- 根目录:
- fs
- autofs4
- expire.c
/* -*- c -*- --------------------------------------------------------------- *
*
* linux/fs/autofs/expire.c
*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
* Copyright 2001-2006 Ian Kent <raven@themaw.net>
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ------------------------------------------------------------------------- */
#include "autofs_i.h"
static unsigned long now;
/* Check if a dentry can be expired */
static inline int autofs4_can_expire(struct dentry *dentry,
unsigned long timeout, int do_now)
{
struct autofs_info *ino = autofs4_dentry_ino(dentry);
/* dentry in the process of being deleted */
if (ino == NULL)
return 0;
if (!do_now) {
/* Too young to die */
if (!timeout || time_after(ino->last_used + timeout, now))
return 0;
}
return 1;
}
/* Check a mount point for busyness */
static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
{
struct dentry *top = dentry;
struct path path = {.mnt = mnt, .dentry = dentry};
int status = 1;
DPRINTK("dentry %p %pd", dentry, dentry);
path_get(&path);
if (!follow_down_one(&path))
goto done;
if (is_autofs4_dentry(path.dentry)) {
struct autofs_sb_info *sbi = autofs4_sbi(path.dentry->d_sb);
/* This is an autofs submount, we can't expire it */
if (autofs_type_indirect(sbi->type))
goto done;
}
/* Update the expiry counter if fs is busy */
if (!may_umount_tree(path.mnt)) {
struct autofs_info *ino = autofs4_dentry_ino(top);
ino->last_used = jiffies;
goto done;
}
status = 0;
done:
DPRINTK("returning = %d", status);
path_put(&path);
return status;
}
/*
* Calculate and dget next entry in the subdirs list under root.
*/
static struct dentry *get_next_positive_subdir(struct dentry *prev,
struct dentry *root)
{
struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
struct list_head *next;
struct dentry *q;
spin_lock(&sbi->lookup_lock);
spin_lock(&root->d_lock);
if (prev)
next = prev->d_child.next;
else {
prev = dget_dlock(root);
next = prev->d_subdirs.next;
}
cont:
if (next == &root->d_subdirs) {
spin_unlock(&root->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return NULL;
}
q = list_entry(next, struct dentry, d_child);
spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
/* Already gone or negative dentry (under construction) - try next */
if (!d_count(q) || !simple_positive(q)) {
spin_unlock(&q->d_lock);
next = q->d_child.next;
goto cont;
}
dget_dlock(q);
spin_unlock(&q->d_lock);
spin_unlock(&root->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return q;
}
/*
* Calculate and dget next entry in top down tree traversal.
*/
static struct dentry *get_next_positive_dentry(struct dentry *prev,
struct dentry *root)
{
struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
struct list_head *next;
struct dentry *p, *ret;
if (prev == NULL)
return dget(root);
spin_lock(&sbi->lookup_lock);
relock:
p = prev;
spin_lock(&p->d_lock);
again:
next = p->d_subdirs.next;
if (next == &p->d_subdirs) {
while (1) {
struct dentry *parent;
if (p == root) {
spin_unlock(&p->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return NULL;
}
parent = p->d_parent;
if (!spin_trylock(&parent->d_lock)) {
spin_unlock(&p->d_lock);
cpu_relax();
goto relock;
}
spin_unlock(&p->d_lock);
next = p->d_child.next;
p = parent;
if (next != &parent->d_subdirs)
break;
}
}
ret = list_entry(next, struct dentry, d_child);
spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
/* Negative dentry - try next */
if (!simple_positive(ret)) {
spin_unlock(&p->d_lock);
lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
p = ret;
goto again;
}
dget_dlock(ret);
spin_unlock(&ret->d_lock);
spin_unlock(&p->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return ret;
}
/*
* Check a direct mount point for busyness.
* Direct mounts have similar expiry semantics to tree mounts.
* The tree is not busy iff no mountpoints are busy and there are no
* autofs submounts.
*/
static int autofs4_direct_busy(struct vfsmount *mnt,
struct dentry *top,
unsigned long timeout,
int do_now)
{
DPRINTK("top %p %pd", top, top);
/* If it's busy update the expiry counters */
if (!may_umount_tree(mnt)) {
struct autofs_info *ino = autofs4_dentry_ino(top);
if (ino)
ino->last_used = jiffies;
return 1;
}
/* Timeout of a direct mount is determined by its top dentry */
if (!autofs4_can_expire(top, timeout, do_now))
return 1;
return 0;
}
/* Check a directory tree of mount points for busyness
* The tree is not busy iff no mountpoints are busy
*/
static int autofs4_tree_busy(struct vfsmount *mnt,
struct dentry *top,
unsigned long timeout,
int do_now)
{
struct autofs_info *top_ino = autofs4_dentry_ino(top);
struct dentry *p;
DPRINTK("top %p %pd", top, top);
/* Negative dentry - give up */
if (!simple_positive(top))
return 1;
p = NULL;
while ((p = get_next_positive_dentry(p, top))) {
DPRINTK("dentry %p %pd", p, p);
/*
* Is someone visiting anywhere in the subtree ?
