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Btrfs: try to only do one btrfs_search_slot in do_setxattr

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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>
This commit is contained in:
Josef Bacik 2011-05-27 12:06:11 -04:00
parent 149e2d76b4
commit fa09200b83
2 changed files with 45 additions and 36 deletions
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9
fs/btrfs/dir-item.c
View File

@ -89,13 +89,8 @@ int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
data_size = sizeof(*dir_item) + name_len + data_len; data_size = sizeof(*dir_item) + name_len + data_len;
dir_item = insert_with_overflow(trans, root, path, &key, data_size, dir_item = insert_with_overflow(trans, root, path, &key, data_size,
name, name_len); name, name_len);
/* if (IS_ERR(dir_item))
* FIXME: at some point we should handle xattr's that are larger than return PTR_ERR(dir_item);
* 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));
memset(&location, 0, sizeof(location)); memset(&location, 0, sizeof(location));
leaf = path->nodes[0]; leaf = path->nodes[0];

72
fs/btrfs/xattr.c
View File

@ -102,43 +102,57 @@ static int do_setxattr(struct btrfs_trans_handle *trans,
if (!path) if (!path)
return -ENOMEM; return -ENOMEM;
/* first lets see if we already have this xattr */ if (flags & XATTR_REPLACE) {
di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name, di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
strlen(name), -1); name_len, -1);
if (IS_ERR(di)) { if (IS_ERR(di)) {
ret = PTR_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;
goto out; goto out;
} } else if (!di) {
ret = btrfs_delete_one_dir_name(trans, root, path, di);
BUG_ON(ret);
btrfs_release_path(path);
/* if we don't have a value then we are removing the xattr */
if (!value)
goto out;
} else {
btrfs_release_path(path);
if (flags & XATTR_REPLACE) {
/* we couldn't find the attr to replace */
ret = -ENODATA; ret = -ENODATA;
goto out; goto out;
} }
ret = btrfs_delete_one_dir_name(trans, root, path, di);
if (ret)
goto out;
btrfs_release_path(path);
} }
/* ok we have to create a completely new xattr */ again:
ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode), ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
name, name_len, value, size); name, name_len, value, size);
BUG_ON(ret); if (ret == -EEXIST) {
if (flags & XATTR_CREATE)
goto out;
/*
* 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;
}
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;
}
}
out: out:
btrfs_free_path(path); btrfs_free_path(path);
return ret; return ret;