[PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[Christian Brauner]

Hey everyone,

After we finished the introduction of the new posix acl api last cycle
we still left the generic POSIX ACL xattr handlers around in the
filesystems xattr handlers for two reasons:

(1) Because a few filesystems rely on the ->list() method of the generic
    POSIX ACL xattr handlers in their ->listxattr() inode operation.
(2) POSIX ACLs are only available if IOP_XATTR is raised. The IOP_XATTR
    flag is raised in inode_init_always() based on whether the
    sb->s_xattr pointer is non-NULL. IOW, the registered xattr handlers
    of the filesystem are used to raise IOP_XATTR.
    If we were to remove the generic POSIX ACL xattr handlers from all
    filesystems we would risk regressing filesystems that only implement
    POSIX ACL support and no other xattrs (nfs3 comes to mind).

This series makes it possible to remove the generic POSIX ACL xattr
handlers from the sb->s_xattr list of all filesystems. This is a crucial
step as the generic POSIX ACL xattr handlers aren't used for POSIX ACLs
anymore and POSIX ACLs don't depend on the xattr infrastructure in a
meaningful way anymore.

Adressing problem (1) will require more work long-term. It would be best
to get rid of the ->list() method of xattr handlers completely if we
can.

For erofs, ext{2,4}, f2fs, jffs2, ocfs2, and reiserfs we keep the dummy
handler around so they can continue to use array-based xattr handler
indexing. The series does simplify the ->listxattr() implementation of
all these filesystems.

This series decouples POSIX ACLs from IOP_XATTR as they don't depend on
xattr handlers anymore. With this we can finally remove the dummy xattr
handlers from all filesystems xattr handlers.

All filesystems with reasonable integration into xfstests have been
tested with:

        ./check -g acl,attr,cap,idmapped,io_uring,perms,unlink

All tests pass without regression on xfstests for-next branch.

Since erofs doesn't have integration into xfstests yet afaict I have
tested it with the testuite available in erofs-utils. They also all pass
without any regressions.

Thanks!
Christian

Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
Changes in v3:
- Decouple POSIX ACLs from IOP_XATTR.
- Allow vfs_listxattr() to function without checking for IOP_XATTR
  making it possible to list POSIX ACLs for filesystems that only
  implement POSIX ACLs and no other xattrs.
- Give reiserfs a set of dedicated inode operation for private inodes
  that have turned of xattrs completely.
- Link to v2: https://lore.kernel.org/r/20230125-fs-acl-remove-generic-xattr-handlers-v2-0-214cfb88bb56@kernel.org

Changes in v2:
- Please see changelogs of the individual patches.
- Christoph & Christian:
  Remove SB_I_XATTR and instead introduce IOP_NOACL so filesystems can
  opt out of POSIX ACLs for specific inodes. Decouple POSIX ACLs from
  IOP_XATTR.
- Keep generic posix acl xattr handlers so filesystems that use array
  based indexing on xattr handlers can continue to do so.
- Minor fixes.
- Link to v1: https://lore.kernel.org/r/20230125-fs-acl-remove-generic-xattr-handlers-v1-0-6cf155b492b6@kernel.org

---
Christian Brauner (10):
      xattr: simplify listxattr helpers
      xattr: add listxattr helper
      xattr: remove unused argument
      fs: drop unused posix acl handlers
      fs: simplify ->listxattr() implementation
      reiserfs: rework ->listxattr() implementation
      fs: rename generic posix acl handlers
      reiserfs: rework priv inode handling
      ovl: check for ->listxattr() support
      acl: don't depend on IOP_XATTR