* If there's no mount we need to check the usage
* count for the autofs dentry.
* If the fs is busy update the expiry counter.
*/
if (d_mountpoint(p)) {
if (autofs4_mount_busy(mnt, p)) {
top_ino->last_used = jiffies;
dput(p);
return 1;
}
} else {
struct autofs_info *ino = autofs4_dentry_ino(p);
unsigned int ino_count = atomic_read(&ino->count);
/* allow for dget above and top is already dgot */
if (p == top)
ino_count += 2;
else
ino_count++;
if (d_count(p) > ino_count) {
top_ino->last_used = jiffies;
dput(p);
return 1;
}
}
}
/* Timeout of a tree mount is ultimately determined by its top dentry */
if (!autofs4_can_expire(top, timeout, do_now))
return 1;
return 0;
}
static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
struct dentry *parent,
unsigned long timeout,
int do_now)
{
struct dentry *p;
DPRINTK("parent %p %pd", parent, parent);
p = NULL;
while ((p = get_next_positive_dentry(p, parent))) {
DPRINTK("dentry %p %pd", p, p);
if (d_mountpoint(p)) {
/* Can we umount this guy */
if (autofs4_mount_busy(mnt, p))
continue;
/* Can we expire this guy */
if (autofs4_can_expire(p, timeout, do_now))
return p;
}
}
return NULL;
}
/* Check if we can expire a direct mount (possibly a tree) */
struct dentry *autofs4_expire_direct(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi,
int how)
{
unsigned long timeout;
struct dentry *root = dget(sb->s_root);
int do_now = how & AUTOFS_EXP_IMMEDIATE;
struct autofs_info *ino;
if (!root)
return NULL;
now = jiffies;
timeout = sbi->exp_timeout;
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(root);
/* No point expiring a pending mount */
if (ino->flags & AUTOFS_INF_PENDING)
goto out;
if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
ino->flags |= AUTOFS_INF_NO_RCU;
spin_unlock(&sbi->fs_lock);
synchronize_rcu();
spin_lock(&sbi->fs_lock);
if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
ino->flags |= AUTOFS_INF_EXPIRING;
smp_mb();
ino->flags &= ~AUTOFS_INF_NO_RCU;
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
return root;
}
ino->flags &= ~AUTOFS_INF_NO_RCU;
}
out:
spin_unlock(&sbi->fs_lock);
dput(root);
return NULL;
}
/* Check if 'dentry' should expire, or return a nearby
* dentry that is suitable.
* If returned dentry is different from arg dentry,
* then a dget() reference was taken, else not.
*/
static struct dentry *should_expire(struct dentry *dentry,
struct vfsmount *mnt,
unsigned long timeout,
int how)
{
int do_now = how & AUTOFS_EXP_IMMEDIATE;
int exp_leaves = how & AUTOFS_EXP_LEAVES;
struct autofs_info *ino = autofs4_dentry_ino(dentry);
unsigned int ino_count;
/* No point expiring a pending mount */
if (ino->flags & AUTOFS_INF_PENDING)
return NULL;
/*
* Case 1: (i) indirect mount or top level pseudo direct mount
* (autofs-4.1).
* (ii) indirect mount with offset mount, check the "/"
* offset (autofs-5.0+).
*/
if (d_mountpoint(dentry)) {
DPRINTK("checking mountpoint %p %pd", dentry, dentry);
/* Can we umount this guy */
if (autofs4_mount_busy(mnt, dentry))
return NULL;
/* Can we expire this guy */
if (autofs4_can_expire(dentry, timeout, do_now))
return dentry;
return NULL;
}
if (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
DPRINTK("checking symlink %p %pd", dentry, dentry);
/*
* A symlink can't be "busy" in the usual sense so
* just check last used for expire timeout.
*/
if (autofs4_can_expire(dentry, timeout, do_now))
return dentry;
return NULL;
}
if (simple_empty(dentry))
return NULL;
/* Case 2: tree mount, expire iff entire tree is not busy */
if (!exp_leaves) {
/* Path walk currently on this dentry? */
ino_count = atomic_read(&ino->count) + 1;
if (d_count(dentry) > ino_count)
return NULL;
if (!autofs4_tree_busy(mnt, dentry, timeout, do_now))
return dentry;
/*
* Case 3: pseudo direct mount, expire individual leaves
* (autofs-4.1).
