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* [PATCH v2 0/2] allow overlayfs to do RCU lookups
@ 2021-08-18 13:33 Miklos Szeredi
  2021-08-18 13:33 ` [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback Miklos Szeredi
                   ` (2 more replies)
  0 siblings, 3 replies; 8+ messages in thread
From: Miklos Szeredi @ 2021-08-18 13:33 UTC (permalink / raw)
  To: Al Viro, Linus Torvalds
  Cc: linux-unionfs, linux-fsdevel, linux-kernel, Andreas Gruenbacher

I'd really like to fix this in some form, but not getting any response
[1][2][3].

Al, Linus, can you please comment?

I'm happy to take this through the overlayfs tree, just need an ACK for the
VFS API change.

Thanks,
Miklos

[1] https://lore.kernel.org/linux-fsdevel/20210323160629.228597-1-mszeredi@redhat.com/
[2] https://lore.kernel.org/linux-fsdevel/CAJfpegv4ttfCZY0DPm+SSc85eL5m3jqhdOS_avu1+WMZhdg7iA@mail.gmail.com/
[3] https://lore.kernel.org/linux-fsdevel/20210810120807.456788-1-mszeredi@redhat.com/

v2: just a minor fix for the CONFIG_FS_POSIX_ACL=n case.
---
Miklos Szeredi (2):
  vfs: add flags argument to ->get_acl() callback
  ovl: enable RCU'd ->get_acl()

 Documentation/filesystems/locking.rst |  2 +-
 Documentation/filesystems/vfs.rst     |  2 +-
 fs/9p/acl.c                           |  5 ++++-
 fs/9p/acl.h                           |  2 +-
 fs/bad_inode.c                        |  2 +-
 fs/btrfs/acl.c                        |  5 ++++-
 fs/btrfs/ctree.h                      |  2 +-
 fs/ceph/acl.c                         |  5 ++++-
 fs/ceph/super.h                       |  2 +-
 fs/erofs/xattr.c                      |  5 ++++-
 fs/erofs/xattr.h                      |  2 +-
 fs/ext2/acl.c                         |  5 ++++-
 fs/ext2/acl.h                         |  2 +-
 fs/ext4/acl.c                         |  5 ++++-
 fs/ext4/acl.h                         |  2 +-
 fs/f2fs/acl.c                         |  5 ++++-
 fs/f2fs/acl.h                         |  2 +-
 fs/fuse/acl.c                         |  5 ++++-
 fs/fuse/fuse_i.h                      |  2 +-
 fs/gfs2/acl.c                         |  5 ++++-
 fs/gfs2/acl.h                         |  2 +-
 fs/jffs2/acl.c                        |  5 ++++-
 fs/jffs2/acl.h                        |  2 +-
 fs/jfs/acl.c                          |  5 ++++-
 fs/jfs/jfs_acl.h                      |  2 +-
 fs/nfs/nfs3_fs.h                      |  2 +-
 fs/nfs/nfs3acl.c                      |  5 ++++-
 fs/ocfs2/acl.c                        |  5 ++++-
 fs/ocfs2/acl.h                        |  2 +-
 fs/orangefs/acl.c                     |  5 ++++-
 fs/orangefs/orangefs-kernel.h         |  2 +-
 fs/overlayfs/inode.c                  |  6 +++++-
 fs/overlayfs/overlayfs.h              |  2 +-
 fs/posix_acl.c                        | 10 ++++++++--
 fs/reiserfs/acl.h                     |  2 +-
 fs/reiserfs/xattr_acl.c               |  5 ++++-
 fs/xfs/xfs_acl.c                      |  5 ++++-
 fs/xfs/xfs_acl.h                      |  4 ++--
 include/linux/fs.h                    |  7 ++++++-
 include/linux/posix_acl.h             |  3 ++-
 40 files changed, 106 insertions(+), 42 deletions(-)

-- 
2.31.1


^ permalink raw reply	[flat|nested] 8+ messages in thread

* [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback
  2021-08-18 13:33 [PATCH v2 0/2] allow overlayfs to do RCU lookups Miklos Szeredi
@ 2021-08-18 13:33 ` Miklos Szeredi
  2021-08-18 13:49   ` Christian Brauner
  2021-08-18 13:34 ` [PATCH v2 2/2] ovl: enable RCU'd ->get_acl() Miklos Szeredi
  2021-08-18 14:26 ` [PATCH v2 0/2] allow overlayfs to do RCU lookups Al Viro
  2 siblings, 1 reply; 8+ messages in thread
From: Miklos Szeredi @ 2021-08-18 13:33 UTC (permalink / raw)
  To: Al Viro, Linus Torvalds
  Cc: linux-unionfs, linux-fsdevel, linux-kernel, Andreas Gruenbacher

Add a flags argument to the ->get_acl() callback, to allow
get_cached_acl_rcu() to call the ->get_acl() method with LOOKUP_RCU.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 Documentation/filesystems/locking.rst | 2 +-
 Documentation/filesystems/vfs.rst     | 2 +-
 fs/9p/acl.c                           | 5 ++++-
 fs/9p/acl.h                           | 2 +-
 fs/bad_inode.c                        | 2 +-
 fs/btrfs/acl.c                        | 5 ++++-
 fs/btrfs/ctree.h                      | 2 +-
 fs/ceph/acl.c                         | 5 ++++-
 fs/ceph/super.h                       | 2 +-
 fs/erofs/xattr.c                      | 5 ++++-
 fs/erofs/xattr.h                      | 2 +-
 fs/ext2/acl.c                         | 5 ++++-
 fs/ext2/acl.h                         | 2 +-
 fs/ext4/acl.c                         | 5 ++++-
 fs/ext4/acl.h                         | 2 +-
 fs/f2fs/acl.c                         | 5 ++++-
 fs/f2fs/acl.h                         | 2 +-
 fs/fuse/acl.c                         | 5 ++++-
 fs/fuse/fuse_i.h                      | 2 +-
 fs/gfs2/acl.c                         | 5 ++++-
 fs/gfs2/acl.h                         | 2 +-
 fs/jffs2/acl.c                        | 5 ++++-
 fs/jffs2/acl.h                        | 2 +-
 fs/jfs/acl.c                          | 5 ++++-
 fs/jfs/jfs_acl.h                      | 2 +-
 fs/nfs/nfs3_fs.h                      | 2 +-
 fs/nfs/nfs3acl.c                      | 5 ++++-
 fs/ocfs2/acl.c                        | 5 ++++-
 fs/ocfs2/acl.h                        | 2 +-
 fs/orangefs/acl.c                     | 5 ++++-
 fs/orangefs/orangefs-kernel.h         | 2 +-
 fs/overlayfs/inode.c                  | 5 ++++-
 fs/overlayfs/overlayfs.h              | 2 +-
 fs/posix_acl.c                        | 2 +-
 fs/reiserfs/acl.h                     | 2 +-
 fs/reiserfs/xattr_acl.c               | 5 ++++-
 fs/xfs/xfs_acl.c                      | 5 ++++-
 fs/xfs/xfs_acl.h                      | 4 ++--
 include/linux/fs.h                    | 2 +-
 39 files changed, 91 insertions(+), 40 deletions(-)

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 2183fd8cc350..a6a8f2b34331 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -70,7 +70,7 @@ prototypes::
 	const char *(*get_link) (struct dentry *, struct inode *, struct delayed_call *);
 	void (*truncate) (struct inode *);
 	int (*permission) (struct inode *, int, unsigned int);
-	int (*get_acl)(struct inode *, int);
+	struct posix_acl * (*get_acl)(struct inode *, int, int);
 	int (*setattr) (struct dentry *, struct iattr *);
 	int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
 	ssize_t (*listxattr) (struct dentry *, char *, size_t);
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 14c31eced416..dc9339acb66f 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -432,7 +432,7 @@ As of kernel 2.6.22, the following members are defined:
 		const char *(*get_link) (struct dentry *, struct inode *,
 					 struct delayed_call *);
 		int (*permission) (struct user_namespace *, struct inode *, int);
-		int (*get_acl)(struct inode *, int);
+		struct posix_acl * (*get_acl)(struct inode *, int, int);
 		int (*setattr) (struct user_namespace *, struct dentry *, struct iattr *);
 		int (*getattr) (struct user_namespace *, const struct path *, struct kstat *, u32, unsigned int);
 		ssize_t (*listxattr) (struct dentry *, char *, size_t);
diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index bb1b286c49ae..3ef7db80fe29 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -97,10 +97,13 @@ static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
 	return acl;
 }
 
-struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type)
+struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type, int flags)
 {
 	struct v9fs_session_info *v9ses;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	v9ses = v9fs_inode2v9ses(inode);
 	if (((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT) ||
 			((v9ses->flags & V9FS_ACL_MASK) != V9FS_POSIX_ACL)) {
diff --git a/fs/9p/acl.h b/fs/9p/acl.h
index e4f7e882272b..7b31cef9ef5a 100644
--- a/fs/9p/acl.h
+++ b/fs/9p/acl.h
@@ -16,7 +16,7 @@
 