 fs/9p/xattr.c                   |   4 --
 fs/btrfs/xattr.c                |   4 --
 fs/ceph/xattr.c                 |   4 --
 fs/cifs/xattr.c                 |   4 --
 fs/ecryptfs/inode.c             |   4 --
 fs/erofs/xattr.c                |  12 +---
 fs/erofs/xattr.h                |  20 ++++---
 fs/ext2/xattr.c                 |  25 ++++----
 fs/ext4/xattr.c                 |  25 ++++----
 fs/f2fs/xattr.c                 |  24 ++++----
 fs/gfs2/xattr.c                 |   2 -
 fs/jffs2/xattr.c                |  29 +++++-----
 fs/jfs/xattr.c                  |   4 --
 fs/nfs/nfs3_fs.h                |   1 -
 fs/nfs/nfs3acl.c                |   6 --
 fs/nfs/nfs3super.c              |   3 -
 fs/nfsd/nfs4xdr.c               |   3 +-
 fs/ntfs3/xattr.c                |   4 --
 fs/ocfs2/xattr.c                |  14 ++---
 fs/orangefs/xattr.c             |   2 -
 fs/overlayfs/copy_up.c          |   3 +-
 fs/overlayfs/super.c            |   8 ---
 fs/posix_acl.c                  |  61 +++++++++++++++-----
 fs/reiserfs/file.c              |   7 +++
 fs/reiserfs/inode.c             |   6 +-
 fs/reiserfs/namei.c             |  50 ++++++++++++++--
 fs/reiserfs/reiserfs.h          |   2 +
 fs/reiserfs/xattr.c             |  55 +++++++++---------
 fs/xattr.c                      | 124 ++++++++++++++++++++--------------------
 fs/xfs/xfs_xattr.c              |   4 --
 include/linux/posix_acl.h       |   7 +++
 include/linux/posix_acl_xattr.h |   5 +-
 include/linux/xattr.h           |  19 +++++-
 mm/shmem.c                      |   4 --
 34 files changed, 292 insertions(+), 257 deletions(-)
---
base-commit: ab072681eabe1ce0a9a32d4baa1a27a2d046bc4a
change-id: 20230125-fs-acl-remove-generic-xattr-handlers-4cfed8558d88

[PATCH v3 06/10] reiserfs: rework ->listxattr() implementation

[Christian Brauner]

Rework reiserfs so it doesn't have to rely on the dummy xattr handlers
in its s_xattr list anymore as this is completely unused for setting and
getting posix acls.

Cc: reiserfs-devel@vger.kernel.org
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
Changes in v3:
  - Patch unchanged.

Changes in v2:
- Rework patch to account for reiserfs quirks.
---
 fs/reiserfs/xattr.c | 46 +++++++++++++++++++++++++---------------------
 1 file changed, 25 insertions(+), 21 deletions(-)

diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index 8b2d52443f41..0b949dc45484 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -52,6 +52,7 @@
 #include <linux/quotaops.h>
 #include <linux/security.h>
 #include <linux/posix_acl_xattr.h>
+#include <linux/xattr.h>
 
 #define PRIVROOT_NAME ".reiserfs_priv"
 #define XAROOT_NAME   "xattrs"
@@ -770,23 +771,34 @@ reiserfs_xattr_get(struct inode *inode, const char *name, void *buffer,
 			(handler) != NULL;			\
 			(handler) = *(handlers)++)
 
+static inline bool reiserfs_posix_acl_list(const char *name,
+					   struct dentry *dentry)
+{
+	return (posix_acl_type(name) >= 0) &&
+	       IS_POSIXACL(d_backing_inode(dentry));
+}
+
 /* This is the implementation for the xattr plugin infrastructure */
-static inline const struct xattr_handler *
-find_xattr_handler_prefix(const struct xattr_handler **handlers,
-			   const char *name)
+static inline bool reiserfs_xattr_list(const struct xattr_handler **handlers,
+				       const char *name, struct dentry *dentry)
 {
-	const struct xattr_handler *xah;
+	if (handlers) {
+		const struct xattr_handler *xah = NULL;
 
-	if (!handlers)
-		return NULL;
+		for_each_xattr_handler(handlers, xah) {
+			const char *prefix = xattr_prefix(xah);
 
-	for_each_xattr_handler(handlers, xah) {
-		const char *prefix = xattr_prefix(xah);
-		if (strncmp(prefix, name, strlen(prefix)) == 0)
-			break;
+			if (strncmp(prefix, name, strlen(prefix)))
+				continue;
+
+			if (!xattr_handler_can_list(xah, dentry))
+				return false;
+
+			return true;
+		}
 	}
 
-	return xah;
+	return reiserfs_posix_acl_list(name, dentry);
 }
 
 struct listxattr_buf {
@@ -807,12 +819,8 @@ static bool listxattr_filler(struct dir_context *ctx, const char *name,
 
 	if (name[0] != '.' ||
 	    (namelen != 1 && (name[1] != '.' || namelen != 2))) {
-		const struct xattr_handler *handler;
-
-		handler = find_xattr_handler_prefix(b->dentry->d_sb->s_xattr,
-						    name);
-		if (!handler /* Unsupported xattr name */ ||
-		    (handler->list && !handler->list(b->dentry)))
+		if (!reiserfs_xattr_list(b->dentry->d_sb->s_xattr, name,
+					 b->dentry))
 			return true;
 		size = namelen + 1;
 		if (b->buf) {
@@ -910,10 +918,6 @@ const struct xattr_handler *reiserfs_xattr_handlers[] = {
 #endif
 #ifdef CONFIG_REISERFS_FS_SECURITY
 	&reiserfs_xattr_security_handler,
-#endif
-#ifdef CONFIG_REISERFS_FS_POSIX_ACL
-	&posix_acl_access_xattr_handler,
-	&posix_acl_default_xattr_handler,
 #endif
 	NULL
 };

-- 
2.34.1

[PATCH v3 08/10] reiserfs: rework priv inode handling

[Christian Brauner]

Reiserfs is the only filesystem that removes IOP_XATTR without also
using a set of dedicated inode operations at the same time that nop all
xattr related inode operations. This means we need to have a IOP_XATTR
check in vfs_listxattr() instead of just being able to check for
->listxatt() being implemented.