*/
} else {
/* Path walk currently on this dentry? */
struct dentry *expired;
ino_count = atomic_read(&ino->count) + 1;
if (d_count(dentry) > ino_count)
return NULL;
expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
if (expired) {
if (expired == dentry)
dput(dentry);
return expired;
}
}
return NULL;
}
/*
* Find an eligible tree to time-out
* A tree is eligible if :-
* - it is unused by any user process
* - it has been unused for exp_timeout time
*/
struct dentry *autofs4_expire_indirect(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi,
int how)
{
unsigned long timeout;
struct dentry *root = sb->s_root;
struct dentry *dentry;
struct dentry *expired;
struct autofs_info *ino;
if (!root)
return NULL;
now = jiffies;
timeout = sbi->exp_timeout;
dentry = NULL;
while ((dentry = get_next_positive_subdir(dentry, root))) {
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
if (ino->flags & AUTOFS_INF_NO_RCU)
expired = NULL;
else
expired = should_expire(dentry, mnt, timeout, how);
if (!expired) {
spin_unlock(&sbi->fs_lock);
continue;
}
ino = autofs4_dentry_ino(expired);
ino->flags |= AUTOFS_INF_NO_RCU;
spin_unlock(&sbi->fs_lock);
synchronize_rcu();
spin_lock(&sbi->fs_lock);
if (should_expire(expired, mnt, timeout, how)) {
if (expired != dentry)
dput(dentry);
goto found;
}
ino->flags &= ~AUTOFS_INF_NO_RCU;
if (expired != dentry)
dput(expired);
spin_unlock(&sbi->fs_lock);
}
return NULL;
found:
DPRINTK("returning %p %pd", expired, expired);
ino->flags |= AUTOFS_INF_EXPIRING;
smp_mb();
ino->flags &= ~AUTOFS_INF_NO_RCU;
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
spin_lock(&sbi->lookup_lock);
spin_lock(&expired->d_parent->d_lock);
spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
list_move(&expired->d_parent->d_subdirs, &expired->d_child);
spin_unlock(&expired->d_lock);
spin_unlock(&expired->d_parent->d_lock);
spin_unlock(&sbi->lookup_lock);
return expired;
}
int autofs4_expire_wait(struct dentry *dentry, int rcu_walk)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
int status;
/* Block on any pending expire */
if (!(ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU)))
return 0;
if (rcu_walk)
return -ECHILD;
spin_lock(&sbi->fs_lock);
if (ino->flags & AUTOFS_INF_EXPIRING) {
spin_unlock(&sbi->fs_lock);
DPRINTK("waiting for expire %p name=%pd", dentry, dentry);
status = autofs4_wait(sbi, dentry, NFY_NONE);
wait_for_completion(&ino->expire_complete);
DPRINTK("expire done status=%d", status);
if (d_unhashed(dentry))
return -EAGAIN;
return status;
}
spin_unlock(&sbi->fs_lock);
return 0;
}
/* Perform an expiry operation */
int autofs4_expire_run(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi,
struct autofs_packet_expire __user *pkt_p)
{
struct autofs_packet_expire pkt;
struct autofs_info *ino;
struct dentry *dentry;
int ret = 0;
memset(&pkt,0,sizeof pkt);
pkt.hdr.proto_version = sbi->version;
pkt.hdr.type = autofs_ptype_expire;
if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
return -EAGAIN;
pkt.len = dentry->d_name.len;
memcpy(pkt.name, dentry->d_name.name, pkt.len);
pkt.name[pkt.len] = '\0';
dput(dentry);
if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
ret = -EFAULT;
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
/* avoid rapid-fire expire attempts if expiry fails */
ino->last_used = now;
ino->flags &= ~AUTOFS_INF_EXPIRING;
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
return ret;
}
int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
struct autofs_sb_info *sbi, int when)
{
struct dentry *dentry;
int ret = -EAGAIN;
if (autofs_type_trigger(sbi->type))
dentry = autofs4_expire_direct(sb, mnt, sbi, when);
else
dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
if (dentry) {
struct autofs_info *ino = autofs4_dentry_ino(dentry);
/* This is synchronous because it makes the daemon a
little easier */
ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
spin_lock(&sbi->fs_lock);
/* avoid rapid-fire expire attempts if expiry fails */
ino->last_used = now;
ino->flags &= ~AUTOFS_INF_EXPIRING;
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
dput(dentry);
}
return ret;
}
/* Call repeatedly until it returns -EAGAIN, meaning there's nothing
more to be done */
int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
struct autofs_sb_info *sbi, int __user *arg)
{
int do_now = 0;
if (arg && get_user(do_now, arg))
return -EFAULT;
return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
}