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cache.c
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/*
* net/sunrpc/cache.c
*
* Generic code for various authentication-related caches
* used by sunrpc clients and servers.
*
* Copyright (C) 2002 Neil Brown <[email protected]>
*
* Released under terms in GPL version 2. See COPYING.
*
*/
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/ctype.h>
#include <asm/uaccess.h>
#include <linux/poll.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/net.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <linux/pagemap.h>
#include <asm/ioctls.h>
#include <linux/sunrpc/types.h>
#include <linux/sunrpc/cache.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include "netns.h"
#define RPCDBG_FACILITY RPCDBG_CACHE
static void cache_defer_req(struct cache_req *req, struct cache_head *item);
static void cache_revisit_request(struct cache_head *item);
static void cache_init(struct cache_head *h)
{
time_t now = seconds_since_boot();
h->next = NULL;
h->flags = 0;
kref_init(&h->ref);
h->expiry_time = now + CACHE_NEW_EXPIRY;
h->last_refresh = now;
}
static inline int cache_is_expired(struct cache_detail *detail, struct cache_head *h)
{
return (h->expiry_time < seconds_since_boot()) ||
(detail->flush_time > h->last_refresh);
}
struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
struct cache_head *key, int hash)
{
struct cache_head **head, **hp;
struct cache_head *new = NULL, *freeme = NULL;
head = &detail->hash_table[hash];
read_lock(&detail->hash_lock);
for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
struct cache_head *tmp = *hp;
if (detail->match(tmp, key)) {
if (cache_is_expired(detail, tmp))
/* This entry is expired, we will discard it. */
break;
cache_get(tmp);
read_unlock(&detail->hash_lock);
return tmp;
}
}
read_unlock(&detail->hash_lock);
/* Didn't find anything, insert an empty entry */
new = detail->alloc();
if (!new)
return NULL;
/* must fully initialise 'new', else
* we might get lose if we need to
* cache_put it soon.
*/
cache_init(new);
detail->init(new, key);
write_lock(&detail->hash_lock);
/* check if entry appeared while we slept */
for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
struct cache_head *tmp = *hp;
if (detail->match(tmp, key)) {
if (cache_is_expired(detail, tmp)) {
*hp = tmp->next;
tmp->next = NULL;
detail->entries --;
freeme = tmp;
break;
}
cache_get(tmp);
write_unlock(&detail->hash_lock);
cache_put(new, detail);
return tmp;
}
}
new->next = *head;
*head = new;
detail->entries++;
cache_get(new);
write_unlock(&detail->hash_lock);
if (freeme)
cache_put(freeme, detail);
return new;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
static void cache_fresh_locked(struct cache_head *head, time_t expiry)
{
head->expiry_time = expiry;
head->last_refresh = seconds_since_boot();
set_bit(CACHE_VALID, &head->flags);
}
static void cache_fresh_unlocked(struct cache_head *head,
struct cache_detail *detail)
{
if (test_and_clear_bit(CACHE_PENDING, &head->flags)) {
cache_revisit_request(head);
cache_dequeue(detail, head);
}
}
struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
struct cache_head *new, struct cache_head *old, int hash)
{
/* The 'old' entry is to be replaced by 'new'.
