在 2024/3/22 23:48, Li Zetao 写道:
Implement the ACLs feature for ubifs based on vfs Posix ACLs,
details as follows:
* Initialize acl for newly created inode.
* Provides get/set interface to access ACLs.
ACLs feature relies on xattr implementation which using specific key
names "system.posix_acl_default" and "system.posix_acl_access". Now Only
the v2 version of POSIX ACLs is supported, and ubifs does not need to
customize the storage format, which can simplify the implementation.
It should be noted that Linux supports updating the file mode through
ACLs. However the acl may not exist, so ubifs_xattr_remove() returns
-ENODATA. Such a scenario needs to be specially handled. At the same
time, it needs to ensure that the updated inode is written to flash.
Signed-off-by: Li Zetao <lizetao1@xxxxxxxxxx>
---
v1 -> v2:
* Get xattr_name by direct expansion instead of posix_acl_xattr_name().
* Modify ubifs_xattr_remove to an external function to remove the xattr of ACL.
* Remove redundant likely() and unlikely().
* Fix updating file mode via ACL and support writing to flash.
v1: https://lore.kernel.org/all/20240319161646.2153867-2-lizetao1@xxxxxxxxxx/
fs/ubifs/Makefile | 1 +
fs/ubifs/acl.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++
fs/ubifs/ubifs.h | 14 ++++
fs/ubifs/xattr.c | 3 +-
4 files changed, 208 insertions(+), 2 deletions(-)
create mode 100644 fs/ubifs/acl.c
[...]
+static int ubifs_update_mode(struct inode *inode, umode_t mode)
+{
+ struct ubifs_inode *ui = ubifs_inode(inode);
+ struct ubifs_info *c = inode->i_sb->s_fs_info;
+ struct ubifs_budget_req req = { .dirtied_ino = 1,
+ .dirtied_ino_d = ALIGN(ui->data_len, 8) };
+ int release;
+ int err;
+
+ err = ubifs_budget_space(c, &req);
+ if (err)
+ return err;
+
+ mutex_lock(&ui->ui_mutex);
+ release = ui->dirty;
+ inode->i_mode = mode;
+ inode_set_ctime_current(inode);
+ mark_inode_dirty_sync(inode);
+ mutex_unlock(&ui->ui_mutex);
+
+ if (release)
+ ubifs_release_budget(c, &req);
+ if (IS_SYNC(inode))
+ err = inode->i_sb->s_op->write_inode(inode, NULL);
+
+ return err;
+}
+
+int ubifs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, struct posix_acl *acl, int type)
+{
+ struct inode *inode = d_inode(dentry);
+ umode_t mode = inode->i_mode;
+ bool update_mode = false;
+ int error;
+
+ if (type == ACL_TYPE_ACCESS && acl) {
+ error = posix_acl_update_mode(idmap, inode, &mode, &acl);
+ if (unlikely(error))
+ return error;
+
+ if (inode->i_mode != mode)
+ update_mode = true;
+ }
+
+ error = __ubifs_set_acl(inode, type, acl, 0);
+ if (!error && update_mode)
+ error = ubifs_update_mode(inode, mode);
Updating inode mode to disk is a right thing. However, this makes
ubifs_set_acl is not atomic, which is manifested in two points:
1. If ubifs_budget_space fails by ENOSPC, __ubifs_set_acl has stored
xattrs into disk, but inode mode is not updated, which makes inode->mode
be inconsistent with acl. This problem can be easily solved by moving
ubifs_budget_space before the __ubifs_set_acl.
2. If ubifs_write_inode fails or a powercut happens between
__ubifs_set_acl and ubifs_write_inode, inode->mode becomes inconsistent
with acl. PS: Ext4 makes set_acl atomic by 'handle'.
+
+ return error;
+
+}
