NFS: Add a new ACCESS rpc call cache to the linux nfs client

The current access cache only allows one entry at a time to be cached for each
inode. Add a per-inode red-black tree in order to allow more than one to
be cached at a time.

Should significantly cut down the time spent in path traversal for shared
directories such as ${PATH}, /usr/share, etc.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 116 insertions, 17 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index e7ffb4deb3e5..094afded2b11 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1638,35 +1638,134 @@ out:
         return error;
 }
 
-int nfs_access_get_cached(struct inode *inode, struct rpc_cred *cred, struct nfs_access_entry *res)
+static void nfs_access_free_entry(struct nfs_access_entry *entry)
+{
+        put_rpccred(entry->cred);
+        kfree(entry);
+}
+
+static void __nfs_access_zap_cache(struct inode *inode)
 {
         struct nfs_inode *nfsi = NFS_I(inode);
-        struct nfs_access_entry *cache = &nfsi->cache_access;
+        struct rb_root *root_node = &nfsi->access_cache;
+        struct rb_node *n, *dispose = NULL;
+        struct nfs_access_entry *entry;
+
+        /* Unhook entries from the cache */
+        while ((n = rb_first(root_node)) != NULL) {
+                entry = rb_entry(n, struct nfs_access_entry, rb_node);
+                rb_erase(n, root_node);
+                n->rb_left = dispose;
+                dispose = n;
+        }
+        nfsi->cache_validity &= ~NFS_INO_INVALID_ACCESS;
+        spin_unlock(&inode->i_lock);
 
-        if (cache->cred != cred
-                        || time_after(jiffies, cache->jiffies + NFS_ATTRTIMEO(inode))
-                        || (nfsi->cache_validity & NFS_INO_INVALID_ACCESS))
-                return -ENOENT;
-        memcpy(res, cache, sizeof(*res));
-        return 0;
+        /* Now kill them all! */
+        while (dispose != NULL) {
+                n = dispose;
+                dispose = n->rb_left;
+                nfs_access_free_entry(rb_entry(n, struct nfs_access_entry, rb_node));
+        }
 }
 
-void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set)
+void nfs_access_zap_cache(struct inode *inode)
 {
-        struct nfs_inode *nfsi = NFS_I(inode);
-        struct nfs_access_entry *cache = &nfsi->cache_access;
+        spin_lock(&inode->i_lock);
+        /* This will release the spinlock */
+        __nfs_access_zap_cache(inode);
+}
 
-        if (cache->cred != set->cred) {
-                if (cache->cred)
-                        put_rpccred(cache->cred);
-                cache->cred = get_rpccred(set->cred);
+static struct nfs_access_entry *nfs_access_search_rbtree(struct inode *inode, struct rpc_cred *cred)
+{
+        struct rb_node *n = NFS_I(inode)->access_cache.rb_node;
+        struct nfs_access_entry *entry;
+
+        while (n != NULL) {
+                entry = rb_entry(n, struct nfs_access_entry, rb_node);
+
+                if (cred < entry->cred)
+                        n = n->rb_left;
+                else if (cred > entry->cred)
+                        n = n->rb_right;
+                else
+                        return entry;
         }
-        /* FIXME: replace current access_cache BKL reliance with inode->i_lock */
+        return NULL;
+}
+
+int nfs_access_get_cached(struct inode *inode, struct rpc_cred *cred, struct nfs_access_entry *res)
+{
+        struct nfs_inode *nfsi = NFS_I(inode);
+        struct nfs_access_entry *cache;
+        int err = -ENOENT;
+
         spin_lock(&inode->i_lock);
-        nfsi->cache_validity &= ~NFS_INO_INVALID_ACCESS;
+        if (nfsi->cache_validity & NFS_INO_INVALID_ACCESS)
+                goto out_zap;
+        cache = nfs_access_search_rbtree(inode, cred);
+        if (cache == NULL)
+                goto out;
+        if (time_after(jiffies, cache->jiffies + NFS_ATTRTIMEO(inode)))
+                goto out_stale;
+        res->jiffies = cache->jiffies;
+        res->cred = cache->cred;
+        res->mask = cache->mask;
+        err = 0;
+out:
+        spin_unlock(&inode->i_lock);
+        return err;
+out_stale:
+        rb_erase(&cache->rb_node, &nfsi->access_cache);
+        spin_unlock(&inode->i_lock);
+        nfs_access_free_entry(cache);
+        return -ENOENT;
+out_zap:
+        /* This will release the spinlock */
+        __nfs_access_zap_cache(inode);
+        return -ENOENT;
+}
+
+static void nfs_access_add_rbtree(struct inode *inode, struct nfs_access_entry *set)
+{
+        struct rb_root *root_node = &NFS_I(inode)->access_cache;
+        struct rb_node **p = &root_node->rb_node;
+        struct rb_node *parent = NULL;
+        struct nfs_access_entry *entry;
+
+        spin_lock(&inode->i_lock);
+        while (*p != NULL) {
+                parent = *p;
+                entry = rb_entry(parent, struct nfs_access_entry, rb_node);
+
+                if (set->cred < entry->cred)
+                        p = &parent->rb_left;
+                else if (set->cred > entry->cred)
+                        p = &parent->rb_right;
+                else
+                        goto found;
+        }
+        rb_link_node(&set->rb_node, parent, p);
+        rb_insert_color(&set->rb_node, root_node);
         spin_unlock(&inode->i_lock);
+        return;
+found:
+        rb_replace_node(parent, &set->rb_node, root_node);
+        spin_unlock(&inode->i_lock);
+        nfs_access_free_entry(entry);
+}
+
+void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set)
+{
+        struct nfs_access_entry *cache = kmalloc(sizeof(*cache), GFP_KERNEL);
+        if (cache == NULL)
+                return;
+        RB_CLEAR_NODE(&cache->rb_node);
         cache->jiffies = set->jiffies;
+        cache->cred = get_rpccred(set->cred);
         cache->mask = set->mask;
+
+        nfs_access_add_rbtree(inode, cache);
 }
 
 static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)