* If 'old' is not VALID, we update it directly,
* otherwise we need to replace it
*/
struct cache_head **head;
struct cache_head *tmp;
if (!test_bit(CACHE_VALID, &old->flags)) {
write_lock(&detail->hash_lock);
if (!test_bit(CACHE_VALID, &old->flags)) {
if (test_bit(CACHE_NEGATIVE, &new->flags))
set_bit(CACHE_NEGATIVE, &old->flags);
else
detail->update(old, new);
cache_fresh_locked(old, new->expiry_time);
write_unlock(&detail->hash_lock);
cache_fresh_unlocked(old, detail);
return old;
}
write_unlock(&detail->hash_lock);
}
/* We need to insert a new entry */
tmp = detail->alloc();
if (!tmp) {
cache_put(old, detail);
return NULL;
}
cache_init(tmp);
detail->init(tmp, old);
head = &detail->hash_table[hash];
write_lock(&detail->hash_lock);
if (test_bit(CACHE_NEGATIVE, &new->flags))
set_bit(CACHE_NEGATIVE, &tmp->flags);
else
detail->update(tmp, new);
tmp->next = *head;
*head = tmp;
detail->entries++;
cache_get(tmp);
cache_fresh_locked(tmp, new->expiry_time);
cache_fresh_locked(old, 0);
write_unlock(&detail->hash_lock);
cache_fresh_unlocked(tmp, detail);
cache_fresh_unlocked(old, detail);
cache_put(old, detail);
return tmp;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_update);
static int cache_make_upcall(struct cache_detail *cd, struct cache_head *h)
{
if (!cd->cache_upcall)
return -EINVAL;
return cd->cache_upcall(cd, h);
}
static inline int cache_is_valid(struct cache_detail *detail, struct cache_head *h)
{
if (!test_bit(CACHE_VALID, &h->flags))
return -EAGAIN;
else {
/* entry is valid */
if (test_bit(CACHE_NEGATIVE, &h->flags))
return -ENOENT;
else
return 0;
}
}
/*
* This is the generic cache management routine for all
* the authentication caches.
* It checks the currency of a cache item and will (later)
* initiate an upcall to fill it if needed.
*
*
* Returns 0 if the cache_head can be used, or cache_puts it and returns
* -EAGAIN if upcall is pending and request has been queued
* -ETIMEDOUT if upcall failed or request could not be queue or
* upcall completed but item is still invalid (implying that
* the cache item has been replaced with a newer one).
* -ENOENT if cache entry was negative
*/
int cache_check(struct cache_detail *detail,
struct cache_head *h, struct cache_req *rqstp)
{
int rv;
long refresh_age, age;
/* First decide return status as best we can */
rv = cache_is_valid(detail, h);
/* now see if we want to start an upcall */
refresh_age = (h->expiry_time - h->last_refresh);
age = seconds_since_boot() - h->last_refresh;
if (rqstp == NULL) {
if (rv == -EAGAIN)
rv = -ENOENT;
} else if (rv == -EAGAIN || age > refresh_age/2) {
dprintk("RPC: Want update, refage=%ld, age=%ld\n",
refresh_age, age);
if (!test_and_set_bit(CACHE_PENDING, &h->flags)) {
switch (cache_make_upcall(detail, h)) {
case -EINVAL:
clear_bit(CACHE_PENDING, &h->flags);
cache_revisit_request(h);
if (rv == -EAGAIN) {
set_bit(CACHE_NEGATIVE, &h->flags);
cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
cache_fresh_unlocked(h, detail);
rv = -ENOENT;
}
break;
case -EAGAIN:
clear_bit(CACHE_PENDING, &h->flags);
cache_revisit_request(h);
break;
}
}
}
if (rv == -EAGAIN) {
cache_defer_req(rqstp, h);
if (!test_bit(CACHE_PENDING, &h->flags)) {
/* Request is not deferred */
rv = cache_is_valid(detail, h);
if (rv == -EAGAIN)
rv = -ETIMEDOUT;
}
}
if (rv)
cache_put(h, detail);
return rv;
}
EXPORT_SYMBOL_GPL(cache_check);
/*
* caches need to be periodically cleaned.
* For this we maintain a list of cache_detail and
* a current pointer into that list and into the table
* for that entry.
*
* Each time clean_cache is called it finds the next non-empty entry
* in the current table and walks the list in that entry
* looking for entries that can be removed.
*
* An entry gets removed if:
* - The expiry is before current time
* - The last_refresh time is before the flush_time for that cache
*
* later we might drop old entries with non-NEVER expiry if that table
* is getting 'full' for some definition of 'full'
*
* The question of "how often to scan a table" is an interesting one
* and is answered in part by the use of the "nextcheck" field in the
* cache_detail.
