Commit b4629fe2 authored by Chuck Lever's avatar Chuck Lever Committed by Trond Myklebust
Browse files

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: default avatarChuck Lever <cel@netapp.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 1356b8c2

fs/namespace.c

+38 −0
Original line number Diff line number Diff line
@@ -399,6 +399,44 @@ struct seq_operations mounts_op = { 
	.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

fs/proc/base.c

+39 −0
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ enum pid_directory_inos { 
	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 @@ enum pid_directory_inos { 
	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 @@ static struct pid_entry tgid_base_stuff[] = { 
	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 @@ static struct file_operations proc_mounts_operations = { 
	.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 @@ static struct dentry *proc_pident_lookup(struct inode *dir, 
			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;

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -1086,6 +1086,7 @@ struct super_operations { 
	void (*umount_begin) (struct super_block *);



	int (*show_options)(struct seq_file *, struct vfsmount *);

	int (*show_stats)(struct seq_file *, struct vfsmount *);



	ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);

	ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);