[PATCH] make /proc/mounts pollable (5addc5dd) · Commits · 戴 / test

fs/namespace.c

+29 −1

Original line number	Diff line number	Diff line
		@@ -39,6 +39,8 @@ static inline int sysfs_init(void)
		/* spinlock for vfsmount related operations, inplace of dcache_lock */
		__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);

		static int event;

		static struct list_head *mount_hashtable;
		static int hash_mask __read_mostly, hash_bits __read_mostly;
		static kmem_cache_t *mnt_cache;
		@@ -111,6 +113,22 @@ static inline int check_mnt(struct vfsmount *mnt)
		return mnt->mnt_namespace == current->namespace;
		}

		static void touch_namespace(struct namespace *ns)
		{
		if (ns) {
		ns->event = ++event;
		wake_up_interruptible(&ns->poll);
		}
		}

		static void __touch_namespace(struct namespace *ns)
		{
		if (ns && ns->event != event) {
		ns->event = event;
		wake_up_interruptible(&ns->poll);
		}
		}

		static void detach_mnt(struct vfsmount mnt, struct nameidata old_nd)
		{
		old_nd->dentry = mnt->mnt_mountpoint;
		@@ -384,6 +402,7 @@ static void umount_tree(struct vfsmount *mnt)
		for (p = mnt; p; p = next_mnt(p, mnt)) {
		list_del(&p->mnt_list);
		list_add(&p->mnt_list, &kill);
		__touch_namespace(p->mnt_namespace);
		p->mnt_namespace = NULL;
		}

		@@ -473,6 +492,7 @@ static int do_umount(struct vfsmount *mnt, int flags)

		down_write(&current->namespace->sem);
		spin_lock(&vfsmount_lock);
		event++;

		retval = -EBUSY;
		if (atomic_read(&mnt->mnt_count) == 2 \|\| flags & MNT_DETACH) {
		@@ -634,6 +654,7 @@ static int graft_tree(struct vfsmount mnt, struct nameidata nd)
		list_splice(&head, current->namespace->list.prev);
		mntget(mnt);
		err = 0;
		touch_namespace(current->namespace);
		}
		spin_unlock(&vfsmount_lock);
		out_unlock:
		@@ -771,6 +792,7 @@ static int do_move_mount(struct nameidata nd, char old_name)

		detach_mnt(old_nd.mnt, &parent_nd);
		attach_mnt(old_nd.mnt, nd);
		touch_namespace(current->namespace);

		/* if the mount is moved, it should no longer be expire
		* automatically */
		@@ -877,6 +899,7 @@ static void expire_mount(struct vfsmount mnt, struct list_head mounts)
		struct nameidata old_nd;

		/* delete from the namespace */
		touch_namespace(mnt->mnt_namespace);
		list_del_init(&mnt->mnt_list);
		mnt->mnt_namespace = NULL;
		detach_mnt(mnt, &old_nd);
		@@ -1114,6 +1137,8 @@ int copy_namespace(int flags, struct task_struct *tsk)
		atomic_set(&new_ns->count, 1);
		init_rwsem(&new_ns->sem);
		INIT_LIST_HEAD(&new_ns->list);
		init_waitqueue_head(&new_ns->poll);
		new_ns->event = 0;

		down_write(&tsk->namespace->sem);
		/* First pass: copy the tree topology */
		@@ -1377,6 +1402,7 @@ asmlinkage long sys_pivot_root(const char __user new_root, const char __user p
		detach_mnt(user_nd.mnt, &root_parent);
		attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */
		attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
		touch_namespace(current->namespace);
		spin_unlock(&vfsmount_lock);
		chroot_fs_refs(&user_nd, &new_nd);
		security_sb_post_pivotroot(&user_nd, &new_nd);
		@@ -1413,6 +1439,8 @@ static void __init init_mount_tree(void)
		atomic_set(&namespace->count, 1);
		INIT_LIST_HEAD(&namespace->list);
		init_rwsem(&namespace->sem);
		init_waitqueue_head(&namespace->poll);
		namespace->event = 0;
		list_add(&mnt->mnt_list, &namespace->list);
		namespace->root = mnt;
		mnt->mnt_namespace = namespace;

fs/proc/base.c

+47 −15

Original line number	Diff line number	Diff line
		@@ -70,6 +70,7 @@
		#include <linux/seccomp.h>
		#include <linux/cpuset.h>
		#include <linux/audit.h>
		#include <linux/poll.h>
		#include "internal.h"

		/*
		@@ -660,26 +661,38 @@ static struct file_operations proc_smaps_operations = {
		#endif

		extern struct seq_operations mounts_op;
		struct proc_mounts {
		struct seq_file m;
		int event;
		};

		static int mounts_open(struct inode inode, struct file file)
		{
		struct task_struct *task = proc_task(inode);
		int ret = seq_open(file, &mounts_op);

		if (!ret) {
		struct seq_file *m = file->private_data;
		struct namespace *namespace;
		struct proc_mounts *p;
		int ret = -EINVAL;

		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;
		if (namespace) {
		ret = -ENOMEM;
		p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL);
		if (p) {
		file->private_data = &p->m;
		ret = seq_open(file, &mounts_op);
		if (!ret) {
		p->m.private = namespace;
		p->event = namespace->event;
		return 0;
		}
		kfree(p);
		}
		put_namespace(namespace);
		}
		return ret;
		}
		@@ -692,11 +705,30 @@ static int mounts_release(struct inode inode, struct file file)
		return seq_release(inode, file);
		}

		static unsigned mounts_poll(struct file file, poll_table wait)
		{
		struct proc_mounts *p = file->private_data;
		struct namespace *ns = p->m.private;
		unsigned res = 0;

		poll_wait(file, &ns->poll, wait);

		spin_lock(&vfsmount_lock);
		if (p->event != ns->event) {
		p->event = ns->event;
		res = POLLERR;
		}
		spin_unlock(&vfsmount_lock);

		return res;
		}

		static struct file_operations proc_mounts_operations = {
		.open = mounts_open,
		.read = seq_read,
		.llseek = seq_lseek,
		.release = mounts_release,
		.poll = mounts_poll,
		};

		#define PROC_BLOCK_SIZE (31024) / 4K page size but our output routines use some slack for overruns */

include/linux/namespace.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -10,6 +10,8 @@ struct namespace {
		struct vfsmount * root;
		struct list_head list;
		struct rw_semaphore sem;
		wait_queue_head_t poll;
		int event;
		};

		extern int copy_namespace(int, struct task_struct *);

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