linux/fs/autofs4/waitq.c
Linus Torvalds 554828ee0d Merge branch 'salted-string-hash'
This changes the vfs dentry hashing to mix in the parent pointer at the
_beginning_ of the hash, rather than at the end.

That actually improves both the hash and the code generation, because we
can move more of the computation to the "static" part of the dcache
setup, and do less at lookup runtime.

It turns out that a lot of other hash users also really wanted to mix in
a base pointer as a 'salt' for the hash, and so the slightly extended
interface ends up working well for other cases too.

Users that want a string hash that is purely about the string pass in a
'salt' pointer of NULL.

* merge branch 'salted-string-hash':
  fs/dcache.c: Save one 32-bit multiply in dcache lookup
  vfs: make the string hashes salt the hash
2016-07-28 12:26:31 -07:00

573 lines
14 KiB
C

/*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* 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 <linux/slab.h>
#include <linux/time.h>
#include <linux/signal.h>
#include <linux/file.h>
#include "autofs_i.h"
/* We make this a static variable rather than a part of the superblock; it
* is better if we don't reassign numbers easily even across filesystems
*/
static autofs_wqt_t autofs4_next_wait_queue = 1;
/* These are the signals we allow interrupting a pending mount */
#define SHUTDOWN_SIGS (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
{
struct autofs_wait_queue *wq, *nwq;
mutex_lock(&sbi->wq_mutex);
if (sbi->catatonic) {
mutex_unlock(&sbi->wq_mutex);
return;
}
pr_debug("entering catatonic mode\n");
sbi->catatonic = 1;
wq = sbi->queues;
sbi->queues = NULL; /* Erase all wait queues */
while (wq) {
nwq = wq->next;
wq->status = -ENOENT; /* Magic is gone - report failure */
kfree(wq->name.name);
wq->name.name = NULL;
wq->wait_ctr--;
wake_up_interruptible(&wq->queue);
wq = nwq;
}
fput(sbi->pipe); /* Close the pipe */
sbi->pipe = NULL;
sbi->pipefd = -1;
mutex_unlock(&sbi->wq_mutex);
}
static int autofs4_write(struct autofs_sb_info *sbi,
struct file *file, const void *addr, int bytes)
{
unsigned long sigpipe, flags;
mm_segment_t fs;
const char *data = (const char *)addr;
ssize_t wr = 0;
sigpipe = sigismember(&current->pending.signal, SIGPIPE);
/* Save pointer to user space and point back to kernel space */
fs = get_fs();
set_fs(KERNEL_DS);
mutex_lock(&sbi->pipe_mutex);
while (bytes) {
wr = __vfs_write(file, data, bytes, &file->f_pos);
if (wr <= 0)
break;
data += wr;
bytes -= wr;
}
mutex_unlock(&sbi->pipe_mutex);
set_fs(fs);
/* Keep the currently executing process from receiving a
* SIGPIPE unless it was already supposed to get one
*/
if (wr == -EPIPE && !sigpipe) {
spin_lock_irqsave(&current->sighand->siglock, flags);
sigdelset(&current->pending.signal, SIGPIPE);
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, flags);
}
return (bytes > 0);
}
static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
struct autofs_wait_queue *wq,
int type)
{
union {
struct autofs_packet_hdr hdr;
union autofs_packet_union v4_pkt;
union autofs_v5_packet_union v5_pkt;
} pkt;
struct file *pipe = NULL;
size_t pktsz;
pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
(unsigned long) wq->wait_queue_token,
wq->name.len, wq->name.name, type);
memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
pkt.hdr.proto_version = sbi->version;
pkt.hdr.type = type;
switch (type) {
/* Kernel protocol v4 missing and expire packets */
case autofs_ptype_missing:
{
struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
pktsz = sizeof(*mp);
mp->wait_queue_token = wq->wait_queue_token;
mp->len = wq->name.len;
memcpy(mp->name, wq->name.name, wq->name.len);
mp->name[wq->name.len] = '\0';
break;
}
case autofs_ptype_expire_multi:
{
struct autofs_packet_expire_multi *ep =
&pkt.v4_pkt.expire_multi;
pktsz = sizeof(*ep);
ep->wait_queue_token = wq->wait_queue_token;
ep->len = wq->name.len;
memcpy(ep->name, wq->name.name, wq->name.len);
ep->name[wq->name.len] = '\0';
break;
}
/*
* Kernel protocol v5 packet for handling indirect and direct
* mount missing and expire requests
*/
case autofs_ptype_missing_indirect:
case autofs_ptype_expire_indirect:
case autofs_ptype_missing_direct:
case autofs_ptype_expire_direct:
{
struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
pktsz = sizeof(*packet);
packet->wait_queue_token = wq->wait_queue_token;
packet->len = wq->name.len;
memcpy(packet->name, wq->name.name, wq->name.len);
packet->name[wq->name.len] = '\0';
packet->dev = wq->dev;
packet->ino = wq->ino;
packet->uid = from_kuid_munged(user_ns, wq->uid);
packet->gid = from_kgid_munged(user_ns, wq->gid);
packet->pid = wq->pid;
packet->tgid = wq->tgid;
break;
}
default:
pr_warn("bad type %d!\n", type);
mutex_unlock(&sbi->wq_mutex);
return;
}
pipe = get_file(sbi->pipe);
mutex_unlock(&sbi->wq_mutex);
if (autofs4_write(sbi, pipe, &pkt, pktsz))
autofs4_catatonic_mode(sbi);
fput(pipe);
}
static int autofs4_getpath(struct autofs_sb_info *sbi,
struct dentry *dentry, char **name)
{
struct dentry *root = sbi->sb->s_root;
struct dentry *tmp;
char *buf;
char *p;
int len;
unsigned seq;
rename_retry:
buf = *name;
len = 0;
seq = read_seqbegin(&rename_lock);
rcu_read_lock();
spin_lock(&sbi->fs_lock);
for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
len += tmp->d_name.len + 1;
if (!len || --len > NAME_MAX) {
spin_unlock(&sbi->fs_lock);
rcu_read_unlock();
if (read_seqretry(&rename_lock, seq))
goto rename_retry;
return 0;
}
*(buf + len) = '\0';
p = buf + len - dentry->d_name.len;
strncpy(p, dentry->d_name.name, dentry->d_name.len);
for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
*(--p) = '/';
p -= tmp->d_name.len;
strncpy(p, tmp->d_name.name, tmp->d_name.len);
}
spin_unlock(&sbi->fs_lock);
rcu_read_unlock();
if (read_seqretry(&rename_lock, seq))
goto rename_retry;
return len;
}
static struct autofs_wait_queue *
autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
{
struct autofs_wait_queue *wq;
for (wq = sbi->queues; wq; wq = wq->next) {
if (wq->name.hash == qstr->hash &&
wq->name.len == qstr->len &&
wq->name.name &&
!memcmp(wq->name.name, qstr->name, qstr->len))
break;
}
return wq;
}
/*
* Check if we have a valid request.
* Returns
* 1 if the request should continue.
* In this case we can return an autofs_wait_queue entry if one is
* found or NULL to idicate a new wait needs to be created.
* 0 or a negative errno if the request shouldn't continue.
*/
static int validate_request(struct autofs_wait_queue **wait,
struct autofs_sb_info *sbi,
struct qstr *qstr,
struct dentry *dentry, enum autofs_notify notify)
{
struct autofs_wait_queue *wq;
struct autofs_info *ino;
if (sbi->catatonic)
return -ENOENT;
/* Wait in progress, continue; */
wq = autofs4_find_wait(sbi, qstr);
if (wq) {
*wait = wq;
return 1;
}
*wait = NULL;
/* If we don't yet have any info this is a new request */
ino = autofs4_dentry_ino(dentry);
if (!ino)
return 1;
/*
* If we've been asked to wait on an existing expire (NFY_NONE)
* but there is no wait in the queue ...
