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Commit d202cce8 authored by NeilBrown's avatar NeilBrown Committed by J. Bruce Fields
Browse files

sunrpc: never return expired entries in sunrpc_cache_lookup 



If sunrpc_cache_lookup finds an expired entry, remove it from
the cache and return a freshly created non-VALID entry instead.
This ensures that we only ever get a usable entry, or an
entry that will become usable once an update arrives.
i.e. we will never need to repeat the lookup.

This allows us to remove the 'is_expired' test from cache_check
(i.e. from cache_is_valid).  cache_check should never get an expired
entry as 'lookup' will never return one.  If it does happen - due to
inconvenient timing - then just accept it as still valid, it won't be
very much past it's use-by date.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
parent 2f50d8b6

net/sunrpc/cache.c

+14 −3
Original line number Original line Diff line number Diff line
@@ -59,7 +59,7 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail, 
				       struct cache_head *key, int hash)

				       struct cache_head *key, int hash)

{

{

	struct cache_head **head,  **hp;

	struct cache_head **head,  **hp;

	struct cache_head *new = NULL;

	struct cache_head *new = NULL, *freeme = NULL;





	head = &detail->hash_table[hash];

	head = &detail->hash_table[hash];
@@ -68,6 +68,9 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail, 
	for (hp=head; *hp != NULL ; hp = &(*hp)->next) {

	for (hp=head; *hp != NULL ; hp = &(*hp)->next) {

		struct cache_head *tmp = *hp;

		struct cache_head *tmp = *hp;

		if (detail->match(tmp, key)) {

		if (detail->match(tmp, key)) {

			if (cache_is_expired(detail, tmp))

				/* This entry is expired, we will discard it. */

				break;

			cache_get(tmp);

			cache_get(tmp);

			read_unlock(&detail->hash_lock);

			read_unlock(&detail->hash_lock);

			return tmp;

			return tmp;
@@ -92,6 +95,13 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail, 
	for (hp=head; *hp != NULL ; hp = &(*hp)->next) {

	for (hp=head; *hp != NULL ; hp = &(*hp)->next) {

		struct cache_head *tmp = *hp;

		struct cache_head *tmp = *hp;

		if (detail->match(tmp, key)) {

		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);

			cache_get(tmp);

			write_unlock(&detail->hash_lock);

			write_unlock(&detail->hash_lock);

			cache_put(new, detail);

			cache_put(new, detail);
@@ -104,6 +114,8 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail, 
	cache_get(new);

	cache_get(new);

	write_unlock(&detail->hash_lock);

	write_unlock(&detail->hash_lock);





	if (freeme)

		cache_put(freeme, detail);

	return new;

	return new;

}

}

EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);

EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
@@ -189,8 +201,7 @@ static int cache_make_upcall(struct cache_detail *cd, struct cache_head *h) 




static inline int cache_is_valid(struct cache_detail *detail, struct cache_head *h)

static inline int cache_is_valid(struct cache_detail *detail, struct cache_head *h)

{

{

	if (!test_bit(CACHE_VALID, &h->flags) ||

	if (!test_bit(CACHE_VALID, &h->flags))

	    cache_is_expired(detail, h))

		return -EAGAIN;

		return -EAGAIN;

	else {

	else {

		/* entry is valid */

		/* entry is valid */