* When a scan of a table begins, the nextcheck field is set to a time
* that is well into the future.
* While scanning, if an expiry time is found that is earlier than the
* current nextcheck time, nextcheck is set to that expiry time.
* If the flush_time is ever set to a time earlier than the nextcheck
* time, the nextcheck time is then set to that flush_time.
*
* A table is then only scanned if the current time is at least
* the nextcheck time.
*
*/
static LIST_HEAD(cache_list);
static DEFINE_SPINLOCK(cache_list_lock);
static struct cache_detail *current_detail;
static int current_index;
static void do_cache_clean(struct work_struct *work);
static struct delayed_work cache_cleaner;
static void sunrpc_init_cache_detail(struct cache_detail *cd)
{
rwlock_init(&cd->hash_lock);
INIT_LIST_HEAD(&cd->queue);
spin_lock(&cache_list_lock);
cd->nextcheck = 0;
cd->entries = 0;
atomic_set(&cd->readers, 0);
cd->last_close = 0;
cd->last_warn = -1;
list_add(&cd->others, &cache_list);
spin_unlock(&cache_list_lock);
/* start the cleaning process */
schedule_delayed_work(&cache_cleaner, 0);
}
static void sunrpc_destroy_cache_detail(struct cache_detail *cd)
{
cache_purge(cd);
spin_lock(&cache_list_lock);
write_lock(&cd->hash_lock);
if (cd->entries || atomic_read(&cd->inuse)) {
write_unlock(&cd->hash_lock);
spin_unlock(&cache_list_lock);
goto out;
}
if (current_detail == cd)
current_detail = NULL;
list_del_init(&cd->others);
write_unlock(&cd->hash_lock);
spin_unlock(&cache_list_lock);
if (list_empty(&cache_list)) {
/* module must be being unloaded so its safe to kill the worker */
cancel_delayed_work_sync(&cache_cleaner);
}
return;
out:
printk(KERN_ERR "nfsd: failed to unregister %s cache\n", cd->name);
}
/* clean cache tries to find something to clean
* and cleans it.
* It returns 1 if it cleaned something,
* 0 if it didn't find anything this time
* -1 if it fell off the end of the list.
*/
static int cache_clean(void)
{
int rv = 0;
struct list_head *next;
spin_lock(&cache_list_lock);
/* find a suitable table if we don't already have one */
while (current_detail == NULL ||
current_index >= current_detail->hash_size) {
if (current_detail)
next = current_detail->others.next;
else
next = cache_list.next;
if (next == &cache_list) {
current_detail = NULL;
spin_unlock(&cache_list_lock);
return -1;
}
current_detail = list_entry(next, struct cache_detail, others);
if (current_detail->nextcheck > seconds_since_boot())
current_index = current_detail->hash_size;
else {
current_index = 0;
current_detail->nextcheck = seconds_since_boot()+30*60;
}
}
/* find a non-empty bucket in the table */
while (current_detail &&
current_index < current_detail->hash_size &&
current_detail->hash_table[current_index] == NULL)
current_index++;
/* find a cleanable entry in the bucket and clean it, or set to next bucket */
if (current_detail && current_index < current_detail->hash_size) {
struct cache_head *ch, **cp;
struct cache_detail *d;
write_lock(¤t_detail->hash_lock);
/* Ok, now to clean this strand */
cp = & current_detail->hash_table[current_index];
for (ch = *cp ; ch ; cp = & ch->next, ch = *cp) {
if (current_detail->nextcheck > ch->expiry_time)
current_detail->nextcheck = ch->expiry_time+1;
if (!cache_is_expired(current_detail, ch))
continue;
*cp = ch->next;
ch->next = NULL;
current_detail->entries--;
rv = 1;
break;
}
write_unlock(¤t_detail->hash_lock);
d = current_detail;
if (!ch)
current_index ++;
spin_unlock(&cache_list_lock);
if (ch) {
if (test_and_clear_bit(CACHE_PENDING, &ch->flags))
cache_dequeue(current_detail, ch);
cache_revisit_request(ch);
cache_put(ch, d);
}
} else
spin_unlock(&cache_list_lock);
return rv;
}
/*
* We want to regularly clean the cache, so we need to schedule some work ...
