[RFC PATCH v2 18/19] {mm,procfs}: Add display file_pins proc

ira.weiny
2019-08-09T23:01:50Z

From: Ira Weiny <ira.weiny@intel.com>

Now that we have the file pins information stored add a new procfs entry
to display them to the user.

NOTE output will be dependant on where the file pin is tied to. Some
processes may have the pin associated with a file descriptor in which
case that file is reported as well.

Others are associated directly with the process mm and are reported as
such.

For example of a file pinned to an RDMA open context (fd 4) and a file
pinned to the mm of that process:

4: /dev/infiniband/uverbs0
/mnt/pmem/foo
/mnt/pmem/bar

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
fs/proc/base.c | 214 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 214 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ebea9501afb8..f4d219172235 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2995,6 +2995,7 @@ static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
*/
static const struct file_operations proc_task_operations;
static const struct inode_operations proc_task_inode_operations;
+static const struct file_operations proc_pid_file_pins_operations;

static const struct pid_entry tgid_base_stuff[] = {
DIR("task", S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
@@ -3024,6 +3025,7 @@ static const struct pid_entry tgid_base_stuff[] = {
ONE("stat", S_IRUGO, proc_tgid_stat),
ONE("statm", S_IRUGO, proc_pid_statm),
REG("maps", S_IRUGO, proc_pid_maps_operations),
+ REG("file_pins", S_IRUGO, proc_pid_file_pins_operations),
#ifdef CONFIG_NUMA
REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
#endif
@@ -3422,6 +3424,7 @@ static const struct pid_entry tid_base_stuff[] = {
ONE("stat", S_IRUGO, proc_tid_stat),
ONE("statm", S_IRUGO, proc_pid_statm),
REG("maps", S_IRUGO, proc_pid_maps_operations),
+ REG("file_pins", S_IRUGO, proc_pid_file_pins_operations),
#ifdef CONFIG_PROC_CHILDREN
REG("children", S_IRUGO, proc_tid_children_operations),
#endif
@@ -3718,3 +3721,214 @@ void __init set_proc_pid_nlink(void)
nlink_tid = pid_entry_nlink(tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
nlink_tgid = pid_entry_nlink(tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
}
+
+/**
+ * file_pin information below.
+ */
+
+struct proc_file_pins_private {
+ struct inode *inode;
+ struct task_struct *task;
+ struct mm_struct *mm;
+ struct files_struct *files;
+ unsigned int nr_pins;
+ struct xarray fps;
+} __randomize_layout;
+
+static void release_fp(struct proc_file_pins_private *priv)
+{
+ up_read(&priv->mm->mmap_sem);
+ mmput(priv->mm);
+}
+
+static void print_fd_file_pin(struct seq_file *m, struct file *file,
+ unsigned long i)
+{
+ struct file_file_pin *fp;
+ struct file_file_pin *tmp;
+
+ if (list_empty_careful(&file->file_pins))
+ return;
+
+ seq_printf(m, "%lu: ", i);
+ seq_file_path(m, file, "\n");
+ seq_putc(m, '\n');
+
+ list_for_each_entry_safe(fp, tmp, &file->file_pins, list) {
+ seq_puts(m, " ");
+ seq_file_path(m, fp->file, "\n");
+ seq_putc(m, '\n');
+ }
+}
+
+/* We are storing the index's within the FD table for later retrieval */
+static int store_fd(const void *priv , struct file *file, unsigned i)
+{
+ struct proc_file_pins_private *fp_priv;
+
+ /* cast away const... */
+ fp_priv = (struct proc_file_pins_private *)priv;
+
+ if (list_empty_careful(&file->file_pins))
+ return 0;
+
