bf5c4a8a56f4e4d6 (diff)
downloadlinux-ed63bb1d1f8469586006a9ca63c42344401aa2ab.tar.xz
dma-buf: give each buffer a full-fledged inode
By traversing /proc/*/fd and /proc/*/map_files, processes with CAP_ADMIN can get a lot of fine-grained data about how shmem buffers are shared among processes. stat(2) on each entry gives the caller a unique ID (st_ino), the buffer's size (st_size), and even the number of pages currently charged to the buffer (st_blocks / 512). In contrast, all dma-bufs share the same anonymous inode. So while we can count how many dma-buf fds or mappings a process has, we can't get the size of the backing buffers or tell if two entries point to the same dma-buf. On systems with debugfs, we can get a per-buffer breakdown of size and reference count, but can't tell which processes are actually holding the references to each buffer. Replace the singleton inode with full-fledged inodes allocated by alloc_anon_inode(). This involves creating and mounting a mini-pseudo-filesystem for dma-buf, following the example in fs/aio.c. Signed-off-by: Greg Hackmann <ghackmann@google.com> Signed-off-by: Chenbo Feng <fengc@google.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/20190613223408.139221-2-fengc@google.com
Diffstat (limited to 'drivers/dma-buf')
-rw-r--r--drivers/dma-buf/dma-buf.c63
1 files changed, 57 insertions, 6 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index f4104a21b069..3612ccededd6 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -34,8 +34,10 @@
#include <linux/poll.h>
#include <linux/reservation.h>
#include <linux/mm.h>
+#include <linux/mount.h>
#include <uapi/linux/dma-buf.h>
+#include <uapi/linux/magic.h>
static inline int is_dma_buf_file(struct file *);
@@ -46,6 +48,25 @@ struct dma_buf_list {
static struct dma_buf_list db_list;
+static const struct dentry_operations dma_buf_dentry_ops = {
+ .d_dname = simple_dname,
+};
+
+static struct vfsmount *dma_buf_mnt;
+
+static struct dentry *dma_buf_fs_mount(struct file_system_type *fs_type,
+ int flags, const char *name, void *data)
+{
+ return mount_pseudo(fs_type, "dmabuf:", NULL, &dma_buf_dentry_ops,
+ DMA_BUF_MAGIC);
+}
+
+static struct file_system_type dma_buf_fs_type = {
+ .name = "dmabuf",
+ .mount = dma_buf_fs_mount,
+ .kill_sb = kill_anon_super,
+};
+
static int dma_buf_release(struct inode *inode, struct file *file)
{
struct dma_buf *dmabuf;
@@ -342,6 +363,31 @@ static inline int is_dma_buf_file(struct file *file)
return file->f_op == &dma_buf_fops;
}
+static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
+{
+ struct file *file;
+ struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
+
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
+ inode->i_size = dmabuf->size;
+ inode_set_bytes(inode, dmabuf->size);
+
+ file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
+ flags, &dma_buf_fops);
+ if (IS_ERR(file))
+ goto err_alloc_file;
+ file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
+ file->private_data = dmabuf;
+
+ return file;
+
+err_alloc_file:
+ iput(inode);
+ return file;
+}
+
/**
* DOC: dma buf device access
*
@@ -436,8 +482,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
}
dmabuf->resv = resv;
- file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf,
- exp_info->flags);
+ file = dma_buf_getfile(dmabuf, exp_info->flags);
if (IS_ERR(file)) {
ret = PTR_ERR(file);
goto err_dmabuf;
@@ -1055,8 +1100,8 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
return ret;
seq_puts(s, "\nDma-buf Objects:\n");
- seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\n",
- "size", "flags", "mode", "count");
+ seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
+ "size", "flags", "mode", "count", "ino");
list_for_each_entry(buf_obj, &db_list.head, list_node) {
ret = mutex_lock_interruptible(&buf_obj->lock);
@@ -1067,11 +1112,12 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
continue;
}
- seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\n",
+ seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\n",
buf_obj->size,
buf_obj->file->f_flags, buf_obj->file->f_mode,
file_count(buf_obj->file),
- buf_obj->exp_name);
+ buf_obj->exp_name,
+ file_inode(buf_obj->file)->i_ino);
robj = buf_obj->resv;
while (true) {
@@ -1167,6 +1213,10 @@ static inline void dma_buf_uninit_debugfs(void)
static int __init dma_buf_init(void)
{
+ dma_buf_mnt = kern_mount(&dma_buf_fs_type);
+ if (IS_ERR(dma_buf_mnt))
+ return PTR_ERR(dma_buf_mnt);
+
mutex_init(&db_list.lock);
INIT_LIST_HEAD(&db_list.head);
dma_buf_init_debugfs();
@@ -1177,5 +1227,6 @@ subsys_initcall(dma_buf_init);
static void __exit dma_buf_deinit(void)
{
dma_buf_uninit_debugfs();
+ kern_unmount(dma_buf_mnt);
}
__exitcall(dma_buf_deinit);