Posix ACL Support

This change adds support for Posix ACLs by storing them as an xattr
which is common practice for many Linux file systems.  Since the
Posix ACL is stored as an xattr it will not overwrite any existing
ZFS/NFSv4 ACLs which may have been set.  The Posix ACL will also
be non-functional on other platforms although it may be visible
as an xattr if that platform understands SA based xattrs.

By default Posix ACLs are disabled but they may be enabled with
the new 'aclmode=noacl|posixacl' property.  Set the property to
'posixacl' to enable them.  If ZFS/NFSv4 ACL support is ever added
an appropriate acltype will be added.

This change passes the POSIX Test Suite cleanly with the exception
of xacl/00.t test 45 which is incorrect for Linux (Ext4 fails too).

  http://www.tuxera.com/community/posix-test-suite/

Signed-off-by: Massimo Maggi <[email protected]>
Signed-off-by: Richard Yao <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #170

2 files changed, 177 insertions, 0 deletions

diff --git a/include/linux/vfs_compat.h b/include/linux/vfs_compat.h
index 17fa3ff7b..e5371dacd 100644
--- a/include/linux/vfs_compat.h
+++ b/include/linux/vfs_compat.h
@@ -174,4 +174,146 @@ lseek_execute(struct file *filp, struct inode *inode,
 }
 #endif /* SEEK_HOLE && SEEK_DATA && !HAVE_LSEEK_EXECUTE */
 
+/*
+ * These functions safely approximates the behavior of posix_acl_release()
+ * which cannot be used because it calls the GPL-only symbol kfree_rcu().
+ * The in-kernel version, which can access the RCU, frees the ACLs after
+ * the grace period expires.  Because we're unsure how long that grace
+ * period may be this implementation conservatively delays for 60 seconds.
+ * This is several orders of magnitude larger than expected grace period.
+ * At 60 seconds the kernel will also begin issuing RCU stall warnings.
+ */
+#include <linux/posix_acl.h>
+#ifndef HAVE_POSIX_ACL_CACHING
+#define ACL_NOT_CACHED ((void *)(-1))
+#endif /* HAVE_POSIX_ACL_CACHING */
+
+#if defined(HAVE_POSIX_ACL_RELEASE) && !defined(HAVE_POSIX_ACL_RELEASE_GPL_ONLY)
+
+#define	zpl_posix_acl_release(arg)		posix_acl_release(arg)
+#define	zpl_set_cached_acl(ip, ty, n)		set_cached_acl(ip, ty, n)
+#define	zpl_forget_cached_acl(ip, ty)		forget_cached_acl(ip, ty)
+
+#else
+
+static inline void
+zpl_posix_acl_free(void *arg) {
+	kfree(arg);
+}
+
+static inline void
+zpl_posix_acl_release(struct posix_acl *acl)
+{
+	if ((acl == NULL) || (acl == ACL_NOT_CACHED))
+		return;
+
+	if (atomic_dec_and_test(&acl->a_refcount)) {
+		taskq_dispatch_delay(system_taskq, zpl_posix_acl_free, acl,
+		    TQ_SLEEP, ddi_get_lbolt() + 60*HZ);
+	}
+}
+
+static inline void
+zpl_set_cached_acl(struct inode *ip, int type, struct posix_acl *newer) {
+#ifdef HAVE_POSIX_ACL_CACHING
+	struct posix_acl *older = NULL;
+
+	spin_lock(&ip->i_lock);
+
+	if ((newer != ACL_NOT_CACHED) && (newer != NULL))
+		posix_acl_dup(newer);
+
+	switch(type) {
+	case ACL_TYPE_ACCESS:
+		older = ip->i_acl;
+		rcu_assign_pointer(ip->i_acl,newer);
+		break;
+	case ACL_TYPE_DEFAULT:
+		older = ip->i_default_acl;
+		rcu_assign_pointer(ip->i_default_acl,newer);
+		break;
+	}
+
+	spin_unlock(&ip->i_lock);
+
+	zpl_posix_acl_release(older);
+#endif /* HAVE_POSIX_ACL_CACHING */
+}
+
+static inline void
+zpl_forget_cached_acl(struct inode *ip, int type) {
+	zpl_set_cached_acl(ip, type, (struct posix_acl *)ACL_NOT_CACHED);
+}
+#endif /* HAVE_POSIX_ACL_RELEASE */
+
+/*
+ * 2.6.38 API change,
+ * The is_owner_or_cap() function was renamed to inode_owner_or_capable().
+ */
+#ifdef HAVE_INODE_OWNER_OR_CAPABLE
+#define	zpl_inode_owner_or_capable(ip)		inode_owner_or_capable(ip)
+#else
+#define	zpl_inode_owner_or_capable(ip)		is_owner_or_cap(ip)
+#endif /* HAVE_INODE_OWNER_OR_CAPABLE */
+
+#ifndef HAVE_POSIX_ACL_CHMOD
+static inline int
+posix_acl_chmod(struct posix_acl **acl, int flags, umode_t umode) {
+	struct posix_acl *oldacl = *acl;
+	mode_t mode = umode;
+	int error;
+
+	*acl = posix_acl_clone(*acl, flags);
+	zpl_posix_acl_release(oldacl);
+
+	if (!(*acl))
+		return (-ENOMEM);
+
+	error = posix_acl_chmod_masq(*acl, mode);
+	if (error) {
+		zpl_posix_acl_release(*acl);
+		*acl = NULL;
+	}
+
+        return (error);
+}
+
+static inline int
+posix_acl_create(struct posix_acl** acl, int flags, umode_t* umodep) {
+	struct posix_acl *oldacl = *acl;
+	mode_t mode = *umodep;
+	int error;
+
+	*acl = posix_acl_clone(*acl, flags);
+	zpl_posix_acl_release(oldacl);
+
+	if (!(*acl))
+		return (-ENOMEM);
+
+	error = posix_acl_create_masq(*acl, &mode);
+	*umodep = mode;
+
+	if (error < 0) {
+		zpl_posix_acl_release(*acl);
+		*acl = NULL;
+	}
+
+	return (error);
+}
+#endif /* HAVE_POSIX_ACL_CHMOD */
+
+#ifndef HAVE_CURRENT_UMASK
+static inline int
+current_umask(void)
+{
+	return (current->fs->umask);
+}
+#endif /* HAVE_CURRENT_UMASK */
+
+#ifdef HAVE_POSIX_ACL_EQUIV_MODE_UMODE_T
+typedef umode_t zpl_equivmode_t;
+#else
+typedef mode_t zpl_equivmode_t;
+#endif /* HAVE_POSIX_ACL_EQUIV_MODE_UMODE_T */
+
 #endif /* _ZFS_VFS_H */
diff --git a/include/linux/xattr_compat.h b/include/linux/xattr_compat.h
index 84d8fdeb8..f06ba1fa0 100644
--- a/include/linux/xattr_compat.h
+++ b/include/linux/xattr_compat.h
@@ -26,6 +26,8 @@
 #ifndef _ZFS_XATTR_H
 #define _ZFS_XATTR_H
 