*/
if (notify == NFY_NONE) {
/*
* Either we've betean the pending expire to post it's
* wait or it finished while we waited on the mutex.
* So we need to wait till either, the wait appears
* or the expire finishes.
*/
while (ino->flags & AUTOFS_INF_EXPIRING) {
mutex_unlock(&sbi->wq_mutex);
schedule_timeout_interruptible(HZ/10);
if (mutex_lock_interruptible(&sbi->wq_mutex))
return -EINTR;
if (sbi->catatonic)
return -ENOENT;
wq = autofs4_find_wait(sbi, qstr);
if (wq) {
*wait = wq;
return 1;
}
}
/*
* Not ideal but the status has already gone. Of the two
* cases where we wait on NFY_NONE neither depend on the
* return status of the wait.
*/
return 0;
}
/*
* If we've been asked to trigger a mount and the request
* completed while we waited on the mutex ...
*/
if (notify == NFY_MOUNT) {
struct dentry *new = NULL;
int valid = 1;
/*
* If the dentry was successfully mounted while we slept
* on the wait queue mutex we can return success. If it
* isn't mounted (doesn't have submounts for the case of
* a multi-mount with no mount at it's base) we can
* continue on and create a new request.
*/
if (!IS_ROOT(dentry)) {
if (d_unhashed(dentry) &&
d_really_is_positive(dentry)) {
struct dentry *parent = dentry->d_parent;
new = d_lookup(parent, &dentry->d_name);
if (new)
dentry = new;
}
}
if (have_submounts(dentry))
valid = 0;
if (new)
dput(new);
return valid;
}
return 1;
}
int autofs4_wait(struct autofs_sb_info *sbi,
struct dentry *dentry, enum autofs_notify notify)
{
struct autofs_wait_queue *wq;
struct qstr qstr;
char *name;
int status, ret, type;
pid_t pid;
pid_t tgid;
/* In catatonic mode, we don't wait for nobody */
if (sbi->catatonic)
return -ENOENT;
/*
* Try translating pids to the namespace of the daemon.
*
* Zero means failure: we are in an unrelated pid namespace.
*/
pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
if (pid == 0 || tgid == 0)
return -ENOENT;
if (d_really_is_negative(dentry)) {
/*
* A wait for a negative dentry is invalid for certain
* cases. A direct or offset mount "always" has its mount
* point directory created and so the request dentry must
* be positive or the map key doesn't exist. The situation
* is very similar for indirect mounts except only dentrys
* in the root of the autofs file system may be negative.
*/
if (autofs_type_trigger(sbi->type))
return -ENOENT;
else if (!IS_ROOT(dentry->d_parent))
return -ENOENT;
}
name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
if (!name)
return -ENOMEM;
/* If this is a direct mount request create a dummy name */
if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
qstr.len = sprintf(name, "%p", dentry);
else {
qstr.len = autofs4_getpath(sbi, dentry, &name);
if (!qstr.len) {
kfree(name);
return -ENOENT;
}
}
qstr.name = name;
qstr.hash = full_name_hash(dentry, name, qstr.len);
if (mutex_lock_interruptible(&sbi->wq_mutex)) {
kfree(qstr.name);
return -EINTR;
}
ret = validate_request(&wq, sbi, &qstr, dentry, notify);
if (ret <= 0) {
if (ret != -EINTR)
mutex_unlock(&sbi->wq_mutex);
kfree(qstr.name);
return ret;
}
if (!wq) {
/* Create a new wait queue */
wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
if (!wq) {
kfree(qstr.name);
mutex_unlock(&sbi->wq_mutex);
return -ENOMEM;
}
wq->wait_queue_token = autofs4_next_wait_queue;
if (++autofs4_next_wait_queue == 0)
autofs4_next_wait_queue = 1;
wq->next = sbi->queues;
sbi->queues = wq;
init_waitqueue_head(&wq->queue);
memcpy(&wq->name, &qstr, sizeof(struct qstr));
wq->dev = autofs4_get_dev(sbi);
wq->ino = autofs4_get_ino(sbi);
wq->uid = current_uid();
wq->gid = current_gid();
wq->pid = pid;
wq->tgid = tgid;
wq->status = -EINTR; /* Status return if interrupted */
wq->wait_ctr = 2;
if (sbi->version < 5) {
if (notify == NFY_MOUNT)
type = autofs_ptype_missing;
else
type = autofs_ptype_expire_multi;
} else {
if (notify == NFY_MOUNT)
type = autofs_type_trigger(sbi->type) ?