 #ifdef CONFIG_9P_FS_POSIX_ACL
 extern int v9fs_get_acl(struct inode *, struct p9_fid *);
-extern struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type);
+extern struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type, int flags);
 extern int v9fs_acl_chmod(struct inode *, struct p9_fid *);
 extern int v9fs_set_create_acl(struct inode *, struct p9_fid *,
 			       struct posix_acl *, struct posix_acl *);
diff --git a/fs/bad_inode.c b/fs/bad_inode.c
index 48e16144c1f7..dd34decddaa6 100644
--- a/fs/bad_inode.c
+++ b/fs/bad_inode.c
@@ -121,7 +121,7 @@ static const char *bad_inode_get_link(struct dentry *dentry,
 	return ERR_PTR(-EIO);
 }
 
-static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type)
+static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type, int flags)
 {
 	return ERR_PTR(-EIO);
 }
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index d95eb5c8cb37..b53d55186e4a 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -16,13 +16,16 @@
 #include "btrfs_inode.h"
 #include "xattr.h"
 
-struct posix_acl *btrfs_get_acl(struct inode *inode, int type)
+struct posix_acl *btrfs_get_acl(struct inode *inode, int type, int flags)
 {
 	int size;
 	const char *name;
 	char *value = NULL;
 	struct posix_acl *acl;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e5e53e592d4f..460a64266066 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3686,7 +3686,7 @@ static inline int __btrfs_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag)
 
 /* acl.c */
 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
-struct posix_acl *btrfs_get_acl(struct inode *inode, int type);
+struct posix_acl *btrfs_get_acl(struct inode *inode, int type, int flags);
 int btrfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		  struct posix_acl *acl, int type);
 int btrfs_init_acl(struct btrfs_trans_handle *trans,
diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
index 529af59d9fd3..61e4f866d162 100644
--- a/fs/ceph/acl.c
+++ b/fs/ceph/acl.c
@@ -29,7 +29,7 @@ static inline void ceph_set_cached_acl(struct inode *inode,
 	spin_unlock(&ci->i_ceph_lock);
 }
 
-struct posix_acl *ceph_get_acl(struct inode *inode, int type)
+struct posix_acl *ceph_get_acl(struct inode *inode, int type, int flags)
 {
 	int size;
 	unsigned int retry_cnt = 0;
@@ -37,6 +37,9 @@ struct posix_acl *ceph_get_acl(struct inode *inode, int type)
 	char *value = NULL;
 	struct posix_acl *acl;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 6b6332a5c113..528975f199eb 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -1087,7 +1087,7 @@ void ceph_release_acl_sec_ctx(struct ceph_acl_sec_ctx *as_ctx);
 /* acl.c */
 #ifdef CONFIG_CEPH_FS_POSIX_ACL
 
-struct posix_acl *ceph_get_acl(struct inode *, int);
+struct posix_acl *ceph_get_acl(struct inode *, int, int);
 int ceph_set_acl(struct user_namespace *mnt_userns,
 		 struct inode *inode, struct posix_acl *acl, int type);
 int ceph_pre_init_acls(struct inode *dir, umode_t *mode,
diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
index 8dd54b420a1d..10c0d639d794 100644
--- a/fs/erofs/xattr.c
+++ b/fs/erofs/xattr.c
@@ -673,12 +673,15 @@ ssize_t erofs_listxattr(struct dentry *dentry,
 }
 
 #ifdef CONFIG_EROFS_FS_POSIX_ACL
-struct posix_acl *erofs_get_acl(struct inode *inode, int type)
+struct posix_acl *erofs_get_acl(struct inode *inode, int type, int flags)
 {
 	struct posix_acl *acl;
 	int prefix, rc;
 	char *value = NULL;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		prefix = EROFS_XATTR_INDEX_POSIX_ACL_ACCESS;
diff --git a/fs/erofs/xattr.h b/fs/erofs/xattr.h
index 366dcb400525..ac35b5886eff 100644
--- a/fs/erofs/xattr.h
+++ b/fs/erofs/xattr.h
@@ -80,7 +80,7 @@ static inline int erofs_getxattr(struct inode *inode, int index,
 #endif	/* !CONFIG_EROFS_FS_XATTR */
 
 #ifdef CONFIG_EROFS_FS_POSIX_ACL
-struct posix_acl *erofs_get_acl(struct inode *inode, int type);
+struct posix_acl *erofs_get_acl(struct inode *inode, int type, int flags);
 #else
 #define erofs_get_acl	(NULL)
 #endif
diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index b9a9db98e94b..e203ebd224c4 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -141,13 +141,16 @@ ext2_acl_to_disk(const struct posix_acl *acl, size_t *size)
  * inode->i_mutex: don't care
  */
 struct posix_acl *
-ext2_get_acl(struct inode *inode, int type)
+ext2_get_acl(struct inode *inode, int type, int flags)
 {
 	int name_index;
 	char *value = NULL;
 	struct posix_acl *acl;
 	int retval;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
diff --git a/fs/ext2/acl.h b/fs/ext2/acl.h
index 917db5f6630a..0bd53a953831 100644
--- a/fs/ext2/acl.h
+++ b/fs/ext2/acl.h
@@ -55,7 +55,7 @@ static inline int ext2_acl_count(size_t size)
 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 
 /* acl.c */
-extern struct posix_acl *ext2_get_acl(struct inode *inode, int type);
+extern struct posix_acl *ext2_get_acl(struct inode *inode, int type, int flags);
 extern int ext2_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 			struct posix_acl *acl, int type);
 extern int ext2_init_acl (struct inode *, struct inode *);
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index c5eaffccecc3..e4e27e34a221 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -142,13 +142,16 @@ ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
  * inode->i_mutex: don't care
  */
 struct posix_acl *
-ext4_get_acl(struct inode *inode, int type)
+ext4_get_acl(struct inode *inode, int type, int flags)
 {
 	int name_index;
 	char *value = NULL;
 	struct posix_acl *acl;
 	int retval;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
diff --git a/fs/ext4/acl.h b/fs/ext4/acl.h
index 84b8942a57f2..b349365c7b33 100644
--- a/fs/ext4/acl.h
+++ b/fs/ext4/acl.h
@@ -55,7 +55,7 @@ static inline int ext4_acl_count(size_t size)
 #ifdef CONFIG_EXT4_FS_POSIX_ACL
 
 /* acl.c */
-struct posix_acl *ext4_get_acl(struct inode *inode, int type);
+struct posix_acl *ext4_get_acl(struct inode *inode, int type, int flags);
 int ext4_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		 struct posix_acl *acl, int type);
 extern int ext4_init_acl(handle_t *, struct inode *, struct inode *);
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index 239ad9453b99..4d1b348a0ab7 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -196,8 +196,11 @@ static struct posix_acl *__f2fs_get_acl(struct inode *inode, int type,
 	return acl;
 }
 
-struct posix_acl *f2fs_get_acl(struct inode *inode, int type)
+struct posix_acl *f2fs_get_acl(struct inode *inode, int type, int flags)
 {
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	return __f2fs_get_acl(inode, type, NULL);
 }
 
diff --git a/fs/f2fs/acl.h b/fs/f2fs/acl.h
index 986fd1bc780b..3b7b0deb2845 100644
--- a/fs/f2fs/acl.h
+++ b/fs/f2fs/acl.h
@@ -33,7 +33,7 @@ struct f2fs_acl_header {
 
 #ifdef CONFIG_F2FS_FS_POSIX_ACL
 
-extern struct posix_acl *f2fs_get_acl(struct inode *, int);
+extern struct posix_acl *f2fs_get_acl(struct inode *, int, int);
 extern int f2fs_set_acl(struct user_namespace *, struct inode *,
 			struct posix_acl *, int);
 extern int f2fs_init_acl(struct inode *, struct inode *, struct page *,
diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
index 52b165319be1..194cb81634f9 100644
--- a/fs/fuse/acl.c
+++ b/fs/fuse/acl.c
@@ -11,7 +11,7 @@
 #include <linux/posix_acl.h>
 #include <linux/posix_acl_xattr.h>
 
-struct posix_acl *fuse_get_acl(struct inode *inode, int type)
+struct posix_acl *fuse_get_acl(struct inode *inode, int type, int flags)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	int size;
@@ -19,6 +19,9 @@ struct posix_acl *fuse_get_acl(struct inode *inode, int type)
 	void *value = NULL;
 	struct posix_acl *acl;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	if (fuse_is_bad(inode))
 		return ERR_PTR(-EIO);
 
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 07829ce78695..ba3a419c6766 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1216,7 +1216,7 @@ extern const struct xattr_handler *fuse_acl_xattr_handlers[];
 extern const struct xattr_handler *fuse_no_acl_xattr_handlers[];
 
 struct posix_acl;
-struct posix_acl *fuse_get_acl(struct inode *inode, int type);
+struct posix_acl *fuse_get_acl(struct inode *inode, int type, int flags);
 int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		 struct posix_acl *acl, int type);
 
diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index 9165d70ead07..956132de223c 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -57,13 +57,16 @@ static struct posix_acl *__gfs2_get_acl(struct inode *inode, int type)
 	return acl;
 }
 
