Posix ACL support for ext 2/3 filesystems

diff -Nru a/fs/xattr_acl.c b/fs/xattr_acl.c
@@ -0,0 +1,99 @@
+/*
+ * linux/fs/xattr_acl.c
+ *
+ * Almost all from linux/fs/ext2/acl.c:
+ * Copyright (C) 2001 by Andreas Gruenbacher, <[email protected]>
+ */
+
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/xattr_acl.h>
+
+
+/*
+ * Convert from extended attribute to in-memory representation.
+ */
+struct posix_acl *
+posix_acl_from_xattr(const void *value, size_t size)
+{
+	xattr_acl_header *header = (xattr_acl_header *)value;
+	xattr_acl_entry *entry = (xattr_acl_entry *)(header+1), *end;
+	int count;
+	struct posix_acl *acl;
+	struct posix_acl_entry *acl_e;
+
+	if (!value)
+		return NULL;
+	if (size < sizeof(xattr_acl_header))
+		 return ERR_PTR(-EINVAL);
+	if (header->a_version != cpu_to_le32(XATTR_ACL_VERSION))
+		return ERR_PTR(-EINVAL);
+
+	count = xattr_acl_count(size);
+	if (count < 0)
+		return ERR_PTR(-EINVAL);
+	if (count == 0)
+		return NULL;
+	
+	acl = posix_acl_alloc(count, GFP_KERNEL);
+	if (!acl)
+		return ERR_PTR(-ENOMEM);
+	acl_e = acl->a_entries;
+	
+	for (end = entry + count; entry != end; acl_e++, entry++) {
+		acl_e->e_tag  = le16_to_cpu(entry->e_tag);
+		acl_e->e_perm = le16_to_cpu(entry->e_perm);
+
+		switch(acl_e->e_tag) {
+			case ACL_USER_OBJ:
+			case ACL_GROUP_OBJ:
+			case ACL_MASK:
+			case ACL_OTHER:
+				acl_e->e_id = ACL_UNDEFINED_ID;
+				break;
+
+			case ACL_USER:
+			case ACL_GROUP:
+				acl_e->e_id = le32_to_cpu(entry->e_id);
+				break;
+
+			default:
+				goto fail;
+		}
+	}
+	return acl;
+
+fail:
+	posix_acl_release(acl);
+	return ERR_PTR(-EINVAL);
+}
+EXPORT_SYMBOL (posix_acl_from_xattr);
+
+/*
+ * Convert from in-memory to extended attribute representation.
+ */
+int
+posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
+{
+	xattr_acl_header *ext_acl = (xattr_acl_header *)buffer;
+	xattr_acl_entry *ext_entry = ext_acl->a_entries;
+	int real_size, n;
+
+	real_size = xattr_acl_size(acl->a_count);
+	if (!buffer)
+		return real_size;
+	if (real_size > size)
+		return -ERANGE;
+	
+	ext_acl->a_version = cpu_to_le32(XATTR_ACL_VERSION);
+
+	for (n=0; n < acl->a_count; n++, ext_entry++) {
+		ext_entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
+		ext_entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
+		ext_entry->e_id   = cpu_to_le32(acl->a_entries[n].e_id);
+	}
+	return real_size;
+}
+EXPORT_SYMBOL (posix_acl_to_xattr);

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