autofs_ptype_missing_direct :
autofs_ptype_missing_indirect;
else
type = autofs_type_trigger(sbi->type) ?
autofs_ptype_expire_direct :
autofs_ptype_expire_indirect;
}
pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
(unsigned long) wq->wait_queue_token, wq->name.len,
wq->name.name, notify);
/*
* autofs4_notify_daemon() may block; it will unlock ->wq_mutex
*/
autofs4_notify_daemon(sbi, wq, type);
} else {
wq->wait_ctr++;
pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
(unsigned long) wq->wait_queue_token, wq->name.len,
wq->name.name, notify);
mutex_unlock(&sbi->wq_mutex);
kfree(qstr.name);
}
/*
* wq->name.name is NULL iff the lock is already released
* or the mount has been made catatonic.
*/
if (wq->name.name) {
/* Block all but "shutdown" signals while waiting */
unsigned long shutdown_sigs_mask;
unsigned long irqflags;
sigset_t oldset;
spin_lock_irqsave(&current->sighand->siglock, irqflags);
oldset = current->blocked;
shutdown_sigs_mask = SHUTDOWN_SIGS & ~oldset.sig[0];
siginitsetinv(&current->blocked, shutdown_sigs_mask);
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
wait_event_interruptible(wq->queue, wq->name.name == NULL);
spin_lock_irqsave(&current->sighand->siglock, irqflags);
current->blocked = oldset;
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
} else {
pr_debug("skipped sleeping\n");
}
status = wq->status;
/*
* For direct and offset mounts we need to track the requester's
* uid and gid in the dentry info struct. This is so it can be
* supplied, on request, by the misc device ioctl interface.
* This is needed during daemon resatart when reconnecting
* to existing, active, autofs mounts. The uid and gid (and
* related string values) may be used for macro substitution
* in autofs mount maps.
*/
if (!status) {
struct autofs_info *ino;
struct dentry *de = NULL;
/* direct mount or browsable map */
ino = autofs4_dentry_ino(dentry);
if (!ino) {
/* If not lookup actual dentry used */
de = d_lookup(dentry->d_parent, &dentry->d_name);
if (de)
ino = autofs4_dentry_ino(de);
}
/* Set mount requester */
if (ino) {
spin_lock(&sbi->fs_lock);
ino->uid = wq->uid;
ino->gid = wq->gid;
spin_unlock(&sbi->fs_lock);
}
if (de)
dput(de);
}
/* Are we the last process to need status? */
mutex_lock(&sbi->wq_mutex);
if (!--wq->wait_ctr)
kfree(wq);
mutex_unlock(&sbi->wq_mutex);
return status;
}
int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
{
struct autofs_wait_queue *wq, **wql;
mutex_lock(&sbi->wq_mutex);
for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
if (wq->wait_queue_token == wait_queue_token)
break;
}
if (!wq) {
mutex_unlock(&sbi->wq_mutex);
return -EINVAL;
}
*wql = wq->next; /* Unlink from chain */
kfree(wq->name.name);
wq->name.name = NULL; /* Do not wait on this queue */
wq->status = status;
wake_up_interruptible(&wq->queue);
if (!--wq->wait_ctr)
kfree(wq);
mutex_unlock(&sbi->wq_mutex);
return 0;
}