-struct posix_acl *gfs2_get_acl(struct inode *inode, int type)
+struct posix_acl *gfs2_get_acl(struct inode *inode, int type, int flags)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder gh;
 	bool need_unlock = false;
 	struct posix_acl *acl;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	if (!gfs2_glock_is_locked_by_me(ip->i_gl)) {
 		int ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
 					     LM_FLAG_ANY, &gh);
diff --git a/fs/gfs2/acl.h b/fs/gfs2/acl.h
index eccc6a43326c..cdf8f12089de 100644
--- a/fs/gfs2/acl.h
+++ b/fs/gfs2/acl.h
@@ -11,7 +11,7 @@
 
 #define GFS2_ACL_MAX_ENTRIES(sdp) ((300 << (sdp)->sd_sb.sb_bsize_shift) >> 12)
 
-extern struct posix_acl *gfs2_get_acl(struct inode *inode, int type);
+extern struct posix_acl *gfs2_get_acl(struct inode *inode, int type, int flags);
 extern int __gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type);
 extern int gfs2_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 			struct posix_acl *acl, int type);
diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
index 55a79df70d24..35f4a0dcbd71 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -173,12 +173,15 @@ static void *jffs2_acl_to_medium(const struct posix_acl *acl, size_t *size)
 	return ERR_PTR(-EINVAL);
 }
 
-struct posix_acl *jffs2_get_acl(struct inode *inode, int type)
+struct posix_acl *jffs2_get_acl(struct inode *inode, int type, int flags)
 {
 	struct posix_acl *acl;
 	char *value = NULL;
 	int rc, xprefix;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		xprefix = JFFS2_XPREFIX_ACL_ACCESS;
diff --git a/fs/jffs2/acl.h b/fs/jffs2/acl.h
index 62c50da9d493..afd6f924aacb 100644
--- a/fs/jffs2/acl.h
+++ b/fs/jffs2/acl.h
@@ -27,7 +27,7 @@ struct jffs2_acl_header {
 
 #ifdef CONFIG_JFFS2_FS_POSIX_ACL
 
-struct posix_acl *jffs2_get_acl(struct inode *inode, int type);
+struct posix_acl *jffs2_get_acl(struct inode *inode, int type, int flags);
 int jffs2_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		  struct posix_acl *acl, int type);
 extern int jffs2_init_acl_pre(struct inode *, struct inode *, umode_t *);
diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
index 43c285c3d2a7..344d047bcb97 100644
--- a/fs/jfs/acl.c
+++ b/fs/jfs/acl.c
@@ -14,13 +14,16 @@
 #include "jfs_xattr.h"
 #include "jfs_acl.h"
 
-struct posix_acl *jfs_get_acl(struct inode *inode, int type)
+struct posix_acl *jfs_get_acl(struct inode *inode, int type, int flags)
 {
 	struct posix_acl *acl;
 	char *ea_name;
 	int size;
 	char *value = NULL;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch(type) {
 		case ACL_TYPE_ACCESS:
 			ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
diff --git a/fs/jfs/jfs_acl.h b/fs/jfs/jfs_acl.h
index 7ae389a7a366..e86997d1f123 100644
--- a/fs/jfs/jfs_acl.h
+++ b/fs/jfs/jfs_acl.h
@@ -7,7 +7,7 @@
 
 #ifdef CONFIG_JFS_POSIX_ACL
 
-struct posix_acl *jfs_get_acl(struct inode *inode, int type);
+struct posix_acl *jfs_get_acl(struct inode *inode, int type, int flags);
 int jfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		struct posix_acl *acl, int type);
 int jfs_init_acl(tid_t, struct inode *, struct inode *);
diff --git a/fs/nfs/nfs3_fs.h b/fs/nfs/nfs3_fs.h
index c8a192802dda..0f3ba2f3b8da 100644
--- a/fs/nfs/nfs3_fs.h
+++ b/fs/nfs/nfs3_fs.h
@@ -11,7 +11,7 @@
  * nfs3acl.c
  */
 #ifdef CONFIG_NFS_V3_ACL
-extern struct posix_acl *nfs3_get_acl(struct inode *inode, int type);
+extern struct posix_acl *nfs3_get_acl(struct inode *inode, int type, int flags);
 extern int nfs3_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 			struct posix_acl *acl, int type);
 extern int nfs3_proc_setacls(struct inode *inode, struct posix_acl *acl,
diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
index 9ec560aa4a50..f94def1342c6 100644
--- a/fs/nfs/nfs3acl.c
+++ b/fs/nfs/nfs3acl.c
@@ -44,7 +44,7 @@ static void nfs3_abort_get_acl(struct posix_acl **p)
 	cmpxchg(p, sentinel, ACL_NOT_CACHED);
 }
 
-struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
+struct posix_acl *nfs3_get_acl(struct inode *inode, int type, int flags)
 {
 	struct nfs_server *server = NFS_SERVER(inode);
 	struct page *pages[NFSACL_MAXPAGES] = { };
@@ -62,6 +62,9 @@ struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
 	};
 	int status, count;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	if (!nfs_server_capable(inode, NFS_CAP_ACLS))
 		return ERR_PTR(-EOPNOTSUPP);
 
diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index 5c72a7e6d6c5..a4df6e30c017 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -289,7 +289,7 @@ int ocfs2_iop_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 	return status;
 }
 
-struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
+struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type, int flags)
 {
 	struct ocfs2_super *osb;
 	struct buffer_head *di_bh = NULL;
@@ -297,6 +297,9 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
 	int had_lock;
 	struct ocfs2_lock_holder oh;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	osb = OCFS2_SB(inode->i_sb);
 	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
 		return NULL;
diff --git a/fs/ocfs2/acl.h b/fs/ocfs2/acl.h
index f59d8d0a61fa..e005c93b9153 100644
--- a/fs/ocfs2/acl.h
+++ b/fs/ocfs2/acl.h
@@ -16,7 +16,7 @@ struct ocfs2_acl_entry {
 	__le32 e_id;
 };
 
-struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type);
+struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type, int flags);
 int ocfs2_iop_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		      struct posix_acl *acl, int type);
 extern int ocfs2_acl_chmod(struct inode *, struct buffer_head *);
diff --git a/fs/orangefs/acl.c b/fs/orangefs/acl.c
index 18852b9ed82b..d93841d478ed 100644
--- a/fs/orangefs/acl.c
+++ b/fs/orangefs/acl.c
@@ -10,12 +10,15 @@
 #include "orangefs-bufmap.h"
 #include <linux/posix_acl_xattr.h>
 
-struct posix_acl *orangefs_get_acl(struct inode *inode, int type)
+struct posix_acl *orangefs_get_acl(struct inode *inode, int type, int flags)
 {
 	struct posix_acl *acl;
 	int ret;
 	char *key = NULL, *value = NULL;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		key = XATTR_NAME_POSIX_ACL_ACCESS;
diff --git a/fs/orangefs/orangefs-kernel.h b/fs/orangefs/orangefs-kernel.h
index 0e6b97682e41..370bd89c670f 100644
--- a/fs/orangefs/orangefs-kernel.h
+++ b/fs/orangefs/orangefs-kernel.h
@@ -106,7 +106,7 @@ enum orangefs_vfs_op_states {
 extern int orangefs_init_acl(struct inode *inode, struct inode *dir);
 extern const struct xattr_handler *orangefs_xattr_handlers[];
 
-extern struct posix_acl *orangefs_get_acl(struct inode *inode, int type);
+extern struct posix_acl *orangefs_get_acl(struct inode *inode, int type, int flags);
 extern int orangefs_set_acl(struct user_namespace *mnt_userns,
 			    struct inode *inode, struct posix_acl *acl,
 			    int type);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 5e828a1c98a8..727154a1d3ce 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -448,12 +448,15 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 	return res;
 }
 
-struct posix_acl *ovl_get_acl(struct inode *inode, int type)
+struct posix_acl *ovl_get_acl(struct inode *inode, int type, int flags)
 {
 	struct inode *realinode = ovl_inode_real(inode);
 	const struct cred *old_cred;
 	struct posix_acl *acl;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
 		return NULL;
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 6ec73db4bf9e..daf6b75b9a54 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -485,7 +485,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 		  void *value, size_t size);
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
-struct posix_acl *ovl_get_acl(struct inode *inode, int type);
+struct posix_acl *ovl_get_acl(struct inode *inode, int type, int flags);
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
 bool ovl_is_private_xattr(struct super_block *sb, const char *name);
 
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index f3309a7edb49..6b7f793e2b6f 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -138,7 +138,7 @@ struct posix_acl *get_acl(struct inode *inode, int type)
 		set_cached_acl(inode, type, NULL);
 		return NULL;
 	}
-	acl = inode->i_op->get_acl(inode, type);
+	acl = inode->i_op->get_acl(inode, type, 0);
 
 	if (IS_ERR(acl)) {
 		/*
diff --git a/fs/reiserfs/acl.h b/fs/reiserfs/acl.h
index fd58618da360..bf10841b892d 100644
--- a/fs/reiserfs/acl.h
+++ b/fs/reiserfs/acl.h
@@ -48,7 +48,7 @@ static inline int reiserfs_acl_count(size_t size)
 }
 
