Xattrs in btrfs are stored in the btree close to the inode item. They use an
indexing scheme very similar to directories.
The max size of a btrfs xattr is limited by the size of a btree item,
or about 4k. A future version will support larger items.
Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
new file mode 100644
index 0000000..7f332e2
--- /dev/null
+++ b/fs/btrfs/xattr.c
@@ -0,0 +1,322 @@
+/*
+ * Copyright (C) 2007 Red Hat. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/rwsem.h>
+#include <linux/xattr.h>
+#include "ctree.h"
+#include "btrfs_inode.h"
+#include "transaction.h"
+#include "xattr.h"
+#include "disk-io.h"
+
+
+ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
+ void *buffer, size_t size)
+{
+ struct btrfs_dir_item *di;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ struct btrfs_path *path;
+ struct extent_buffer *leaf;
+ int ret = 0;
+ unsigned long data_ptr;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ /* lookup the xattr by name */
+ di = btrfs_lookup_xattr(NULL, root, path, inode->i_ino, name,
+ strlen(name), 0);
+ if (!di || IS_ERR(di)) {
+ ret = -ENODATA;
+ goto out;
+ }
+
+ leaf = path->nodes[0];
+ /* if size is 0, that means we want the size of the attr */
+ if (!size) {
+ ret = btrfs_dir_data_len(leaf, di);
+ goto out;
+ }
+
+ /* now get the data out of our dir_item */
+ if (btrfs_dir_data_len(leaf, di) > size) {
+ ret = -ERANGE;
+ goto out;
+ }
+ data_ptr = (unsigned long)((char *)(di + 1) +
+ btrfs_dir_name_len(leaf, di));
+ read_extent_buffer(leaf, buffer, data_ptr,
+ btrfs_dir_data_len(leaf, di));
+ ret = btrfs_dir_data_len(leaf, di);
+
+out:
+ btrfs_free_path(path);
+ return ret;
+}
+
+int __btrfs_setxattr(struct inode *inode, const char *name,
+ const void *value, size_t size, int flags)
+{
+ struct btrfs_dir_item *di;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ struct btrfs_trans_handle *trans;
+ struct btrfs_path *path;
+ int ret = 0, mod = 0;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ trans = btrfs_start_transaction(root, 1);
+ btrfs_set_trans_block_group(trans, inode);
+
+ /* first lets see if we already have this xattr */
+ di = btrfs_lookup_xattr(trans, root, path, inode->i_ino, 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;
+ goto out;
+ }
+
+ ret = btrfs_delete_one_dir_name(trans, root, path, di);
+ if (ret)
+ goto out;
+ btrfs_release_path(root, path);
+
+ /* if we don't have a value then we are removing the xattr */
+ if (!value) {
+ mod = 1;
+ goto out;
+ }
+ } else {
+ btrfs_release_path(root, path);
+
+ if (flags & XATTR_REPLACE) {
+ /* we couldn't find the attr to replace */
+ ret = -ENODATA;
+ goto out;
+ }
+ }
+
+ /* ok we have to create a completely new xattr */
+ ret = btrfs_insert_xattr_item(trans, root, name, strlen(name),
+ value, size, inode->i_ino);
+ if (ret)
+ goto out;
+ mod = 1;
+
+out:
+ if (mod) {
+ inode->i_ctime = CURRENT_TIME;
+ ret = btrfs_update_inode(trans, root, inode);
+ }
+
+ btrfs_end_transaction(trans, root);
+ btrfs_free_path(path);
+ return ret;
+}
+
+ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+ struct btrfs_key key, found_key;
+ struct inode *inode = dentry->d_inode;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ struct btrfs_path *path;
+ struct btrfs_item *item;
+ struct extent_buffer *leaf;
+ struct btrfs_dir_item *di;
+ int ret = 0, slot, advance;
+ size_t total_size = 0, size_left = size;
+ unsigned long name_ptr;
+ size_t name_len;
+ u32 nritems;
+
+ /*
+ * ok we want all objects associated with this id.
