vfs: embed struct filename inside of names_cache allocation if possible
In the common case where a name is much smaller than PATH_MAX, an extra
allocation for struct filename is unnecessary. Before allocating a
separate one, try to embed the struct filename inside the buffer first. If
it turns out that that's not long enough, then fall back to allocating a
separate struct filename and redoing the copy.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index 80b162b..d1895f3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -119,40 +119,69 @@
*/
void final_putname(struct filename *name)
{
- __putname(name->name);
- kfree(name);
+ if (name->separate) {
+ __putname(name->name);
+ kfree(name);
+ } else {
+ __putname(name);
+ }
}
+#define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
+
static struct filename *
getname_flags(const char __user *filename, int flags, int *empty)
{
struct filename *result, *err;
- char *kname;
int len;
+ long max;
+ char *kname;
result = audit_reusename(filename);
if (result)
return result;
- /* FIXME: create dedicated slabcache? */
- result = kzalloc(sizeof(*result), GFP_KERNEL);
+ result = __getname();
if (unlikely(!result))
return ERR_PTR(-ENOMEM);
- kname = __getname();
- if (unlikely(!kname)) {
- err = ERR_PTR(-ENOMEM);
- goto error_free_name;
- }
-
+ /*
+ * First, try to embed the struct filename inside the names_cache
+ * allocation
+ */
+ kname = (char *)result + sizeof(*result);
result->name = kname;
- result->uptr = filename;
- len = strncpy_from_user(kname, filename, PATH_MAX);
+ result->separate = false;
+ max = EMBEDDED_NAME_MAX;
+
+recopy:
+ len = strncpy_from_user(kname, filename, max);
if (unlikely(len < 0)) {
err = ERR_PTR(len);
goto error;
}
+ /*
+ * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
+ * separate struct filename so we can dedicate the entire
+ * names_cache allocation for the pathname, and re-do the copy from
+ * userland.
+ */
+ if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
+ kname = (char *)result;
+
+ result = kzalloc(sizeof(*result), GFP_KERNEL);
+ if (!result) {
+ err = ERR_PTR(-ENOMEM);
+ result = (struct filename *)kname;
+ goto error;
+ }
+ result->name = kname;
+ result->separate = true;
+ max = PATH_MAX;
+ goto recopy;
+ }
+
/* The empty path is special. */
if (unlikely(!len)) {
if (empty)
@@ -163,15 +192,15 @@
}
err = ERR_PTR(-ENAMETOOLONG);
- if (likely(len < PATH_MAX)) {
- audit_getname(result);
- return result;
- }
+ if (unlikely(len >= PATH_MAX))
+ goto error;
+
+ result->uptr = filename;
+ audit_getname(result);
+ return result;
error:
- __putname(kname);
-error_free_name:
- kfree(result);
+ final_putname(result);
return err;
}