 #ifdef CONFIG_REISERFS_FS_POSIX_ACL
-struct posix_acl *reiserfs_get_acl(struct inode *inode, int type);
+struct posix_acl *reiserfs_get_acl(struct inode *inode, int type, int flags);
 int reiserfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		     struct posix_acl *acl, int type);
 int reiserfs_acl_chmod(struct inode *inode);
diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
index a9547144a099..0fdb4f531098 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -190,13 +190,16 @@ static void *reiserfs_posix_acl_to_disk(const struct posix_acl *acl, size_t * si
  * inode->i_mutex: down
  * BKL held [before 2.5.x]
  */
-struct posix_acl *reiserfs_get_acl(struct inode *inode, int type)
+struct posix_acl *reiserfs_get_acl(struct inode *inode, int type, int flags)
 {
 	char *name, *value;
 	struct posix_acl *acl;
 	int size;
 	int retval;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
index d02bef24b32b..5f9b541e029d 100644
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -125,7 +125,7 @@ xfs_acl_to_disk(struct xfs_acl *aclp, const struct posix_acl *acl)
 }
 
 struct posix_acl *
-xfs_get_acl(struct inode *inode, int type)
+xfs_get_acl(struct inode *inode, int type, int flags)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
@@ -137,6 +137,9 @@ xfs_get_acl(struct inode *inode, int type)
 	};
 	int			error;
 
+	if (flags)
+		return ERR_PTR(-EINVAL);
+
 	trace_xfs_get_acl(ip);
 
 	switch (type) {
diff --git a/fs/xfs/xfs_acl.h b/fs/xfs/xfs_acl.h
index 7bdb3a4ed798..38f933f2e281 100644
--- a/fs/xfs/xfs_acl.h
+++ b/fs/xfs/xfs_acl.h
@@ -10,13 +10,13 @@ struct inode;
 struct posix_acl;
 
 #ifdef CONFIG_XFS_POSIX_ACL
-extern struct posix_acl *xfs_get_acl(struct inode *inode, int type);
+extern struct posix_acl *xfs_get_acl(struct inode *inode, int type, int flags);
 extern int xfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 		       struct posix_acl *acl, int type);
 extern int __xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
 void xfs_forget_acl(struct inode *inode, const char *name);
 #else
-static inline struct posix_acl *xfs_get_acl(struct inode *inode, int type)
+static inline struct posix_acl *xfs_get_acl(struct inode *inode, int type, int flags)
 {
 	return NULL;
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 640574294216..1c56d4fc4efe 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2065,7 +2065,7 @@ struct inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
 	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
 	int (*permission) (struct user_namespace *, struct inode *, int);
-	struct posix_acl * (*get_acl)(struct inode *, int);
+	struct posix_acl * (*get_acl)(struct inode *, int, int);
 
 	int (*readlink) (struct dentry *, char __user *,int);
 
-- 
2.31.1


^ permalink raw reply	[flat|nested] 8+ messages in thread

* [PATCH v2 2/2] ovl: enable RCU'd ->get_acl()
  2021-08-18 13:33 [PATCH v2 0/2] allow overlayfs to do RCU lookups Miklos Szeredi
  2021-08-18 13:33 ` [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback Miklos Szeredi
@ 2021-08-18 13:34 ` Miklos Szeredi
  2021-08-18 18:34   ` Linus Torvalds
  2021-08-18 14:26 ` [PATCH v2 0/2] allow overlayfs to do RCU lookups Al Viro
  2 siblings, 1 reply; 8+ messages in thread
From: Miklos Szeredi @ 2021-08-18 13:34 UTC (permalink / raw)
  To: Al Viro, Linus Torvalds
  Cc: linux-unionfs, linux-fsdevel, linux-kernel, Andreas Gruenbacher,
	garyhuang

Overlayfs does not cache ACL's (to avoid double caching).  Instead it just
calls the underlying filesystem's i_op->get_acl(), which will return the
cached value, if possible.

In rcu path walk, however, get_cached_acl_rcu() is employed to get the
value from the cache, which will fail on overlayfs resulting in dropping
out of rcu walk mode.  This can result in a big performance hit in certain
situations.

Fix by calling ->get_acl() with LOOKUP_RCU flag in case of ACL_DONT_CACHE
(which indicates pass-through)

Reported-by: garyhuang <zjh.20052005@163.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/inode.c      | 7 ++++---
 fs/posix_acl.c            | 8 +++++++-
 include/linux/fs.h        | 5 +++++
 include/linux/posix_acl.h | 3 ++-
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 727154a1d3ce..6a55231b262a 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -13,6 +13,7 @@
 #include <linux/fiemap.h>
 #include <linux/fileattr.h>
 #include <linux/security.h>
+#include <linux/namei.h>
 #include "overlayfs.h"
 
 
@@ -454,12 +455,12 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, int flags)
 	const struct cred *old_cred;
 	struct posix_acl *acl;
 
-	if (flags)
-		return ERR_PTR(-EINVAL);
-
 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
 		return NULL;
 
+	if (flags & LOOKUP_RCU)
+		return get_cached_acl_rcu(realinode, type);
+
 	old_cred = ovl_override_creds(inode->i_sb);
 	acl = get_acl(realinode, type);
 	revert_creds(old_cred);
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 6b7f793e2b6f..4d1c6c266cf0 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -22,6 +22,7 @@
 #include <linux/xattr.h>
 #include <linux/export.h>
 #include <linux/user_namespace.h>
+#include <linux/namei.h>
 
 static struct posix_acl **acl_by_type(struct inode *inode, int type)
 {
@@ -56,7 +57,12 @@ EXPORT_SYMBOL(get_cached_acl);
 
 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
 {
-	return rcu_dereference(*acl_by_type(inode, type));
+	struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
+
+	if (acl == ACL_DONT_CACHE)
+		acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
+
+	return acl;
 }
 EXPORT_SYMBOL(get_cached_acl_rcu);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1c56d4fc4efe..20b7db2d0a85 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -581,6 +581,11 @@ static inline void mapping_allow_writable(struct address_space *mapping)
 
 struct posix_acl;
 #define ACL_NOT_CACHED ((void *)(-1))
+/*
+ * ACL_DONT_CACHE is for stacked filesystems, that rely on underlying fs to
+ * cache the ACL.  This also means that ->get_acl() can be called in RCU mode
+ * with the LOOKUP_RCU flag.
+ */
 #define ACL_DONT_CACHE ((void *)(-3))
 
 static inline struct posix_acl *
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index 307094ebb88c..b65c877d92b8 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -72,6 +72,8 @@ extern struct posix_acl *get_posix_acl(struct inode *, int);
 extern int set_posix_acl(struct user_namespace *, struct inode *, int,
 			 struct posix_acl *);
 
+struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
+
 #ifdef CONFIG_FS_POSIX_ACL
 int posix_acl_chmod(struct user_namespace *, struct inode *, umode_t);
 extern int posix_acl_create(struct inode *, umode_t *, struct posix_acl **,
@@ -84,7 +86,6 @@ extern int simple_set_acl(struct user_namespace *, struct inode *,
 extern int simple_acl_create(struct inode *, struct inode *);
 
 struct posix_acl *get_cached_acl(struct inode *inode, int type);
-struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl);
 void forget_cached_acl(struct inode *inode, int type);
 void forget_all_cached_acls(struct inode *inode);
-- 
2.31.1


^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback
  2021-08-18 13:33 ` [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback Miklos Szeredi
@ 2021-08-18 13:49   ` Christian Brauner
  0 siblings, 0 replies; 8+ messages in thread
From: Christian Brauner @ 2021-08-18 13:49 UTC (permalink / raw)
  To: Miklos Szeredi
  Cc: Al Viro, Linus Torvalds, linux-unionfs, linux-fsdevel,
	linux-kernel, Andreas Gruenbacher

