NFSD: Fix the filecache LRU shrinker

Without LRU item rotation, the shrinker visits only a few items on
the end of the LRU list, and those would always be long-term OPEN
files for NFSv4 workloads. That makes the filecache shrinker
completely ineffective.

Adopt the same strategy as the inode LRU by using LRU_ROTATE.

Suggested-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 69d1ab6cfc148b304f3dbb11c51fdcba05acba8f..380f6c0da465af21f26a6ad9b04fd2b7e706c127 100644 (file)
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -446,6 +446,7 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose)
  *
  * Return values:
  *   %LRU_REMOVED: @item was removed from the LRU
+ *   %LRU_ROTATE: @item is to be moved to the LRU tail
  *   %LRU_SKIP: @item cannot be evicted
  */
 static enum lru_status
@@ -484,7 +485,7 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
 
        if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags)) {
                trace_nfsd_file_gc_referenced(nf);
-               return LRU_SKIP;
+               return LRU_ROTATE;
        }
 
        if (!test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
@@ -526,7 +527,7 @@ nfsd_file_gc(void)
        unsigned long ret;
 
        ret = list_lru_walk(&nfsd_file_lru, nfsd_file_lru_cb,
-                           &dispose, LONG_MAX);
+                           &dispose, list_lru_count(&nfsd_file_lru));
        trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
        nfsd_file_gc_dispose_list(&dispose);
 }