*/
static void do_cache_clean(struct work_struct *work)
{
int delay = 5;
if (cache_clean() == -1)
delay = round_jiffies_relative(30*HZ);
if (list_empty(&cache_list))
delay = 0;
if (delay)
schedule_delayed_work(&cache_cleaner, delay);
}
/*
* Clean all caches promptly. This just calls cache_clean
* repeatedly until we are sure that every cache has had a chance to
* be fully cleaned
*/
void cache_flush(void)
{
while (cache_clean() != -1)
cond_resched();
while (cache_clean() != -1)
cond_resched();
}
EXPORT_SYMBOL_GPL(cache_flush);
void cache_purge(struct cache_detail *detail)
{
detail->flush_time = LONG_MAX;
detail->nextcheck = seconds_since_boot();
cache_flush();
detail->flush_time = 1;
}
EXPORT_SYMBOL_GPL(cache_purge);
/*
* Deferral and Revisiting of Requests.
*
* If a cache lookup finds a pending entry, we
* need to defer the request and revisit it later.
* All deferred requests are stored in a hash table,
* indexed by "struct cache_head *".
* As it may be wasteful to store a whole request
* structure, we allow the request to provide a
* deferred form, which must contain a
* 'struct cache_deferred_req'
* This cache_deferred_req contains a method to allow
* it to be revisited when cache info is available
*/
#define DFR_HASHSIZE (PAGE_SIZE/sizeof(struct list_head))
#define DFR_HASH(item) ((((long)item)>>4 ^ (((long)item)>>13)) % DFR_HASHSIZE)
#define DFR_MAX 300 /* ??? */
static DEFINE_SPINLOCK(cache_defer_lock);
static LIST_HEAD(cache_defer_list);
static struct hlist_head cache_defer_hash[DFR_HASHSIZE];
static int cache_defer_cnt;
static void __unhash_deferred_req(struct cache_deferred_req *dreq)
{
hlist_del_init(&dreq->hash);
if (!list_empty(&dreq->recent)) {
list_del_init(&dreq->recent);
cache_defer_cnt--;
}
}
static void __hash_deferred_req(struct cache_deferred_req *dreq, struct cache_head *item)
{
int hash = DFR_HASH(item);
INIT_LIST_HEAD(&dreq->recent);
hlist_add_head(&dreq->hash, &cache_defer_hash[hash]);
}
static void setup_deferral(struct cache_deferred_req *dreq,
struct cache_head *item,
int count_me)
{
dreq->item = item;
spin_lock(&cache_defer_lock);
__hash_deferred_req(dreq, item);
if (count_me) {
cache_defer_cnt++;
list_add(&dreq->recent, &cache_defer_list);
}
spin_unlock(&cache_defer_lock);
}
struct thread_deferred_req {
struct cache_deferred_req handle;
struct completion completion;
};
static void cache_restart_thread(struct cache_deferred_req *dreq, int too_many)
{
struct thread_deferred_req *dr =
container_of(dreq, struct thread_deferred_req, handle);
complete(&dr->completion);
}
static void cache_wait_req(struct cache_req *req, struct cache_head *item)
{
struct thread_deferred_req sleeper;
struct cache_deferred_req *dreq = &sleeper.handle;
sleeper.completion = COMPLETION_INITIALIZER_ONSTACK(sleeper.completion);
dreq->revisit = cache_restart_thread;
setup_deferral(dreq, item, 0);
if (!test_bit(CACHE_PENDING, &item->flags) ||
wait_for_completion_interruptible_timeout(
&sleeper.completion, req->thread_wait) <= 0) {
/* The completion wasn't completed, so we need
* to clean up
*/
spin_lock(&cache_defer_lock);
if (!hlist_unhashed(&sleeper.handle.hash)) {
__unhash_deferred_req(&sleeper.handle);
spin_unlock(&cache_defer_lock);
} else {
/* cache_revisit_request already removed
* this from the hash table, but hasn't
* called ->revisit yet. It will very soon
* and we need to wait for it.