On Wed, Aug 18, 2021 at 03:33:59PM +0200, Miklos Szeredi wrote:
> Add a flags argument to the ->get_acl() callback, to allow
> get_cached_acl_rcu() to call the ->get_acl() method with LOOKUP_RCU.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> ---
>  Documentation/filesystems/locking.rst | 2 +-
>  Documentation/filesystems/vfs.rst     | 2 +-
>  fs/9p/acl.c                           | 5 ++++-
>  fs/9p/acl.h                           | 2 +-
>  fs/bad_inode.c                        | 2 +-
>  fs/btrfs/acl.c                        | 5 ++++-
>  fs/btrfs/ctree.h                      | 2 +-
>  fs/ceph/acl.c                         | 5 ++++-
>  fs/ceph/super.h                       | 2 +-
>  fs/erofs/xattr.c                      | 5 ++++-
>  fs/erofs/xattr.h                      | 2 +-
>  fs/ext2/acl.c                         | 5 ++++-
>  fs/ext2/acl.h                         | 2 +-
>  fs/ext4/acl.c                         | 5 ++++-
>  fs/ext4/acl.h                         | 2 +-
>  fs/f2fs/acl.c                         | 5 ++++-
>  fs/f2fs/acl.h                         | 2 +-
>  fs/fuse/acl.c                         | 5 ++++-
>  fs/fuse/fuse_i.h                      | 2 +-
>  fs/gfs2/acl.c                         | 5 ++++-
>  fs/gfs2/acl.h                         | 2 +-
>  fs/jffs2/acl.c                        | 5 ++++-
>  fs/jffs2/acl.h                        | 2 +-
>  fs/jfs/acl.c                          | 5 ++++-
>  fs/jfs/jfs_acl.h                      | 2 +-
>  fs/nfs/nfs3_fs.h                      | 2 +-
>  fs/nfs/nfs3acl.c                      | 5 ++++-
>  fs/ocfs2/acl.c                        | 5 ++++-
>  fs/ocfs2/acl.h                        | 2 +-
>  fs/orangefs/acl.c                     | 5 ++++-
>  fs/orangefs/orangefs-kernel.h         | 2 +-
>  fs/overlayfs/inode.c                  | 5 ++++-
>  fs/overlayfs/overlayfs.h              | 2 +-
>  fs/posix_acl.c                        | 2 +-
>  fs/reiserfs/acl.h                     | 2 +-
>  fs/reiserfs/xattr_acl.c               | 5 ++++-
>  fs/xfs/xfs_acl.c                      | 5 ++++-
>  fs/xfs/xfs_acl.h                      | 4 ++--
>  include/linux/fs.h                    | 2 +-
>  39 files changed, 91 insertions(+), 40 deletions(-)
> 
> diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
> index 2183fd8cc350..a6a8f2b34331 100644
> --- a/Documentation/filesystems/locking.rst
> +++ b/Documentation/filesystems/locking.rst
> @@ -70,7 +70,7 @@ prototypes::
>  	const char *(*get_link) (struct dentry *, struct inode *, struct delayed_call *);
>  	void (*truncate) (struct inode *);
>  	int (*permission) (struct inode *, int, unsigned int);
> -	int (*get_acl)(struct inode *, int);
> +	struct posix_acl * (*get_acl)(struct inode *, int, int);
>  	int (*setattr) (struct dentry *, struct iattr *);
>  	int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
>  	ssize_t (*listxattr) (struct dentry *, char *, size_t);
> diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
> index 14c31eced416..dc9339acb66f 100644
> --- a/Documentation/filesystems/vfs.rst
> +++ b/Documentation/filesystems/vfs.rst
> @@ -432,7 +432,7 @@ As of kernel 2.6.22, the following members are defined:
>  		const char *(*get_link) (struct dentry *, struct inode *,
>  					 struct delayed_call *);
>  		int (*permission) (struct user_namespace *, struct inode *, int);
> -		int (*get_acl)(struct inode *, int);
> +		struct posix_acl * (*get_acl)(struct inode *, int, int);

Fwiw, I think this series is sane. The only thing I'd like to see change
is that the flag argument should really be "unsigned int" not "int".
Other than that:

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

>  		int (*setattr) (struct user_namespace *, struct dentry *, struct iattr *);
>  		int (*getattr) (struct user_namespace *, const struct path *, struct kstat *, u32, unsigned int);
>  		ssize_t (*listxattr) (struct dentry *, char *, size_t);
> diff --git a/fs/9p/acl.c b/fs/9p/acl.c
> index bb1b286c49ae..3ef7db80fe29 100644
> --- a/fs/9p/acl.c
> +++ b/fs/9p/acl.c
> @@ -97,10 +97,13 @@ static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
>  	return acl;
>  }
>  
> -struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type)
> +struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct v9fs_session_info *v9ses;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	v9ses = v9fs_inode2v9ses(inode);
>  	if (((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT) ||
>  			((v9ses->flags & V9FS_ACL_MASK) != V9FS_POSIX_ACL)) {
> diff --git a/fs/9p/acl.h b/fs/9p/acl.h
> index e4f7e882272b..7b31cef9ef5a 100644
> --- a/fs/9p/acl.h
> +++ b/fs/9p/acl.h
> @@ -16,7 +16,7 @@
>  
>  #ifdef CONFIG_9P_FS_POSIX_ACL
>  extern int v9fs_get_acl(struct inode *, struct p9_fid *);
> -extern struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type);
> +extern struct posix_acl *v9fs_iop_get_acl(struct inode *inode, int type, int flags);
>  extern int v9fs_acl_chmod(struct inode *, struct p9_fid *);
>  extern int v9fs_set_create_acl(struct inode *, struct p9_fid *,
>  			       struct posix_acl *, struct posix_acl *);
> diff --git a/fs/bad_inode.c b/fs/bad_inode.c
> index 48e16144c1f7..dd34decddaa6 100644
> --- a/fs/bad_inode.c
> +++ b/fs/bad_inode.c
> @@ -121,7 +121,7 @@ static const char *bad_inode_get_link(struct dentry *dentry,
>  	return ERR_PTR(-EIO);
>  }
>  
> -static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type)
> +static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type, int flags)
>  {
>  	return ERR_PTR(-EIO);
>  }
> diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
> index d95eb5c8cb37..b53d55186e4a 100644
> --- a/fs/btrfs/acl.c
> +++ b/fs/btrfs/acl.c
> @@ -16,13 +16,16 @@
>  #include "btrfs_inode.h"
>  #include "xattr.h"
>  
> -struct posix_acl *btrfs_get_acl(struct inode *inode, int type)
> +struct posix_acl *btrfs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	int size;
>  	const char *name;
>  	char *value = NULL;
>  	struct posix_acl *acl;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		name = XATTR_NAME_POSIX_ACL_ACCESS;
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index e5e53e592d4f..460a64266066 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -3686,7 +3686,7 @@ static inline int __btrfs_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag)
>  
>  /* acl.c */
>  #ifdef CONFIG_BTRFS_FS_POSIX_ACL
> -struct posix_acl *btrfs_get_acl(struct inode *inode, int type);
> +struct posix_acl *btrfs_get_acl(struct inode *inode, int type, int flags);
>  int btrfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		  struct posix_acl *acl, int type);
>  int btrfs_init_acl(struct btrfs_trans_handle *trans,
> diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
> index 529af59d9fd3..61e4f866d162 100644
> --- a/fs/ceph/acl.c
> +++ b/fs/ceph/acl.c
> @@ -29,7 +29,7 @@ static inline void ceph_set_cached_acl(struct inode *inode,
>  	spin_unlock(&ci->i_ceph_lock);
>  }
>  
> -struct posix_acl *ceph_get_acl(struct inode *inode, int type)
> +struct posix_acl *ceph_get_acl(struct inode *inode, int type, int flags)
>  {
>  	int size;
>  	unsigned int retry_cnt = 0;
> @@ -37,6 +37,9 @@ struct posix_acl *ceph_get_acl(struct inode *inode, int type)
>  	char *value = NULL;
>  	struct posix_acl *acl;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		name = XATTR_NAME_POSIX_ACL_ACCESS;
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index 6b6332a5c113..528975f199eb 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -1087,7 +1087,7 @@ void ceph_release_acl_sec_ctx(struct ceph_acl_sec_ctx *as_ctx);
>  /* acl.c */
>  #ifdef CONFIG_CEPH_FS_POSIX_ACL
>  
> -struct posix_acl *ceph_get_acl(struct inode *, int);
> +struct posix_acl *ceph_get_acl(struct inode *, int, int);
>  int ceph_set_acl(struct user_namespace *mnt_userns,
>  		 struct inode *inode, struct posix_acl *acl, int type);
>  int ceph_pre_init_acls(struct inode *dir, umode_t *mode,
> diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
> index 8dd54b420a1d..10c0d639d794 100644
> --- a/fs/erofs/xattr.c
> +++ b/fs/erofs/xattr.c
> @@ -673,12 +673,15 @@ ssize_t erofs_listxattr(struct dentry *dentry,
>  }
>  
>  #ifdef CONFIG_EROFS_FS_POSIX_ACL
> -struct posix_acl *erofs_get_acl(struct inode *inode, int type)
> +struct posix_acl *erofs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct posix_acl *acl;
>  	int prefix, rc;
>  	char *value = NULL;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		prefix = EROFS_XATTR_INDEX_POSIX_ACL_ACCESS;
> diff --git a/fs/erofs/xattr.h b/fs/erofs/xattr.h
> index 366dcb400525..ac35b5886eff 100644
> --- a/fs/erofs/xattr.h
> +++ b/fs/erofs/xattr.h
> @@ -80,7 +80,7 @@ static inline int erofs_getxattr(struct inode *inode, int index,
>  #endif	/* !CONFIG_EROFS_FS_XATTR */
>  
>  #ifdef CONFIG_EROFS_FS_POSIX_ACL
> -struct posix_acl *erofs_get_acl(struct inode *inode, int type);
> +struct posix_acl *erofs_get_acl(struct inode *inode, int type, int flags);
>  #else
>  #define erofs_get_acl	(NULL)
>  #endif
> diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
> index b9a9db98e94b..e203ebd224c4 100644
> --- a/fs/ext2/acl.c
> +++ b/fs/ext2/acl.c
> @@ -141,13 +141,16 @@ ext2_acl_to_disk(const struct posix_acl *acl, size_t *size)
>   * inode->i_mutex: don't care
>   */
>  struct posix_acl *
> -ext2_get_acl(struct inode *inode, int type)
> +ext2_get_acl(struct inode *inode, int type, int flags)
>  {
>  	int name_index;
>  	char *value = NULL;
>  	struct posix_acl *acl;
>  	int retval;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
> diff --git a/fs/ext2/acl.h b/fs/ext2/acl.h
> index 917db5f6630a..0bd53a953831 100644
> --- a/fs/ext2/acl.h
> +++ b/fs/ext2/acl.h
> @@ -55,7 +55,7 @@ static inline int ext2_acl_count(size_t size)
>  #ifdef CONFIG_EXT2_FS_POSIX_ACL
>  
>  /* acl.c */
> -extern struct posix_acl *ext2_get_acl(struct inode *inode, int type);
> +extern struct posix_acl *ext2_get_acl(struct inode *inode, int type, int flags);
>  extern int ext2_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  			struct posix_acl *acl, int type);
>  extern int ext2_init_acl (struct inode *, struct inode *);
> diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
> index c5eaffccecc3..e4e27e34a221 100644
> --- a/fs/ext4/acl.c
> +++ b/fs/ext4/acl.c
> @@ -142,13 +142,16 @@ ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
>   * inode->i_mutex: don't care
>   */
>  struct posix_acl *
> -ext4_get_acl(struct inode *inode, int type)
> +ext4_get_acl(struct inode *inode, int type, int flags)
>  {
>  	int name_index;
>  	char *value = NULL;
>  	struct posix_acl *acl;
>  	int retval;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
> diff --git a/fs/ext4/acl.h b/fs/ext4/acl.h
> index 84b8942a57f2..b349365c7b33 100644
> --- a/fs/ext4/acl.h
> +++ b/fs/ext4/acl.h
> @@ -55,7 +55,7 @@ static inline int ext4_acl_count(size_t size)
>  #ifdef CONFIG_EXT4_FS_POSIX_ACL
>  
>  /* acl.c */
> -struct posix_acl *ext4_get_acl(struct inode *inode, int type);
> +struct posix_acl *ext4_get_acl(struct inode *inode, int type, int flags);
>  int ext4_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		 struct posix_acl *acl, int type);
>  extern int ext4_init_acl(handle_t *, struct inode *, struct inode *);
> diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
> index 239ad9453b99..4d1b348a0ab7 100644
> --- a/fs/f2fs/acl.c
> +++ b/fs/f2fs/acl.c
> @@ -196,8 +196,11 @@ static struct posix_acl *__f2fs_get_acl(struct inode *inode, int type,
>  	return acl;
>  }
>  
> -struct posix_acl *f2fs_get_acl(struct inode *inode, int type)
> +struct posix_acl *f2fs_get_acl(struct inode *inode, int type, int flags)
>  {
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	return __f2fs_get_acl(inode, type, NULL);
>  }
>  
> diff --git a/fs/f2fs/acl.h b/fs/f2fs/acl.h
> index 986fd1bc780b..3b7b0deb2845 100644
> --- a/fs/f2fs/acl.h
> +++ b/fs/f2fs/acl.h
> @@ -33,7 +33,7 @@ struct f2fs_acl_header {
>  
>  #ifdef CONFIG_F2FS_FS_POSIX_ACL
>  
> -extern struct posix_acl *f2fs_get_acl(struct inode *, int);
> +extern struct posix_acl *f2fs_get_acl(struct inode *, int, int);
>  extern int f2fs_set_acl(struct user_namespace *, struct inode *,
>  			struct posix_acl *, int);
>  extern int f2fs_init_acl(struct inode *, struct inode *, struct page *,
> diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
> index 52b165319be1..194cb81634f9 100644
> --- a/fs/fuse/acl.c
> +++ b/fs/fuse/acl.c
> @@ -11,7 +11,7 @@
>  #include <linux/posix_acl.h>
>  #include <linux/posix_acl_xattr.h>
>  
> -struct posix_acl *fuse_get_acl(struct inode *inode, int type)
> +struct posix_acl *fuse_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct fuse_conn *fc = get_fuse_conn(inode);
>  	int size;
> @@ -19,6 +19,9 @@ struct posix_acl *fuse_get_acl(struct inode *inode, int type)
>  	void *value = NULL;
>  	struct posix_acl *acl;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	if (fuse_is_bad(inode))
>  		return ERR_PTR(-EIO);
>  
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 07829ce78695..ba3a419c6766 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -1216,7 +1216,7 @@ extern const struct xattr_handler *fuse_acl_xattr_handlers[];
>  extern const struct xattr_handler *fuse_no_acl_xattr_handlers[];
>  
>  struct posix_acl;
> -struct posix_acl *fuse_get_acl(struct inode *inode, int type);
> +struct posix_acl *fuse_get_acl(struct inode *inode, int type, int flags);
>  int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		 struct posix_acl *acl, int type);
>  
> diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
> index 9165d70ead07..956132de223c 100644
> --- a/fs/gfs2/acl.c
> +++ b/fs/gfs2/acl.c
> @@ -57,13 +57,16 @@ static struct posix_acl *__gfs2_get_acl(struct inode *inode, int type)
>  	return acl;
>  }
>  
> -struct posix_acl *gfs2_get_acl(struct inode *inode, int type)
> +struct posix_acl *gfs2_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct gfs2_inode *ip = GFS2_I(inode);
>  	struct gfs2_holder gh;
>  	bool need_unlock = false;
>  	struct posix_acl *acl;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	if (!gfs2_glock_is_locked_by_me(ip->i_gl)) {
>  		int ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
>  					     LM_FLAG_ANY, &gh);
> diff --git a/fs/gfs2/acl.h b/fs/gfs2/acl.h
> index eccc6a43326c..cdf8f12089de 100644
> --- a/fs/gfs2/acl.h
> +++ b/fs/gfs2/acl.h
> @@ -11,7 +11,7 @@
>  
>  #define GFS2_ACL_MAX_ENTRIES(sdp) ((300 << (sdp)->sd_sb.sb_bsize_shift) >> 12)
>  
> -extern struct posix_acl *gfs2_get_acl(struct inode *inode, int type);
> +extern struct posix_acl *gfs2_get_acl(struct inode *inode, int type, int flags);
>  extern int __gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type);
