cregit-Linux how code gets into the kernel

Release 4.11 net/sunrpc/cache.c

Directory: net/sunrpc
/*
 * net/sunrpc/cache.c
 *
 * Generic code for various authentication-related caches
 * used by sunrpc clients and servers.
 *
 * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
 *
 * 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 <linux/string_helpers.h>
#include <linux/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 bool 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, struct cache_detail *detail)
{
	time_t now = seconds_since_boot();
	INIT_HLIST_NODE(&h->cache_list);
	h->flags = 0;
	kref_init(&h->ref);
	h->expiry_time = now + CACHE_NEW_EXPIRY;
	if (now <= detail->flush_time)
		/* ensure it isn't already expired */
		now = detail->flush_time + 1;
	h->last_refresh = now;
}


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Neil Brown6890.67%457.14%


Kinglong Mee56.67%114.29%


Andi Kleen11.33%114.29%


Adrian Bunk11.33%114.29%


Total75100.00%7100.00%






struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
				       struct cache_head *key, int hash)
{
	struct cache_head *new = NULL, *freeme = NULL, *tmp = NULL;
	struct hlist_head *head;

	head = &detail->hash_table[hash];

	read_lock(&detail->hash_lock);

	hlist_for_each_entry(tmp, head, cache_list) {
		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);
	detail->init(new, key);

	write_lock(&detail->hash_lock);

	/* check if entry appeared while we slept */
	hlist_for_each_entry(tmp, head, cache_list) {
		if (detail->match(tmp, key)) {
			if (cache_is_expired(detail, tmp)) {
				hlist_del_init(&tmp->cache_list);
				detail->entries --;
				freeme = tmp;
				break;
			}
			cache_get(tmp);
			write_unlock(&detail->hash_lock);
			cache_put(new, detail);
			return tmp;
		}
	}

	hlist_add_head(&new->cache_list, head);
	detail->entries++;
	cache_get(new);
	write_unlock(&detail->hash_lock);

	if (freeme)
		cache_put(freeme, detail);
	return new;
}

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Neil Brown24086.64%480.00%


Kinglong Mee3713.36%120.00%


Total277100.00%5100.00%




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,
			       struct cache_detail *detail)
{
	time_t now = seconds_since_boot();
	if (now <= detail->flush_time)
		/* ensure it isn't immediately treated as expired */
		now = detail->flush_time + 1;
	head->expiry_time = expiry;
	head->last_refresh = now;
	smp_wmb(); /* paired with smp_rmb() in cache_is_valid() */
	set_bit(CACHE_VALID, &head->flags);
}


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Neil Brown6494.12%375.00%


J. Bruce Fields45.88%125.00%


Total68100.00%4100.00%






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);
	}
}


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Neil Brown42100.00%2100.00%


Total42100.00%2100.00%






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 *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, detail);
			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);
	detail->init(tmp, old);

	write_lock(&detail->hash_lock);
	if (test_bit(CACHE_NEGATIVE, &new->flags))
		set_bit(CACHE_NEGATIVE, &tmp->flags);
	else
		detail->update(tmp, new);
	hlist_add_head(&tmp->cache_list, &detail->hash_table[hash]);
	detail->entries++;
	cache_get(tmp);
	cache_fresh_locked(tmp, new->expiry_time, detail);
	cache_fresh_locked(old, 0, detail);
	write_unlock(&detail->hash_lock);
	cache_fresh_unlocked(tmp, detail);
	cache_fresh_unlocked(old, detail);
	cache_put(old, detail);
	return tmp;
}

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Neil Brown28495.62%480.00%


Kinglong Mee134.38%120.00%


Total297100.00%5100.00%




EXPORT_SYMBOL_GPL(sunrpc_cache_update);




static int cache_make_upcall(struct cache_detail *cd, struct cache_head *h)
{
	if (cd->cache_upcall)
		return cd->cache_upcall(cd, h);
	return sunrpc_cache_pipe_upcall(cd, h);
}


