make /proc/mounts pollable

@@ -37,7 +37,9 @@ static inline int sysfs_init(void)
 #endif
 
 /* spinlock for vfsmount related operations, inplace of dcache_lock */
- __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_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;

@@ -111,6 +113,22 @@ static inline int check_mnt(struct vfsmo
 	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 
 	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 *mn
 
 	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 *m
 		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 nameidat
 
 	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
 		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 tas
 	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 cha
 	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;

90 lines not on this page · raw message

@@ -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 *);

diff ./fs/sysfs/dir.c~current~ ./fs/sysfs/dir.c
@@ -45,6 +45,7 @@ static struct sysfs_dirent * sysfs_new_d
 	atomic_set(&sd->s_count, 1);
 	INIT_LIST_HEAD(&sd->s_children);
 	list_add(&sd->s_sibling, &parent_sd->s_children);
+	init_waitqueue_head(&sd->s_poll);
 	sd->s_element = element;
 
 	return sd;

diff ./fs/sysfs/file.c~current~ ./fs/sysfs/file.c
@@ -7,6 +7,7 @@
 #include <linux/kobject.h>
 #include <linux/namei.h>
 #include <linux/limits.h>
+#include <linux/poll.h>
 
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>

@@ -59,6 +60,7 @@ struct sysfs_buffer {
 	struct sysfs_ops	* ops;
 	struct semaphore	sem;
 	int			needs_read_fill;
+	int			event;
 };
 
 

@@ -305,10 +307,12 @@ static int check_perm(struct inode * ino
 	 */
 	buffer = kmalloc(sizeof(struct sysfs_buffer),GFP_KERNEL);
 	if (buffer) {
+		struct sysfs_dirent * sd = file->f_dentry->d_fsdata;
 		memset(buffer,0,sizeof(struct sysfs_buffer));
 		init_MUTEX(&buffer->sem);
 		buffer->needs_read_fill = 1;
 		buffer->ops = ops;
+		buffer->event = sd->s_event;
 		file->private_data = buffer;
 	} else
 		error = -ENOMEM;

@@ -357,12 +361,42 @@ static int sysfs_release(struct inode * 
 	return 0;
 }
 
+static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
+{
+	struct sysfs_buffer * buffer = filp->private_data;
+	struct sysfs_dirent * sd = filp->f_dentry->d_fsdata;
+	int res = 0;
+
+	poll_wait(filp, &sd->s_poll, wait);
+
+	if (buffer->event != sd->s_event) {
+		sd->s_event = buffer->event;
+		res = POLLERR;
+	}
+	return res;
+}
+
+void sysfs_notify(struct kobject * k, char *dir, char *attr)
+{
+	struct sysfs_dirent *sd = k->dentry->d_fsdata;
+	if (sd && dir)
+		sd = sysfs_find(sd, dir);
+	if (sd && attr)
+		sd = sysfs_find(sd, attr);
+	if (sd) {
+		sd->s_event++;
+		wake_up_interruptible(&sd->s_poll);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_notify);
+
 struct file_operations sysfs_file_operations = {
 	.read		= sysfs_read_file,
 	.write		= sysfs_write_file,
 	.llseek		= generic_file_llseek,
 	.open		= sysfs_open_file,
 	.release	= sysfs_release,
+	.poll		= sysfs_poll,
 };
 
 

diff ./fs/sysfs/inode.c~current~ ./fs/sysfs/inode.c
@@ -247,3 +247,23 @@ void sysfs_hash_and_remove(struct dentry
 }
 
 
+struct sysfs_dirent *sysfs_find(struct sysfs_dirent *dir, const char * name)
+{
+	struct sysfs_dirent * sd, * rv = NULL;
+
+	if (dir->s_dentry == NULL ||
+	    dir->s_dentry->d_inode == NULL)
+		return NULL;
+
+	down(&dir->s_dentry->d_inode->i_sem);
+	list_for_each_entry(sd, &dir->s_children, s_sibling) {
+		if (!sd->s_element)
+			continue;
+		if (!strcmp(sysfs_get_name(sd), name)) {
+			rv = sd;
+			break;
+		}
+	}
+	up(&dir->s_dentry->d_inode->i_sem);
+	return rv;
+}

diff ./fs/sysfs/sysfs.h~current~ ./fs/sysfs/sysfs.h
@@ -10,6 +10,7 @@ extern int sysfs_make_dirent(struct sysf
 
 extern int sysfs_add_file(struct dentry *, const struct attribute *, int);
 extern void sysfs_hash_and_remove(struct dentry * dir, const char * name);
+extern struct sysfs_dirent *sysfs_find(struct sysfs_dirent *dir, const char * name);
 
 extern int sysfs_create_subdir(struct kobject *, const char *, struct dentry **);
 extern void sysfs_remove_subdir(struct dentry *);

diff ./include/linux/sysfs.h~current~ ./include/linux/sysfs.h
@@ -11,6 +11,7 @@
 #define _SYSFS_H_
 
 #include <asm/atomic.h>
+#include <linux/wait.h>
 
 struct kobject;
 struct module;

@@ -74,6 +75,8 @@ struct sysfs_dirent {
 	umode_t			s_mode;
 	struct dentry		* s_dentry;
 	struct iattr		* s_iattr;
+	int			s_event;
+	wait_queue_head_t	s_poll;
 };
 
 #define SYSFS_ROOT		0x0001