>  extern int gfs2_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  			struct posix_acl *acl, int type);
> diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
> index 55a79df70d24..35f4a0dcbd71 100644
> --- a/fs/jffs2/acl.c
> +++ b/fs/jffs2/acl.c
> @@ -173,12 +173,15 @@ static void *jffs2_acl_to_medium(const struct posix_acl *acl, size_t *size)
>  	return ERR_PTR(-EINVAL);
>  }
>  
> -struct posix_acl *jffs2_get_acl(struct inode *inode, int type)
> +struct posix_acl *jffs2_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct posix_acl *acl;
>  	char *value = NULL;
>  	int rc, xprefix;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		xprefix = JFFS2_XPREFIX_ACL_ACCESS;
> diff --git a/fs/jffs2/acl.h b/fs/jffs2/acl.h
> index 62c50da9d493..afd6f924aacb 100644
> --- a/fs/jffs2/acl.h
> +++ b/fs/jffs2/acl.h
> @@ -27,7 +27,7 @@ struct jffs2_acl_header {
>  
>  #ifdef CONFIG_JFFS2_FS_POSIX_ACL
>  
> -struct posix_acl *jffs2_get_acl(struct inode *inode, int type);
> +struct posix_acl *jffs2_get_acl(struct inode *inode, int type, int flags);
>  int jffs2_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		  struct posix_acl *acl, int type);
>  extern int jffs2_init_acl_pre(struct inode *, struct inode *, umode_t *);
> diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
> index 43c285c3d2a7..344d047bcb97 100644
> --- a/fs/jfs/acl.c
> +++ b/fs/jfs/acl.c
> @@ -14,13 +14,16 @@
>  #include "jfs_xattr.h"
>  #include "jfs_acl.h"
>  
> -struct posix_acl *jfs_get_acl(struct inode *inode, int type)
> +struct posix_acl *jfs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct posix_acl *acl;
>  	char *ea_name;
>  	int size;
>  	char *value = NULL;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch(type) {
>  		case ACL_TYPE_ACCESS:
>  			ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
> diff --git a/fs/jfs/jfs_acl.h b/fs/jfs/jfs_acl.h
> index 7ae389a7a366..e86997d1f123 100644
> --- a/fs/jfs/jfs_acl.h
> +++ b/fs/jfs/jfs_acl.h
> @@ -7,7 +7,7 @@
>  
>  #ifdef CONFIG_JFS_POSIX_ACL
>  
> -struct posix_acl *jfs_get_acl(struct inode *inode, int type);
> +struct posix_acl *jfs_get_acl(struct inode *inode, int type, int flags);
>  int jfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		struct posix_acl *acl, int type);
>  int jfs_init_acl(tid_t, struct inode *, struct inode *);
> diff --git a/fs/nfs/nfs3_fs.h b/fs/nfs/nfs3_fs.h
> index c8a192802dda..0f3ba2f3b8da 100644
> --- a/fs/nfs/nfs3_fs.h
> +++ b/fs/nfs/nfs3_fs.h
> @@ -11,7 +11,7 @@
>   * nfs3acl.c
>   */
>  #ifdef CONFIG_NFS_V3_ACL
> -extern struct posix_acl *nfs3_get_acl(struct inode *inode, int type);
> +extern struct posix_acl *nfs3_get_acl(struct inode *inode, int type, int flags);
>  extern int nfs3_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  			struct posix_acl *acl, int type);
>  extern int nfs3_proc_setacls(struct inode *inode, struct posix_acl *acl,
> diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
> index 9ec560aa4a50..f94def1342c6 100644
> --- a/fs/nfs/nfs3acl.c
> +++ b/fs/nfs/nfs3acl.c
> @@ -44,7 +44,7 @@ static void nfs3_abort_get_acl(struct posix_acl **p)
>  	cmpxchg(p, sentinel, ACL_NOT_CACHED);
>  }
>  
> -struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
> +struct posix_acl *nfs3_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct nfs_server *server = NFS_SERVER(inode);
>  	struct page *pages[NFSACL_MAXPAGES] = { };
> @@ -62,6 +62,9 @@ struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
>  	};
>  	int status, count;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	if (!nfs_server_capable(inode, NFS_CAP_ACLS))
>  		return ERR_PTR(-EOPNOTSUPP);
>  
> diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
> index 5c72a7e6d6c5..a4df6e30c017 100644
> --- a/fs/ocfs2/acl.c
> +++ b/fs/ocfs2/acl.c
> @@ -289,7 +289,7 @@ int ocfs2_iop_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  	return status;
>  }
>  
> -struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
> +struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct ocfs2_super *osb;
>  	struct buffer_head *di_bh = NULL;
> @@ -297,6 +297,9 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
>  	int had_lock;
>  	struct ocfs2_lock_holder oh;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	osb = OCFS2_SB(inode->i_sb);
>  	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
>  		return NULL;
> diff --git a/fs/ocfs2/acl.h b/fs/ocfs2/acl.h
> index f59d8d0a61fa..e005c93b9153 100644
> --- a/fs/ocfs2/acl.h
> +++ b/fs/ocfs2/acl.h
> @@ -16,7 +16,7 @@ struct ocfs2_acl_entry {
>  	__le32 e_id;
>  };
>  
> -struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type);
> +struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type, int flags);
>  int ocfs2_iop_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		      struct posix_acl *acl, int type);
>  extern int ocfs2_acl_chmod(struct inode *, struct buffer_head *);
> diff --git a/fs/orangefs/acl.c b/fs/orangefs/acl.c
> index 18852b9ed82b..d93841d478ed 100644
> --- a/fs/orangefs/acl.c
> +++ b/fs/orangefs/acl.c
> @@ -10,12 +10,15 @@
>  #include "orangefs-bufmap.h"
>  #include <linux/posix_acl_xattr.h>
>  
> -struct posix_acl *orangefs_get_acl(struct inode *inode, int type)
> +struct posix_acl *orangefs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct posix_acl *acl;
>  	int ret;
>  	char *key = NULL, *value = NULL;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		key = XATTR_NAME_POSIX_ACL_ACCESS;
> diff --git a/fs/orangefs/orangefs-kernel.h b/fs/orangefs/orangefs-kernel.h
> index 0e6b97682e41..370bd89c670f 100644
> --- a/fs/orangefs/orangefs-kernel.h
> +++ b/fs/orangefs/orangefs-kernel.h
> @@ -106,7 +106,7 @@ enum orangefs_vfs_op_states {
>  extern int orangefs_init_acl(struct inode *inode, struct inode *dir);
>  extern const struct xattr_handler *orangefs_xattr_handlers[];
>  
> -extern struct posix_acl *orangefs_get_acl(struct inode *inode, int type);
> +extern struct posix_acl *orangefs_get_acl(struct inode *inode, int type, int flags);
>  extern int orangefs_set_acl(struct user_namespace *mnt_userns,
>  			    struct inode *inode, struct posix_acl *acl,
>  			    int type);
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 5e828a1c98a8..727154a1d3ce 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -448,12 +448,15 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
>  	return res;
>  }
>  
> -struct posix_acl *ovl_get_acl(struct inode *inode, int type)
> +struct posix_acl *ovl_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct inode *realinode = ovl_inode_real(inode);
>  	const struct cred *old_cred;
>  	struct posix_acl *acl;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
>  		return NULL;
>  
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index 6ec73db4bf9e..daf6b75b9a54 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -485,7 +485,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
>  int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
>  		  void *value, size_t size);
>  ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
> -struct posix_acl *ovl_get_acl(struct inode *inode, int type);
> +struct posix_acl *ovl_get_acl(struct inode *inode, int type, int flags);
>  int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
>  bool ovl_is_private_xattr(struct super_block *sb, const char *name);
>  
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index f3309a7edb49..6b7f793e2b6f 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -138,7 +138,7 @@ struct posix_acl *get_acl(struct inode *inode, int type)
>  		set_cached_acl(inode, type, NULL);
>  		return NULL;
>  	}
> -	acl = inode->i_op->get_acl(inode, type);
> +	acl = inode->i_op->get_acl(inode, type, 0);
>  
>  	if (IS_ERR(acl)) {
>  		/*
> diff --git a/fs/reiserfs/acl.h b/fs/reiserfs/acl.h
> index fd58618da360..bf10841b892d 100644
> --- a/fs/reiserfs/acl.h
> +++ b/fs/reiserfs/acl.h
> @@ -48,7 +48,7 @@ static inline int reiserfs_acl_count(size_t size)
>  }
>  
>  #ifdef CONFIG_REISERFS_FS_POSIX_ACL
> -struct posix_acl *reiserfs_get_acl(struct inode *inode, int type);
> +struct posix_acl *reiserfs_get_acl(struct inode *inode, int type, int flags);
>  int reiserfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		     struct posix_acl *acl, int type);
>  int reiserfs_acl_chmod(struct inode *inode);
> diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
> index a9547144a099..0fdb4f531098 100644
> --- a/fs/reiserfs/xattr_acl.c
> +++ b/fs/reiserfs/xattr_acl.c
> @@ -190,13 +190,16 @@ static void *reiserfs_posix_acl_to_disk(const struct posix_acl *acl, size_t * si
>   * inode->i_mutex: down
>   * BKL held [before 2.5.x]
>   */
> -struct posix_acl *reiserfs_get_acl(struct inode *inode, int type)
> +struct posix_acl *reiserfs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	char *name, *value;
>  	struct posix_acl *acl;
>  	int size;
>  	int retval;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		name = XATTR_NAME_POSIX_ACL_ACCESS;
> diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
> index d02bef24b32b..5f9b541e029d 100644
> --- a/fs/xfs/xfs_acl.c
> +++ b/fs/xfs/xfs_acl.c
> @@ -125,7 +125,7 @@ xfs_acl_to_disk(struct xfs_acl *aclp, const struct posix_acl *acl)
>  }
>  
>  struct posix_acl *
> -xfs_get_acl(struct inode *inode, int type)
> +xfs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	struct xfs_inode	*ip = XFS_I(inode);
>  	struct xfs_mount	*mp = ip->i_mount;
> @@ -137,6 +137,9 @@ xfs_get_acl(struct inode *inode, int type)
>  	};
>  	int			error;
>  
> +	if (flags)
> +		return ERR_PTR(-EINVAL);
> +
>  	trace_xfs_get_acl(ip);
>  
>  	switch (type) {
> diff --git a/fs/xfs/xfs_acl.h b/fs/xfs/xfs_acl.h
> index 7bdb3a4ed798..38f933f2e281 100644
> --- a/fs/xfs/xfs_acl.h
> +++ b/fs/xfs/xfs_acl.h
> @@ -10,13 +10,13 @@ struct inode;
>  struct posix_acl;
>  
>  #ifdef CONFIG_XFS_POSIX_ACL
> -extern struct posix_acl *xfs_get_acl(struct inode *inode, int type);
> +extern struct posix_acl *xfs_get_acl(struct inode *inode, int type, int flags);
>  extern int xfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>  		       struct posix_acl *acl, int type);
>  extern int __xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
>  void xfs_forget_acl(struct inode *inode, const char *name);
>  #else
> -static inline struct posix_acl *xfs_get_acl(struct inode *inode, int type)
> +static inline struct posix_acl *xfs_get_acl(struct inode *inode, int type, int flags)
>  {
>  	return NULL;
>  }
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 640574294216..1c56d4fc4efe 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2065,7 +2065,7 @@ struct inode_operations {
>  	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
>  	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
>  	int (*permission) (struct user_namespace *, struct inode *, int);
> -	struct posix_acl * (*get_acl)(struct inode *, int);
> +	struct posix_acl * (*get_acl)(struct inode *, int, int);
>  
>  	int (*readlink) (struct dentry *, char __user *,int);
>  
> -- 
> 2.31.1
> 

