VFS: New /proc file /proc/self/mountstats
Create a new file under /proc/self, called mountstats, where mounted file
systems can export information (configuration options, performance counters,
and so on). Use a mechanism similar to /proc/mounts and s_ops->show_options.
This mechanism does not violate namespace security, and is safe to use while
other processes are unmounting file systems.
Thanks to Mike Waychison for his review and comments.
Test-plan:
Test concurrent mount/unmount operations while cat'ing /proc/self/mountstats.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/namespace.c b/fs/namespace.c
index 39c81a8..71e75bc 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -399,6 +399,44 @@
.show = show_vfsmnt
};
+static int show_vfsstat(struct seq_file *m, void *v)
+{
+ struct vfsmount *mnt = v;
+ int err = 0;
+
+ /* device */
+ if (mnt->mnt_devname) {
+ seq_puts(m, "device ");
+ mangle(m, mnt->mnt_devname);
+ } else
+ seq_puts(m, "no device");
+
+ /* mount point */
+ seq_puts(m, " mounted on ");
+ seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
+ seq_putc(m, ' ');
+
+ /* file system type */
+ seq_puts(m, "with fstype ");
+ mangle(m, mnt->mnt_sb->s_type->name);
+
+ /* optional statistics */
+ if (mnt->mnt_sb->s_op->show_stats) {
+ seq_putc(m, ' ');
+ err = mnt->mnt_sb->s_op->show_stats(m, mnt);
+ }
+
+ seq_putc(m, '\n');
+ return err;
+}
+
+struct seq_operations mountstats_op = {
+ .start = m_start,
+ .next = m_next,
+ .stop = m_stop,
+ .show = show_vfsstat,
+};
+
/**
* may_umount_tree - check if a mount tree is busy
* @mnt: root of mount tree
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 20feb75..8f1f49c 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -104,6 +104,7 @@
PROC_TGID_MAPS,
PROC_TGID_NUMA_MAPS,
PROC_TGID_MOUNTS,
+ PROC_TGID_MOUNTSTATS,
PROC_TGID_WCHAN,
#ifdef CONFIG_MMU
PROC_TGID_SMAPS,
@@ -144,6 +145,7 @@
PROC_TID_MAPS,
PROC_TID_NUMA_MAPS,
PROC_TID_MOUNTS,
+ PROC_TID_MOUNTSTATS,
PROC_TID_WCHAN,
#ifdef CONFIG_MMU
PROC_TID_SMAPS,
@@ -201,6 +203,7 @@
E(PROC_TGID_ROOT, "root", S_IFLNK|S_IRWXUGO),
E(PROC_TGID_EXE, "exe", S_IFLNK|S_IRWXUGO),
E(PROC_TGID_MOUNTS, "mounts", S_IFREG|S_IRUGO),
+ E(PROC_TGID_MOUNTSTATS, "mountstats", S_IFREG|S_IRUSR),
#ifdef CONFIG_MMU
E(PROC_TGID_SMAPS, "smaps", S_IFREG|S_IRUGO),
#endif
@@ -732,6 +735,38 @@
.poll = mounts_poll,
};
+extern struct seq_operations mountstats_op;
+static int mountstats_open(struct inode *inode, struct file *file)
+{
+ struct task_struct *task = proc_task(inode);
+ int ret = seq_open(file, &mountstats_op);
+
+ if (!ret) {
+ struct seq_file *m = file->private_data;
+ struct namespace *namespace;
+ task_lock(task);
+ namespace = task->namespace;
+ if (namespace)
+ get_namespace(namespace);
+ task_unlock(task);
+
+ if (namespace)
+ m->private = namespace;
+ else {
+ seq_release(inode, file);
+ ret = -EINVAL;
+ }
+ }
+ return ret;
+}
+
+static struct file_operations proc_mountstats_operations = {
+ .open = mountstats_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = mounts_release,
+};
+
#define PROC_BLOCK_SIZE (3*1024) /* 4K page size but our output routines use some slack for overruns */
static ssize_t proc_info_read(struct file * file, char __user * buf,
@@ -1730,6 +1765,10 @@
inode->i_fop = &proc_smaps_operations;
break;
#endif
+ case PROC_TID_MOUNTSTATS:
+ case PROC_TGID_MOUNTSTATS:
+ inode->i_fop = &proc_mountstats_operations;
+ break;
#ifdef CONFIG_SECURITY
case PROC_TID_ATTR:
inode->i_nlink = 2;