Introduce a dedicated set of nop inode operations that are used when
IOP_XATTR is removed, allowing us to remove that check from
vfs_listxattr(). This in turn allows us to completely decouple POSIX ACLs from
IOP_XATTR.

Cc: reiserfs-devel@vger.kernel.org
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
Changes in v3:
- Patch introduced.
---
 fs/reiserfs/file.c     |  7 +++++++
 fs/reiserfs/inode.c    |  6 ++----
 fs/reiserfs/namei.c    | 50 +++++++++++++++++++++++++++++++++++++++++++++-----
 fs/reiserfs/reiserfs.h |  2 ++
 fs/reiserfs/xattr.c    |  9 +++------
 5 files changed, 59 insertions(+), 15 deletions(-)

diff --git a/fs/reiserfs/file.c b/fs/reiserfs/file.c
index 467d13da198f..b54cc7048f02 100644
--- a/fs/reiserfs/file.c
+++ b/fs/reiserfs/file.c
@@ -261,3 +261,10 @@ const struct inode_operations reiserfs_file_inode_operations = {
 	.fileattr_get = reiserfs_fileattr_get,
 	.fileattr_set = reiserfs_fileattr_set,
 };
+
+const struct inode_operations reiserfs_priv_file_inode_operations = {
+	.setattr = reiserfs_setattr,
+	.permission = reiserfs_permission,
+	.fileattr_get = reiserfs_fileattr_get,
+	.fileattr_set = reiserfs_fileattr_set,
+};
diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index c7d1fa526dea..4ec357919588 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -2087,10 +2087,8 @@ int reiserfs_new_inode(struct reiserfs_transaction_handle *th,
 	 * Mark it private if we're creating the privroot
 	 * or something under it.
 	 */
-	if (IS_PRIVATE(dir) || dentry == REISERFS_SB(sb)->priv_root) {
-		inode->i_flags |= S_PRIVATE;
-		inode->i_opflags &= ~IOP_XATTR;
-	}
+	if (IS_PRIVATE(dir) || dentry == REISERFS_SB(sb)->priv_root)
+		reiserfs_init_priv_inode(inode);
 
 	if (reiserfs_posixacl(inode->i_sb)) {
 		reiserfs_write_unlock(inode->i_sb);
diff --git a/fs/reiserfs/namei.c b/fs/reiserfs/namei.c
index 0b8aa99749f1..2f0c721c8ac9 100644
--- a/fs/reiserfs/namei.c
+++ b/fs/reiserfs/namei.c
@@ -378,13 +378,11 @@ static struct dentry *reiserfs_lookup(struct inode *dir, struct dentry *dentry,
 
 		/*
 		 * Propagate the private flag so we know we're
-		 * in the priv tree.  Also clear IOP_XATTR
+		 * in the priv tree.  Also clear xattr support
 		 * since we don't have xattrs on xattr files.
 		 */
-		if (IS_PRIVATE(dir)) {
-			inode->i_flags |= S_PRIVATE;
-			inode->i_opflags &= ~IOP_XATTR;
-		}
+		if (IS_PRIVATE(dir))
+			reiserfs_init_priv_inode(inode);
 	}
 	reiserfs_write_unlock(dir->i_sb);
 	if (retval == IO_ERROR) {
@@ -1649,6 +1647,48 @@ static int reiserfs_rename(struct user_namespace *mnt_userns,
 	return retval;
 }
 
