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/* -*- c -*- --------------------------------------------------------------- *
*
* linux/fs/autofs/expire.c
*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
*
* 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"
/*
* Determine if a subtree of the namespace is busy.
*
* mnt is the mount tree under the autofs mountpoint
*/
static inline int is_vfsmnt_tree_busy(struct vfsmount *mnt)
{
struct vfsmount *this_parent = mnt;
struct list_head *next;
int count;
count = atomic_read(&mnt->mnt_count) - 1;
repeat:
next = this_parent->mnt_mounts.next;
DPRINTK(("is_vfsmnt_tree_busy: mnt=%p, this_parent=%p, next=%p\n",
mnt, this_parent, next));
resume:
for( ; next != &this_parent->mnt_mounts; next = next->next) {
struct vfsmount *p = list_entry(next, struct vfsmount,
mnt_child);
/* -1 for struct vfs_mount's normal count,
-1 to compensate for child's reference to parent */
count += atomic_read(&p->mnt_count) - 1 - 1;
DPRINTK(("is_vfsmnt_tree_busy: p=%p, count now %d\n",
p, count));
if (!list_empty(&p->mnt_mounts)) {
this_parent = p;
goto repeat;
}
/* root is busy if any leaf is busy */
if (atomic_read(&p->mnt_count) > 1)
return 1;
}
/* All done at this level ... ascend and resume the search. */
if (this_parent != mnt) {
next = this_parent->mnt_child.next;
this_parent = this_parent->mnt_parent;
goto resume;
}
DPRINTK(("is_vfsmnt_tree_busy: count=%d\n", count));
return count != 0; /* remaining users? */
}
/* Traverse a dentry's list of vfsmounts and return the number of
non-busy mounts */
static int check_vfsmnt(struct vfsmount *mnt, struct dentry *dentry)
{
int ret = dentry->d_mounted;
struct vfsmount *vfs = lookup_mnt(mnt, dentry);
if (vfs && is_vfsmnt_tree_busy(vfs))
ret--;
DPRINTK(("check_vfsmnt: ret=%d\n", ret));
return ret;
}
/* Check dentry tree for busyness. If a dentry appears to be busy
because it is a mountpoint, check to see if the mounted
filesystem is busy. */
static int is_tree_busy(struct vfsmount *topmnt, struct dentry *top)
{
struct dentry *this_parent;
struct list_head *next;
int count;
count = atomic_read(&top->d_count);
DPRINTK(("is_tree_busy: top=%p initial count=%d\n",
top, count));
this_parent = top;
if (is_autofs4_dentry(top)) {
count--;
DPRINTK(("is_tree_busy: autofs; count=%d\n", count));
}
if (d_mountpoint(top))
count -= check_vfsmnt(topmnt, top);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
int adj = 0;
struct dentry *dentry = list_entry(next, struct dentry,
d_child);
next = next->next;
count += atomic_read(&dentry->d_count) - 1;
if (d_mountpoint(dentry))
adj += check_vfsmnt(topmnt, dentry);
if (is_autofs4_dentry(dentry)) {
adj++;
DPRINTK(("is_tree_busy: autofs; adj=%d\n",
adj));
}
count -= adj;
if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
goto repeat;
}
if (atomic_read(&dentry->d_count) != adj) {
DPRINTK(("is_tree_busy: busy leaf (d_count=%d adj=%d)\n",
atomic_read(&dentry->d_count), adj));
return 1;
}
}
/* All done at this level ... ascend and resume the search. */
if (this_parent != top) {
next = this_parent->d_child.next;
this_parent = this_parent->d_parent;
goto resume;
}
DPRINTK(("is_tree_busy: count=%d\n", count));
return count != 0; /* remaining users? */
}
/*
* 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
*/
static struct dentry *autofs4_expire(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi,
int do_now)
{
unsigned long now = jiffies;
unsigned long timeout;
struct dentry *root = sb->s_root;
struct list_head *tmp;
if (!sbi->exp_timeout || !root)
return NULL;
timeout = sbi->exp_timeout;
spin_lock(&dcache_lock);
for(tmp = root->d_subdirs.next;
tmp != &root->d_subdirs;
tmp = tmp->next) {
struct autofs_info *ino;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
if (dentry->d_inode == NULL)
continue;
ino = autofs4_dentry_ino(dentry);
if (ino == NULL) {
/* dentry in the process of being deleted */
continue;
}
/* No point expiring a pending mount */
if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
continue;
if (!do_now) {
/* Too young to die */
if (time_after(ino->last_used + timeout, now))
continue;
/* update last_used here :-
- obviously makes sense if it is in use now
- less obviously, prevents rapid-fire expire
attempts if expire fails the first time */
ino->last_used = now;
}
if (!is_tree_busy(mnt, dentry)) {
DPRINTK(("autofs_expire: returning %p %.*s\n",
dentry, (int)dentry->d_name.len, dentry->d_name.name));
/* Start from here next time */
list_del(&root->d_subdirs);
list_add(&root->d_subdirs, &dentry->d_child);
dget(dentry);
spin_unlock(&dcache_lock);
return dentry;
}
}
spin_unlock(&dcache_lock);
return NULL;
}
/* Perform an expiry operation */
int autofs4_expire_run(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi,
struct autofs_packet_expire *pkt_p)
{
struct autofs_packet_expire pkt;
struct dentry *dentry;
memset(&pkt,0,sizeof pkt);
pkt.hdr.proto_version = sbi->version;
pkt.hdr.type = autofs_ptype_expire;
if ((dentry = autofs4_expire(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)) )
return -EFAULT;
return 0;
}
/* 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 *arg)
{
struct dentry *dentry;
int ret = -EAGAIN;
int do_now = 0;
if (arg && get_user(do_now, arg))
return -EFAULT;
if ((dentry = autofs4_expire(sb, mnt, sbi, do_now)) != NULL) {
struct autofs_info *de_info = autofs4_dentry_ino(dentry);
/* This is synchronous because it makes the daemon a
little easier */
de_info->flags |= AUTOFS_INF_EXPIRING;
ret = autofs4_wait(sbi, &dentry->d_name, NFY_EXPIRE);
de_info->flags &= ~AUTOFS_INF_EXPIRING;
dput(dentry);
}
return ret;
}
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