*/
spin_unlock(&cache_defer_lock);
wait_for_completion(&sleeper.completion);
}
}
}
static void cache_limit_defers(void)
{
/* Make sure we haven't exceed the limit of allowed deferred
* requests.
*/
struct cache_deferred_req *discard = NULL;
if (cache_defer_cnt <= DFR_MAX)
return;
spin_lock(&cache_defer_lock);
/* Consider removing either the first or the last */
if (cache_defer_cnt > DFR_MAX) {
if (net_random() & 1)
discard = list_entry(cache_defer_list.next,
struct cache_deferred_req, recent);
else
discard = list_entry(cache_defer_list.prev,
struct cache_deferred_req, recent);
__unhash_deferred_req(discard);
}
spin_unlock(&cache_defer_lock);
if (discard)
discard->revisit(discard, 1);
}
static void cache_defer_req(struct cache_req *req, struct cache_head *item)
{
struct cache_deferred_req *dreq;
if (req->thread_wait) {
cache_wait_req(req, item);
if (!test_bit(CACHE_PENDING, &item->flags))
return;
}
dreq = req->defer(req);
if (dreq == NULL)
return;
setup_deferral(dreq, item, 1);
if (!test_bit(CACHE_PENDING, &item->flags))
/* Bit could have been cleared before we managed to
* set up the deferral, so need to revisit just in case
*/
cache_revisit_request(item);
cache_limit_defers();
}
static void cache_revisit_request(struct cache_head *item)
{
struct cache_deferred_req *dreq;
struct list_head pending;
struct hlist_node *lp, *tmp;
int hash = DFR_HASH(item);
INIT_LIST_HEAD(&pending);
spin_lock(&cache_defer_lock);
hlist_for_each_entry_safe(dreq, lp, tmp, &cache_defer_hash[hash], hash)
if (dreq->item == item) {
__unhash_deferred_req(dreq);
list_add(&dreq->recent, &pending);
}
spin_unlock(&cache_defer_lock);
while (!list_empty(&pending)) {
dreq = list_entry(pending.next, struct cache_deferred_req, recent);
list_del_init(&dreq->recent);
dreq->revisit(dreq, 0);
}
}
void cache_clean_deferred(void *owner)
{
struct cache_deferred_req *dreq, *tmp;
struct list_head pending;
INIT_LIST_HEAD(&pending);
spin_lock(&cache_defer_lock);
list_for_each_entry_safe(dreq, tmp, &cache_defer_list, recent) {
if (dreq->owner == owner) {
__unhash_deferred_req(dreq);
list_add(&dreq->recent, &pending);
}
}
spin_unlock(&cache_defer_lock);
while (!list_empty(&pending)) {
dreq = list_entry(pending.next, struct cache_deferred_req, recent);
list_del_init(&dreq->recent);
dreq->revisit(dreq, 1);
}
}
/*
* communicate with user-space
*
* We have a magic /proc file - /proc/sunrpc/<cachename>/channel.
* On read, you get a full request, or block.
* On write, an update request is processed.
* Poll works if anything to read, and always allows write.
*
* Implemented by linked list of requests. Each open file has
* a ->private that also exists in this list. New requests are added
* to the end and may wakeup and preceding readers.
* New readers are added to the head. If, on read, an item is found with
* CACHE_UPCALLING clear, we free it from the list.