+static const struct inode_operations reiserfs_priv_dir_inode_operations = {
+	.create = reiserfs_create,
+	.lookup = reiserfs_lookup,
+	.link = reiserfs_link,
+	.unlink = reiserfs_unlink,
+	.symlink = reiserfs_symlink,
+	.mkdir = reiserfs_mkdir,
+	.rmdir = reiserfs_rmdir,
+	.mknod = reiserfs_mknod,
+	.rename = reiserfs_rename,
+	.setattr = reiserfs_setattr,
+	.permission = reiserfs_permission,
+	.fileattr_get = reiserfs_fileattr_get,
+	.fileattr_set = reiserfs_fileattr_set,
+};
+
+static const struct inode_operations reiserfs_priv_symlink_inode_operations = {
+	.get_link	= page_get_link,
+	.setattr = reiserfs_setattr,
+	.permission = reiserfs_permission,
+};
+
+static const struct inode_operations reiserfs_priv_special_inode_operations = {
+	.setattr = reiserfs_setattr,
+	.permission = reiserfs_permission,
+};
+
+void reiserfs_init_priv_inode(struct inode *inode)
+{
+	inode->i_flags |= S_PRIVATE;
+	inode->i_opflags &= ~IOP_XATTR;
+
+	if (S_ISREG(inode->i_mode))
+		inode->i_op = &reiserfs_priv_file_inode_operations;
+	else if (S_ISDIR(inode->i_mode))
+		inode->i_op = &reiserfs_priv_dir_inode_operations;
+	else if (S_ISLNK(inode->i_mode))
+		inode->i_op = &reiserfs_priv_symlink_inode_operations;
+	else
+		inode->i_op = &reiserfs_priv_special_inode_operations;
+}
+
 /* directories can handle most operations...  */
 const struct inode_operations reiserfs_dir_inode_operations = {
 	.create = reiserfs_create,
diff --git a/fs/reiserfs/reiserfs.h b/fs/reiserfs/reiserfs.h
index 3aa928ec527a..d4dd39a66d80 100644
--- a/fs/reiserfs/reiserfs.h
+++ b/fs/reiserfs/reiserfs.h
@@ -3106,6 +3106,7 @@ int reiserfs_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 int __reiserfs_write_begin(struct page *page, unsigned from, unsigned len);
 
 /* namei.c */
+void reiserfs_init_priv_inode(struct inode *inode);
 void set_de_name_and_namelen(struct reiserfs_dir_entry *de);
 int search_by_entry_key(struct super_block *sb, const struct cpu_key *key,
 			struct treepath *path, struct reiserfs_dir_entry *de);
@@ -3175,6 +3176,7 @@ void reiserfs_unmap_buffer(struct buffer_head *);
 
 /* file.c */
 extern const struct inode_operations reiserfs_file_inode_operations;
+extern const struct inode_operations reiserfs_priv_file_inode_operations;
 extern const struct file_operations reiserfs_file_operations;
 extern const struct address_space_operations reiserfs_address_space_operations;
 
diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index 0b949dc45484..11b32bbd656d 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -896,8 +896,7 @@ static int create_privroot(struct dentry *dentry)
 		return -EOPNOTSUPP;
 	}
 
-	d_inode(dentry)->i_flags |= S_PRIVATE;
-	d_inode(dentry)->i_opflags &= ~IOP_XATTR;
+	reiserfs_init_priv_inode(d_inode(dentry));
 	reiserfs_info(dentry->d_sb, "Created %s - reserved for xattr "
 		      "storage.\n", PRIVROOT_NAME);
 
@@ -979,10 +978,8 @@ int reiserfs_lookup_privroot(struct super_block *s)
 	if (!IS_ERR(dentry)) {
 		REISERFS_SB(s)->priv_root = dentry;
 		d_set_d_op(dentry, &xattr_lookup_poison_ops);
-		if (d_really_is_positive(dentry)) {
-			d_inode(dentry)->i_flags |= S_PRIVATE;
-			d_inode(dentry)->i_opflags &= ~IOP_XATTR;
-		}
+		if (d_really_is_positive(dentry))
+			reiserfs_init_priv_inode(d_inode(dentry));
 	} else
 		err = PTR_ERR(dentry);
 	inode_unlock(d_inode(s->s_root));

-- 
2.34.1

Re: [PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[Christoph Hellwig]

This version looks good to me, but I'd really prefer if a reiserfs
insider could look over the reiserfs patches.

Re: [PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[Christian Brauner]

On Wed, Feb 01, 2023 at 02:30:20PM +0100, Christoph Hellwig wrote:
> This version looks good to me, but I'd really prefer if a reiserfs
> insider could look over the reiserfs patches.

I consider this material for v6.4 even with an -rc8 for v6.3. So there's
time but we shouldn't block it on reiserfs. Especially, since it's
marked deprecated.

Fwiw, I've tested reiserfs with xfstests on a kernel with and without
this series applied and there's no regressions. But it's overall pretty
buggy at least according to xfstests. Which is expected, I guess.