+ * NOTE: we set key.offset = 0; because we want to start with the
+ * first xattr that we find and walk forward
+ */
+ key.objectid = inode->i_ino;
+ btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
+ key.offset = 0;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+ path->reada = 2;
+
+ /* search for our xattrs */
+ ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+ if (ret < 0)
+ goto err;
+ ret = 0;
+ advance = 0;
+ while (1) {
+ leaf = path->nodes[0];
+ nritems = btrfs_header_nritems(leaf);
+ slot = path->slots[0];
+
+ /* this is where we start walking through the path */
+ if (advance || slot >= nritems) {
+ /*
+ * if we've reached the last slot in this leaf we need
+ * to go to the next leaf and reset everything
+ */
+ if (slot >= nritems-1) {
+ ret = btrfs_next_leaf(root, path);
+ if (ret)
+ break;
+ leaf = path->nodes[0];
+ nritems = btrfs_header_nritems(leaf);
+ slot = path->slots[0];
+ } else {
+ /*
+ * just walking through the slots on this leaf
+ */
+ slot++;
+ path->slots[0]++;
+ }
+ }
+ advance = 1;
+
+ item = btrfs_item_nr(leaf, slot);
+ btrfs_item_key_to_cpu(leaf, &found_key, slot);
+
+ /* check to make sure this item is what we want */
+ if (found_key.objectid != key.objectid)
+ break;
+ if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
+ break;
+
+ di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
+
+ name_len = btrfs_dir_name_len(leaf, di);
+ total_size += name_len + 1;
+
+ /* we are just looking for how big our buffer needs to be */
+ if (!size)
+ continue;
+
+ if (!buffer || (name_len + 1) > size_left) {
+ ret = -ERANGE;
+ goto err;
+ }
+
+ name_ptr = (unsigned long)(di + 1);
+ read_extent_buffer(leaf, buffer, name_ptr, name_len);
+ buffer[name_len] = '\0';
+
+ size_left -= name_len + 1;
+ buffer += name_len + 1;
+ }
+ ret = total_size;
+
+err:
+ btrfs_free_path(path);
+
+ return ret;
+}
+
+/*
+ * List of handlers for synthetic system.* attributes. All real ondisk
+ * attributes are handled directly.
+ */
+struct xattr_handler *btrfs_xattr_handlers[] = {
+#ifdef CONFIG_FS_POSIX_ACL
+ &btrfs_xattr_acl_access_handler,
+ &btrfs_xattr_acl_default_handler,
+#endif
+ NULL,
+};
+
+/*
+ * Check if the attribute is in a supported namespace.
+ *
+ * This applied after the check for the synthetic attributes in the system
+ * namespace.
+ */
+static bool btrfs_is_valid_xattr(const char *name)
+{
+ return !strncmp(name, XATTR_SECURITY_PREFIX,
+ XATTR_SECURITY_PREFIX_LEN) ||
+ !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
+ !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
+ !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
+}
+
+ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
+ void *buffer, size_t size)
+{
+ /*
+ * If this is a request for a synthetic attribute in the system.*
+ * namespace use the generic infrastructure to resolve a handler
+ * for it via sb->s_xattr.
+ */
+ if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ return generic_getxattr(dentry, name, buffer, size);
+
+ if (!btrfs_is_valid_xattr(name))
+ return -EOPNOTSUPP;
+ return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
+}
+
+int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
+ size_t size, int flags)
+{
+ /*
+ * If this is a request for a synthetic attribute in the system.*
+ * namespace use the generic infrastructure to resolve a handler
+ * for it via sb->s_xattr.
+ */
+ if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ return generic_setxattr(dentry, name, value, size, flags);
+
+ if (!btrfs_is_valid_xattr(name))
+ return -EOPNOTSUPP;
+
+ if (size == 0)
+ value = ""; /* empty EA, do not remove */
+ return __btrfs_setxattr(dentry->d_inode, name, value, size, flags);
+}
+
+int btrfs_removexattr(struct dentry *dentry, const char *name)
+{
+ /*
+ * If this is a request for a synthetic attribute in the system.*
+ * namespace use the generic infrastructure to resolve a handler
+ * for it via sb->s_xattr.
+ */
+ if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ return generic_removexattr(dentry, name);
+
+ if (!btrfs_is_valid_xattr(name))
+ return -EOPNOTSUPP;
+ return __btrfs_setxattr(dentry->d_inode, name, NULL, 0, XATTR_REPLACE);
+}
diff --git a/fs/btrfs/xattr.h b/fs/btrfs/xattr.h
new file mode 100644
index 0000000..5b1d08f
--- /dev/null
+++ b/fs/btrfs/xattr.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2007 Red Hat. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __XATTR__
+#define __XATTR__
+
+#include <linux/xattr.h>
+
+extern struct xattr_handler btrfs_xattr_acl_access_handler;
+extern struct xattr_handler btrfs_xattr_acl_default_handler;
+extern struct xattr_handler *btrfs_xattr_handlers[];
+
+extern ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
+ void *buffer, size_t size);
+extern int __btrfs_setxattr(struct inode *inode, const char *name,
+ const void *value, size_t size, int flags);
+
+extern ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
+ void *buffer, size_t size);
+extern int btrfs_setxattr(struct dentry *dentry, const char *name,
+ const void *value, size_t size, int flags);
+extern int btrfs_removexattr(struct dentry *dentry, const char *name);
+
+#endif /* __XATTR__ */
--
1.6.0.2
--
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