[PATCH] NFSv4: client-side caching NFSv4 ACLs

 Add nfs4_acl field to the nfs_inode, and use it to cache acls.  Only cache
 acls of size up to a page.  Also prepare for up to a page of acl data even
 when the user doesn't pass in a buffer, as when they want to get the acl
 length to decide what size buffer to allocate.

 Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 123 insertions, 13 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index c45bd52cc1d7..350c48c12639 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -142,10 +142,6 @@ nfs_delete_inode(struct inode * inode)
         clear_inode(inode);
 }
 
-/*
- * For the moment, the only task for the NFS clear_inode method is to
- * release the mmap credential
- */
 static void
 nfs_clear_inode(struct inode *inode)
 {
@@ -1923,6 +1919,9 @@ static struct inode *nfs_alloc_inode(struct super_block *sb)
         if (!nfsi)
                 return NULL;
         nfsi->flags = 0;
+#ifdef CONFIG_NFS_V4
+        nfsi->nfs4_acl = NULL;
+#endif /* CONFIG_NFS_V4 */
         return &nfsi->vfs_inode;
 }
 
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index d969dd13e7db..128d01cfea19 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2188,9 +2188,75 @@ static void buf_to_pages(const void *buf, size_t buflen,
         }
 }
 
-static ssize_t nfs4_proc_get_acl(struct inode *inode, void *buf, size_t buflen)
+struct nfs4_cached_acl {
+        int cached;
+        size_t len;
+        char data[];
+};
+
+static void nfs4_set_cached_acl(struct inode *inode, struct nfs4_cached_acl *acl)
+{
+        struct nfs_inode *nfsi = NFS_I(inode);
+
+        spin_lock(&inode->i_lock);
+        kfree(nfsi->nfs4_acl);
+        nfsi->nfs4_acl = acl;
+        spin_unlock(&inode->i_lock);
+}
+
+static void nfs4_zap_acl_attr(struct inode *inode)
+{
+        nfs4_set_cached_acl(inode, NULL);
+}
+
+static inline ssize_t nfs4_read_cached_acl(struct inode *inode, char *buf, size_t buflen)
+{
+        struct nfs_inode *nfsi = NFS_I(inode);
+        struct nfs4_cached_acl *acl;
+        int ret = -ENOENT;
+
+        spin_lock(&inode->i_lock);
+        acl = nfsi->nfs4_acl;
+        if (acl == NULL)
+                goto out;
+        if (buf == NULL) /* user is just asking for length */
+                goto out_len;
+        if (acl->cached == 0)
+                goto out;
+        ret = -ERANGE; /* see getxattr(2) man page */
+        if (acl->len > buflen)
+                goto out;
+        memcpy(buf, acl->data, acl->len);
+out_len:
+        ret = acl->len;
+out:
+        spin_unlock(&inode->i_lock);
+        return ret;
+}
+
+static void nfs4_write_cached_acl(struct inode *inode, const char *buf, size_t acl_len)
+{
+        struct nfs4_cached_acl *acl;
+
+        if (buf && acl_len <= PAGE_SIZE) {
+                acl = kmalloc(sizeof(*acl) + acl_len, GFP_KERNEL);
+                if (acl == NULL)
+                        goto out;
+                acl->cached = 1;
+                memcpy(acl->data, buf, acl_len);
+        } else {
+                acl = kmalloc(sizeof(*acl), GFP_KERNEL);
+                if (acl == NULL)
+                        goto out;
+                acl->cached = 0;
+        }
+        acl->len = acl_len;
+out:
+        nfs4_set_cached_acl(inode, acl);
+}
+
+static inline ssize_t nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
 {
-        struct nfs_server *server = NFS_SERVER(inode);
         struct page *pages[NFS4ACL_MAXPAGES];
         struct nfs_getaclargs args = {
                 .fh = NFS_FH(inode),
@@ -2198,24 +2264,66 @@ static ssize_t nfs4_proc_get_acl(struct inode *inode, void *buf, size_t buflen)
                 .acl_len = buflen,
         };
         size_t resp_len = buflen;
+        void *resp_buf;
         struct rpc_message msg = {
                 .rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_GETACL],
                 .rpc_argp = &args,
                 .rpc_resp = &resp_len,
         };
+        struct page *localpage = NULL;
         int ret;
 
-        if (!nfs4_server_supports_acls(server))
-                return -EOPNOTSUPP;
-        buf_to_pages(buf, buflen, args.acl_pages, &args.acl_pgbase);
+        if (buflen < PAGE_SIZE) {
+                /* As long as we're doing a round trip to the server anyway,
+                 * let's be prepared for a page of acl data. */
+                localpage = alloc_page(GFP_KERNEL);
+                resp_buf = page_address(localpage);
+                if (localpage == NULL)
+                        return -ENOMEM;
+                args.acl_pages[0] = localpage;
+                args.acl_pgbase = 0;
+                args.acl_len = PAGE_SIZE;
+        } else {
+                resp_buf = buf;
+                buf_to_pages(buf, buflen, args.acl_pages, &args.acl_pgbase);
+        }
         ret = rpc_call_sync(NFS_CLIENT(inode), &msg, 0);
-        if (buflen && resp_len > buflen)
-                return -ERANGE;
-        if (ret == 0)
-                ret = resp_len;
+        if (ret)
+                goto out_free;
+        if (resp_len > args.acl_len)
+                nfs4_write_cached_acl(inode, NULL, resp_len);
+        else
+                nfs4_write_cached_acl(inode, resp_buf, resp_len);
+        if (buf) {
+                ret = -ERANGE;
+                if (resp_len > buflen)
+                        goto out_free;
+                if (localpage)
+                        memcpy(buf, resp_buf, resp_len);
+        }
+        ret = resp_len;
+out_free:
+        if (localpage)
+                __free_page(localpage);
         return ret;
 }
 
+static ssize_t nfs4_proc_get_acl(struct inode *inode, void *buf, size_t buflen)
+{
+        struct nfs_server *server = NFS_SERVER(inode);
+        int ret;
+
+        if (!nfs4_server_supports_acls(server))
+                return -EOPNOTSUPP;
+        ret = nfs_revalidate_inode(server, inode);
+        if (ret < 0)
+                return ret;
+        ret = nfs4_read_cached_acl(inode, buf, buflen);
+        if (ret != -ENOENT)
+                return ret;
+        return nfs4_get_acl_uncached(inode, buf, buflen);
+}
+
 static int nfs4_proc_set_acl(struct inode *inode, const void *buf, size_t buflen)
 {
         struct nfs_server *server = NFS_SERVER(inode);
@@ -2236,6 +2344,8 @@ static int nfs4_proc_set_acl(struct inode *inode, const void *buf, size_t buflen
                 return -EOPNOTSUPP;
         buf_to_pages(buf, buflen, arg.acl_pages, &arg.acl_pgbase);
         ret = rpc_call_sync(NFS_SERVER(inode)->client, &msg, 0);
+        if (ret == 0)
+                nfs4_write_cached_acl(inode, buf, buflen);
         return ret;
 }
 
@@ -2907,6 +3017,7 @@ struct nfs_rpc_ops	nfs_v4_clientops = {
         .file_open      = nfs4_proc_file_open,
         .file_release   = nfs4_proc_file_release,
         .lock           = nfs4_proc_lock,
+        .clear_acl_cache = nfs4_zap_acl_attr,
 };
 
 /*