*
*/
static DEFINE_SPINLOCK(queue_lock);
static DEFINE_MUTEX(queue_io_mutex);
struct cache_queue {
struct list_head list;
int reader; /* if 0, then request */
};
struct cache_request {
struct cache_queue q;
struct cache_head *item;
char * buf;
int len;
int readers;
};
struct cache_reader {
struct cache_queue q;
int offset; /* if non-0, we have a refcnt on next request */
};
static ssize_t cache_read(struct file *filp, char __user *buf, size_t count,
loff_t *ppos, struct cache_detail *cd)
{
struct cache_reader *rp = filp->private_data;
struct cache_request *rq;
struct inode *inode = filp->f_path.dentry->d_inode;
int err;
if (count == 0)
return 0;
mutex_lock(&inode->i_mutex); /* protect against multiple concurrent
* readers on this file */
again:
spin_lock(&queue_lock);
/* need to find next request */
while (rp->q.list.next != &cd->queue &&
list_entry(rp->q.list.next, struct cache_queue, list)
->reader) {
struct list_head *next = rp->q.list.next;
list_move(&rp->q.list, next);
}
if (rp->q.list.next == &cd->queue) {
spin_unlock(&queue_lock);
mutex_unlock(&inode->i_mutex);
BUG_ON(rp->offset);
return 0;
}
rq = container_of(rp->q.list.next, struct cache_request, q.list);
BUG_ON(rq->q.reader);
if (rp->offset == 0)
rq->readers++;
spin_unlock(&queue_lock);
if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) {
err = -EAGAIN;
spin_lock(&queue_lock);
list_move(&rp->q.list, &rq->q.list);
spin_unlock(&queue_lock);
} else {
if (rp->offset + count > rq->len)
count = rq->len - rp->offset;
err = -EFAULT;
if (copy_to_user(buf, rq->buf + rp->offset, count))
goto out;
rp->offset += count;
if (rp->offset >= rq->len) {
rp->offset = 0;
spin_lock(&queue_lock);
list_move(&rp->q.list, &rq->q.list);
spin_unlock(&queue_lock);
}
err = 0;
}
out:
if (rp->offset == 0) {
/* need to release rq */
spin_lock(&queue_lock);
rq->readers--;
if (rq->readers == 0 &&
!test_bit(CACHE_PENDING, &rq->item->flags)) {
list_del(&rq->q.list);
spin_unlock(&queue_lock);
cache_put(rq->item, cd);
kfree(rq->buf);
kfree(rq);
} else
spin_unlock(&queue_lock);
}
if (err == -EAGAIN)
goto again;
mutex_unlock(&inode->i_mutex);
return err ? err : count;
}
static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
size_t count, struct cache_detail *cd)
{
ssize_t ret;
if (copy_from_user(kaddr, buf, count))
return -EFAULT;
kaddr[count] = '\0';
ret = cd->cache_parse(cd, kaddr, count);
if (!ret)
ret = count;
return ret;
}
static ssize_t cache_slow_downcall(const char __user *buf,
size_t count, struct cache_detail *cd)
{
static char write_buf[8192]; /* protected by queue_io_mutex */
ssize_t ret = -EINVAL;
if (count >= sizeof(write_buf))
goto out;
mutex_lock(&queue_io_mutex);
ret = cache_do_downcall(write_buf, buf, count, cd);
mutex_unlock(&queue_io_mutex);
out:
return ret;
}
static ssize_t cache_downcall(struct address_space *mapping,
const char __user *buf,
size_t count, struct cache_detail *cd)
{
struct page *page;
char *kaddr;
ssize_t ret = -ENOMEM;
if (count >= PAGE_CACHE_SIZE)
goto out_slow;
page = find_or_create_page(mapping, 0, GFP_KERNEL);
if (!page)
goto out_slow;
kaddr = kmap(page);
ret = cache_do_downcall(kaddr, buf, count, cd);
kunmap(page);
unlock_page(page);
