The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. Since some filesystem rely on the dentry being available to them when setting posix acls (e.g., 9p and cifs) they cannot rely on the old get acl inode operation to retrieve posix acl and need to implement their own custom handlers because of that. In a previous patch we renamed the old get acl inode operation to ->get_inode_acl(). We decided to rename it and implement a new one since ->get_inode_acl() is called generic_permission() and inode_permission() both of which can be called during an filesystem's ->permission() handler. So simply passing a dentry argument to ->get_acl() would have amounted to also having to pass a dentry argument to ->permission(). We avoided that change. This adds a new ->get_acl() inode operations which takes a dentry argument which filesystems such as 9p, cifs, and overlayfs can implement to get posix acls. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@xxxxxxxxxx [1] Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> --- Notes: /* v2 */ unchanged Documentation/filesystems/locking.rst | 2 ++ Documentation/filesystems/vfs.rst | 1 + include/linux/fs.h | 2 ++ 3 files changed, 5 insertions(+) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 1cd2930e54ee..4a0fcaeec58c 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -83,6 +83,7 @@ prototypes:: int (*fileattr_set)(struct user_namespace *mnt_userns, struct dentry *dentry, struct fileattr *fa); int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa); + struct posix_acl * (*get_acl)(struct user_namespace *, struct dentry *, int); locking rules: all may block @@ -104,6 +105,7 @@ get_link: no setattr: exclusive permission: no (may not block if called in rcu-walk mode) get_inode_acl: no +get_acl: no getattr: no listxattr: no fiemap: no diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 4fc6f1e23012..344f5f421c64 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -440,6 +440,7 @@ As of kernel 2.6.22, the following members are defined: int (*atomic_open)(struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode); int (*tmpfile) (struct user_namespace *, struct inode *, struct dentry *, umode_t); + struct posix_acl * (*get_acl)(struct user_namespace *, struct dentry *, int); int (*set_acl)(struct user_namespace *, struct inode *, struct posix_acl *, int); int (*fileattr_set)(struct user_namespace *mnt_userns, struct dentry *dentry, struct fileattr *fa); diff --git a/include/linux/fs.h b/include/linux/fs.h index 11cddd040578..badff81b9dde 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2168,6 +2168,8 @@ struct inode_operations { umode_t create_mode); int (*tmpfile) (struct user_namespace *, struct inode *, struct dentry *, umode_t); + struct posix_acl *(*get_acl)(struct user_namespace *, struct dentry *, + int); int (*set_acl)(struct user_namespace *, struct dentry *, struct posix_acl *, int); int (*fileattr_set)(struct user_namespace *mnt_userns, -- 2.34.1