+ /* can't sleep in the iterate of the fd table */
+ xa_store(&fp_priv->fps, fp_priv->nr_pins, xa_mk_value(i), GFP_ATOMIC);
+ fp_priv->nr_pins++;
+
+ return 0;
+}
+
+static void store_mm_pins(struct proc_file_pins_private *priv)
+{
+ struct mm_file_pin *fp;
+ struct mm_file_pin *tmp;
+
+ list_for_each_entry_safe(fp, tmp, &priv->mm->file_pins, list) {
+ xa_store(&priv->fps, priv->nr_pins, fp, GFP_KERNEL);
+ priv->nr_pins++;
+ }
+}
+
+
+static void *fp_start(struct seq_file *m, loff_t *ppos)
+{
+ struct proc_file_pins_private *priv = m->private;
+ unsigned int pos = *ppos;
+
+ priv->task = get_proc_task(priv->inode);
+ if (!priv->task)
+ return ERR_PTR(-ESRCH);
+
+ if (!priv->mm || !mmget_not_zero(priv->mm))
+ return NULL;
+
+ priv->files = get_files_struct(priv->task);
+ down_read(&priv->mm->mmap_sem);
+
+ xa_destroy(&priv->fps);
+ priv->nr_pins = 0;
+
+ /* grab fds of "files" which have pins and store as xa values */
+ if (priv->files)
+ iterate_fd(priv->files, 0, store_fd, priv);
+
+ /* store mm_file_pins as xa entries */
+ store_mm_pins(priv);
+
+ if (pos >= priv->nr_pins) {
+ release_fp(priv);
+ return NULL;
+ }
+
+ return xa_load(&priv->fps, pos);
+}
+
+static void *fp_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct proc_file_pins_private *priv = m->private;
+
+ (*pos)++;
+ if ((*pos) >= priv->nr_pins) {
+ release_fp(priv);
+ return NULL;
+ }
+
+ return xa_load(&priv->fps, *pos);
+}
+
+static void fp_stop(struct seq_file *m, void *v)
+{
+ struct proc_file_pins_private *priv = m->private;
+
+ if (v)
+ release_fp(priv);
+
+ if (priv->task) {
+ put_task_struct(priv->task);
+ priv->task = NULL;
+ }
+
+ if (priv->files) {
+ put_files_struct(priv->files);
+ priv->files = NULL;
+ }
+}
+
+static int show_fp(struct seq_file *m, void *v)
+{
+ struct proc_file_pins_private *priv = m->private;
+
+ if (xa_is_value(v)) {
+ struct file *file;
+ unsigned long fd = xa_to_value(v);
+
+ rcu_read_lock();
+ file = fcheck_files(priv->files, fd);
+ if (file)
+ print_fd_file_pin(m, file, fd);
+ rcu_read_unlock();
+ } else {
+ struct mm_file_pin *fp = v;
+
+ seq_puts(m, "mm: ");
+ seq_file_path(m, fp->file, "\n");
+ }
+
+ return 0;
+}
+
+static const struct seq_operations proc_pid_file_pins_op = {
+ .start = fp_start,
+ .next = fp_next,
+ .stop = fp_stop,
+ .show = show_fp
+};
+
+static int proc_file_pins_open(struct inode *inode, struct file *file)
+{
+ struct proc_file_pins_private *priv = __seq_open_private(file,
+ &proc_pid_file_pins_op,
+ sizeof(*priv));
+
+ if (!priv)
+ return -ENOMEM;
+
+ xa_init(&priv->fps);
+ priv->inode = inode;
+ priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
+ priv->task = NULL;
+ if (IS_ERR(priv->mm)) {
+ int err = PTR_ERR(priv->mm);
+
+ seq_release_private(inode, file);
+ return err;
+ }
+
+ return 0;
+}
+
+static int proc_file_pins_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq = file->private_data;
+ struct proc_file_pins_private *priv = seq->private;
+
+ /* This is for "protection" not sure when these may end up not being
+ * NULL here... */
+ WARN_ON(priv->files);
+ WARN_ON(priv->task);
+
+ if (priv->mm)
+ mmdrop(priv->mm);
+
+ xa_destroy(&priv->fps);
+
+ return seq_release_private(inode, file);
+}
+
+static const struct file_operations proc_pid_file_pins_operations = {
+ .open = proc_file_pins_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = proc_file_pins_release,
+};
--
2.20.1