On Mon, Feb 06 2017, Kinglong Mee wrote:
> User always free the cache_detail after sunrpc_destroy_cache_detail(),
> so, it must cleanup up entries that left in the cache_detail,
> otherwise, NULL reference may be caused when using the left entries.
>
> Also, NeriBrown suggests "write a stand-alone cache_purge()."
>
> v2, a stand-alone cache_purge(), not only for sunrpc_destroy_cache_detail
>
> Signed-off-by: Kinglong Mee <kinglongmee@xxxxxxxxx>
> ---
> net/sunrpc/cache.c | 39 ++++++++++++++++++++++++---------------
> 1 file changed, 24 insertions(+), 15 deletions(-)
>
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index 8147e8d..bd6ee79 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -362,11 +362,6 @@ 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) {
> - write_unlock(&cd->hash_lock);
> - spin_unlock(&cache_list_lock);
> - goto out;
> - }
> if (current_detail == cd)
> current_detail = NULL;
> list_del_init(&cd->others);
> @@ -376,9 +371,6 @@ void sunrpc_destroy_cache_detail(struct cache_detail *cd)
> /* module must be being unloaded so its safe to kill the worker */
> cancel_delayed_work_sync(&cache_cleaner);
> }
> - return;
> -out:
> - printk(KERN_ERR "RPC: failed to unregister %s cache\n", cd->name);
> }
> EXPORT_SYMBOL_GPL(sunrpc_destroy_cache_detail);
>
> @@ -497,13 +489,30 @@ EXPORT_SYMBOL_GPL(cache_flush);
>
> void cache_purge(struct cache_detail *detail)
> {
> - time_t now = seconds_since_boot();
> - if (detail->flush_time >= now)
> - now = detail->flush_time + 1;
> - /* 'now' is the maximum value any 'last_refresh' can have */
> - detail->flush_time = now;
> - detail->nextcheck = seconds_since_boot();
> - cache_flush();
> + 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);
> + cache_fresh_unlocked(ch, detail);
> + cache_put(ch, detail);
I'm a little bothered by calling cache_fresh_unlocked() while holding
->hash_lock. No other code does that.
You could probably argue that we don't need ->hash_lock at all here
because by the time we call cache_purge(), there cannot safely be any
other users. Should we just drop the write_lock() call?
NeilBrown
> + }
> + }
> + write_unlock(&detail->hash_lock);
> }
> EXPORT_SYMBOL_GPL(cache_purge);
>
> --
> 2.9.3
>
> --
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