+#include <linux/posix_acl_xattr.h>
+
 /*
  * 2.6.35 API change,
  * The const keyword was added to the 'struct xattr_handler' in the
@@ -92,4 +94,37 @@ fn(struct inode *ip, const char *name, const void *buffer,		\
 	security_inode_init_security(ip, dip, nm, val, len)
 #endif /* HAVE_6ARGS_SECURITY_INODE_INIT_SECURITY */
 
+/*
+ * Linux 3.7 API change. posix_acl_{from,to}_xattr gained the user_ns
+ * parameter.  For the HAVE_POSIX_ACL_FROM_XATTR_USERNS version the
+ * userns _may_ not be correct because it's used outside the RCU.
+ */
+#ifdef HAVE_POSIX_ACL_FROM_XATTR_USERNS
+static inline struct posix_acl *
+zpl_acl_from_xattr(const void *value, int size)
+{
+	return posix_acl_from_xattr(CRED()->user_ns, value, size);
+}
+
+static inline int
+zpl_acl_to_xattr(struct posix_acl *acl, void *value, int size)
+{
+	return posix_acl_to_xattr(CRED()->user_ns,acl, value, size);
+}
+
+#else
+
+static inline struct posix_acl *
+zpl_acl_from_xattr(const void *value,int size)
+{
+	return posix_acl_from_xattr(value, size);
+}
+
+static inline int
+zpl_acl_to_xattr(struct posix_acl *acl, void *value, int size)
+{
+	return posix_acl_to_xattr(acl, value, size);
+}
+#endif /* HAVE_POSIX_ACL_FROM_XATTR_USERNS */
+
 #endif /* _ZFS_XATTR_H */