page_cache_release(page);
return ret;
out_slow:
return cache_slow_downcall(buf, count, cd);
}
static ssize_t cache_write(struct file *filp, const char __user *buf,
size_t count, loff_t *ppos,
struct cache_detail *cd)
{
struct address_space *mapping = filp->f_mapping;
struct inode *inode = filp->f_path.dentry->d_inode;
ssize_t ret = -EINVAL;
if (!cd->cache_parse)
goto out;
mutex_lock(&inode->i_mutex);
ret = cache_downcall(mapping, buf, count, cd);
mutex_unlock(&inode->i_mutex);
out:
return ret;
}
static DECLARE_WAIT_QUEUE_HEAD(queue_wait);
static unsigned int cache_poll(struct file *filp, poll_table *wait,
struct cache_detail *cd)
{
unsigned int mask;
struct cache_reader *rp = filp->private_data;
struct cache_queue *cq;
poll_wait(filp, &queue_wait, wait);
/* alway allow write */
mask = POLL_OUT | POLLWRNORM;
if (!rp)
return mask;
spin_lock(&queue_lock);
for (cq= &rp->q; &cq->list != &cd->queue;
cq = list_entry(cq->list.next, struct cache_queue, list))
if (!cq->reader) {
mask |= POLLIN | POLLRDNORM;
break;
}
spin_unlock(&queue_lock);
return mask;
}
static int cache_ioctl(struct inode *ino, struct file *filp,
unsigned int cmd, unsigned long arg,
struct cache_detail *cd)
{
int len = 0;
struct cache_reader *rp = filp->private_data;
struct cache_queue *cq;
if (cmd != FIONREAD || !rp)
return -EINVAL;
spin_lock(&queue_lock);
/* only find the length remaining in current request,
* or the length of the next request
*/
for (cq= &rp->q; &cq->list != &cd->queue;
cq = list_entry(cq->list.next, struct cache_queue, list))
if (!cq->reader) {
struct cache_request *cr =
container_of(cq, struct cache_request, q);
len = cr->len - rp->offset;
break;
}
spin_unlock(&queue_lock);
return put_user(len, (int __user *)arg);
}
static int cache_open(struct inode *inode, struct file *filp,
struct cache_detail *cd)
{
struct cache_reader *rp = NULL;
if (!cd || !try_module_get(cd->owner))
return -EACCES;
nonseekable_open(inode, filp);
if (filp->f_mode & FMODE_READ) {
rp = kmalloc(sizeof(*rp), GFP_KERNEL);
if (!rp)
return -ENOMEM;
rp->offset = 0;
rp->q.reader = 1;
atomic_inc(&cd->readers);
spin_lock(&queue_lock);
list_add(&rp->q.list, &cd->queue);
spin_unlock(&queue_lock);
}
filp->private_data = rp;
return 0;
}
static int cache_release(struct inode *inode, struct file *filp,
struct cache_detail *cd)
{
struct cache_reader *rp = filp->private_data;
if (rp) {
spin_lock(&queue_lock);
if (rp->offset) {
struct cache_queue *cq;
for (cq= &rp->q; &cq->list != &cd->queue;
cq = list_entry(cq->list.next, struct cache_queue, list))
if (!cq->reader) {
container_of(cq, struct cache_request, q)
->readers--;
break;
}
rp->offset = 0;
}
list_del(&rp->q.list);
spin_unlock(&queue_lock);
filp->private_data = NULL;
kfree(rp);
cd->last_close = seconds_since_boot();
atomic_dec(&cd->readers);
}
module_put(cd->owner);
return 0;
}
static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch)
{
struct cache_queue *cq;
spin_lock(&queue_lock);
list_for_each_entry(cq, &detail->queue, list)
if (!cq->reader) {
struct cache_request *cr = container_of(cq, struct cache_request, q);
if (cr->item != ch)
continue;
if (cr->readers != 0)
continue;
list_del(&cr->q.list);
spin_unlock(&queue_lock);