cifs: avoid extra allocation for small cifs.idmap keys

[pandora-kernel.git] / fs / cifs / cifsacl.c

diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index f4508ee..751d34b 100644 (file)
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -49,6 +49,20 @@ cifs_idmap_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
 {
        char *payload;
 
+       /*
+        * If the payload is less than or equal to the size of a pointer, then
+        * an allocation here is wasteful. Just copy the data directly to the
+        * payload.value union member instead.
+        *
+        * With this however, you must check the datalen before trying to
+        * dereference payload.data!
+        */
+       if (prep->datalen <= sizeof(void *)) {
+               key->payload.value = 0;
+               memcpy(&key->payload.value, prep->data, prep->datalen);
+               key->datalen = prep->datalen;
+               return 0;
+       }
        payload = kmalloc(prep->datalen, GFP_KERNEL);
        if (!payload)
                return -ENOMEM;
@@ -62,7 +76,8 @@ cifs_idmap_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
 static inline void
 cifs_idmap_key_destroy(struct key *key)
 {
-       kfree(key->payload.data);
+       if (key->datalen > sizeof(void *))
+               kfree(key->payload.data);
 }
 
 static struct key_type cifs_idmap_key_type = {
@@ -245,7 +260,7 @@ sid_to_id(struct cifs_sb_info *cifs_sb, struct cifs_sid *psid,
         * probably a safe assumption but might be better to check based on
         * sidtype.
         */
-       if (sidkey->datalen < sizeof(uid_t)) {
+       if (sidkey->datalen != sizeof(uid_t)) {
                rc = -EIO;
                cFYI(1, "%s: Downcall contained malformed key "
                        "(datalen=%hu)", __func__, sidkey->datalen);
@@ -253,9 +268,9 @@ sid_to_id(struct cifs_sb_info *cifs_sb, struct cifs_sid *psid,
        }
 
        if (sidtype == SIDOWNER)
-               fuid = *(uid_t *)sidkey->payload.value;
+               memcpy(&fuid, &sidkey->payload.value, sizeof(uid_t));
        else
-               fgid = *(gid_t *)sidkey->payload.value;
+               memcpy(&fgid, &sidkey->payload.value, sizeof(gid_t));
 
 out_key_put:
        key_put(sidkey);