Btrfs: try to only do one btrfs_search_slot in do_setxattr

I've been watching how many btrfs_search_slot()'s we do and I noticed that when
we create a file with selinux enabled we were doing 2 each time we initialize
the security context.  That's because we lookup the xattr first so we can delete
it if we're setting a new value to an existing xattr.  But in the create case we
don't have any xattrs, so it is completely useless to have the extra lookup.  So
re-arrange things so that we only lookup first if we specifically have
XATTR_REPLACE.  That way in the basic case we only do 1 search, and in the more
complicated case we do the normal 2 lookups.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index 685f259..c360a84 100644 (file)
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -89,13 +89,8 @@ int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
        data_size = sizeof(*dir_item) + name_len + data_len;
        dir_item = insert_with_overflow(trans, root, path, &key, data_size,
                                        name, name_len);
-       /*
-        * FIXME: at some point we should handle xattr's that are larger than
-        * what we can fit in our leaf.  We set location to NULL b/c we arent
-        * pointing at anything else, that will change if we store the xattr
-        * data in a separate inode.
-        */
-       BUG_ON(IS_ERR(dir_item));
+       if (IS_ERR(dir_item))
+               return PTR_ERR(dir_item);
        memset(&location, 0, sizeof(location));
 
        leaf = path->nodes[0];

diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 5366fe4..d733b9c 100644 (file)
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -102,43 +102,57 @@ static int do_setxattr(struct btrfs_trans_handle *trans,
        if (!path)
                return -ENOMEM;
 
-       /* first lets see if we already have this xattr */
-       di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
-                               strlen(name), -1);
-       if (IS_ERR(di)) {
-               ret = PTR_ERR(di);
-               goto out;
-       }
-
-       /* ok we already have this xattr, lets remove it */
-       if (di) {
-               /* if we want create only exit */
-               if (flags & XATTR_CREATE) {
-                       ret = -EEXIST;
+       if (flags & XATTR_REPLACE) {
+               di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
+                                       name_len, -1);
+               if (IS_ERR(di)) {
+                       ret = PTR_ERR(di);
+                       goto out;
+               } else if (!di) {
+                       ret = -ENODATA;
                        goto out;
                }
-
                ret = btrfs_delete_one_dir_name(trans, root, path, di);
-               BUG_ON(ret);
+               if (ret)
+                       goto out;
                btrfs_release_path(path);
+       }
 
-               /* if we don't have a value then we are removing the xattr */
-               if (!value)
+again:
+       ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
+                                     name, name_len, value, size);
+       if (ret == -EEXIST) {
+               if (flags & XATTR_CREATE)
                        goto out;
-       } else {
+               /*
+                * We can't use the path we already have since we won't have the
+                * proper locking for a delete, so release the path and
+                * re-lookup to delete the thing.
+                */
                btrfs_release_path(path);
+               di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
+                                       name, name_len, -1);
+               if (IS_ERR(di)) {
+                       ret = PTR_ERR(di);
+                       goto out;
+               } else if (!di) {
+                       /* Shouldn't happen but just in case... */
+                       btrfs_release_path(path);
+                       goto again;
+               }
 
-               if (flags & XATTR_REPLACE) {
-                       /* we couldn't find the attr to replace */
-                       ret = -ENODATA;
+               ret = btrfs_delete_one_dir_name(trans, root, path, di);
+               if (ret)
                        goto out;
+
+               /*
+                * We have a value to set, so go back and try to insert it now.
+                */
+               if (value) {
+                       btrfs_release_path(path);
+                       goto again;
                }
        }
-
-       /* ok we have to create a completely new xattr */
-       ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
-                                     name, name_len, value, size);
-       BUG_ON(ret);
 out:
        btrfs_free_path(path);
        return ret;