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2 0/2] allow overlayfs to do RCU lookups
  2021-08-18 13:33 [PATCH v2 0/2] allow overlayfs to do RCU lookups Miklos Szeredi
  2021-08-18 13:33 ` [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback Miklos Szeredi
  2021-08-18 13:34 ` [PATCH v2 2/2] ovl: enable RCU'd ->get_acl() Miklos Szeredi
@ 2021-08-18 14:26 ` Al Viro
  2021-08-18 15:03   ` Miklos Szeredi
  2 siblings, 1 reply; 8+ messages in thread
From: Al Viro @ 2021-08-18 14:26 UTC (permalink / raw)
  To: Miklos Szeredi
  Cc: Linus Torvalds, linux-unionfs, linux-fsdevel, linux-kernel,
	Andreas Gruenbacher

On Wed, Aug 18, 2021 at 03:33:58PM +0200, Miklos Szeredi wrote:
> I'd really like to fix this in some form, but not getting any response
> [1][2][3].
> 
> Al, Linus, can you please comment?
> 
> I'm happy to take this through the overlayfs tree, just need an ACK for the
> VFS API change.

Looks reasonable enough; I'm not too happy about yet another place LOOKUP_...
details get tangled into, though.  Do we want it to be more than just a
bool rcu?

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2 0/2] allow overlayfs to do RCU lookups
  2021-08-18 14:26 ` [PATCH v2 0/2] allow overlayfs to do RCU lookups Al Viro
@ 2021-08-18 15:03   ` Miklos Szeredi
  0 siblings, 0 replies; 8+ messages in thread
From: Miklos Szeredi @ 2021-08-18 15:03 UTC (permalink / raw)
  To: Al Viro
  Cc: Miklos Szeredi, Linus Torvalds, overlayfs, linux-fsdevel,
	linux-kernel, Andreas Gruenbacher

On Wed, 18 Aug 2021 at 16:27, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Wed, Aug 18, 2021 at 03:33:58PM +0200, Miklos Szeredi wrote:
> > I'd really like to fix this in some form, but not getting any response
> > [1][2][3].
> >
> > Al, Linus, can you please comment?
> >
> > I'm happy to take this through the overlayfs tree, just need an ACK for the
> > VFS API change.
>
> Looks reasonable enough; I'm not too happy about yet another place LOOKUP_...
> details get tangled into, though.  Do we want it to be more than just a
> bool rcu?

I'd be fine with that change.   Calling with false/true is less
descriptive than calling with 0/LOOKUP_RCU but I guess we can leave
the actual calls to use the latter?

Thanks,
Miklos

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2 2/2] ovl: enable RCU'd ->get_acl()
  2021-08-18 13:34 ` [PATCH v2 2/2] ovl: enable RCU'd ->get_acl() Miklos Szeredi
@ 2021-08-18 18:34   ` Linus Torvalds
  2021-08-18 18:53     ` Miklos Szeredi
  0 siblings, 1 reply; 8+ messages in thread
From: Linus Torvalds @ 2021-08-18 18:34 UTC (permalink / raw)
  To: Miklos Szeredi
  Cc: Al Viro, linux-unionfs, linux-fsdevel, Linux Kernel Mailing List,
	Andreas Gruenbacher, garyhuang

On Wed, Aug 18, 2021 at 6:34 AM Miklos Szeredi <mszeredi@redhat.com> wrote:
>
>  struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
>  {
> -       return rcu_dereference(*acl_by_type(inode, type));
> +       struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
> +
> +       if (acl == ACL_DONT_CACHE)
> +               acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
> +
> +       return acl;
>  }

What? No.

You just made get_cached_acl_rcu() return ERR_PTR(-EINVAL) for most filesystems.

So now you've changed the behavior of get_cached_acl_rcu() ENTIRELY.

It used to return either
 (a) the ACL
 (b) NULL
 (c) ACL_DONT_CACHE/ACL_NOT_CACHED

but now you've changed that (c) case to "ACL_NOT_CACHED or random error value".

You can't just mix these kinds of entirely different return values like that.

So no, this is not at all acceptable.

I would suggest:

 (a) make the first patch actually test explicitly for LOOKUP_RCU, so
that it's clear to the filesystems what is going on.

     So instead of that pattern of

        if (flags)
                return ERR_PTR(-EINVAL);

     I'd suggest using

        if (flags & LOOKUP_RCU)
                return ERR_PTR(-ECHILD);

   so that it actually matches what lookup does for the "I can't do
this under RCU", and so that any reader of the code understands what
"flags" is all about.

And then

 (b) make the get_cached_acl_rcu() case handle errors _properly_
instead of mixing the special ACL cache markers with error returns.

     So instead of

        if (acl == ACL_DONT_CACHE)
                acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);

     maybe something more along the lines of

        if (acl == ACL_DONT_CACHE) {
                struct posix_acl *lookup_acl;
                lookup_acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
                if (!IS_ERR(lookup_acl))
                        acl = lookup_acl;
        }

     or whatever.

I disagree with Al that a "bool" would be better. I think LOOKUP_RCU
is good documentation, and consistent with lookup, but it really needs
to be *consistent*.  Thus that

        if (flags & LOOKUP_RCU)
                return ERR_PTR(-ECHILD);

pattern, not some "test underscibed flags, return -EINVAL" pattern
that looks entirely nonsensical.

               Linus

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2 2/2] ovl: enable RCU'd ->get_acl()
  2021-08-18 18:34   ` Linus Torvalds
@ 2021-08-18 18:53     ` Miklos Szeredi
  0 siblings, 0 replies; 8+ messages in thread
From: Miklos Szeredi @ 2021-08-18 18:53 UTC (permalink / raw)
  To: Linus Torvalds
  Cc: Miklos Szeredi, Al Viro, overlayfs, linux-fsdevel,
	Linux Kernel Mailing List, Andreas Gruenbacher, garyhuang

On Wed, 18 Aug 2021 at 20:34, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, Aug 18, 2021 at 6:34 AM Miklos Szeredi <mszeredi@redhat.com> wrote:
> >
> >  struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
> >  {
> > -       return rcu_dereference(*acl_by_type(inode, type));
> > +       struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
> > +
> > +       if (acl == ACL_DONT_CACHE)
> > +               acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
> > +
> > +       return acl;
> >  }
>
> What? No.
>
> You just made get_cached_acl_rcu() return ERR_PTR(-EINVAL) for most filesystems.
>
> So now you've changed the behavior of get_cached_acl_rcu() ENTIRELY.
>
> It used to return either
>  (a) the ACL
>  (b) NULL
>  (c) ACL_DONT_CACHE/ACL_NOT_CACHED
>
> but now you've changed that (c) case to "ACL_NOT_CACHED or random error value".
>
> You can't just mix these kinds of entirely different return values like that.
>
> So no, this is not at all acceptable.
>
> I would suggest:
>
>  (a) make the first patch actually test explicitly for LOOKUP_RCU, so
> that it's clear to the filesystems what is going on.
>
>      So instead of that pattern of
>
>         if (flags)
>                 return ERR_PTR(-EINVAL);
>
>      I'd suggest using
>
>         if (flags & LOOKUP_RCU)
>                 return ERR_PTR(-ECHILD);

Okay.

>
>    so that it actually matches what lookup does for the "I can't do
> this under RCU", and so that any reader of the code understands what
> "flags" is all about.
>
> And then
>
>  (b) make the get_cached_acl_rcu() case handle errors _properly_
> instead of mixing the special ACL cache markers with error returns.
>
>      So instead of
>
>         if (acl == ACL_DONT_CACHE)
>                 acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
>
>      maybe something more along the lines of
>
>         if (acl == ACL_DONT_CACHE) {
>                 struct posix_acl *lookup_acl;
>                 lookup_acl = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
>                 if (!IS_ERR(lookup_acl))
>                         acl = lookup_acl;
>         }
>
>      or whatever.

Yes, that's better.   Just to explain why my version was not actually
buggy:  ACL_DONT_CACHE is only used in overlayfs and not in any other
filesystem, so ->get_acl(... LOOKUP_RCU) not returning an error was
implicit in the implementation.   But your version makes that error
handling explicit, which is definitely an improvement.

>
> I disagree with Al that a "bool" would be better. I think LOOKUP_RCU
> is good documentation, and consistent with lookup, but it really needs
> to be *consistent*.  Thus that
>
>         if (flags & LOOKUP_RCU)
>                 return ERR_PTR(-ECHILD);
>
> pattern, not some "test underscibed flags, return -EINVAL" pattern
> that looks entirely nonsensical.

Al suggested:

 if (rcu)
   return ERR_PTR(-ECHILD);

which is also good documentation.  It also makes sure that "flags" is
not overloaded with other functionality (which was the reason for the
defensive "if any flag set return error" pattern).

Thanks,
Miklos

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2021-08-18 18:53 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-18 13:33 [PATCH v2 0/2] allow overlayfs to do RCU lookups Miklos Szeredi
2021-08-18 13:33 ` [PATCH v2 1/2] vfs: add flags argument to ->get_acl() callback Miklos Szeredi
2021-08-18 13:49   ` Christian Brauner
2021-08-18 13:34 ` [PATCH v2 2/2] ovl: enable RCU'd ->get_acl() Miklos Szeredi
2021-08-18 18:34   ` Linus Torvalds
2021-08-18 18:53     ` Miklos Szeredi
2021-08-18 14:26 ` [PATCH v2 0/2] allow overlayfs to do RCU lookups Al Viro
2021-08-18 15:03   ` Miklos Szeredi

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