sunrpc: clean cache_detail immediately when flush is written frequently

We will write /proc/net/rpc/xxx/flush if we want to clean cache_detail.
This updates nextcheck to the current time and calls cache_flush -->
cache_clean to clean cache_detail.
If we write this interface again within one second, it will only increase
flush_time and nextcheck without actually cleaning cache_detail.
Therefore, if we keep writing this interface repeatedly within one second,
flush_time and nextcheck will keep increasing, even far exceeding the
current time, making it impossible to clear cache_detail through the flush
interface or cache_cleaner.
If someone frequently calls the flush interface, we should immediately
clean the corresponding cache_detail instead of continuously accumulating
nextcheck.

Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 7ce5e28a6c0316f9c2cbcc2b939d8ce661dd064a..004cdb59f0106cc0ff3aaa48f7203b9629620dcd 100644 (file)
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1536,9 +1536,13 @@ static ssize_t write_flush(struct file *file, const char __user *buf,
         * or by one second if it has already reached the current time.
         * Newly added cache entries will always have ->last_refresh greater
         * that ->flush_time, so they don't get flushed prematurely.
+        *
+        * If someone frequently calls the flush interface, we should
+        * immediately clean the corresponding cache_detail instead of
+        * continuously accumulating nextcheck.
         */
 
-       if (cd->flush_time >= now)
+       if (cd->flush_time >= now && cd->flush_time < (now + 5))
                now = cd->flush_time + 1;
 
        cd->flush_time = now;