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Trond Myklebust1947.50%133.33%


Neil Brown1332.50%133.33%


Stanislav Kinsbursky820.00%133.33%


Total40100.00%3100.00%






static inline int cache_is_valid(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 {
			/*
                         * In combination with write barrier in
                         * sunrpc_cache_update, ensures that anyone
                         * using the cache entry after this sees the
                         * updated contents:
                         */
			smp_rmb();
			return 0;
		}
	}
}


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Neil Brown5389.83%266.67%


J. Bruce Fields610.17%133.33%


Total59100.00%3100.00%






static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h)
{
	int rv;

	write_lock(&detail->hash_lock);
	rv = cache_is_valid(h);
	if (rv == -EAGAIN) {
		set_bit(CACHE_NEGATIVE, &h->flags);
		cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY,
				   detail);
		rv = -ENOENT;
	}
	write_unlock(&detail->hash_lock);
	cache_fresh_unlocked(h, detail);
	return rv;
}


Contributors
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J. Bruce Fields7888.64%133.33%


Neil Brown1011.36%266.67%


Total88100.00%3100.00%



/*
 * 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(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 ||
		   (h->expiry_time != 0 && 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:
				rv = try_to_negate_entry(detail, h);
				break;
			case -EAGAIN:
				cache_fresh_unlocked(h, detail);
				break;
			}
		}
	}

	if (rv == -EAGAIN) {
		if (!cache_defer_req(rqstp, h)) {
			/*
                         * Request was not deferred; handle it as best
                         * we can ourselves:
                         */
			rv = cache_is_valid(h);
			if (rv == -EAGAIN)
				rv = -ETIMEDOUT;
		}
	}
	if (rv)
		cache_put(h, detail);
	return rv;
}

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Neil Brown20594.04%861.54%


J. Bruce Fields115.05%323.08%


Andi Kleen10.46%17.69%


Chuck Lever10.46%17.69%


Total218100.00%13100.00%




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 cache_clean 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;




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 */
	queue_delayed_work(system_power_efficient_wq, &cache_cleaner, 0);
}

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Trond Myklebust5557.89%120.00%


J. Bruce Fields2526.32%120.00%


Neil Brown1212.63%240.00%


Ke Wang33.16%120.00%


Total95100.00%5100.00%




EXPORT_SYMBOL_GPL(sunrpc_init_cache_detail);




void sunrpc_destroy_cache_detail(struct cache_detail *cd)
{
	cache_purge(cd);
	spin_lock(&cache_list_lock);
	write_lock(&cd->hash_lock);
	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);
	}
}

Contributors
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Neil Brown4355.13%545.45%


J. Bruce Fields1620.51%19.09%


Trond Myklebust1215.38%218.18%


Wang Chen33.85%19.09%


Andrew Morton33.85%19.09%


Denis V. Lunev11.28%19.09%


Total78100.00%11100.00%




EXPORT_SYMBOL_GPL(sunrpc_destroy_cache_detail);

/* 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 &&
	       hlist_empty(&current_detail->hash_table[current_index]))
		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 = NULL;
		struct cache_detail *d;
		struct hlist_head *head;
		struct hlist_node *tmp;

		write_lock(&current_detail->hash_lock);

		/* Ok, now to clean this strand */

		head = &current_detail->hash_table[current_index];
		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
			if (current_detail->nextcheck > ch->expiry_time)
				current_detail->nextcheck = ch->expiry_time+1;
			if (!cache_is_expired(current_detail, ch))
				continue;

			hlist_del_init(&ch->cache_list);
			current_detail->entries--;
			rv = 1;
			break;
		}

		write_unlock(&current_detail->hash_lock);
		d = current_detail;
		if (!ch)
			current_index ++;
		spin_unlock(&cache_list_lock);
		if (ch) {
			set_bit(CACHE_CLEANED, &ch->flags);
			cache_fresh_unlocked(ch, d);
			cache_put(ch, d);
		}
	} else
		spin_unlock(&cache_list_lock);

	return rv;
}


Contributors
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Neil Brown24272.89%1047.62%


