Commit 5addc5dd authored by Al Viro's avatar Al Viro Committed by Linus Torvalds
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[PATCH] make /proc/mounts pollable


Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 1abe77b0
......@@ -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 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;
......
......@@ -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);
struct namespace *namespace;
struct proc_mounts *p;
int ret = -EINVAL;
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;
task_lock(task);
namespace = task->namespace;
if (namespace)
get_namespace(namespace);
task_unlock(task);
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 (3*1024) /* 4K page size but our output routines use some slack for overruns */
......
......@@ -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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