Re: [PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[Christian Brauner]

From: Christian Brauner (Microsoft) <brauner@kernel.org>


On Wed, 01 Feb 2023 14:14:51 +0100, Christian Brauner wrote:
> Hey everyone,
> 
> After we finished the introduction of the new posix acl api last cycle
> we still left the generic POSIX ACL xattr handlers around in the
> filesystems xattr handlers for two reasons:
> 
> (1) Because a few filesystems rely on the ->list() method of the generic
>     POSIX ACL xattr handlers in their ->listxattr() inode operation.
> (2) POSIX ACLs are only available if IOP_XATTR is raised. The IOP_XATTR
>     flag is raised in inode_init_always() based on whether the
>     sb->s_xattr pointer is non-NULL. IOW, the registered xattr handlers
>     of the filesystem are used to raise IOP_XATTR.
>     If we were to remove the generic POSIX ACL xattr handlers from all
>     filesystems we would risk regressing filesystems that only implement
>     POSIX ACL support and no other xattrs (nfs3 comes to mind).
> 
> [...]

With v6.3-rc1 out, I've applied this now. Please keep an eye out for any
regressions as this has been a delicate undertaking: 

[01/10] xattr: simplify listxattr helpers
        commit: f2620f166e2a4db08f016b7b30b904ab28c265e4
[02/10] xattr: add listxattr helper
        commit: 2db8a948046cab3a2f707561592906a3d096972f
[03/10] xattr: remove unused argument
        commit: 831be973aa21d1cf8948bf4b1d4e73e6d5d028c0
[04/10] fs: drop unused posix acl handlers
        commit: 0c95c025a02e477b2d112350e1c78bb0cc994c51
[05/10] fs: simplify ->listxattr() implementation
        commit: a5488f29835c0eb5561b46e71c23f6c39aab6c83
[06/10] reiserfs: rework ->listxattr() implementation
        commit: 387b96a5891c075986afbf13e84cba357710068e
[07/10] fs: rename generic posix acl handlers
        commit: d549b741740e63e87e661754e2d1b336fdc51d50
[08/10] reiserfs: rework priv inode handling
        commit: d9f892b9bdc22b12bc960837a09f014d5a324975
[09/10] ovl: check for ->listxattr() support
        commit: a1fbb607340d49f208e90cc0d7bdfff2141cce8d
[10/10] acl: don't depend on IOP_XATTR
        commit: e499214ce3ef50c50522719e753a1ffc928c2ec1

Christian

Re: [PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[Christian Brauner]

On Wed, Feb 01, 2023 at 02:42:54PM +0100, Christian Brauner wrote:
> On Wed, Feb 01, 2023 at 02:30:20PM +0100, Christoph Hellwig wrote:
> > This version looks good to me, but I'd really prefer if a reiserfs
> > insider could look over the reiserfs patches.
> 
> I consider this material for v6.4 even with an -rc8 for v6.3. So there's
> time but we shouldn't block it on reiserfs. Especially, since it's
> marked deprecated.

So I've applied this now. If there's still someone interested in
checking the reiserfs bits more than what we did with xfstests they
should please do so. But I don't want to hold up this series waiting for
that to happen.

> 
> Fwiw, I've tested reiserfs with xfstests on a kernel with and without
> this series applied and there's no regressions. But it's overall pretty
> buggy at least according to xfstests. Which is expected, I guess.

Re: [f2fs-dev] [PATCH v3 00/10] acl: drop posix acl handlers from xattr handlers

[patchwork-bot+f2fs]

Hello:

This patch was applied to jaegeuk/f2fs.git (dev)
by Christian Brauner (Microsoft) <brauner@kernel.org>:

On Wed, 01 Feb 2023 14:14:51 +0100 you wrote:
> Hey everyone,
> 
> After we finished the introduction of the new posix acl api last cycle
> we still left the generic POSIX ACL xattr handlers around in the
> filesystems xattr handlers for two reasons:
> 
> (1) Because a few filesystems rely on the ->list() method of the generic
>     POSIX ACL xattr handlers in their ->listxattr() inode operation.
> (2) POSIX ACLs are only available if IOP_XATTR is raised. The IOP_XATTR
>     flag is raised in inode_init_always() based on whether the
>     sb->s_xattr pointer is non-NULL. IOW, the registered xattr handlers
>     of the filesystem are used to raise IOP_XATTR.
>     If we were to remove the generic POSIX ACL xattr handlers from all
>     filesystems we would risk regressing filesystems that only implement
>     POSIX ACL support and no other xattrs (nfs3 comes to mind).
> 
> [...]

Here is the summary with links:
  - [f2fs-dev,v3,05/10] fs: simplify ->listxattr() implementation
    https://git.kernel.org/jaegeuk/f2fs/c/a5488f29835c

You are awesome, thank you!
-- 
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