Kinglong Mee329.64%14.76%


Andrew Morton298.73%314.29%


J. Bruce Fields236.93%419.05%


Trond Myklebust41.20%29.52%


Andi Kleen20.60%14.76%


Total332100.00%21100.00%



/*
 * 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)
		queue_delayed_work(system_power_efficient_wq,
				   &cache_cleaner, delay);
}



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Neil Brown4983.05%233.33%


Ke Wang35.08%116.67%


David Howells35.08%116.67%


Anton Blanchard35.08%116.67%


Adrian Bunk11.69%116.67%


Total59100.00%6100.00%



/*
 * 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();
}

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Neil Brown29100.00%1100.00%


Total29100.00%1100.00%




EXPORT_SYMBOL_GPL(cache_flush);




void cache_purge(struct cache_detail *detail)
{
	struct cache_head *ch = NULL;
	struct hlist_head *head = NULL;
	struct hlist_node *tmp = NULL;
	int i = 0;

	write_lock(&detail->hash_lock);
	if (!detail->entries) {
		write_unlock(&detail->hash_lock);
		return;
	}

	dprintk("RPC: %d entries in %s cache\n", detail->entries, detail->name);
	for (i = 0; i < detail->hash_size; i++) {
		head = &detail->hash_table[i];
		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
			hlist_del_init(&ch->cache_list);
			detail->entries--;

			set_bit(CACHE_CLEANED, &ch->flags);
			write_unlock(&detail->hash_lock);
			cache_fresh_unlocked(ch, detail);
			cache_put(ch, detail);
			write_lock(&detail->hash_lock);
		}
	}
	write_unlock(&detail->hash_lock);
}

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Kinglong Mee14683.43%133.33%


Neil Brown2916.57%266.67%


Total175100.00%3100.00%




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--;
	}
}


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Neil Brown2251.16%360.00%


J. Bruce Fields2046.51%120.00%


Adrian Bunk12.33%120.00%


Total43100.00%5100.00%






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]);
}


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J. Bruce Fields2554.35%114.29%


Neil Brown1941.30%571.43%


Andrew Morton24.35%114.29%


Total46100.00%7100.00%






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);

}


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Neil Brown5484.38%450.00%


J. Bruce Fields57.81%225.00%


Andrew Morton46.25%112.50%


Adrian Bunk11.56%112.50%


Total64100.00%8100.00%




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);
}


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J. Bruce Fields2567.57%120.00%


Neil Brown1232.43%480.00%


Total37100.00%5100.00%






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);
		}
	}
}


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Neil Brown8561.15%571.43%


J. Bruce Fields5438.85%228.57%


Total139100.00%7100.00%






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 (prandom_u32() & 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);
}


Contributors
PersonTokensPropCommitsCommitProp
Neil Brown7475.51%562.50%


J. Bruce Fields1919.39%112.50%


Andrew Morton44.08%112.50%


Aruna-Hewapathirane11.02%112.50%


Total98100.00%8100.00%



/* Return true if and only if a deferred request is queued. */



static bool 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 false;
	}
	dreq = req->defer(req);
	if (dreq == NULL)
		return false;
	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();
	return true;
}


Contributors
PersonTokensPropCommitsCommitProp
Neil Brown6764.42%675.00%


J. Bruce Fields3735.58%225.00%


Total104100.00%8100.00%






static void cache_revisit_request(struct cache_head *item)
{
	struct cache_deferred_req *dreq;
	struct list_head pending;
	struct hlist_node *tmp;
	int hash = DFR_HASH(item);

	INIT_LIST_HEAD(&pending);
	spin_lock(&cache_defer_lock);

	hlist_for_each_entry_safe(dreq, 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